Showing papers in "The Wilson Journal of Ornithology in 1998"
TL;DR: Hoover et al. as mentioned in this paper characterized nest sites and compared specific nest-site characteristics to nesting success for Wood Thrushes (Hylocichla mustelina) nesting in southeastern Pennsylvania in 1991.
Abstract: -We characterized nest sites and compared specific nest-site characteristics to nesting success for Wood Thrushes (Hylocichla mustelina) nesting in southeastern Pennsylvania in 1991. We determined if nests were placed in areas that differed from randomly selected points within a given tract of forest and compared specific nest-site characteristics for successful nests (those that produced at least one fledgling) and nests that failed because of predation. Wood Thrushes selected nest sites non-randomly within a tract of forest, and female Wood Thrushes built nests in areas that had a higher density of trees, higher canopy, higher density of shrubs, and higher average shrub height than randomly selected points. Specific nest-site characteristics had little effect on the ultimate success or failure of nests. The only specific nest-site characteristic included in a stepwise logistic regression model comparing successful and failed nesting attempts was the concealment of the nest from above and below. The average concealment of successful nests was greater than unsuccessful nests, but the model that included nest concealment did not give good fit to the data. Rather, a landscape-level feature, size of forest tract, had the greatest influence on the success and failure of nests for Wood Thrushes in this region. Received 10 Feb. 1997, accepted 20 April 1998. The Wood Thrush (Hylocichla mustelina) is a neotropical migrant that has undergone significant population declines in recent decades (Sauer et al. 1996). Poor reproductive success, particularly as a result of high rates of nest predation, has been cited as one probable cause of the decline (Robinson 1992, Roth and Johnson 1993, Hoover et al. 1995). Identification of specific habitat features associated with nest sites and nesting success, and a calculation of the probability of success given certain characteristics are needed in order to develop long-term strategies for reversing declines in populations of Wood Thrushes and other neotropical migrants (Martin 1992). Also, information on nest-site selection may be applied to management of habitat for this and other species of neotropical migrants. General characteristics of the forest habitat where Wood Thrushes are found during the breeding season have been described by other researchers (Bertin 1977, James et al. 1984, Roth 1987). In addition, other researchers have documented the influence of landscape features such as forest patch size and proximity to edge habitat on the probability of nest success (e.g., Robinson 1988, 1992; Hoover et al. 1995). In this study, we looked at nestsite selection by Wood Thrushes in two different ways. We first determrined whether or not Wood Thrushes, within the forest, used particular areas for nesting based on the structure of the vegetation. We then measured microhabitat characteristics of successful nests and nests that were lost to predators. Our specific objectives were to: (1) determine the characteristics of the vegetation that influenced the probability that a site would be used for nesting by a Wood Thrush, and (2) determine whether or not microhabitat characteristics at the nest site influenced the probability of nesting success.
TL;DR: The observations of trios support the idea that Monk Parakeets are similar to coop- erative breeders, but the lack of cooperation in nest building indicates that colonial nesting may be a result of other benefits of group living, such as improved predator detection.
Abstract: The Monk Parakeet (Myiopsitta monachus) is unique among parrots because it constructs stick nests rather than nesting in holes. This study provides a detailed description of the species' breeding biology and provides evidence that this species might breed cooperatively. Although many parakeet pairs were observed roosting in solitary nests, breeding occurred only in nests within colonies or chambers within compound nests housing other parakeets. The male was responsible for all or most of the nest construction and maintenance. He fed the female during the incubation and early nestling periods, but later in the nestling period both the male and female fed the nestlings. Most breeding attempts involved a male-female pair, but three separate breeding attempts were made by trios (two trios included a female and two males, and the third trio was composed of a male and two females). In the trios, one of the auxiliary bird contributed less to the breeding effort than the primary male and female. The observations of trios support the idea that Monk Parakeets are similar to coop- erative breeders, but the lack of cooperation in nest building indicates that colonial nesting may be a result of other benefits of group living, such as improved predator detection. Received 7 Jan. 1998, accepted I6 Aug. 1998. The social behavior of most parrots has re- mained unstudied, at least partly because of the difficulty of observing birds that are typ- ically far-ranging and often dwell in forest canopies. Compared to most of its relatives, the Monk Parakeet (Myiopsittu monachus) is a relatively tractable species for behavioral study. It is common throughout its range, gen- erally lives in semi-open habitat, and spends a large amount of time in the vicinity of its nests. Monk Parakeets are unusual among par- rots for building large domed nests instead of nesting in holes (Forshaw 1989). These nests are built of twigs and may include several chambers, each occupied by a different pair or group of birds. Nests are often clustered in the same or nearby trees to form colonies, and they are used for roosting as well as for breed- ing (Forshaw 1989). In Bolivia, Monk Para- keets (M. m. Zuchsi) build their stick nests on cliffs rather than in trees (Lanning 1991). The strong tendency to breed colonially, along with delayed breeding, reduced dispersal, and incidental helping led Bucher and coworkers (1991) to suggest that the Monk Parakeet breeding system shares some characteristics with cooperatively breeding species. The large stick nests built by these parrots are the center of much of their daily activity.
TL;DR: The Znga overstory was an important foraging site for most species suggesting that plantations without a shade overstory will have a lower diversity and abundance of food and hence are less attractive to birds than traditional shade plantations.
Abstract: We quantified foraging behavior of 19 bird species in shade coffee plantations in the Domin- ican Republic to document and evaluate their use of food resources in the shade overstory relative to the coffee understory. All species were observed foraging in the Znga "era overstory, and 18 of the 19 species had median foraging heights significantly above the median maximum coffee height. Eight species (42%) foraged exclusively in the canopy or subcanopy and not in the coffee understory. No species foraged exclusively in the coffee, although the Narrow-billed Tody (To&s angustirostn's) foraged mostly in coffee. A negative correlation was found between a species' median foraging height in our shade plantations and its abundance in nearby sun coffee plantations. Invertebrates and nectar were the most important food items in the Znga overstory where 95% of the species gleaned leaf surfaces, 63% probed flowers, 58% gleaned or probed wood, 47% used epiphytes (for invertebrates or fruits), and 26% gleaned or probed Inga fruit. In contrast, birds in coffee foraged primarily for invertebrate prey as 42% of all species gleaned leaf surfaces, 21% gleaned or probed wood, 21% gleaned or probed fruit, and 5% probed flowers. The Znga overstory was an important foraging site for most species suggesting that plantations without a shade overstory (i.e., sun coffee) will have a lower diversity and abundance of food and hence are less attractive to birds than traditional shade plantations. Received 5 May 1997, accepted
TL;DR: In this paper, the Nazca Booby (Sulu ductylutru) was recognized as a separate species based on morphological and biological differences, including positive assortative mating.
Abstract: Two distinct forms of Masked Booby (S&a dactyl&-a) occur in the eastern Pacific: (1) a yellow-billed form that includes a population on Clipper-ton Island and islands off western Mexico (S. d. "cal- ifornica"), and another, unnamed, population on Las Islas Desventuradas, Chile, and (2) an orange-billed form (S. (d.) grunti) that nests almost exclusively on the islands of the Galapagos and on Malpelo Island, Colombia. Quantitative comparisons, including discriminant function analysis (DFA) of standard morphological characters indicated that yellow-billed populations are only marginally different from one another, and neither is consistently separable from 5. d. personata, a yellow-billed form that ranges over most of the tropical Pacific. Further, we found no consistent differences in bare-part coloration or plumage among yellow-billed populations. In contrast, DFA indicated morphological differences between orange- and yellow-billed populations. The orange-billed bird is smaller with a significantly shorter, shallower bill, shorter tarsus, and longer wings and tail. It is also more sexually dimorphic and has distinct plumage characters. Biological observations also support the distinctness of orange-billed birds. They typically nest on cliffs and steep slopes, whereas yellow-billed forms nest mainly on low, flat areas. A difference in habitat preference at sea resulted in a parapatric distribution: orange-billed birds away from colonies concentrated in nearshore waters off the coast of the Americas, whereas the yellow-billed forms foraged much farther offshore. Most importantly, orange- and yellow-billed birds paired assortatively where they nested sympatrically. Thus, based on morphological and biological differences, including positive assortative mating, we recommend that SuZa granti be recognized as a separate species, the Nazca Booby. Received 24 May 1997, accepted 30 March 1998. Geographic variation in the Masked (or Blue-faced) Booby (Sulu ductylutru) has been over-described but under-studied. Most of the seven proposed races of this common pan- tropical seabird date from an era of excessive splitting and were based almost entirely on foot and bill coloration. Plumage and size (with one exception) were ignored, perhaps because few collections contained enough ma- terial to allow study of variation in those char-
TL;DR: It is argued that current reports on overlapping of molt and migration based on observations of molting individuals out of the breeding range could be misleading because some individuals may leave the breeding area to molt in other places before starting a true migration.
