Showing papers in "The Auk in 1994"
TL;DR: In this paper, the consequences of between-observer differences in counts for estimation of population trends in the North American Breeding Bird Survey (NBBS) were assessed. But observer quality is often ignored in analyses of population changes from survey data, but observers differ in methods and capabilities and hence tend to count different numbers of birds.
Abstract: Because count data collected in many bird surveys are only an index to pop- ulation size, factors that can influence the counts must be identified and incorporated into analyses. Observer quality is often ignored in analyses of population changes from survey data, but observers differ in methods and capabilities and, hence, tend to count different numbers of birds. We assess the consequences of between-observer differences in counts for estimation of population trends in the North American Breeding Bird Survey. Observer differences in numbers of birds counted were found in 50% of the 369 species we examined. For many species, observers in later years tended to count more birds than observers in earlier years, suggesting an increase in observer quality over time. Analysis of population trends from 1966 through 1991 indicates that failure to include observers as covariables in the analysis results in an overly optimistic view of population trends. Received 8 March 1993, accepted 24 October 1993.
400 citations
TL;DR: The birds of western palearctic Vol. VI. Warblers and thruches as discussed by the authors, and the birds of the western Palearctic vol. VII. Flycatchers to skrikes
Abstract: The birds of western palearctic Vol. VI. Warblers and thruches. The birds of the western Palearctic Vol VII. Flycatchers to skrikes
238 citations
TL;DR: Investigation of whether plasma metabolites correlate with body-mass change, and which metabolites could be used to predict body- mass change in birds caught once, found metabolites that are known to characterize resorption were elevated in birds gaining body mass and metabolites characteristic of fasting were elevate in birds losing body mass.
Abstract: -Change in body mass is an important measurement in many studies addressing changes in energy stores or condition. Usually, change in body mass is measured in birds caught twice, but this has a number of drawbacks (e.g. low number of retraps, retraps not representative of all first captures, adverse effects of first capture on body-mass development). Therefore, we investigated whether plasma metabolites correlate with body-mass change, and which metabolites could be used to predict body-mass change in birds caught once. In an experiment, 20 Garden Warblers (Sylvia borin) were given different amounts of food to induce stable, increasing, and decreasing body masses. Most of the eight plasma metabolites we examined were significantly correlated with the change in body mass between early morning and midday, the time of blood sampling, but not with body mass or various measures of activity. Metabolites that are known to characterize resorption were elevated in birds gaining body mass and metabolites characteristic of fasting were elevated in birds losing body mass. Triglycerides and ,B-hydroxy-butyrate together explained 61% of the variation in body-mass change (triglycerides alone 44% and ,3-hydroxy-butyrate alone 51%). These metabolites may be used to predict body-mass change in birds caught once, provided that the reliability and sensitivity of this method are checked in field tests. Received 27 September 1993, accepted 30 January 1994. BIRDS MAY FACE DEFICITS in their energy balance during the nonactive period of the day, during periods of several days, or even over a series of weeks. They usually build up energy stores in anticipation of such periods and as an adaptive compromise to different selective pressures (e.g. Lima 1986, Lehikoinen 1987, Moreno 1989, Ekman and Hake 1990, Rogers and Smith 1993). This results in fluctuating energy stores between foraging and nonforaging periods (usually day and night) superimposed on longer periods of net energy storage and net energy expenditure (King 1972). For instance, cold and short winter days, bad weather, incubation, feeding young, and migration may all be associated with decreasing energy stores and preceded by energy storage. Body mass is a crude but widely used estimate of energy stores because it is easy and harmless to measure. If corrected for size, body mass may be used as an indication of condition (e.g. Blem 1990). Changes in body mass may give a fairly accurate picture of the fluctuations in energy stores (e.g. Rogers and Rogers 1990). The measurement of changes in body mass of free-living birds is important in a variety of contexts. For instance, it may allow the assessment of the effects of food availability on energy storage in different habitats, under different weather conditions, and under different degrees of competition or predation (e.g. Bibby et al. 1976, Bibby and Green 1983, Buchanan et al. 1985, Lima 1985, Lindstrom 1990, Moore and Yong 1991). Body-mass changes may indicate periods of constraints and periods of adaptive mass variations during the annual cycle (Moreno 1989). Evaluation of body-mass changes may allow study of the pattern and environmental influences of energy storage during stopovers by migrants (e.g. Bibby et al. 1976, Mehlum 1983a, b, Biebach 1985, Biebach et al. 1986, Alerstam and Lindstrom 1990). In free-living birds, changes in body mass generally are measured in birds caught at least twice, usually at the same place. This, however, has a number of drawbacks: (1) changes in body mass are measured only in the subsample of retraps and this may reduce the sample size drastically, especially when trap shyness is a factor; (2) a certain group of birds may not be recaught and, thus, the sample of retraps may not be representative (e.g. Bibby et al. 1976, Biebach et al. 1986, Veiga 1986, Winker et al. 1992); and (3) first capture may have an adverse
221 citations
TL;DR: In this paper, the authors present 14 such predictions, and review data currently available to assess their relevance to observed declines in Nearctic migrant populations, showing that populations of many species of Nearctic migrants appear to be controlled by wintering-ground events.
