Showing papers in "The Condor in 1975"

An Experimental and Teleonomic Investigation of Avian Brood Parasitism

Abstract: The term “teleonomy” has been suggested by Williams (1966:258) to describe the scientific study of adaptations. Williams indicated that relatively few evolutionary studies deal primarily with teleonomy despite the fact that adaptation is the most basic feature of evolution and of all biology. Avian brood parasitism, the phenomenon in which certain birds, the parasites, deposit their eggs in the nests of other birds, their hosts, is especially well suited to teleonomic studies since it provides a system in which the presence or absence of relatively obvious adaptations can be examined in two interacting genetic lineages. Parasitism is typically detrimental to the host’ s reproductive efforts and selection favors defenses that reduce the impact of the parasite. These host defenses are in turn damaging to the parasite’ s reproductive efforts and selection favors counter-adaptations by the parasite. cause the death of all of the host’ s own young through competition for food (Friedmann 1963 ) . In certain cases, brood parasites seem to have extirpated or caused declines of local host populations (Schiermann in Southern 1954:221, Bond in Friedmann 1971:250, Mayfield 1961a). Thus, the adaptive value of host defenses is clearly very great.

Raptor Predation on Wintering Shorebirds

Abstract: Although high mortality rates have been demand mud flats form the major feeding habitat for onstrated for shorebirds by the analysis of large numbers of shorebirds that winter on the estuary. band recoveries and studies of marked birds (Martin-LGf 1961; Boyd 1962; Holmes 1966; METHODS Soikelli 1970), there is little information on Using a spotting scope and binoculars, we watched the causes of shorebird mortality. Goss-Cusmany diurnal raptors while they hunted on Bolinas tard (1970) theorized that flocking by some Lagoon. When we saw a raptor eat prey, we col-

Weather-Dependent Foraging Behavior of Some Birds Wintering in a Deciduous Woodland

Abstract: Terrestrial organisms are surrounded by a microclimate composed of four independent variables: humidity, radiation, wind velocity, and air temperature (Porter and Gates 1969). The metabolic responses of animals to some of these climatic variables have been studied in the laboratory. For instance, below the lower critical temperature (about 250C; Helms 1968) metabolic rates of birds are inversely correlated with ambient temperature (Kendeigh 1949, 1969, Steen 1958, Brooks 1968, Helms 1968, Kontogiannis 1968), but the metabolic cost of low temperature is moderated by artificial insolation (Lustick 1969, Lustick et al. 1970). Porter and Gates (1969) added air movement and derived theoretical "climate

Digestive Adaptations of Phainopepla nitens Associated with the Eating of Mistletoe Berries

Abstract: The Phainopepla, Phainopepla nitens, inhabits arid and semiarid areas in Mexico and the southwestern United States, where it associates closely with the Desert Mistletoe, Phoradendron californicum (Cowles 1936, 1972, Crouch 1943). This mistletoe parasitizes Sonoran desert wash plants such as Mesquite, Prosopis juliflora; Ironwood, Olneya tesota; Palo Verde, Cercidium floridum; and Catsclaw, Acacia greggi. The Phainopepla is a common winter and spring resident in these washes and is often seen feeding at the large fruiting clumps of mistletoe. The small (3-5 mm) berries of this mistletoe provide an abundant and succulent food source in this arid habitat. Besides P. nitens, a number of other birds feed upon these berries, including Gambel Quail, Lophortyx gambelii; Bluebirds, Sialis spp.; Mockingbirds, Mimus polyglottus; and House Finches, Carpodacus mexicanus (Cowles 1936, 1972). However, I have observed that none of these species are as closely associated with Desert Mistletoe or feed on it