Abstract: Documentation of the scheclule and pattern of molt and their relation to reproduction and migration departure are important, but often neglected, areas of knowledge. We radio-tagged Wood Thrushes (Hylocichla mustelina), and monitored their movements and behavior on the U.S. Marine Corps Base, Quantico, Virginia (38? 40' N, 770 30' W) from May-Oct. of 1993-1995. The molt period in adults extended from late July to early October. Molt of flight feathers lasted an average of 38 days (n = 17 birds) and there was no significant difference in duration between sexes. In 21 observed and captured individuals, all the rectrices were lost simultaneously or nearly so, and some individuals dropped several primaries over a few days. Extensive molt in Wood Thrushes apparently impaired flight efficiency, and birds at this stage were remarkably cautious and difficult to capture and observe. All breeding individuals were observed molting 1-4 days after fledgling independence or last-clutch predation, except for one pair that began molt while still caring for fledglings. Our data indicate that energetics or flight efficiency constraints may dictate a separation of molt and migration. We did not observe Wood Thrushes leaving the Marine Base before completion of flight-feather molt. Departure of individuals with molt in body and head, however, was common. We caution against interpreting the lack of observations or captures of molting individuals on breeding sites as evidence that birds actually have left the area. We argue also that current reports on overlapping of molt and migration based on observations of molting individuals out of the breeding range could be misleading because some individuals may leave the breeding area to molt in other places before starting a true migration. Received 30 June 1997, accepted 18 March 1998. The Wood Thrush (Hylocichla mustelina) is one of the most studied avian species in North America, and details about its natural history are relatively well known (Roth et al. 1996 and citations therein). Despite this, information about its molt is limited and details on how molt is integrated with reproduction and migration departure are lacking. Separation of reproduction, molt, and migration within the annual cycle is considered an evoltutionary strategy to reduce energetic stress (Payne 1972, Ginn and Melville 1983), but exceptions exist. Overlap of reproduction with flightfeather and extensive body molt is apparently common in tropical species (Payne 1972, Foster 1974). In temperate regions, its occurrence has been reported in some species that breed at high latitudes where food resources are abundant only briefly (Payne 1972). Joint occurrence of molt and migration is less common, except for species with a slow, diurnal migration with frequent feeding stops (e.g., hirundinids; Niles 1972). The scarcity of information about timing and patterns of molt in Wood Thrushes and many other species is not unexpected. During the molt period, birds become secretive and less likely to be observed or caught, making documentation of activities during this period difficult (Ginn and Melville 1983). Because individuals of some species move away from their breeding territory for molting (Nolan 1978, Cherry 1985, Rappole and Ballard 1987) following these individuals can be difficult. Consequently, molt data often come from observations and/or recoveries of individuals of unknown breeding history or when known, these relationships have not yet been investigated. In recent years there has been an increased interest in use of radiotelemetry for the study of small birds, mainly because of the improvement in transmitter technology (i.e., smaller size). Transmitters are still relatively expensive and of limited range and life, but radiotelemetry-based studies can provide information that otherwise would be difficult to obtain. The objectives of the study were (1) to provide information on the patterns and chronology of the prebasic molt in the Wood Thrush, I Virginia Polytechnic Institute and State Univ., Dept. of Fisheries and Wildlife Sciences, Blacksburg, VA
TL;DR: These were the first comprehensive ground surveys of shorebirds conducted in western Mexico, and the composition was characterized by those species spending their non-breeding period on the Pacific Coast of North America.
Abstract: On 6-9 December 1993 andc 14-18 February 1994 ground surveys of shorebirds were con- ducted in Ensenada Pabellones and Bahia Santa Maria, Sinaloa, Mexico These were the first comprehensive ground surveys of shorebirds conducted in western Mexico Twenty-nine species of shorebirds were recorded The composition was characterized by those species spending their non-breeding period on the Pacific Coast of North America Total numbers of shorebirds estimated were 340,063 birds (December) and 405,483 birds (Feb- ruary) in Ensenada Pabellones and 248,044 birds (December) and 389,841 birds (February) in Bahia Santa Maria Western Sandpiper (Calidris mauri) comprised 82% of shorebirds present in both bays American Avocet (Recurvirostra americana; 6% average total), dowitchers (Limnodromus spp; 6% average total), and Least Sandpiper (Calidris minutilla; 3% average total) were also abundant These bays hold approximately 30% of the shorebirds wintering in Pacific coastal regions of North America Using Western Hemisphere Shorebird Reserve Network criteria, both bays are of international importance for shorebirds Ensenada Pabellones is of regional importance for American Avocets supporting nearly 10% of the total world population Both bays would qualify as wetlands of international importance as defined by the Ramsar Convention on international wetlands Received 28 Aug 1997, accepted 18 April 1998
TL;DR: Monitoring of 54 pairs of Northem Flickers during three breeding seasons in Ohio found that the presence of nest boxes did not appear to help nesting flickers and in fact may have deterred them by attracting additional starlings.
Abstract: I monitored 54 pairs of Northem Flickers (Colaptes auratus), with artificial nest boxes placed near their nest cavities, during three breeding seasons in Ohio to determine whether such boxes would help reduce nest-site competition by European Starlings (Sturnus vulgaris). Twenty-seven of 40 flicker pairs in the presence of starlings (68%) lost a total of 42 cavities to starlings in spite of the presence of a nearby flicker nest box, and nine of these pairs lost two or more cavities to starlings. Thus, the presence of nest boxes did not appear to help nesting flickers and in fact may have deterred them by attracting additional starlings. During initial nest attempts, flicker pairs without starlings produced larger clutches, more nestlings and more fledglings than flickers with starlings. Flicker pairs without starlings were not adversely affected by the presence of a nearby nest box and 64% of such pairs eventually fledged young from their excavated nest cavities. Conversely, no pairs without starlings and only one pair with starlings opted to nest in a nest box versus their excavated or renovated nest cavity. Only 3 of 40 starling pairs opted to nest in a box when excavated flicker cavities were available. However, starlings eventually fledged young in only 9 of the 42 flicker cavities they usurped (21%). Received 10 June 1997, accepted 13 Jan. 1998.
TL;DR: It is found that breeding populations of Red Phalaropes, Black-bellied Plovers, American Golden-Plovers, and King Eiders in the 1990s had decreased substantially from their numbers in the 1970s, and numbers of other shorebird species did not decrease significantly.