Abstract: -Population declines have been reported for nearly one-third of all Nearctic migrant birds that winter in the Neotropics. Speculative explanations for these reports have been presented emphasizing the importance of events occurring during one portion of the annual cycle versus another. These explanations are difficult to test directly. However, certain predictions can be made regarding the characteristics of populations controlled by breedingground factors as opposed to those associated with migration or wintering-ground phenomena. These characteristics can be measured for and tested experimentally on a species-byspecies basis. We present 14 such predictions, and review data currently available to assess their relevance to observed declines. Based on these data, populations of many species of Nearctic migrants appear to be controlled by wintering-ground events. Received 30 September 1993, accepted 5 January 1994. DECLINES IN AT LEAST 109 species of Nearctic migrants have been reported by one or more survey methods (Droege and Sauer 1989, Morton and Greenberg 1989, Terborgh 1989, Robbins et al. 1989a, Askins et al. 1990, DeGraaf and Rappole in press). These figures are cause for concern despite conflicting regional population trends (Sauer and Droege 1992), and despite arguments that at least some purported evidence of decline may be the result of procedural errors (e.g. survey design and analysis flaws; Hutto 1988, James et al. 1990, 1992, Rappole et al. 1993a). If the declines are real, what are the
215 citations
TL;DR: It is concluded that olfactory-searching predators can cue on human odors left in the area of artificial nests, but that either rain or scents can be used to decrease this potential bias.
Abstract: We examined the effects of two potential olfactory cues on the outcome of experiments using artificial nests to assay predation on open-cup nesting songbirds. In two experiments lasting 15 days each and replicated two times at three sites, bamboo nests baited with Japanese Quail (Corturnix japonica) eggs were placed on the ground in a 5 x 4 grid array with 50 m between adjacent nests. Egg survivorship was monitored every five days, and remote cameras were used to take photographs of animals removing bait eggs from nests. One experiment consisted of four treatments that varied the type and amount of olfactory information provided by the investigator: (1) human scent; (2) "no scent"; (3) "deer scent"; and (4) perfume. Artificial scents were applied to shoes, clothing, and skin during the ex- periment set-up and monitoring. For the first experiment, rates of nest loss were greater for the human-scent treatment than deer-scent and/or no-scent treatments in one-half of the spatial/temporal replicates. Rain appears to have complicated the effects of the scent treat- ments in some of the spatial/temporal replicates. Final levels of nest loss, however, were greater for perfume and human-scent treatments than deer-scent and no-scent treatments regardless of spatial/temporal replicate. The second experiment consisted of two treatments, one in which eggs were replaced periodically, and the other in which eggs were not replaced for the duration of the experiment. Both treatments had similar rates and final levels of nest loss. Approximately 90% of 51 photographs were of olfactory-searching, predominantly noc- turnal mammals. We conclude that olfactory-searching predators can cue on human odors left in the area of artificial nests, but that either rain or scents (e.g. the deer scent) can be used to decrease this potential bias. In contrast, changing egg qualities over the time scale
195 citations
TL;DR: The contention that hybridization between Mallards and nondimorphic species involves primarily Mallard males with females of the other species is not upheld for this example from New Zealand, and the speciation process appears to be undergoing reversal.
Abstract: ABSTP,CT.--One of the more well-known examples of hybridization in birds is the frequently documented occurrence between sexually dimorphic Mallards (Anas platyrhynchos) and several closely related nondimorphic species in the mallard complex. In New Zealand, the Grey Duck (Anas superciliosa superciliosa) is the indigenous, nondimorphic Mallardlike species, and extensive hybridization with introduced Mallards has been implicated in the population decline of Grey Ducks. Individuals from throughout the country were classified phenotypically as parentals or hybrids based on variation in plumage, bill color, and leg color. We confirmed species-specific mitochondrial DNA haplotypes by comparing restrictionenzyme fragment patterns in Grey Ducks and New Zealand Mallards to those of Pacific Black Ducks (A. superciliosa rogersi) from Australia and Mallards from North America, respectively. Our data indicate that hybridization has led not only to introgression of Grey Duck mtDNA into Mallard populations (the predicted direction of gene flow), but also to significant introgression of Mallard mtDNA into Grey Duck populations. Thus, the contention that hybridization between Mallards and nondimorphic species involves primarily Mallard males with females of the other species is not upheld for this example from New Zealand. The speciation process appears to be undergoing reversal. Received I April 1993, accepted 2 July 1993. THE INCIDENCE OF interspecific and intergeneric hybridization in the order Anseriformes is higher than in any other order of birds, reaching 30 to 40% by some estimates (Grant and Grant 1992). In addition, a substantial proportion of interspecific hybrids (20%) in this order have been reported to be fertile (Scherer and Hilsberg 1982), so there is potential for extensive gene flow and introgression between some species. Among the more well-known examples is the frequently documented incidence of hybridization between sexually dimorphic Mallards (Anas platyrhynchos) and several closely related, nondimorphic species. For instance, in North America, hybridization with Mallards has been implicated as one factor in the population decline of American Black Ducks (A. rubripes; Johnsgard 1967, Heusmann 1974, Ankney et al. 1987), Hawaiian Ducks (A. wyvilliana; Griffin et al. 1989), and Mexican Ducks (A. platyrhynchos diazi; Hubbard 1977). Increasing numbers of
166 citations
TL;DR: The distribution of migratory shorebirds within Delaware Bay, New Jersey, was examined relative to prey abundance and the physical characteristics of the intertidal beaches as mentioned in this paper, and the most abundant food item on these beaches was horseshoe crab (Limulus polyphemus) eggs, and there were few other available macroinvertebrates.