The timing of endothermy in the development of altrical birds

Abstract: Nestlings of altricial birds are unable to maintain homeothermic body temperatures at hatching, and their abilities to thermoregulate improve gradually during growth. Numerous studies have indicated the ages at which various species become essentially homeothermic (the "age of endothermy," e.g., Dawson and Evans 1957, 1960, Maher 1964, Ricklefs and Hainsworth 1969). However, little is known of the degree of flexibility of that age with respect to other growth processes, or of the adaptive significance of its timing. Dawson and Evans (1957) noted a correlation between the age of endothermy and the length of the nestling period for several species of altricial birds. Contrary results were found by Maher (1964) who demonstrated nearly identical ages of endothermy in the Snow Bunting (Plectrophenax nivalis) and the Lapland Longspur (Calcarius lapponicus) in spite of the former's markedly longer nestling period. On the other hand, Morton and Carey (1971) stated that rapid acquisition of endothermy is a primitive characteristic of the Fringillidae and that the Snow Bunting has more recently acquired a protected nest site and a longer nestling period. Ricklefs and Hainsworth (1968) were able to show that the age of endothermy does not occur at the same stage of growth in all species. Thus, the age of endothermy normally may be flexible with respect to growth and most directly dependent on the length of the nestling period. This paper examines the correlations among various growth parameters, nestling period, and the age of endothermy for a variety of altricial species to determine which factors best predict that age.

The relation of foliage complexity to ecological diversity of three amazonian bird communities

Abstract: The relation between foliage complexity and bird species diversity has been studied by several investigators. Some (MacArthur and MacArthur 1961, MacArthur et al., 1962, Recher 1969, Karr 1971, Karr and Roth 1971) found that the complexity of the vertical distribution of leaves, as measured by foliage height diversity ( FHD ) , was a good predictor of bird species diversity (BSD). Other investigators (Terborgh 1967, Balda 1969, Lovejoy 1972) have found little correlation between FHD and BSD. BSD, as measured by a statistic derived from information theory, necessitates knowledge of the number of individuals of each species as well as number of species. In mature tropical forests, estimates of population size are difficult because such a large proportion of the bird species do not typically occur in low strata where they can be readily netted and marked. Orians ( 1969) avoided this problem in Costa Rican forests by comparing only the number of bird species (bird species richness, BSR) to FHD. He suggested that the range of resource types permanently above threshold values in tropical forests was the major factor determining bird species richness. However, in all these relations between foliage complexity and the number of bird species inhabiting the foliage, the assumption is made that the community is in an equilibrium or saturated state, that is, new species can enter the community only if they exclude a species already present. The Amazon Basin presents a distinct difficulty in applying FHD-BSD (BSR) correlations. Due to numerous historical changes in climate, continuous forest apparently alternated with forest islands (refugia) surrounded by non-forest vegetation throughout the Pleistocene and post-Pleistocene (Haffer 1969, Vanzolini 1973). It is now generally recognized that islands with similar habitat harbor different numbers of species depending on the area and distance of the island from the mainland species pool (MacArthur and Wilson 1967). Island-like effects are also recognized for continental habitats that occur in patches

Effects of human disturbance on the breeding success of gulls

Abstract: DRENT, R., G. F. VAN TETS, F. TOMPA, AND K. VERMEER. 1964. The breeding birds of Mandarte Island, British Columbia. Can. Field-Nat. 78:208-263. EMLEN, J. T., JR. 1956. Juvenile mortality in a Ring-billed Gull colony. Wilson Bull. 68:232238. GILLETT, W. H. 1973. The effect of model gull orientation and movement on the responses of a Glaucous-winged Gull to the model. M.A. Diss., Andrews University. HARRIS, M. P. 1964. Aspects of the breeding biology of the gulls Larus argentatus, L. fuscus, and L. marinus. Ibis 106:432-456. HAYWARD, J. L. 1974. Orientation and sequences of behavior during aggressive communication by the Glaucous-winged Gull (Larus glaucescens). M.A. Diss., Andrews University. KADLEC, J. A., AND W. H. DRURY, JR. 1968. Structure of the New England Herring Gull population. Ecology 49:644-676. KADLEC, J. A., W. H. DRURY, JR., AND D. K. ONION. 1969. Growth and mortality of Herring Gull chicks. Bird-Banding 40:222-223. LUDWIG, J. P. 1966. Herring and Ring-billed Gull populations of the Great Lakes 1960-1965. Pub. No. 15, Great Lakes Res. Div., Univ. Michigan, pp. 80-89. PALUDAN, K. 1951. Contributions to the breeding biology of Larus argentatus and Larus fuscus. Ejnar Munksgaard, Copenhagen. PAYNTER, A. 1949. Clutch-size and egg and chick mortality of Kent Island Herring gulls. Ecology 30:146-166.