Abstract: Historical records of population numbers are almost entirely lacking for shorebirds and some species of waterfowl breeding in the Nearctic. In 1975 and 1976, ground surveys of breeding birds were un- dertaken in the Rasmussen Lowlands, Northwest Territories. We carried out similar censuses in the same area during the summers of 1994 and 1995. Weather conditions and methods were very similar during the two sets of surveys. For all years, we compared densities in different habitat types, as well as estimates for the entire region of total numbers of breeding Red Phalaropes (Phalaropus fulicaria), Pectoral Sandpipers, (Calidris me- lanotos), White-rumped Sandpipers (C. fuscicollis), Semipalmated Sandpipers (C. pusilla), Black-bellied Plovers (Pluvialis squatarola), American Golden-Plovers (Pluvialis dominica), Dunlin (C. alpina), Baird's Sandpipers (C. bairdii), and King Eiders (Somateria spectabilis). We found that breeding populations of Red Phalaropes, Black-bellied Plovers, American Golden-Plovers, and King Eiders in the 1990s had decreased substantially (76- 87%) from their numbers in the 1970s. Numbers of other shorebird species did not decrease significantly (17- 48%). Numbers of Black-bellied Plovers have apparently decreased at staging sites on the east coast of the United States and Canada. However, for American Golden-Plovers, there is no evidence of a decline on the east coast or in at least one other area in the eastern Nearctic. No other population information exists for Red Phalaropes breeding in the eastern Nearctic. Eider numbers appear to be decreasing throughout the Arctic. Possible reasons for declines are habitat changes in migratory staging sites and southern wintering areas. We need more consistent monitoring of arctic shorebirds in order to identify species with continual population declines. Further studies should emphasize Nearctic populations of species showing substantial declines in this study, examining consistency of decreases throughout the Nearctic, and reasons for such changes. Received 9 Oct. 1997, accepted 15 Mav 1998.
TL;DR: Estimates differed significantly between years and confidence intervals were wide, suggesting that longer-term studies of lame numbers of owls will be reauired to obtain accurate and precise estimates of juvenile survival.
Abstract: We monitored dispersal movements of 19 radiotagged juvenile Mexican Spotted Owls (Strix occidentalis Zucida) in northern Arizona during 1994 and 1995. All juveniles initiated dispersal movements in September or October during both years, with most dispersing during September. Initial dispersal movements were rapid and abrupt, but lacked a significant directional pattern. Distance from the nest to the last observed location and the most distant location reached ranged from 0.6-72.1 and 2.1-73.5 km for individual owls, respectively. These distances represent minimum estimates of dispersal capability because only one individual was tracked until it settled on a territory and paired. Owls used a variety of habitat types during dispersal, some of which differed markedly from typical nesting habitat for Mexican Spotted Owls. Four of five owls that were tracked past mid-November moved to lower elevation pinyon-juniper woodlands and at least one overwintered in pinyon-juniper woodland. Kaplan-Meier estimates of annual survival rate ranged from 20.5-28.7%, depending on whether we censored all owls with unknown fates or included suspected deaths as mortality events. Estimates differed significantly between years and confidence intervals were wide, suggesting that longer-term studies of lame numbers of owls will be reauired to obtain accurate and precise estimates of juvenile survival. Received
TL;DR: Baird's Sparrows appear to be a good quality host for cowbirds in southwestern Manitoba as 21% of cowbird eggs laid fledged young with 0.5 cowbirds fledging per parasitized nest.
Abstract: Very few studies have documented aspects of Baird's Sparrow (Ammodramus bairdii) nesting biology, apparently because of difficulty in locating their nests. Subsequently much of the information regarding the breeding biology of the Baird's Sparrow is based on small samples of nests and anecdotal information. We studied the nesting biology of the Baird's Sparrow in southwestern Manitoba, during 1991-1992. Baird's Spar- rows arrived in the first two weeks of May and initiated clutches as early as 2.5 May. Clutch initiation peaked between 29 May and 4 June with a second smaller peak occurring in mid- to late July. Seventy-six nests were located with a mean clutch size of 4.6 eggs. The incubation period extended 11-12 days and young fledged between 8 and 11 days of age. Mayfield nest success was 37% with predation being the primary cause of nest loss. Brown-headed Cowbirds (Molothrus ater) parasitized 36% of the nests with 67% of these nests containing more than one cowbird egg (2 = 2.0 2 0.2 S.E., range = l-4). Hatching success of non-parasitized nests was significantly higher than that of parasitized nests. In addition, significantly fewer young fledged from successful parasitized nests than from successful non-parasitized nests resulting in an average cost of 1.1 Baird's Sparrow fledglings per parasitized nest. Egg removal by cowbirds was likely the primary cause of lowered productivity in parasitized nests. Baird's Sparrows appear to be a good quality host for cowbirds in southwestern Manitoba as 21% of cowbird eggs laid fledged young with 0.5 cowbirds fledging per parasitized nest. Received 15 Aug.
TL;DR: The findings suggest that nocturnal foraging by most shorebird species at a northern temperate, intertidal site did not increase during periods of short daylength, and interspecific variation in diurnal andNocturnal feeding patterns of shorebirds is associated mostly with variation in tidal, seasonal, and moonlight conditions.
Abstract: -Knowledge of abiotic factors influencing the foraging ecology of nonbreeding shorebirds (Charadriiformes: Charadrii) is based on research conducted almost exclusively during the day. Consequently, we examined the relative contributions of environmental variables to diurnal and nocturnal foraging patterns (presence/absence) of nonbreeding shorebirds at Humboldt Bay, California, USA from January 1992 to January 1993. The influence of environmental variables on foraging patterns differed between day and night. Most notably, the diurnal presence of birds increased with: (1) shorter daylength [Black-bellied Plover (Pluvialis squatarola), dowitchers (Limnodromus spp.), and small sandpipers (Calidris mauri and C. minutilla)]; and (2) shorter durations of mud flat exposure [American Avocet (Recurvirostra americana), Marbled Godwit (Limosa fedoa), and Dunlin (Calidris alpina)]. By contrast, the nocturnal presence of most species increased during the fall [Marbled Godwit, dowitchers, Black-bellied Plover, Semipalmated Plover (Charadrius semipalmatus), and Dunlin] and on nights with a visible moon [Marbled Godwit, Willet (Catoptrophorus semipalmatus), dowitchers, Semipalmated Plover, and Dunlin]. Our results suggest that interspecific variation in diurnal and nocturnal feeding patterns of shorebirds is associated mostly with variation in tidal, seasonal, and moonlight conditions. Furthermore, our findings suggest that nocturnal foraging by most shorebird species at a northern temperate, intertidal site did not increase during periods of short daylength. Received 28 July 1997, accepted 13 Jan. 1998. Nonbreeding distributions of shorebirds in coastal habitats are influenced by numerous environmental factors, especially tides and weather (see Burger 1984), which influence the availability of food resources. Tides predictably alter the amount of available foraging habitat, and variation in temperature, wind, and daylength further influence the availability of intertidal prey (Evans 1976). These generalizations, however, are based largely on research conducted during the day despite the growing body of literature (e.g., McNeil 1991, Dodd and Colwell 1996, McNeil and Rodriguez S. 1996) documenting nocturnal foraging by shorebirds. Consequently, the environmental correlates of nocturnal foraging by shorebirds remain poorly understood. Only one study (Robert et al. 1989) has quantified environmental influences of both diurnal and nocturnal distributions of shorebirds. Most studies (e.g., Heppleston 1971, Zwarts et al. 1990, Evans and Harris 1994, Thibault and McNeil 1994) have evaluated the contributions of one environmental factor (moonlight) to nocturnal foraging by shorebirds. Furthermore, with the exception of Robert and coworkers (1989) and Zwarts and coworkers (1990), most researchers have focused on a single species. Findings from these studies suggest that the nocturnal foraging ecology of shorebirds is influenced by variation in tides (Robert et al. 1989), moonlight (Heppleston 1971, Robert et al. 1989, Zwarts et al. 1990, Evans and Harris 1994, Thibault and McNeil 1994), and season (Rompre and McNeil 1994, Dodd and Colwell 1996). In this paper, we examine the relative contributions of environmental variables to diurnal and nocturnal foraging by eight shorebird species at Humboldt Bay, California, USA, an important Pacific Coast estuary for nonbreeding shorebirds (Colwell 1994). Elsewhere (Dodd and Colwell 1996), we showed that shorebirds at North Humboldt Bay foraged principally during the day, although diurnal and nocturnal distributions varied both among seasons and species. STUDY AREA AND METHODS We studied shorebirds (Charadriiformes: Charadrii) from 10 January 1992-10 January 1993 at the Arcata Marsh Project in North Humboldt Bay, Humboldt Co., California, USA. North Humboldt Bay is the largest of three basins comprising Humboldt Bay with approximately 12.2 km2 of exposed tidal mud flat at mean low tide (Costa and Stork 1984). Local tides are I Deptartment of Wildlife, Humboldt State Univ.,
TL;DR: The density and distribution of mesquite (Prosopir velutina) exerted the strongest influence on the grassland bird cotnmunity, andShrub- dependent bird species dominated the community, accounting for 12 of the 18 species and 557 of the 815 individuals detected.