Abstract: -The distribution of migratory shorebirds within Delaware Bay, New Jersey, was examined relative to prey abundance and the physical characteristics of the intertidal beaches. Red Knots (Calidris canutus), Sanderlings (C. alba), Ruddy Turnstones (Arenaria interpres), and "peeps" comprised nearly 100% of the shorebirds on seven study beaches from mid-May to early June in both 1990 and 1991. The most abundant food item on these beaches was horseshoe crab (Limulus polyphemus) eggs, and there were few other available macroinvertebrates. Beaches preferred by shorebirds had higher numbers of crab eggs; the density of eggs in some surface (0-5 cm) sediments exceeded 1 05 / M2. In general, both horseshoe crab eggs and shorebirds increased along the bay shore from Higbee's Beach (near Cape May Point) to Moore's Beach, 32 km up-bay. However, shorebirds were widely distributed within the bay, possibly because eggs were sufficiently abundant on most beaches to support foraging by at least four birds per meter of shoreline. Shorebirds aggregated near shoreline discontinuities, such as salt-marsh creeks and jetties, that acted as concentrating mechanisms for passively drifting eggs. Sediment grain size and heterogeneity were probably not a primary determinant of shorebird distribution within Delaware Bay. Intertidal sand flats were not extensively used by foraging shorebirds, but the potential importance of nearby salt marshes as foraging sites requires further investigation. Received 20 January 1993, accepted 27 March
154 citations
TL;DR: A comparison between metabolism during singing and resting showed that the cost of singing in male Carolina Wrens is higher than the costs of other common activities of passerines except flight.
Abstract: A technique was developed to measure oxygen consumption during singing in captive male Carolina Wrens (Thryothorus ludovicianus). Oxygen consumption during sing- ing varied between individuals, which may have been a result of variation in singing rates. The average basal rate of metabolism was estimated to be 3.31 cm3 02 g-' h-I from standard metabolism measurements made at night. Oxygen consumption during singing ranged from 9.07 to 28.69 cm3 03 g - h -'. Captive study animals used singing rates similar to wild wrens. A comparison between metabolism during singing and resting showed that the cost of singing in male Carolina Wrens is higher than the costs of other common activities of passerines except flight. Received 31 July 1992, accepted 25 November 1992.
135 citations
TL;DR: Plumage coloration of the Great Tit Parus major in relation to habitat, season, and food and lowered blood carotenoid levels in chickens infected with coccidia are studied.
Abstract: aculeatus) as an indicator of energy investment in vigour. Evol. Ecol. 7:439-450. GOODWIN, T. W. 1980. The biochemistry of carotenoids. Vol. 1, Plants (2nd ed.). Chapman and Hall, New York. GOODWIN, T. W. 1984. The biochemistry of carotenoids. Vol. 2, Animals (2nd ed.). Chapman and Hall, New York. GRINNELL, J. 1911. The linnet of the Hawaiian Islands: A problem in speciation. Univ. Calif. Publ. Zool. 7:79-95. HILL, G. E. 1990. Female House Finches prefer colourful males: Sexual selection for a conditiondependent trait. Anim. Behav. 40:563-572. HILL, G. E. 1991. Plumage coloration is a sexually selected indicator of male quality. Nature 350: 337-339. HILL, G. E. 1992. The proximate basis of variation in carotenoid pigmentation in male House Finches. Auk 109:1-12. HILL, G. E. 1993a. Geographic variation in carotenoid plumage pigmentation of House Finches. Biol. J. Linn. Soc. 49:63-86. HILL, G. E. 1993b. The proximate basis of interand intra-population variation in female plumage coloration in the House Finch. Can. J. Zool. 71: 619-627. HILL, G. E. 1993c. House Finch. In Birds of North America (A. Poole, P. Stettenheim, and F. Gill, Eds.). No. 46. Academy of Natural Sciences, Philadelphia, and American Ornithologists' Union, Washington, D.C. HILL, G. E. 1994. Geographic variation in male ornamentation and female mate preference in the House Finch: A comparative test of models of sexual selection. Behav. Ecol. 5:64-73. HIRAI, L. T. 1975. The Hawaiian House Finch. Elepaio 36:1-5. HUDON, J. 1994. Showiness, carotenoids, and captivity: A comment on Hill (1992). Auk 111:218221. KOCH, E. L. 1939. Zur Frage der Beeinfluf3barkeit der Gefiederfarben der Vogel. Z. Wiss. Zool. 152: 27-82. LEE, W. L. 1966. Pigmentation of the marine isopod Idotheamontereyensis. Comp. Biochem. Physiol. 18: 17-36. MURPHY, M. E., J. R. KING, AND J. Lu. 1988. Malnutrition during the postnuptial molt of Whitecrowned Sparrows: Feather growth and quality. Can. J. Zool. 66:1403-1413. NEWTON, I. 1972. Finches. Collins, London. RUFF, M. D., W. M. REID, AND J. K. JOHNSON. 1974. Lowered blood carotenoid levels in chickens infected with coccidia. Poult. Sci. 53:1801-1809. SLAGSVOLD, T., AND J. T. LIFJELD. 1985. Variation in plumage coloration of the Great Tit Parus major in relation to habitat, season, and food. J. Zool. (Lond.) 206A:321-328. WEBER, H. 1953. Bewirkung des Fabwechsels bei mannlichen Kreuzschnabein. J. Ornithol. 94:342346. WEBER, H. 1961. Uber die Ursache des Verlustes der roten Federfarbe bei gekafigten Birkenzeisigen. J. Ornithol. 102:158-163. WILLIAMS, J. H., G. BRITTON, AND T. W. GOODWIN. 1967. The biosynthesis of cyclic carotenes. Biochem. J. 105:99-105. ZUK, M., R. THORNHILL, AND J. D. LIGON. 1990. Parasites and mate choice in Red Jungle Fowl. Am. Zool. 235-244.
128 citations
TL;DR: It is concluded that the data in Sibley and Ahlquist's phylogeny of the birds, properly analyzed, have a strong phylogenetic signal.