Song Dialects and Colonization in the House Finch, Carpodacus mexicanus, on the East Coast

Abstract: Since the description of local song dialects in Chaffinches (Fringilla coelebs) (Poulsen 1951, Marler 1952), this form of song variation has been described in a number of passerines (Nottebohm 1969, Payne 1973, reviewed in Thielke 1969). Recent workers have focused on the function and biological significance of song dialects (Nottebohm 1969, Nottebohm and Selander 1972, Baker 1975), but have also warned that the usefulness of the emerging dialect concept may be impaired if the term is applied uncritically. The term, “dialect,” should meet specific criteria. Marler and Tamura’ s (1962) analysis of song dialects in the White-crowned Sparrow (Zonotrichia leucophrys) remains the classic study. They found consistent differences in song patterns among populations, but within a population they found extreme stereotypy in some aspects of song patterning which was repeated from one year to the next. Working with the closely related Chingolo (Zonotrichiu capensis), Nottebohm (1969) found that where contiguous populations meet, the integrity of the respective dialects is maintained with a boundary between them. These attributes provide a reasonable definition of song dialect. As part of a study of song ontogeny in the House Finch, Carpodacus mexicanus (Mundinger, in prep. ) , I recorded examples of natural song. Preliminary spectrographic analysis of the songs of wild House Finches nesting in the vicinity of New York City suggested that this finch may have song dialects. The occurrence of song dialects in this species would be significant since the House Finch was introduced to the east coast only recently (Elliott and Arbib 1953), and the recency of this event would provide known time limits for the emergence of new dialect patterns. The analysis of geographic variation in House Finch song was expanded to determine if populations on the east coast had song dialects, and to relate the pattern of song variation to the history of House Finch colonization.

The Overlap of Molting and Breeding in Some Tropical Birds

Abstract: Studies of temperate and tropical land birds reveal that the resource-demanding activities of the life cycle generally are mutually exclusive in an individual (Miller 1963, Farner 1964, Fogden 1972). Presumably food (calories, specific organic or inorganic nutrients, or the time to gather them) is limiting, and temporal spacing has evolved in response to the high requirements of each event. Thus an activity is timed to occur when environmental conditions are favorable and when interference from other activities is minimal.

Effects of Human Activity on Egg and Chick Mortality in a Glaucous-Winged Gull Colony

Abstract: EVANS, R. M. 1970. Parental recognition and the "mew call" in Black-billed gulls (Larus bulleri). Auk 87:503-513. HAARTMAN, L. vON. 1953. Was reizt den Trauerfliegenschnapper (Muscicapa hypoleuca) zu futtern? Die Vogelwarte 16:157-164. IMPEKOVEN, M. 1971. Calls of very young Blackheaded gull chicks under different motivational states. Ibis 113:91-96. NORTON-GRIFFITHS, M. 1969. The organization, control, and development of parental feeding in the Oystercatcher (Haematopus ostralegus). Behaviour 24:57-114. TINBERGEN, N. 1953. The Herring Gull's world. Collins, London. VERMEER, K. 1963. The breeding ecology of the Glaucous-winged Gull (Larus glaucescens) on Mandarte Island, B.C. Occ. Pap. British Columbia Prov. Mus. 13:1-104. WARD, J. 1973. Reproductive success, food supply, and the evolution of clutch size in the Glaucouswinged gull. Ph.D. Diss., Univ. British Columbia.