Abstract: We determined which vegetal features influenced the distribution and abundance of grassland birds at the Buenos Aires National Wildlife Refuge, Arizona The density and distribution of mesquite (Prosopir velutina) exerted the strongest influence on the grassland bird cotnmunity Abundances of Pyrrhuloxia (Cardi- nalis sinuatus; 9 = 0363, P = 0025) and Lucy's Warbler (Vermivora luciae; 9 = 0348, P = 004) and total abundance of birds (rZ = 0358, P = 004) were positively correlated with increasing density of mesquite (Prosopis velutina), whereas abundance of Cactus Wren (Campylorhynchus brunneicapillus; 9 = 0452 P = 002) was negatively correlated with increasing mesquite density Abundance of Loggerhead Shrike (Lanius ludovicianus; r2 = 0693, P < 0001) was positively correlated with an increasing patchiness of mesquite Shrub- dependent bird species dominated the community, accounting for 12 of the 18 species and 557 of the 815 individuals detected Species relying on extensive areas of open grassland were largely absent from the study area perhaps a result of the recent invasion of mesquite into this semi-desert grassland Received 15 Aug 1997, accepted 19 Mar 1998
TL;DR: In this paper, the authors used radio-telemetry to track the movements of seven adult male Ferruginous Hawks (Buteo regalis) in southcentral Washington and estimated home range size for each male using minimum convex polygon, harmonic mean, adaptive kernel, and fixed kernel-based methods.
Abstract: -We used radio-telemetry to track movements of seven adult male Ferruginous Hawks (Buteo regalis) in southcentral Washington. Home range size was estimated for each male using minimum convex polygon, harmonic mean, adaptive kernel, and fixed kernel-based methods. Minimum convex polygon and harmonic mean home ranges were significantly larger than those previously reported for Ferruginous Hawks. Home ranges varied substantially among males (mean = 90.3 km2, range = 17.7-136.4 kM2). There was no relationship between home range size and brood size; however, there was a significant relationship (r2 = 0.964, P = 0.018) between home range size and the distance from the nest site to the nearest irrigated agricultural field where some males hunted. Kernel-based estimates showed two distinct core areas for most males, one around the nest and a second in the agricultural fields where they hunted. Received 25 Aug. 1997, accepted 29 Oct. 1997. The Ferruginous Hawk (Buteo regalis) is a large grassland raptor that breeds in the shrubsteppe and semi-arid regions of western North America (Olendorff 1993). The species is thought to be sensitive to human-caused disturbance in its nesting areas (Lokemoen and Duebbert 1976, Bechard et al. 1990). Habitat degradation caused by agriculture and overgrazing have been reported as a threat to the species' survival in North America (Howard 1975, Thurow et al. 1980, Cottrell 1981, Gilmer and Stewart 1983). In Oregon and Washington, the species is on the periphery of its range and is currently listed as Threatened in Washington which has an estimated population of 50 to 60 breeding pairs (Wash. Dept. Fish Wildl. 1996). This study was undertaken to provide information about the spatial use patterns of the Ferruginous Hawk in southcentral Washington for use by the state Department of Fish and Wildlife in their recovery plan for the species. Herein, we report home range estimates for adult male Ferruginous Hawks in southcentral Washington and compare them with results previously reported in the literature. We estimate home range size using four different techniques: the minimum convex polygon (MCP; Mohr 1947), harmonic mean (Dixon and Chapman 1980), fixed kernel, and adaptive kernel-based (Worton 1989, Kenward 1990) methods. Lastly, we relate variability in individual home ranges to factors such as brood size and habitat type around the nest site, and examine possible effects of habitat
TL;DR: The results in this study suggest that the shifting mosaic of vegetation on Fort Riley resulting from training and range management practices maintains adequate habitat for breeding shrikes.
Abstract: This study was conducted to determine landscape and fine-scale vegetative variables associated with breeding Loggerhead Shrikes (Lanius ludovicianus) on Fort Riley Military Reservation, Kansas. Because Fort Riley is an Army training site, the influences of training disturbance to the vegetation, and range manage- ment practices on bird habitat patterns were also investigated. Breeding birds were surveyed in 1995 and 1996 using point counts. Survey plots were identified, a priori, at the landscape scale as either grassland, savannah, or woodland edge according to cover by woody vegetation. In 1996, fine-scale habitat at survey points and at bird use sites was measured and a principal components analysis used to characterize the fine-scale herbaceous vegetation structure. A military disturbance index was developed to quantify the severity of vehicle disturbance to the vegetation at survey and bird use sites. Shrikes were associated with savannah habitat at the landscape scale. Sites used by Loggerhead Shrikes were characterized at the fine-scale by tall, sparse, structurally hetero- geneous herbaceous vegetation with high standing dead plant cover and low litter cover. At the fine-scale, tree and shrub density did not differ between sites used and not used by shrikes. Used sites did not differ from survey sites with respect to military training disturbance, hay harvest, or the number of years since a site was last burned. Our results in this study suggest that the shifting mosaic of vegetation on Fort Riley resulting from training and range management practices maintains adequate habitat for breeding shrikes. Received 25 Sept. 1997, accepted 18 June 1998.
TL;DR: The behavior of adults and nestlings at nine Eastern Screech-owl (Otis ash) nests in central Kentucky was monitored by videotaping the owls in specially-constructed nest boxes, and no siblicide or other aggression between siblings was observed.
Abstract: The behavior of adults and nestlings at nine Eastern Screech-owl (Otis ash) nests in central Kentucky was monitored by videotaping the owls in specially-constructed nest boxes. Adult screech-owls delivered 1281 prey items during 164 h of taping. Nestlings fed first by adults started to beg significantly earlier, extended their beaks higher and closer to the adult, and called at higher rates and with greater volume than did siblings that were not fed first. In addition, nestlings fed first started begging earlier, stretched their beaks higher, positioned their beaks closer to the adult, and vocalized at a higher rate than when they were not fed first. In addition, after being returned to the nest, nestling screech-owls temporarily deprived of food begged with greater intensity and were fed more often than siblings. Such results provide further evidence for the positive relationship between hunger, begging intensity, and the chances of being fed. Our results also indicate, however, that nestling mass may be important in determining which nestlings will be fed when differences in the mass of siblings reach a certain level. We observed no siblicide or other aggression between siblings. Contributing to this absence of aggression may have been the large boxes used for videotaping and an abundant food supply. It is also possible, however, that aggression and siblicide occur infre-
TL;DR: This study demonstrates that two characteristics of a relatively unimpacted landscape in the central Everglades are higher avian species richness and a more distinct avian community in bayheads than in willowheads or marshes.
Abstract: We compared avian community composition, species richness, and total bird abundance among three vegetation types (bayheads, willowheads and marshes), and between a reduced-hydroperiod and relatively unimpacted landscape in the central Everglades during July-August, 1996. Our results showed that the collective Everglades bird community contained a substantial number of forest birds as well as marsh species. Red-winged Blackbirds (Agelaius phoeniceus), Common Yellowthroats (Geothlypis trichas), and White-eyed Vireos (Vireo griseus) accounted for 65% of total individual birds during the period of study. Wading birds accounted for a relatively small proportion of the total avian community. White-eyed Vireo was the most abundant bird species in bayheads and was closely associated with that habitat. Red-winged Blackbird and Common Yellowthroat were the most abundant species in both willowheads and marsh vegetation. We found no significant difference in bird abundance among vegetation types (P > 0.05) nor between landscapes (P > 0.05). We also found no difference in species richness between landscapes (P > 0.05). A significant (P = 0.02) interaction between vegetation and landscape indicated that species richness differed among vegetation types in the unimpacted landscape, but not in the reduced-hydroperiod landscape. In the unimpacted landscape we detected significantly more species in bayheads than the other two vegetation types (both tests, P ' 0.004). An ordination revealed that in the unimpacted landscape, bird communities were more specific to vegetation types than in the reduced- hydroperiod landscape. Our study demonstrates that two characteristics of a relatively unimpacted landscape in the central Everglades are higher avian species richness and a more distinct avian community in bayheads than in willowheads or marshes. The Everglades restoration process will promote the conservation of avian diversity by restoring the landscape matrix of both marsh and bayhead vegetation. Received 8 May 1997, accepted 3 Oct. 1997.