Abstract: ABsTRAcr.-Sibley and Ahlquist's phylogeny of the birds ("The Tapestry") has drawn both praise and criticism. Two major criticisms are that trees were based on incomplete distance matrices and that their tree-building algorithm (UPGMA) was inappropriate. Their 1990 book answered critics by including several complete matrices analyzed by the Fitch-Margoliash algorithm. Matrices were constructed by combining species into composite taxa, which requires additional (possibly defensible) assumptions and introduces additional (probably random) error. Three problems remain: (1) The algorithm used does not always find the bestfit topology, depending on taxon order. (2) The error variance of the data does not fit the assumptions of the Fitch-Margoliash algorithm. The assumptions of the algorithms of Fitch and Margoliash and of Cavalli-Sforza and Edwards are limiting cases that bracket the truth. (3) Even a matrix with no phylogenetic content has a best-fit topology; some test of the strength of support for branches on a tree is required. To address these problems, I analyzed: (1) each matrix several times with different orderings of taxa and with user-defined trees; (2) each matrix with both algorithms; (3) upper-right and lower-left halves of each matrix separately, performed a complete set of single-taxon jackknifings, and created a jackknife strict consensus of all best-fit trees using both algorithms. Based on these analyses, 97 of 173 interior branches (56%) on the FITCH trees published by Sibley and Ahlquist (1990) were still present in my consensus trees. Many trees remained nearly intact; others collapsed into polytomies. I found that 11 of 97 remaining branches (11%) contradict the Tapestry. I conclude that the data in Sibley and Ahlquist (1990), properly analyzed, have a strong phylogenetic signal.
121 citations
TL;DR: Brown-headed Cowbirds are an obligate brood parasite and a potential threat to some populations of migratory songbirds; Midwestern cowbirds show the same pattern of commuting between disjunct breeding and feeding areas as elsewhere in their range.
Abstract: Brown-headed Cowbirds (Molothrus ater) are an obligate brood parasite and a potential threat to some populations of migratory songbirds. I used radio-telemetry to study temporal patterns in behavior, habitat use, and sociality, as well as spatial patterns and movements among breeding, feeding, and roosting areas. I obtained a mean of 42 locations of 84 radio-tagged female cowbirds on three study sites in Illinois and Missouri. Radio-tagged females usually were located in forest and shrub-sapling habitats with a mean of 1.4 males during the morning breeding period. During midmorning to early afternoon, females commuted to short-grass, cropland, and feedlot habitats; they fed in small flocks. At dusk females roosted singly or in small groups near breeding or feeding areas, or commuted to a large communal roost. Behavior and time of day, behavior and habitat use, and habitat use and time of day were highly associated. For approximately 90% of the radio-tagged cowbirds, breeding, feeding, and roosting locations were distributed nonrandomly within home ranges, and came from distinct utilization distributions. Cowbirds moved an average of 3.6 km between roosting and breeding locations, 1.2 km between breeding and feeding locations, and 2.6 km between feeding and roosting locations. Midwestern cowbirds show the same pattern of commuting between disjunct breeding and feeding areas as elsewhere in their range.
TL;DR: It is reasoned that birds in depressed body condition will be unable to thermoregulate at low ambient temperatures, but that they can do so when roosting in cavities with conspecifics, and the energetic benefits of Green Woodhoopoes' communal cavity-roosting behavior are examined.
Abstract: -Green Woodhoopoes (Phoeniculus purpureus) roost in cavities in groups throughout the year. It has been proposed that the energy savings achieved by roosting with conspecifics in a cavity could enable birds in poor body condition to remain normothermic during inclement weather. We tested the hypothesis that woodhoopoes conserve energy by roosting with conspecifics in cavities and found that a woodhoopoe roosting with four conspecifics can reduce its nighttime energy expenditure by 30% or more when the minimum ambient temperature is about 5?C. In areas where nocturnal temperatures sometimes drop below freezing, such energy savings are associated with mortality patterns among adults during winter. Our data support the idea that energy considerations may have been important in the evolution and/or maintenance of sociality in this species. Received 14 August 1992, accepted 25 November 1992. GREEN WOODHOOPOES (Phoeniculus purpureus; also known as Red-billed Woodhoopoes) are cooperative breeders that live in groups of 2 to 12 individuals (Ligon and Ligon 1978). Woodhoopoes obligately roost communally in cavities throughout their range even though they are unable to excavate these holes themselves. This dependence appears critical for their survival by either providing energetic benefits to individuals, protection against predators, or both (Ligon and Ligon 1978, 1988, Ligon et al. 1988, Du Plessis 1989a, b, Williams et al. 1991). The energy savings associated with communal cavity roosting have been implicated as an important driving force in the evolution of sociality in this species (Williams et al. 1991). In an earlier paper, Williams et al. (1991) reported that Green Woodhoopoes maintained normothermic body temperatures at ambient temperatures from -1O? to 40?C. However, birds that were in apparently poor body condition, as judged by their unusually low body mass, exhibited body temperatures slightly below 39?C, even at moderate ambient temperatures. We reasoned that birds in depressed body condition will be unable to thermoregulate at low ambient temperatures, but that they can do so when roosting in cavities with conspecifics. We suggested that I Present address: Department of Physiology, College of Medicine, University of Arizona, Tuscon, Arizona 85724, USA. cavity roosting may be particularly critical to first-year birds, and that it may also be important to adults that have experienced periods of food shortage. In this paper we examine the energetic benefits of Green Woodhoopoes' communal cavity-roosting behavior.
TL;DR: It is argued that between-habitat differences, especially seasonal stability of vegetation features and food abundances in mangrove habitats, affect winter habitat quality for nonbreeding redstarts.