Growth, Body Components and Energy Content of Nestling Double-Crested Cormorants

Abstract: Most growth studies are confined to measurement of weight gain and external measurements, but the growth process involves a great many internal changes as well. As precocial chicks are much more mature at hatching than altricial young, it is not surprising that their internal and external development differs (Ricklefs 1973, 1974). But growth processes also vary among species of the same developmental mode, and detailed studies should be of value in analyzing differences in ecological adaptation (Dunn 1973, 1975b). This paper presents the results of a detailed study on growth of nestling Double-crested Cormorants, Phalacrocorax auritus. (Unless otherwise noted, all references here to cormorants mean this species.) Measurements were taken of overall weight gain, several external linear dimensions, growth of internal organs, changes in fat and water content, and caloric density. Although primarily a descriptive paper, comparisons are drawn to data for other species and basic differences between precocial and altricial development are noted. The cormorant is the largest altricial species studied to date, and should indicate how much variation in growth is related to size.

“Prostitution” Behavior in a Tropical Hummingbird

Abstract: For an animal to survive, it must acquire sufficient energy to meet metabolic requirements. In many vertebrates a territory helps insure adequate energy for the resident (Brown 1964, Fisler 1969). The size and quality of the territory will depend on the spatial and temporal characteristics of the food supply and competition for the food (Holmes 1970, Wolf and Stiles 1970). Most hummingbirds feed principally on nectar although they also eat small insects (Wagner 1946, Stiles 1971, Wolf and Hainsworth 1971). Male hummingbirds of many species defend groups of flowers from other hummingbirds, from other nectar-eating birds, and sometimes from insects. The ability of a male to maintain a territory depends on the relative dispersion of flowers and his dominance relationships with other species and individuals in the area (Brown 1964, Stiles and Wolf 1970, Wolf and Hainsworth 1971). In most hummingbirds that have been studied to date, males generally dominate females; there are a few exceptions (Wolf 1969). Male dominance over females may restrict the availability of energy to the female. Thus, when food is scarce or when the optimum resources can be controlled easily by the males, the subordinate females usually must exploit poorer nectar sources than the males. Female hummingbirds of most species apparently are solely responsible for the nesting effort and there is no long-term pair-bond (Wagner 1954, Wolf 1964, Lack 1968), although males of some species may provide indirect aid (Wolf and Stiles 1970, Snow and Snow 1973). This means that even during the breeding season, females of most species are not able to cohabit or regularly to use an area defended by the male. In most species nesting females do not and probably cannot hold territories around flowers (Wolf and Wolf 1971, Stiles 1973) and they are forced to forage at energetically poor, undefended sites. Females whose behavior enables them to exploit food defended by males would seem to have a selective advantage in both the breeding and nonbreeding season. This report describes use of aspects of mating behavior in the nonbreeding season by female Purplethroated Carib Hummingbirds (Eulampis jugularis) to gain ready access to nectar supplies on male territories. Since sexual behavior in these cases is being used for an energetic benefit for the female, I term this "prostitution" behavior.