TL;DR: Because the Alaka'i studies were seminal in the development of the current AOU classification of Hawaiian native passerines, they defend that classification against recent challenges and further refine it.
Abstract: We observed, tape recorded, and photographed birds of the Alaka'i Plateau on Kaua'i, Hawai'i for one week during the summer of 1975. We observed all but one of the island's historically known species and compared the Alaka'i Plateau with the more accessible Koke'e area. Ours were the last studies before catastrophic changes in the Kaua'i avifauna and included many observations that cannot now be repeated. This retrospective report presents our findings in the light of subsequent events. Because our Alaka'i studies were seminal in the development of the current AOU classification of Hawaiian native passerines, we defend that classification against recent challenges and further refine it. The controversial genus Hemignathus is shown to be supported by a suite of synapomorphies of plumage, bill morphology, and vocalizations. We advocate removal of the 'Anianiau from Hemignathus and classify it as Magumma parva. Our studies of foraging behavior and vocalizations support the recent recognition of the Kaua'i 'Amakihi (H. kauaiensis) as a separate species and suggest that the 'Elepaio (Chasiempis) is best split into three species (sckzteri, ibidis, and sandwichensis). Major hurricanes in 1983 and 1992 appear to have severely impacted Alaka'i bird populations with the subsequent extinction of the Kaua'i '0'0 (Moho braccatus) and possibly the Kama'o (Myadestes myadestinus), and the island population of 'O'u (Psittirostra psittacea). We report some of the last natural history observations on these species. Formerly adaptive strategies for storm survival, including taking refuge in valleys, are no longer effective because the lowlands are now infested with mosquito-borne avian diseases. The Puaiohi (M. palmen'), a ravine specialist, suffered less from the storms although its population remains perilously low. Other forest birds, especially the 'Akikiki (Oreomystis bairdi), show noticeable declines since 1975. We speculate that intro- duced organisms such as alien plants can have a deleterious effect on ecosystems by altering feeding methods of birds even in areas where the weeds do not occur. We caution against the overly conservative use of species- level taxa for setting conservation priorities on remote islands. Received 24 October 19%, accepted 27 June 1997.
TL;DR: Fisher et al. as discussed by the authors used radiotelemetry to determine habitat use by Flammulated Owls (Otus flammeolus) during the breeding season on 452 ha of montane conifer forest in central Colorado in 1982-1983.
Abstract: -We used radiotelemetry to determine habitat use by Flammulated Owls (Otus flammeolus) during the breeding season on 452 ha of montane conifer forest in central Colorado in 1982-1983. Mean size and SD of home ranges was 11.1 ? 1.9 ha (range = 8.5-12.5 ha, n = 4) in 1982 and 18.3 ? 5.1 ha (range = 14.0-24.0 ha, n = 3) in 1983. Habitat use by nesting males was affected by distribution of old forests of ponderosa pine (Pinus ponderosa) mixed with Douglas-fir (Pseudotsuga menziesii), by topography, and by juxtaposition of home ranges of conspecifics. In spring, both new and returning owls settled into areas containing more old ponderosa pine/Douglas-fir than in other overstory types available in the study area. After settling, males foraged significantly more often in old ponderosa pine/Douglas-fir than in other overstory types available within home ranges. Eighty-one percent of foraging locations by males occurred in one to four intensive foraging areas within each home range. Mean size of intensive foraging areas was 0.5 + 0.4 ha (range = 0.1-1.4 ha). Eighty percent of intensive foraging areas consisted entirely of old ponderosa pine/Douglas-fir. Use of this overstory type by Flammulated Owls is probably related to its composition and structure, and prey availability. Received 24 Jan. 1997, accepted 19 April 1998. When settling into landscapes birds must distinguish among available habitats, each of which may differ in quantity and quality of requisite resources (Fretwell and Lucas 1970). Habitat selection during settling likely involves an hierarchically-ordered series of choices during which a bird selects a geographic area (first-order), types of habitat in which the territory is established (secondorder), and specific microhabitats for activities such as nesting, foraging, and roosting (thirdorder; Johnson 1980). At each order of selection a species may use different criteria for discriminating among available habitats. Western Kingbirds (Tyrannus verticalis), for example, may select territories on the basis of maximum canopy height, and nest-sites (microhabitats) on the basis of tree characteristics (Bergin 1992). Habitats selected at each order are limited by the preceding choice because movements of breeding birds are energetically limited to some finite area around nests. Descriptions of habitat are therefore scale-dependent (Wiens 1986, Kotliar and Wiens 1990) and focusing on a single order may preclude discerning patterns at other orders (Maurer 1985). Understanding a species' habitat selection requires the consideration of choices at each scale. The breeding range of Flammulated Owls (Otus flammeolus) is from the Rocky Mountains to the Pacific Coast Mountains (except Oregon and Washington) and from south-central British Columbia to Veracruz, Mexico (McCallum 1994). Flammulated Owls are migratory and may winter from the southern United States to as far south as El Salvador (Phillips et al. 1964, American Ornithologists' Union 1983). Habitats within home ranges of Flammulated Owls have not been compared to habitats available within landscapes. Nesting Flammulated Owls have been reported in yellow pine [subsect. Ponderosae (Critchfield and Little 1966)] and mixed-conifer forests. These forests were often mixed with oak (Quercus sp.) or pinyon (Pinus edulis) at lower elevations, and fir (Abies sp.), Douglas-fir (Pseudotsuga menziesii), or quaking aspen (Populus tremuloides) at higher elevations (e.g., Marshall 1957, Bull and Anderson 1978, Richmond et al. 1980, Goggans 1986, Reynolds and Linkhart 1987, McCallum and Gehlbach 1988). Nesting Flammulated Owls were occasionally found in pinyon (Huey 1932) and Douglas-fir forests (Howie and Ritcey 1987, Powers et al. 1996). We determined habitat selection by Flammulated Owls at multiple scales by comparing forests within owl home ranges to forests ' USDA Forest Service, Rocky Mountain Research Station, 240 West Prospect, Fort Collins, CO 80526. 2 Department of Fishery and Wildlife Biology, Colorado State University, Fort Collins, CO 80523. 1 Current Address: Dept. of Environmental, Population, and Organismic Biology, Univ. of Colorado, Boulder, CO 80309; E-mail: email@example.com. 4Corresponding author.
TL;DR: The effects of growing season and dormant season prescribed fire on the winter bird communities in mature pine stands on Fort Benning Military Reservation, Georgia were compared and no differences in mean bird abundance or species richness between burn treatments were detected.