Abstract: ABsnTRCr.-We tested the hypothesis that wintering populations of American Redstarts (Setophaga ruticilla) segregate into different habitats by sex in response to ecological conditions associated with an extensive dry season, which typically develops after migrants arrive in northern Neotropical sites. Sex-specific distribution and overwinter persistence of redstarts were quantified at a Jamaican mangrove-scrub ecotone. We also contrasted vegetation structure and food availability in winter territories of the two sexes and in both habitats within and between seasons. Male and female redstarts were significantly segregated by habitat, with males holding territories in mangroves and females predominantly in contiguous scrub habitat. However, we found no significant sex-based difference in overwinter persistence on territories. The average mangrove territory had a higher canopy and more-open understory, higher relative humidity, and greater insect biomass within a season for several insect orders important in redstart diets. Canopy (leaf) cover and abundances of several insect taxa remained more constant over the dry season in mangrove than in scrub habitat. We argue that these between-habitat differences, especially seasonal stability of vegetation features and food abundances in mangrove habitats, affect winter habitat quality for nonbreeding redstarts. Received 3 March 1993, accepted 31 May 1993.
Journal Article•
TL;DR: The results indicate that reintroductions of vultures and similar species should use adults that have bred in captivity instead of immature birds that have been released into the wild.
Abstract: Little is known of the life history of vultures. The reintroduction program of Griffon Vultures (Gyps fulvus fulvus) in the Causses (south of the Massif Central, France) and extensive monitoring by capture-mark-resighting of the released birds allowed us to obtain the first estimates of their survival. Adult survival rates are high (x = 0.987 ? SE of 0.006). A release effect on adult survival was detected (only 0.743 ? 0.006 survival during the first year after release). Young born in the wild (less than three years old) had an annual survival rate of 0.858 ? 0.039. Mortality causes and erratic behavior of immature birds are considered in order to assess the effectiveness of this reintroduction program. Our results indicate that reintroductions of vultures and similar species should use adults that have bred in captivity
TL;DR: DNA sequences spanning 1,042 nucleotide bases of the mitochondrial cytochrome-b gene are reported for all 15 species and selected subspecies of cranes and an outgroup, the Limpkin, to suggest a rapid evolutionary diversification of these lineages.
Abstract: ABS?RACr.--DNA sequences spanning 1,042 nucleotide bases of the mitochondrial cytochrome-b gene are reported for all 15 species and selected subspecies of cranes and an outgroup, the Limpkin (Aramus guarauna). Levels of sequence divergence coincide approximately with current taxonomic ranks at the subspecies, species, and subfamilial level, but not at the generic level within Gruinae. In particular, the two putative species of Balearica (B. pavonina and B. regulorum) are as distinct as most pairs of gruine species. Phylogenetic analysis of the sequences produced results that are strikingly congruent with previous DNADNA hybridization and behavior studies. Among gruine cranes, five major lineages are identified. Two of these comprise single species (Grus leucogeranus, G. canadensis), while the others are species groups: Anthropoides and Bugeranus; G. antigone, G. rubicunda, and G. vipio; and G. grus, G. monachus, G. nigricollis, G. americana, and G. japonensis. Within the latter group, G. monachus and G. nigricollis are sister species, and G. japonensis appears to be the sister group to the other four species. The data provide no resolution of branching order for major groups, but suggest a rapid evolutionary diversification of these lineages. Received 19 March 1993, accepted 19 August 1993. THE 15 EXTANT SPECIES of cranes comprise the nominate family (Gruidae) of the order Gruiformes, and are currently divided into two subfamilies, Balearicinae and Gruinae (Brodkorb 1967). Balearicine cranes are anatomically unspecialized relative to gruines and are represented by only two extant species in the genus Balearica (the crowned cranes of Africa). Gruines share derived anatomical features such as an anteriorly sculpted sternum (often associated with tracheal coiling inside keel) in which the furcular process is fused to the anteroventral tip of the keel. Three extant gruine genera are recognized: Grus (10 species), Anthropoides (2 species), and Bugeranus (1 species). These genera are defined on the basis of soft anatomical features, although their monophyly has not been addressed by phylogenetic analysis. Fossil balearicines are known from the lower Eocene and later deposits in Eurasia, whereas Gruines date from the late Miocene (Brodkorb 1967). Evolutionary relationships among cranes have been addressed with a variety of different approaches during the past two decades. Archibald (1976) derived the species groups shown in Table 1 on the basis of similarities in unison
TL;DR: Results suggest that malelike coloration in females does not function in competitive interactions with males, and intense competition for winter territories coupled with reduced survivorship of winter floaters could constrain breeding strategies if young produced late in the summer have little chance of obtaining winter territories.