Nest site selection by Williamson and red-naped sapsuckers

Abstract: Two congeneric woodpeckers, the Williamson Sapsucker (Sphyrapicus thyroideus) and the Red-naped Sapsucker (S. [varius] nuchalis) are sympatric throughout much of the Rocky Mountain region of the western United States. Although these two picids are closely enough related that two probable hybrids have been reported (Short and Morony 1970), there is generally effective reproductive isolation between them. This reproductive isolation apparently is not due to different nest site preferences. Bent (1939), Packard (1945), Bailey and Niedrach (1965), and Burleigh (1972) reported that Red-naped Sapsuckers prefer deciduous trees, especially aspen (Populus tremuloides), while Williamson Sapsuckers favor conifers. However, Rasmussen (1941), Hubbard (1965), and Tatschl (1967) noted that thyroideus nest in aspen, which Ligon (1961) suggested was their preferred nest tree in northern New Mexico. These differences in the literature led us to investigate the nesting habitat preferences of the two sapsuckers in Colorado and Wyoming. We use the name "Rednaped" for the Rocky Mountain form of the Yellowbellied Sapsucker (S. varius) complex, as suggested by Short (1969) and Short and Morony (1970). We examined a total of 57 thyroideus and 46 nuchalis nests at two locations in Colorado and one location in Wyoming. Both species nested at each location and were provided a choice of nest trees by the close proximity of conifers and aspen (fig. 1 and 2). At each nest site, we recorded the species and condition of the nest tree, its diameter at breast height (dbh, measured at 4.5 feet above the ground), the height of the nest hole, and the compass direction that the hole faced. We also measured various nest stand parameters, including stand density and stand size. These data were examined for significance using t-test and Chi-square statistical analyses. The primary study area, in northern Colorado, consisted of six sites within the eastern half of Rocky Mountain National Park, Larimer County. Elevations at which nests were found ranged from 2440 to 2800 m, roughly corresponding to the upper montane region and the upper montane/subalpine ecotone region of Marr (1967). The area was predominantly an open forest of ponderosa pine (Pinus ponderosa) and Douglas-fir (Pseudotsuga menziesii), with lodgepole pine (P. contorta) on cooler north-facing slopes and with limber pine (P. flexilis) in exposed areas above 2700 m. Aspen occurred in discrete stands along permanent to ephemeral drainages within the coniferous forest (fig. 1). The understory was highly variable due to topographic differences but was always rather sparse and low. The second Colorado study area was located on Missionary Ridge, about 20 mi NE of Durango, La Plata County. Elevations here ranged from 2500 m at Wallace Lake to 2900 m atop surrounding hillsides. Mature aspen ringed the ephemeral lake and extended up the adjacent slopes along drainages (fig. 2). Drier areas were covered by a coniferous forest of ponderosa pine, Douglas-fir, white fir (Abies concolor), and blue spruce (Picea pungens). Open areas on hillsides were covered by a dense growth of scrub oak (Quercus gambelii) and snowberry (Symphoricarpos oreophilus). Grasses, sedges, and forbs grew in a lush understory beneath the aspen, with kinnikinnik (Arctostaphylos uva-ursi) under the denser spruce/fir forest. Ground cover was sparse under the Douglas-fir/pine forest. The third study area was located in the Bridger Wilderness on the west slope of the Wind River Mountains, 40 mi NE of Pinedale, Sublette County, Wyoming. Nests were found from 2440 to 3200 m. Areas at lower elevations were covered by a forest of aspen interspersed with Englemann spruce (P. englemannii), Douglas-fir, and lodgepole pine. Areas at higher elevations had a forest of mixed spruce and subalpine fir (A. lasiocarpa) with patches of lodgepole pine and small stands of aspen, the latter occurring as late seral stages and being replaced by spruce and fir. At all three study locations, the two sapsucker species showed a strong preference for aspen (table 1), in which 85 percent of thyroideus nests and 100 percent of nuchalis nests were located. The close proximity of aspen and conifers at the three sites

The Migrations of Allen's and Other Hummingbirds

Abstract: tually migrates southward in numbers in late spring; further, its route soon veers away, geographically and ecologically, from the northward return route used chiefly in winter. Allen's Hummingbird (Selasphorus sasin) is remarkable in that it breeds only in California, barely overlapping that State's borders, and normally (at least until recent years) only in a narrow coastal strip. Of the few endemic California species, it is the only wholly migratory one! This distinction belongs to the northern, nominate race. The southern S. s. sedentarius Grinnell has the opposite distinction of being the only virtually sedentary hummingbird or nectar-feeder of any kind in the continental United States (see below). These amazing, somewhat elliptical migrations at the wrong seasons remain unappreciated because of: (1) the few records, mostly unpublished, between early September and mid-February; (2) reluctance to admit migrations in Californian endemics or ignorance in official check-lists (cf. for example, Swarth 1914:38, 90, on both Allen's and Anna's Hummingbirds, Calypte anna, in Arizona); (3) their seasonal displacement; and (4) failure to distinguish age/sex classes, or even the species (vs. the extremely similar Rufous Hummingbird, Selasphorus rufus), whose migrations are asynchronous. Authorities disagree widely on migrations and winter ranges (see A.O.U. 1931, 1957, Berlioz 1932, Friedmann et al. 1950). Loye H. Miller first pointed out (in Willett 1933:97) that even adult males of Allen's Hummingbird are not always safely distinguishable in color. This important fact is still generally overlooked; Peterson and Chalif (1973), Robbins et al. (1966), and Stiles (1972:31) all described the back of adult male S. rufus as rufous, or "sometimes with scattered green feathers," thus not contrasting to the rufous tail and coverts as in S. sasin. But