Abstract: -We compared the effects of growing season and dormant season prescribed fire on the winter bird communities in mature pine stands on Fort Benning Military Reservation, Georgia. We surveyed the avian community using fixed-radius point counts from I December 1995 to 28 February 1996, one year after burning. We detected no differences in mean bird abundance or species richness between burn treatments. No species was observed more or less frequently in either burn treatment. Season of burn had little apparent effect on the composition of wintering bird communities in managed mature pine forests. Received 31 March 1998, accepted 30 July 1998. Winter mortality may be a limiting factor for many resident birds in North America (Arcese et al. 1992), and the alteration or loss of winter habitats could contribute to avian population declines (Terborgh 1989, Morton 1992). Consequently, conditions on the wintering ground can influence breeding populations in following years (Baillie and Peach 1992) through competition for winter habitats I Daniel B. Warnell School of Forest Resources, Univ. of Georgia, Athens, GA 30602. 2 Corresponding author; E-mail: chapmanC@smokey.forestry.uga.edu This content downloaded from 220.127.116.11 on Sun, 26 Jun 2016 06:57:19 UTC All use subject to http://about.jstor.org/terms SHORT COMMUNICATIONS 571 TABLE 1. Vegetation characteristics, expressed as X (t SE), for growing and dormant season prescription burned mature pine stands on Fort Benning Military Reservation, Georgia (July-August 1995). Growing Dormant Habitat characteristic (n = 9) (n = 9) F-Value P-Value Stand age (years) 51.6 (4.3) 57.7 (4.0) 0.22 >0.05 Basal area (m2/ha) 11.8 (1.4) 13.9 (1.8) 0.54 >0.05 Canopy closure (%) 31.7 (0.9) 31.0 (0.8) 0.12 >0.05 Shrub density (no./0.04 ha) 10.2 (0.8) 8.2 (0.8) 0.62 >0.05 (Holmes et al. 1989, Rappole et al. 1989) and effects on winter site fidelity (Kricher and Davis 1986, Sherry and Holmes 1992). Therefore, it is important to understand how land management activities may affect avian use of winter habitats. In the southeastern United States, prescribed burning is a widely used silvicultural tool in the management of pine forests. Historically, lightning caused fires have been a major ecological force in southeastern ecosystems (Komarek 1962, Landers 1987). Such fires usually occurred during the growing season (Komarek 1968, Taylor 1969), but during this century forest managers have relied predominately upon prescribed fires during the dormant season to manage forest understories. Burns conducted during the winter months provide conditions such as high moisture content of the vegetation, low ambient temperatures, and consistent winds, that reduce the chances of wildfire. Recently, growing season burns are being used more frequently by forest managers because they more closely mimic natural fire regimes and provide greater control of hardwoods. Although some researchers report favorable responses of breeding bird communities to burned versus unburned habitats (Emlen 1970, Wilson et al. 1995), research on the effects of prescribed fire on wintering bird communities is limited (Blake 1982). Because the season of burn can influence the vegetational structure of a habitat (Waldrop et al. 1992), we deemed it important to compare wintering avian communities in growing season and dormant season prescription-burned mature pine stands. STUDY AREA AND METHODS Our study was conducted at the Fort Benning Military Reservation near Columbus, Georgia. Fort Benning is located in the Upper Coastal Plain of westcentral Georgia. The vegetation on Fort Benning is dominated by pure and mixed stands of longleaf (Pinus palustris), loblolly (P. taeda), and shortleaf pine (P. echinata) with open understories consisting mainly of sweetgum (Liquidambar styraciflua), flowering dogwood (Cornus florida), andropogon (Andropogon spp.), blackberry (Rubus spp.), gallberry (Ilex spp.), and wax myrtle (Myrica cerifera). Pine stands on the reservation are managed with both growing season and dormant season prescribed fires on 3-year rotations. Many of the stands are managed to provide required habitat conditions for the Red-cockaded Woodpecker (Picoides borealis), an endangered species endemic to mature pine forests in the southeastern United States (U.S. Fish and Wildlife Service 1985). These stands are burned by prescription every 2-4 years. We selected for study 9 plots that were bumed in the growing season (April-August) and 9 plots that were burned in the dormant season (January-March) of 1994. All plots were located in mature pine stands within managed Red-cockaded Woodpecker habitat and were similar in basal area, canopy closure, and shrub density (Table 1). Because our interest was in comparing the avifauna of growing season burned areas to dormant season burned areas, we did not sample unburned plots. When comparing conditions in fire-maintained habitats, fire exclusion usually is considered a treatment rather than a control (Platt et al. 1988). We censused birds in each plot along a line transect consisting of 9 census points located at least 122 m apart within managed, mature pine stands. Transect points were placed in 3 X 3 grids and were located at least 100 m from roads and other open areas (White et al. 1996). We conducted biweekly counts from midDecember 1995 through mid-February 1996, using the fixed-radius point count method (Hutto et al. 1986). Census methods were derived from Ralph and coworkers (1995). To reduce bias, plots were censused at alternate times between sunrise and 10:30 EST (Robbins 1981, Blake et al. 1991) and were alternated between observers (Erwin 1982). During each count, observers sampled each survey point for 5 minutes and all birds detected aurally or visually within a 61 m radius were counted. Flagging tape streamers were placed 15 m, 30 m, 45 m, and 61 m in the four cardinal directions from each point to assist observers in estimating bird distances. Birds flushed when observers were approaching or leaving a survey point were recorded, but birds flying over the plot were not included in the data analysis. Because all plots were relatively This content downloaded from 18.104.22.168 on Sun, 26 Jun 2016 06:57:19 UTC All use subject to http://about.jstor.org/terms 572 THE WILSON BULLETIN * Vol. 110, No. 4, December 1998 TABLE 2. Mean (SE) nonbreeding bird abundance (mean no./per plot) on growing and dormant season prescription burned mature pine stands at Fort Benning Military Reservation, Georgia, December 1995 through
TL;DR: This work recorded and analyzed vocalizations of Synallaxis albescens from three populations in Ven- ezuela, two continental and one island, to assess the extent of geographic variation for a species of the family Furnariidae and tested the sound environment hypothesis.
Abstract: I recorded and analyzed vocalizations of Synallaxis albescens from three populations in Ven- ezuela, two continental and one island, to assess the extent of geographic variation for a species of the family Furnariidae. Previous work on geographic variation in suboscines has focused on species of the Tyrannidae. I also tested the sound environment hypothesis. From nine vocalization characters I created discriminant functions that best separated the three populations. I then used classification analyses to determine how well the discrim- inant function models assigned individuals to their home populations. Classification analyses using discriminant functions created from first songs of recorded individuals correctly assigned individuals to their home populations 74.1% of the time and 66.7% of the time for functions created from arbitrarily chosen sixth songs. The island population was significantly more variable than either of the continental populations for the first syllable length but not for the frequency-modulated portion of the second syllable. The results demonstrate that geographic variation exists among populations although a sufficient amount of similarity prevents unequivocal classification of ?h to 1/3 of individuals to their home populations. The results regarding vocalization variability provide weak support for the sound-environment hypothesis. Received 30 June 1997, accepted 9 Feb. 1998.
TL;DR: In this article, the structure and floristic composition of the habitats were described for the Kirtland's Warbler in Bahama Archipelago, and a crude estimate of potential winter habitat for the current small population of warblers (733 singing males in 1997) was provided.
Abstract: Habitats of Kl high coppice was not used. The structure and floristic composition of the habitats are described. Observations (n = 4.51) of a Kirtland's Warbler male (uniquely color banded) and female over three months indicated the birds generally stayed within 3 m of the ground (98% of observations), and used a territory of 8.3 ha. A crude estimate of potential winter habitat suggests that not only is there more than an adequate amount in the Bahama Archipelago for the current small population of warblers (733 singing males in 1997), but also enough for a considerably larger population. No serious future threat to the amount of that habitat is foreseen. Received 5 May 1997, accepted I3 Jan. 1998.
TL;DR: A recent field study has revealed many species of birds new for El Salvador suggesting that the country's few protected areas may be especially important for conserving regional biodiversity as discussed by the authors, suggesting that conservation of these areas is particularly important for saving regional biodiversity.
Abstract: Recent field studies have revealed many species of birds new for El Salvador suggesting that the country's few protected areas may be especially important for conserving regional biodiversity. Seventeen percent of the landscape or 359,000 ha is covered with natural forest or scrub habitats, of which 38,000 ha are coastal mangrove forests. An additional 196,000 ha (9% of El Salvador) are coffee plantations, a forest-like habitat used by many birds. Of 508 bird species known to occur in the country, 310 are breeding residents; the others are migratory visitors, transients, or vagrants. Seventeen species occurring in El Salvador are endemic to the highlands of northern Central America and one species is endemic to the Pacific slope lowlands of northern Central America. About 270 species are habitat specialists with highly restricted ranges within El Salvador. In all, 254 species (>50% of the avifauna) are threatened by habitat loss, pollution, hunting, and exploitation for the pet trade. Of these, 117 are in danger of extinction at the national level and three are believed already extirpated. Much additional field work is needed to understand the status and abundance of El Salvador's birds. This report includes a complete list of reported species with classification of residency status, threatened status, and distribution. This list can serve as a resource for interpreting field observations produced by environmental impact studies or conservation projects in El Salvador. A second list includes 73 species that probably occur in El Salvador but have not been reported.