Abstract: -Hooded Warblers (Wilsonia citrina) defend long-term feeding territories during the nonbreeding season. Experimental removals of territory owners early in the fall in Mexico resulted in rapid replacement by nonterritorial individuals ("floaters"). The sex ratio of replacement birds was similar to that of territory owners in the same habitat, but virtually all replacements were hatching-year (HY) birds. Females were able to acquire and defend territories in the presence of male floaters. Loss of wintering habitat would likely increase the proportion of nonterritorial birds and, therefore, increase overwinter mortality rates, especially of HY birds. The extent of malelike coloration of females was not correlated with habitat, indicating that dark females were not more likely to obtain territories in forested habitat where males predominate. Furthermore, the aggressive response of male territory owners toward models did not depend on intruder color. These results suggest that malelike coloration in females does not function in competitive interactions with males. Intense competition for winter territories coupled with reduced survivorship of winter floaters could constrain breeding strategies if young produced late in the summer have little chance of obtaining winter territories. Received 5 April 1993, accepted 30 September 1993. NEOTROPICAL MIGRANT songbird populations have declined in recent years (Askins et al. 1990). Habitat loss and fragmentation in the tropics is a major potential cause of this decline (Robbins et al. 1989). If habitat loss has a detrimental effect on wintering populations, then densities must be high relative to the carrying capacity of the habitat (Winker et al. 1990). Although many migrants are territorial on their wintering grounds (e.g. Greenberg 1986, Holmes et al. 1989), little is known about the intensity of competition for those territories (Morton et al. 1987, Winker et al. 1990) or the effects of such competition on population dynamics (Marra et al. 1993). When resources become limiting, are females at a disadvantage in competing for territories with males? Do yearling birds have difficulty obtaining territories? Age or sex biases in competitive ability for winter territories could have important implications for overwinter survival and productivity on the breeding grounds (Marra et al. 1993). The existence of nonterritorial "floating" populations on the wintering grounds has been well documented only for the Wood Thrush (Hylochichla mustelina; Rappole et al. 1989, Winker et al. 1990) and American Redstart (Setophaga ruticilla; Marra et al. 1993), and has been reported anecdotally for the Blackthroated Blue Warbler (Dendroica caerulescens; Holmes et al. 1989) and Hooded Warbler (Wilsonia citrina; Rappole and Warner 1980, Morton et al. 1987). Experimental removal of territory owners is an important tool for studying floating populations (e.g. Krebs 1971), but has been performed on the wintering grounds for only a few species (Rappole and Warner 1980, Morton et al. 1987, Winker et al. 1990, Marra et al. 1993). I conducted removal experiments with wintering Hooded Warblers to determine: (1) the size of the nonterritorial floater population; and (2) the relative abilities of birds in particular age/ sex classes to obtain territories. The winter ecology of the Hooded Warbler is among the best studied of any Neotropical migrant (Rappole and Warner 1980, Lynch et al. 1985, Morton et al. 1987, Morton 1990, Morton et al. 1993). There is habitat segregation by sex, such that most birds in the forest are males; however, both males and females are found in scrub habitat (Lynch et al. 1985). When territorial males are removed from forest habitat, females in adjacent scrub habitat do not move onto those territories even when such territories remain undefended, indicating that females are not being excluded from forest habitat (Morton et al. 1987). Experiments with hand-raised individuals and field data suggest that habitat segregation results from innate habitat preferences by each sex (Morton 1990, Morton et al. 1993). During winter females must compete directly
TL;DR: The data suggest that, even for birds known for their mimetic abilities, social interaction, reference, and full contextual experience are important factors in learning to produce and comprehend an allospecific code.
Abstract: in the code, and the interactive aspect provides explicit training that is constantly adjusted to the level of the learner. To obtain information on the relative importance of these three aspects of input on learning in a mimetic species, I used three different conditions to train two juvenile Grey Parrots (Psittacus erithacus) to produce English labels to identify various common objects. Each bird experienced: (1) audiotaped tutoring, which was nonreferential, noninteractive, and did not demonstrate contextual applicability; (2) videotapes, which provided reference and limited information about context, but which were noninteractive; and (3) live human tutors, who interactively modeled the meaning and use of the labels to be learned. The birds learned only from the live tutors. A third parrot, trained on a separate set of labels by tutors who provided only limited reference and context for those vocalizations, learned to produce that set of labels without comprehension. The data suggest that, even for birds known for their mimetic abilities, social interaction, reference, and full contextual experience are important factors in learning to produce and comprehend an allospecific code. Received 22 April 1993, accepted 10 October 1993. IN THE LAST DECADE, studies have shown how
TL;DR: The data suggest that chronic petroleum pollution is a significant mortality factor for adult Magellanic Penguins along the coast of Argentina and may be depressing population numbers.
Abstract: -In March of 1982-1984 and 1986-1990 we counted carcasses of Magellanic Penguins (Spheniscus magellanicus) along the Chubut coast of Argentina. The number of carcasses found per kilometer of beach on the shoreline ranged from 49 in 1982 to 9 in 1990. In 1984, 22% of the dead penguins were oiled as compared to 66% in 1987. Oiled penguins were found along all parts of the Chubut coast showing that chronic oil pollution is not a local problem. Oiled carcasses were more common near oil ports, where oil pollution is probably worse, and they were more common on headlands than away from the ports or in bays. More fledglings than adults were found dead along the coast. Approximately 65% of dead adults and 31% of dead fledglings were oiled. In years when the natural mortality rate was low for adults (1986 and 1987), a higher percent of the carcasses had petroleum, suggesting oil was an important cause of adult mortality. Starvation appeared to be the most common cause of death for fledglings, whereas petroleum pollution was the main cause of death for adults. We estimate that at least 1.1% of the adult population and 6.0% of the fledglings are oiled in February and March of each year. Since penguins migrate twice a year, more than 20,000 adults and 22,000 juveniles may be killed along 3,000 km of Argentine coast (Chubut and Santa Cruz) each year due to oil pollution. These data suggest that chronic petroleum pollution is a significant mortality factor for adult Magellanic Penguins along the coast of Argentina and may be depressing population numbers. Received 29 June 1992, accepted 29
TL;DR: Seasonality of food resources, as measured by actual evapotranspiration (AE), does not explain much of the variation in clutch size, especially when controlling for latitude, and shows that either seasonality is unimportant or that AE is a poor indicator of the food available to House Wrens.
Abstract: ABsTRAcr.-I report on geographic variation and seasonal decline in clutch size in House Wrens (Troglodytes aedon), a species that breeds throughout much of the New World. Nest records from British Columbia to Tierra del Fuego (n = 3,246 clutches) show that clutch size increases with latitude in both the Northern and Southern hemispheres. Seasonality of food resources, as measured by actual evapotranspiration (AE), does not explain much of the variation in clutch size, especially when controlling for latitude. This result shows that either seasonality is unimportant or that AE is a poor indicator of the food available to House Wrens. Seasonal decline in clutch size varies geographically such that in northern populations, clutch size declines much more rapidly during the breeding season than in low latitude populations. A model explaining this pattern, the offspring-survivorship hypothesis, predicts that the rate of seasonal decline in clutch size is related to the difference in survivorship between earlyand late-fledged young. Field study in Monteverde, Costa Rica, showed that clutch size did not change seasonally and that late-fledged young were at least as likely to survive to the following breeding season as early-fledged young. This pattern is in contrast to North Temperate areas where clutch size declines sharply during the breeding season and late-fledged young are much less likely to survive to the following year than early-fledged young. Received
TL;DR: It is hypothesized that meal size in Common Eiders is regulated in response to defecation rate, and mass of food significantly increases wing loading and is associated with a reluctance or a possible inability to take flight.