Song Patterning in the Rock Wren

Abstract: Nearly all bird species, and especially those living in a particular geographical region, can be identified by their vocalizations. Several characteristics of singing contribute to specific distinctiveness among the Oscines, but two of the most notable differences among species are the number of different song types per individual and the manner of presentation of those song types during a singing performance. Individuals of a relatively few species possess a single song, and will utter that one song type with very little variation throughout the adult life. Common examples include the Chipping Sparrow (Spizella passerina), White-crowned Sparrow (Zonotrichia leucophrys), and the Common Yellowthroat (Geothlypis trichas) (Borror 1959, Marler 1970, Borror 1967). Most species, however, are more versatile, and individuals possess more than one song theme; singing behaviors are extremely varied, and temporal and sequential aspects of theme delivery may aid in specific recognition. Some species are of the AAA. .. BBB... variety, where one song type is repeated several times before another is introduced: silent intervals between songs are usually four to five times the length of the song. Examples include the Song Sparrow (Melospiza melodia), Rufous-sided Towhee (Pipilo erythrophthalmus), and Plain Titmouse (Parus inornatus) (Mulligan 1966, Kroodsma 1971b, Dixon 1969). At the other extreme are species in which males sing long sequences with no theme repetition. Such singing might be denoted ABCDEFGHI.... Although intersong pauses may be seven to eight times the length of the song (e.g., Largefooted Finch, Pezopetes capitalis, Kroodsma, unpubl. data), they are generally briefer, as in the Long-billed Marsh Wren (Telmatodytes palustris; Jared Verner, in press). In some of the more "continuous" songsters (e.g., Brown Thrasher, Toxostoma rufum), pauses may be so brief that individual songs are practically unidentifiable. Intermediate between these two singing behaviors, i.e., between the AAA... BBB... and the ABCD

Flow of digesta in the intestine and caecum of the rock ptarmigan

Abstract: The role of the cecum in digestion of foodstuffs and production of vitamins is not well known for ptarmigan and grouse species. Presumably the function of the avian cecum is to digest and ferment complex carbohydrate molecules, proteins and other nutrients that escape intestinal absorption. The extent of fermentation in the cecum is a product of forage quality, cecum size and mean residence time of dry matter (DM), therefore mechanisms controlling filling and emptying of the cecum determine the kinetics and

Foraging Behavior of the Starling (Sturnus vulgaris) in Maryland

Abstract: numbers has been phenomenal (Kessel 1953; Davis 1960). Elton (1958) postulated that the Starling had found a new "feeding niche" in the United States and thus did not compete actively with native birds. It seems an equally plausible hypothesis that a species so numerous, and so capable of range expansion, has almost certainly affected the numbers and distribution of other open-ground foraging birds. Delineating the foraging behavior of the Starling would appear to be the key in measuring the importance of this species' presence to native ones, and in determining the nature and extent of suspected interactions. This paper presents the results of a study designed to provide baseline information on the foraging behaviors of this species throughout a year, as well as a more detailed analysis of foraging strategies of Starling flocks under various environmental conditions. We introduce a technique, the fixed grid, which appears generally useful for delineating the foraging strategies of open-ground feeders. A critique of this method is included.