TL;DR: Results indicate that nest predation is a major influence on this population, despite the size of the forest tract, and nesting success showing a trend of increasing late in the breeding season.
Abstract: From 1993-1995, we located and monitored 601 Acadian Flycatcher (Empidonax virescens) nests in a large contiguous tract of bottomland hardwood forest on the White River National Wildlife Refuge, Arkansas. Annual reproductive success was significantly different among years; ranging from 10-25% (Mayfield estimate) over the three years of the study. There was no significant difference in nest success among study plots, with nesting success showing a trend of increasing late in the breeding season. Clutch size for nonpar- asitized nests averaged 2.9 ? 0.02 (SE) eggs with a mode of 3. Rates of Brown-headed Cowbird (Mol-othrus ater) parasitism were low (21 %), accounting for 7% of all nest failures. However, parasitism by cowbirds resulted in a reduction of clutch size for nests initiated early (i.e., first nests and replacements) in the breeding season. Predation was the leading cause of nest failures, accounting for 75% of all failures. Snakes and avian predators were thought to be the leading cause of nest failures. Although additional factors must be investigated, prelim- inary results indicate that nest predation is a major influence on this population, despite the size of the forest tract. Received 10 June 1997; accepted 27 Oct. i997.
TL;DR: Clutch size, number of broods/season, and fledging success did not vary among species, but overall, Tree Swallows grew the fastest and peak nestling mass was substantially higher in Cliff Swallows than the other species.
Abstract: We compared the breeding biology of sympatric and contemporaneously breeding populations of Tree (Tachycineta bicolor), Barn (Hirundo rustica) and Cliff swallows (Petrochelidon pyrrhonota) in 1994 and 1995 in central New York to characterize their life histories under common environmental conditions. Laying dates did not vary among species, but average clutch sizes were largest in Tree Swallows (5.7 eggs), intermediate in Barn Swallows (4.7 eggs) and smallest in Cliff Swallows (3.5 eggs). Two broods were common in Barn Swallows, but Tree Swallows raised only one, and we suspect that Cliff Swallows raised only a single brood. Relative egg mass (egg mass/female mass) was higher in Barn than in Tree swallows. Most nests fledged young, and fledging success did not vary among species. Growth rates of four nestling traits were measured (mass, wing chord, tarsus and bill), and overall, Tree Swallows grew the fastest. Peak nestling mass was substantially higher in Cliff Swallows than the other species, probably because they gained the most fat. A literature survey of hirundinid growth rates also suggested that Tree Swallows grew faster than the other species. Per capita provisioning rates of parents (trips/nestling/h) increased seasonally and were highest in Barn Swallows. Slower growth despite high feeding rates suggests either lower feeding efficiency or more severe effects of ectoparasitism in Barn Swallows compared to the other species. Our results show that clutch size, number of broods/season
TL;DR: The absence of any change in feeding rates with increased brood size suggests that food requirements per nestling decrease as brood size increases, perhaps because of differences in thermoregulatory costs.
Abstract: Observations of parental feeding roles were made at 19 Yellow-breasted Chat (Icteria virens) nests during the 1994 breeding season in central Kentucky. Male and female chats fed nestlings at similar rates, and adult feeding rates were unaffected by brood size. The absence of any change in feeding rates with increased brood size suggests that food requirements per nestling decrease as brood size increases, perhaps because of differences in thermoregulatory costs. In contrast to the results of many other studies, provisioning rates and load sizes (number of prey delivered per visit) did not increase with nestling age. However, our observations at chat nests did not begin until nestlings were 3 or 4 days old. Studies of other species have revealed that 1-3 day old nestlings may be visited less frequently and provided with smaller loads than older nestlings, and observations of nestling chats during this early period might have revealed similar behavior. Received 2 Aug. 1996, accepted 30 April 1998. Among altricial birds, the behavior of par- ents providing food for nestlings may be in- fluenced by several factors. For example, dif- ferences in brood size and nestling age may contribute to changes in feeding rates or the size and type of prey delivered to nestlings. However, previous work has revealed inter- specific differences in how parents respond to changes in these and other factors. For ex- ample, adult Bachman's Sparrows (Aimophila aestivalis) make more feeding visits to large broods than to small broods (Haggerty 1992), but adult Field Sparrows (Spizella pusilla) do not (Best 1977). Previous studies have also revealed interspecific differences in the re- spective roles of males and females in provi- sioning nestlings. In some species, males and females provision nestlings at similar rates
TL;DR: Vocalization rates increased in alarm contexts and during the non-breeding season, probably as a result of increasing interactions between individuals, and it is suggested that songs were derived from a process of repetition and increasing variability from gutural calls.
Abstract: The calls of the Blue-fronted Amazon (Amazona aestiva) are described and their possible function within the social organization of the species during breeding and non-breeding seasons are discussed. We identified 9 vocalizations; six ("wak-wak", "wa-wawawa", transitions, "gu-gugu", guturals, "ka-kaka") were nonspecific and were given in several circumstances: alarm, contact, feeding, and flying. The remaining had specific contexts: "waahh" (agonistic), "grr-uip" (contact in flight), and songs (reproduction-territorial). Vocalization rates increased in alarm contexts and during the non-breeding season, probably as a result of increasing interactions between individuals. The frequency containing the greatest amount of energy was a useful variable to characterize Blue-fronted Amazon calls, particularly at the species level. The most commonly used vocalization, "wak-wak", has structural features that promote directionality and short-range transmission, en- hancing its usefulness for the aggregation of individuals. It is suggested that songs were derived from a process of repetition and increasing variability from gutural calls. The highly contextual variability of these calls may be due to an incompletely specialized repertoire or a vocal system based upon combinations of calls for con- veying messages. Received 5 May 1997, accepted 17 Mar. 1998.
TL;DR: Male aerial territorial displays of Sprague's Pipits (Anithus spragueii) are described in detail for the first time, with four males' average display rates ranging from 11.8-34.8 min.
Abstract: -Male aerial territorial displays of Sprague's Pipits (Anithus spragueii) are described in detail for the first time. Aerial displays were performed primarily in the morning, with four males' average display rates ranging from 11.8-34.8 min. One male displayed continuously for 3 hrs; no other passerine has been documented to have such prolonged aerial displays. Display flight energetics were estimated with implications explored. Received 6 March 1997, accepted 17 March 1998. Among the least known resident North American passerines is the Sprague's Pipit (Anthus spragueii). The dearth of information on this species is not surprising given its highly cryptic plumage and habits. In fact, even territorial males' persistent and relatively conspicuous flight display have never been described in detail. Here, I present the first information on male display rates and energetics of Sprague's Pipit. STUDY AREA AND METHODS Territorial males were studied during 15-20 June 1995 and 20-23 May 1996, just north of Thompson Lake, Lostwood National Wildlife Refuge, Burke County, North Dakota. This location is precisely where Green (1992) censused annually breeding grassland passerine species, including Sprague's Pipits, during 1987-1990. The study site is rolling, mixed grass prairie (Stipa spp., Agropyron spp.), interspersed with small seasonal wetlands, in the Missouri Coteau physiographic region (Green 1992). The study area was prescribe-burned on 14 August 1980, 8 August 1982, 9 July 1985, and 15 May 1992. More than 90% of above ground plant growth and litter was eliminated in the burns (Green 1992; K. Smith, pers. comm.). Territorial males were not marked in 1995; however, the sex of birds studied was confirmed by collection at the end of the observation period. In 1996, three territorial males were captured with mist-nets using a study skin as a lure. A recording of flight display calls was played from the grass beneath the lure. Captured males were color-marked on the lower abdomen with a non-toxic, permanent ink marker ("Magic Marker" by Binney & Smith Inc., Easton, PA). This ink wears off within a week or two, leaving the bird unharmed (pers. obs.). In this paper, "T" followed by a number is used to designate 1995 territorial males, and initials refer to 1996 color marked territorial males. Total number of observation hours were: May (24.75 morning, 6.5 afternoon), June (24.5 morning, 10.0 afternoon). Contiguous territorial male display rates were simultaneously quantified on several occasions, hence the hourly totals of individual males under Display Rate section exceed the above totals. Observations of displaying males were made from the periphery of each display area. The following parameters were recorded: number of display calls, number of wing beats between display calls, duration of display, wind speed and direction, and temperature. A stopwatch was used to quantify aspects of the display flight. Limited tape recordings were made of displaying males with Sony TCM5000EV and Sony TCD5Pro II cassette recorders, and Sennheiser ME 80 and ME 66 microphones. Estimates of display flight energetics were calculated using Pennycuick's (1989) computer software program (Program # 1). Flight speed used in predicting energy expenditure of flight by Program # I was zero. Mass (x = 23.5 g) and wing span (x = 255 mm) were measured from two territorial males (KU 87231-2) before preparation. Hourly windspeed data were obtained from Lostwood N.W.R. headquarters (681 m in elevation), about 2 km from the study area.