Abstract: Rates of ingestion and digestion for wintering Common Eiders (Somateria mol- lissima) feeding on blue mussels (Mytilus edulis) were estimated using information on average meal size, feeding- and resting-bout durations, and transit time. Rate of ingestion of mussel shells is two times higher than defecation rate; as a consequence, shells accumulate in the gut as ingestion progresses. On average, eiders shot when flying (n = 92) had 1.1% of their body mass as prey compared with 3.7 and 6.4% for eiders foraging in small and large flocks (n = 77), respectively, suggesting that eiders tend to minimize the transportation of surplus mass when flying. Wing loading of the Common Eider averages 2.0 g.cm-2, which is among the highest values determined for a bird species capable of flight. Maximum gut contents were between 8 and 11% of body mass for eiders foraging in large rafts; such mass of food significantly increases wing loading and is associated with a reluctance or a possible inability to take flight. I hypothesize that meal size in Common Eiders is regulated in response to
TL;DR: The basal-metabolic-rate levels in adult terms, however, do not match this latitudinal pattern for the growing chicks, and Ontogenetic studies over a longer time scale would be required to clarify these discrepancies.
Abstract: I compared the energetics of Arctic Tern (Sterna paradisaea) chicks from Spitsbergen and The Netherlands, Common Tern (S. hirundo) chicks and Sandwich Tern (S. sandvicensis) chicks from The Netherlands, and Antarctic Tern (S. vittata) chicks from King George Island. Daily energy expenditure (DEE), measured using doubly-labeled water, was only slightly higher in the chicks from the polar environments, despite the higher levels of basal metabolisms (BMR) and higher costs for thermoregulation. Apparently, thermoregulatory cost as part of the DEE of the chick is only a minor item thanks to parental brooding, which may account for energy savings ranging from 40 to 80%. A simple model indicates that the magnitude of these savings is dictated by the parental time budget (i.e. the minimal foraging time needed to meet age-dependent energy requirements of chick). Basal metabolic rate in chicks of the six available studies increased with latitude. The differences could relate to a higher capacity to produce heat, which is necessary in polar environments. The basal-metabolic-rate levels in adult terms, however, do not match this latitudinal pattern for the growing chicks. Ontogenetic studies over a longer time scale would be required to clarify these discrepancies in latitudinal pattern of BMR, for which a functional explanation is given in terms of differences in migratory biology.
TL;DR: It is demonstrated that male hummingbirds in the genus Colibri share song types and the resultant geographic variation in song is due to cultural drift acquired through song learning.
Abstract: ABSTRACr.-We have demonstrated that male hummingbirds in the genus Colibri share song types. The Sparkling Violet-ear (C. coruscans) from an Ecuadorian population and Green Violetear (C. thalassinus) from populations in Costa Rica form aggregates or neighborhoods. Males of a neighborhood sing the same song type and those of distant neighborhoods have different song types. The resultant geographic variation in song, we suggest, is due to cultural drift acquired through song learning. Song sharing was determined not only by traditional, visual examination of spectrograms of song but with a relatively new, digital cross-correlation method that permits statistical treatment. The statistical procedures included cluster analysis that reflects the distribution of songs in geographic space and an evaluation for randomness of that distribution by use of the Mantel test. Received 13 May 1993, accepted 30 September 1993.
TL;DR: Overall results indicate that syringeal morphology is conservative, with most of the informative variation occurring at higher systematic levels, and supports the monophyly of the Falconiformes.
Abstract: ABSTRACr.-The systematic relationships of the diurnal birds of prey (Falconiformes) are unresolved. The monophyly of the order has not been established, and the relationships of the families within the order and of genera within the three polytypic families are unclear. To derive a phylogeny for the order and to assess the usefulness of the syrinx for resolving the systematics of nonpasserines, I analyzed variation in syringeal morphology of genera within each of the currently recognized families in the order as well as among four orders of outgroups. The phylogeny derived from these syringeal data supports the monophyly of the Falconiformes. In addition, syringeal data provide strong support for the monophyly of three clades within the Falconiformes: the Cathartidae; the Falconidae; and an AccipitrinaeSagittariidae-Pandioninae cluster. The Cathartidae are positioned as basal to the other two clades. Overall results indicate that syringeal morphology is conservative, with most of the informative variation occurring at higher systematic levels. Received 10 May 1993, accepted 24 October 1993.
TL;DR: These results provide an independent confirmation of relationships proposed in both the morphological and molecular studiesthat New World barbets and toucans are sister taxa with respect to Old World barbet taxa.
Abstract: ABSTRACr.-An 888-base-pair segment of the mitochondrial cytochrome-b gene was sequenced for New World barbets, Old World barbets, toucans, and several outgroup taxa. Toucans were consistently identified as the sister taxon of the New World barbets by a variety of analyses. These data are fundamentally different from earlier morphological analyses and the DNA-DNA hybridization study of these same taxa. Our results provide an independent confirmation of relationships proposed in both the morphological and molecular studiesthat New World barbets and toucans are sister taxa with respect to Old World barbets. Received 19 June 1992, accepted 25 November 1992. TRADITIONAL MORPHOLOGICAL analyses have disagreed on the phylogenetic relationships among the barbets (Capitonidae), a pantropical assemblage of frugivorous birds, traditionally placed in the Piciformes with woodpeckers,
TL;DR: In this article, the authors measured daily energy expenditure (DEE) and water turnover of Ruddy Turnstones (Arenaria interpres) during the incubation phase on Rowley Island in Foxe Basin, N.W.T., Canada, at 69 degrees-N, using the doubly-labeled-water technique.