Ecological overlap and the problem of competition and sympatry in the western and hammond's flycatchers

Abstract: In western North America, Hammond's Flycatcher (Empidonax hammondii) and the Western Flycatcher (E. difficilis) are sympatric north of Mexico. E. difficilis breeds on south into Honduras where E. hammondii is absent (AOU 1957). Both species may be found in local sympatry in habitat within their common ranges. When one species is abundant, the other is usually rare or absent (Johnson 1966a, pers. comm.). Both species have very similar body size, general appearance, and foraging behavior. These similarities led Johnson to conclude that E. hammondii and E. difficilis are "ecological equivalents" and occupy very similar niches. Consequently, Johnson speculated that competition between these two species is very likely when they come into contact.

Patterns of Growth in Birds. III. Growth and Development of the Cactus Wren

Abstract: This paper continues a comparative study of growth and development in birds by describing chemical and anatomical changes in the Cactus Wren (Campylorhynchus brunneicapillus) during the postembryonic period of development. Patterns of weight increase have been reported for many species (for reviews, see Ricklefs 1968a, 1973). Changes in body composition have been analyzed for some of these (Ricklefs 1967b, 1968b; Myrcha and Pinowski 1969; Brisbin 1969; Norton 1970; Dunn 1973; Brisbin and Talley 1973) in studies that deal primarily with energetic aspects of growth (Ricklefs 1974). Attempts to identify factors that could influence the evolution of growth rate suggest that the allocation of tissue to various organs and the degree of functional maturity of those organs-the basic organization of the body plan-may also influence growth rate (Ricklefs 1969). This study on the Cactus Wren is the first of a series of similar analyses of species with different rates of growth and development of mature functions (see Ricklefs 1973). The Cactus Wren is representative of small altricial species with long nestling periods (21 days) and relatively slow growth rate (Ricklefs 1968a). The species was chosen for analysis because its nests are abundant and readily found. Moreover, while the young remain in the nest for about 3 weeks, fledglings stay in their parents' territory and sleep in roosting nests for more than a month after fledging. Therefore, young birds can be collected throughout the entire growth period. Anderson and Anderson (1961, 1973) give an excellent general account of the development of nestlings in their description of the life history of the species in Tucson, Arizona. Aspects of nestling behavior and the development of temperature regulation have also been studied (Ricklefs 1966; Ricklefs and Hainsworth 1968b, 1969). Analyses of growth in the Cactus Wren are presented in the following order: (1) age and body weight growth; (2) increase in linear measurements of the body, limbs, and feathers; (3) increase in body constituents (water, lean dry weight, fat, and ash) with resulting changes in the percentage composition of the body and its caloric density; and (4) increase in weight of major body components and organs and their relative growth rates with respect to the body as a whole.

Seed Selection and Handling Ability of Four Species of Darwin’s Finches

Abstract: Although Darwin's finches have figured importantly in modern ideas of evolution and ecology, only one detailed study of their feeding behavior has been published (Bowman 1961). In that study stomach contents were analyzed, but the size of seeds and fruits taken was not related in any quantitative way to bill differences among species. In a 4-month study (by I.A. and L.A.) of the foraging behavior of the Geospiza finches at eight sites on seven Galapagos islands, we sought to test the rival hypotheses of Lack (1947) and Bowman (1961) concerning the evolution and ecology of Darwin's finches. During this study, we conducted feeding experiments with four species of Geospiza of two islands. The aim of the experiments was to determine feeding rates on rice grains of different hardness and length but of similar depth and width, and to relate these to bill dimensions.

Heat Loss from Ducks’ Feet Immersed in Cold Water

Abstract: The feet of birds are important in the regulation of core temperature (Kahl 1963, Steen and Steen 1965, Johansen and Millard 1973) and are particularly effective in heat transfer when birds are normoor hyperthennic (Steen and Steen 1965). Under natural conditions, they must also be sites of considerable heat loss when they are immersed in cold water or in contact with cold substrates (e.g., ice). However, the heat loss during cold stress can be substantially reduced by altering the pattern of blood flow to the feet (Grant and Bland 1931, Johansen and Millard 1973) and/or by transfer of heat from the arterial to the venous blood in vascular retes (Ederstrom and Brumleve 1964, Steen and Steen 1965). Nevertheless, since tissues in the feet of birds presumably are maintained at or above 0°C (Irving and Krog 1955), some heat must be lost from the feet. We expected that, at temperatures below the freezing point, additional heat would be required to keep the feet from freezing, and that this amount of heat would increase with decreasing temperature. We therefore used calorimetric measurements to determine the exact amount of heat lost from the feet of Mallards (Anus platyrhynchos) when their feet are immersed in fluids at low and subfreezing temperatures.