TL;DR: Two observations of cowbirds near host nests that are consistent with two hypotheses, nesting-cue and "flush" method, regarding techniques cowbirds may use to find host nests are reported.
Abstract: Unlike most birds, brood parasitic Brown-headed Cowbirds (Molothrus ater) must find host nests in which to lay their eggs. Female cowbirds have been reported using several methods to find nests. Here, I report on two observations of cowbirds near host nests that are consistent with two hypotheses, nesting-cue and "flush" method, regarding techniques cowbirds may use to find host nests. The nesting-cue hypothesis poses that cowbirds are directed to host nests by host's typically increasing aggressive behavior towards cowbirds as they approach the nest, whereas the flush method poses that cowbirds attempt to spot a concealed nest by rousing the host from it with intentionally noisy behavior near the nest. Unlike other reported observations of female cowbirds near potential host nests, male cowbirds were present during both observations. Received 20 June 1997, accepted 27 Oct.
TL;DR: Foraging behavior of Red-cockaded woodpeckers in the Ouachita National Forest in western Arkansas was studied in this article, where the terrain was characterized by steep ridge and ravine topography and shortleaf pine (Pinus echinata) was the only pine.
Abstract: We obtained data for 23 habitat characteristics from plots at foraging sites of five groups of Red-cockaded Woodpeckers (Picoides borealis) and compared to randomly selected plots. Five groups occupied an average home range size of 24.82 ha. The birds foraged mainly in large pines having high crown volume and a long exposed bole. Foraging birds also favored stands with little understory and open spacing between foraging trees and neighboring ones. Shortleaf pine (Pinus echinata) was used in foraging 95% of the time over hardwoods. Woodpecker home range sizes in this shortleaf pine habitat were much smaller than in other types of forests. This may be due to the physical attributes of shortleaf pines combined with the ridged topography of the Ouachita Mountains. The vegetational requirements for foraging stressed the largest pines, open forest, and reduced hardwood understory, thus agreeing with other foraging studies of Red-cockaded Woodpeckers. Received 31 Oct. 1996, accepted 10 Oct. 1997. The numerous studies of Red-cockaded Woodpeckers (Picoides borealis) have almost all been conducted in areas of level terrain and in forests dominated by either longleaf (Pinus palustrus) or loblolly pine (Pinus taeda), or both. Our study, conducted in the Ouachita National Forest in western Arkansas, is quite different in that the terrain was characterized by steep ridge and ravine topography and shortleaf pine (Pinus echinata) was the only pine. Our objective was to gain information on home range size and foraging habitat for the endangered woodpecker in this different environment.
TL;DR: The Outer Banks emerged as an important staging area for the Atlantic populations of Piping Plovers, Whimbrels, and Sanderlings when compared to 7 other areas along the eastern U.S. coast.
Abstract: We documented the seasonal abundance, distribution, and relative importance of outer beach habitats to shorebirds on the Outer Banks of North Carolina. The Outer Banks span 228 km and attract millions of tourists every year, underscoring the need for baseline data for conservation. Twenty-one species were recorded during the study. The most abundant were Sanderling (Calidris alba), Red Knot (Calidris canutus), and Willet (Catoptrophorus semipalmatus). As an assemblage, shorebirds were most abundant in May and August. Peak numbers for each species were recorded between April-May and July-September. The greatest numbers were recorded on North Beach and the lowest on South Beach (1992) and Bodie Island (1993). Shorebird abundance was greater during fall (68 birds/km) than in spring (50 birds/km). Patterns of abundance of the eight most abundant species were examined in detail. Black-bellied Plovers (Pluvialis squatarola), Willets, Whimbrels (Numenius phaeopus), Ruddy Turnstones (Arenaria interpres) and Sanderlings were most abundant on North Beach. North Core Banks harbored the highest numbers of Piping Plovers (Charadrius melodus), American Oystercatchers (Haematopus palliatus), and Red Knots. American Oystercatchers and Whimbrels were significantly more abundant during spring than fall, whereas Willet and Sanderlings were more abundant during fall. The Outer Banks emerged as an important staging area for the Atlantic populations of Piping Plovers, Whimbrels, and Sanderlings when compared to 7 other areas along the eastern U.S. coast. The importance of the area to Sanderlings was reaffirmed by return rates of 58%, most (69-89%) returning to the beach stretch where they were banded. The area gains special significance because it also supports a nesting population of Piping Plovers. Our findings confirm that the Outer Banks of North Carolina provide a critical link in the migratory path of several shorebird species. Habitat loss or alteration could adversely affect the Atlantic Flyway population of several species (e.g., Sanderlings) as well as the threatened Piping Plover. Received I May 1997, accepted 13 Jan. 1998. Many migrant shorebirds rely on a few, key stopover sites to complete their annual migratory cycle (Myers et al. 1987). These sites often provide a unique combination of food resources and habitat necessary to support a large number of birds (Myers 1986, Myers et al. 1987). Examples of important sites in North America are Delaware Bay (Clark et al. 1993), the Bay of Fundy (Hicklin 1987), the Copper River Delta of Alaska (Isleib 1979, Senner 1979), and Grays Harbor in Oregon (Senner and Howe 1984). Because a large proportion of a species' population may be concentrated at one or a few sites during migration, shorebirds are particularly vulnerable to habitat loss and degradation, and thus to population decline (see Gill and Handel 1990). Coastal areas, where the vast majority of these key sites occur, are seriously threatened by habitat alteration and destruction by human development (Senner and Howe 1984, Davidson and Pienkowski 1987). Survey information for additional or alternative sites is lacking, mostly because resources to implement adequate survey programs have not been available (Senner and Howe 1984). Such information is needed in the event of losses of key sites. The Outer Banks of North Carolina constitute a prime example of a potentially important area for which only limited information on migratory shorebirds is available (Buckley and Buckley 1973, Root 1988, Senner and Howe 1984, Boone 1988). Previous information was gathered as part of short-term surveys and Christmas Bird Counts. From these efforts, it was estimated that 20,000 shorebirds used the Outer Banks annually during autumn. At least 15 species of shorebirds used the Outer Banks during winter. Abundant spe' North Carolina Cooperative Fish and Wildlife Research Unit, Biological Resources Division, U. S. Geological Survey, North Carolina State Univ., Raleigh, NC 27695 2 Current address: Dept. of Fishery and Wildlife Biology, Colorado State Univ., Fort Collins, CO 80523 1 Dept. of Zoology, North Carolina State Univ., Box 7617, Raleigh, NC 27695 4 Current address: Dept. of Biology, Virginia Polytechnic Institute and State Univ., Blacksburg, VA 29061 s Corresponding author; E-mail: Jaime_Collazo@ncsu.edu