Abstract: To investigate whether shorebirds breeding in the High Arctic have relatively high rates of energy expenditure due to the harsh climatic conditions that prevail even in summer, we measured daily energy expenditure (DEE) and water turnover of Ruddy Turnstones (Arenaria interpres) during the incubation phase on Rowley Island in Foxe Basin, N.W.T., Canada, at 69-degrees-N, using the doubly-labeled-water technique. Simultaneously, we conducted detailed measurements of ambient climatic conditions, including in situ measurements with heated taxidermic mounts. A series of 11 doubly-labeled-water measurements with eight individual Ruddy Turnstones, of which at least seven successfully hatched eggs, yielded a mean DEE of 4.08 W. This is a relatively high value for a 108-g bird, equalling four times their basal metabolic rate (BMR). Most variation in DEE was attributable to standard operative temperature, which combines the effects of air temperature, wind and radiation on heat loss from the turnstone's point of view. On average, 25% of DEE was attributable to BMR, 31% to the cost of thermoregulation, and 44% to the cost of activity. The average value for water turnover of 96.6 g/day is high compared to published values for other birds and confirms the large requirement for food (which is water-rich) of incubating Ruddy Turnstones. An analysis of the climatic conditions prevalent in Foxe Basin during the breeding seasons of Ruddy Turnstones, based on the 33-year period 1958-1990, indicated that they faced thermostatic hardships, defined as energy expenditure exceeding the maximum sustained working level (estimated at 4.5 times BMR), on 15% of the days. Climatic conditions were most severe in the early 1960s, but have improved since.
TL;DR: This chapter discusses the ecology and evolution of sequential polyandry in Galapagos cormorants (Compsohalieus [Nannopterum] harrisi) and the role of parental care in this evolution.
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TL;DR: Evidence is obtained that olfactory behavior may differ before and after locating odor sources, as well as vary according to oceanic zones, and the hypothesis that certain species rely mainly on visual cues, recognizing and following species that are tracking foodrelated odors is discussed.
Abstract: --OIfactory foraging, although very rare among birds, is frequently found in members of the Procellariiformes; this finding is based on a small number of field studies using a standardized method (i.e. raft tests). Reactions of seven species previously tested under artificial conditions were tested again under natural feeding conditions (fish-oil slicks) to check validity. Concurrently, we compared the flight behavior of two groups of species (with and without olfactory capacities) when approaching an odor source. A large-scale experiment was then conducted in pelagic waters to test the reaction of a community of procellariiforms (15 species) to a food-related odor diffusing within a principal feeding area. We observed the same reactions (attraction or indifference) to oil slicks as to test rafts in all species evaluated. Results obtained with the standardized method thus hold under natural conditions. Species guided by oilaction approached the odor source by flying against the wind very dose to (< 1 m) the surface, whereas other species approached from a direction independent of wind direction and from a greater height (>6 m). Thus, specific searching behavior is associated with olfactory foraging and we found it to be closely related to direction, height, and speed of odor diffusion by wind. Reaction to the odor test varied according to families or subfamilies, some taxa showing consistent responses (attraction or indifference) to several experiments and some taxa showing conflicting reactions. We obtained some evidence that olfactory behavior may differ before and after locating odor sources, as well as vary according to oceanic zones (coastal vs. pelagic). We discuss the hypothesis that certain species rely mainly on visual cues, recognizing and following species that are tracking foodrelated odors. Finally, we propose some new ideas about the evolution of oilaction in birds. Received 3 August 1992, accepted 25 November 1992. ALTHOUGH OLFACTORY sensitivity in birds is now documented in a growing number of species (see a review in Waldvogel 1989), olfactory foraging remains unusual. In terrestrial environments, only two species have been shown to locate their food by smell: the Kiwi (Apteryx australis; Wenzel 1971) and the Turkey Vulture (Cathartes aura; Stager 1964). Some others have shown good capacities under artificial conditions, including honeyguides (Indicator indicator and 1. minor; Stager 1967) and Black-billed Magpies (Pica pica; Buitron and Nuechterlein 1985). In contrast, there is evidence that at least 22 procellariiform species may use olfaction when foraging (reviewed in Lequette et al. 1989). The existence of such a widespread ability and the extreme development of olfactory structures (Wood Jones 1937, Cobb 1960, Bang 1966, 1971, Bang and Cobb 1968) make this order unique among birds, and may explain its success in exploiting the pelagic environment. Very few laboratory studies have been conducted (Wenzel 1967, Wenzel and Sieck 1972, Jouventin 1977). Our present knowledge comes mainly from a small number of field studies in the North Atlantic (Grubb 1972), the North Pacific (Hutchison and Wenzel 1980, Hutchison et al. 1984), the Antarctic (Jouventin and Robin 1983), and the South Indian Ocean (Lequette et al. 1989). These studies used a standardized method under artificial conditions (rafts) and showed that olfactory capacities are partly related to phylogeny and anatomy. Feeding ecology, particularly diet and feeding techniques, also play a role in olfactory ability (Lequette et al. 1989). Seabirds using olfaction employ search patterns that seem to depend on wind conditions (Hutchison and Wenzel 1980, Hutchison et al. 1984). Nonetheless, important questions remain unsolved. First, can we extend the results obtained under the artificial conditions of the standardized method to natural feeding situations? Second, are there specific search behaviors in those species which do rely on olfactory cues and, if so, how are they related to wind? We report the results of field experiments designed to answer these questions, and provide new data for 15 species of procellariiforms. We