Intra- and Interspecific Aggression in House Finches and House Sparrows

Abstract: Although House Finches (Carpodacus mexicanus) and House Sparrows (Passer domesticus) are distinct taxonomically, they share several ecological and behavioral similarities. Both are gregarious and are semi-colonial nesters, defending only a small, variable territory surrounding the nest (Thompson 1960a, Summers-Smith 1963). Both species are conspicuously well adapted to man-modified habitats and regularly build nests on manmade structures. Further, numerous observers have reported interspecific conflict between the two species involving nest sites (Gilman 1908, Bergtold 1913, Evenden 1957, and Thompson 1960a). Both species feed extensively in a group and overlap considerably in food selection. The diet of the House Finch

The Nesting and Reproductive Success of Red-Tailed Hawks and Red-Shouldered Hawks in Orange County, California, 1973

Abstract: This paper describes nesting and reproductive performance of the Red-tailed Hawk (Buteo jamaicensis) and the Red-shouldered Hawk (Buteo Ziwatus) in Orange County, California, during 1973. The field work was conducted from January through July 1973, coincidental to a more comprehensive investigation of the biology of the Red-shouldered Hawk. Several population studies of the Red-tailed Hawk have been carried out in North America: California-Fitch et al. (1946); Wisconsin-Gates (1972), Orians and Kuhlman ( 1956) ; New York-Hagar ( 1957) ; Michigan and Wyoming-Craighead and Craighead (1956); Alberta-Luttich et al. (1971); and Montana-Seidensticker and Reynolds (1971). Less work has been done on the Red-shouldered Hawk: Maryland-Stewart ( 1949)) Henny et al. (1973); and Michigan-Craighead and Craighead ( 1956).

Song Dialects in Several Populations of Mountain White-Crowned Sparrows (Zonotrichia Leucophrys Oriantha) in the Sierra Nevada

Abstract: Species identification is one of the basic functions attributed to bird song, although little is known about the actual parameters which make it specific. In order to elucidate such species-specific parameters, several studies have concentrated on the evolution of intraspecific variation in song patterns. Intraspecific variations have been analyzed in terms of subunits of song. These subunits may vary in frequency distribution within a population of birds or between geographically separated populations of birds (Emlen 1972, Helb 1973). Geographic variation in the song of a species refers to differences in song over distance and between populations which normally do not mix (Nottebohm 1969). Vocal differences occurring in neighboring populations are often called dialects. The songs of the Chaffinch (Fringilla coelebs) (Thorpe 1958), Cardinal (Cardinalis cardinalis) (Lemon 1966), and Song Sparrow (Melospiza melodia) (Borror 1965, Harris and Lemon 1972) show differences between neighboring populations. Additional examples have been noted by Thielcke (1969). Vocal variation within subspecies in crowned sparrows (Zonotrichia) has been described by Chapman (1940), Marler and Tamura (1962), Borror and Gunn (1965), Nottebohm (1969), and Baptista (1973, 1974). Marler and Tamura (1962) showed the existence of a system of dialects for the Whitecrowned Sparrow (Zonotrichia leucophrys nuttalli). They found great stereotypy among the members of a population and differences between neighboring populations. Nottebohm (1969), Egli (1971), and King (1972) also found differences between neighboring populations of Rufous-collared Sparrows (Zonotrichia capensis). The present study was undertaken with the hope of providing a detailed analysis of intrapopulation and interpopulation variation of song in the Mountain White-crowned Sparrow (Zonotrichia leucophrys oriantha) in the Sierra Nevada of California.