The Condor

The populations of many species are declining worldwide, and conservation efforts struggle to keep pace with extinction rates. Conservation biologists commonly employ strategies such as translocation and reintroduction, which move individuals of endangered species from one part of their range to another. Because individuals from endangered populations are nonexpendable, identifying any potential barriers to the establishment of viable populations prior to release of individuals should be a priority. This study evaluates the potential for learned communication signals to constrain conservation strategies such as reintroduction in an endangered species, the Thick-billed Parrot (Rhynchopsitta pachyrhyncha). We conducted vocal surveys at three geographically distinct breeding populations in the Sierra Madre Occidental of Chihuahua, Mexico. Acoustic analyses utilizing both spectrogram cross-correlations and parameter measurements from spectrograms revealed no significant differences among the three sites in two common call types. Calls did vary among individuals within a site. The apparent lack of significant geographic variation across sampled sites suggests that differences in learned communication signals are unlikely to pose a barrier to the integration of translocated individuals from different populations into newly established populations.

The strain of West Nile virus (WNV) currently epidemic in North America contains a genetic mutation elevating its virulence in birds, especially species in the family Corvidae. Although dead American Crows (Corvus brachyrhynchos) have been the hallmark of the epidemic, the overall impact of WNV on North America's avifauna remains poorly understood and has not been addressed thoroughly in California. Here, we evaluate variation by species in the effect of WNV on California birds from 2004 to 2007 by using (1) seroprevalence in free-ranging birds, (2) percentage of carcasses of each species reported by the public that tested positive for WNV, (3) mortality determined from experimental infections, and (4) population declines detected by trend analysis of Breeding Bird Survey (BBS) data. Using Bayesian linear models, we extrapolate trends in BBS data from 1980-2003 (pre-WNV) to 2004-2007 (post-WNV). We attribute significant declines from expected abundance trends in areas supporting epiornitics to WNV transmission. We combine risk assessed from each of the four data sets to generate an overall score describing WNV risk by species. The susceptibility of California avifauna to WNV varies widely, with overall risk scores ranging from low for the refractory Rock Pigeon (Columba livia) through high for the susceptible American Crow. Other species at high risk include, in descending order, the House Finch (Carpodacus mexicanus), Black-crowned Night-Heron (Nycticorax nycticorax), Western Scrub-Jay (Aphelocoma californica), and Yellow-billed Magpie (Pica nuttalli). Our analyses emphasize the importance of multiple data sources in assessing the effect of an invading pathogen.

The collection of papers in this special section explores the premise that avian habitat ecology can be approached as an interaction between choices made by individuals and consequences of those choices. This seemingly simple distinction between choices and consequences is emerging as a powerful unifying concept in avian habitat ecology. It allows a richer understanding of the behavioral process by which habitat choices are made, and links behavior to populations. It allows apparently pathological, maladaptive behaviors to be understood simply as one point along a continuum of the same process that produces adaptive habitat choice, such as the ideal-free distribution, by allowing choices and consequences to be based on different habitat characteristics. The diversity of topics covered in this special section provides an overview of the benefits we expect to obtain from treating habitat ecology as an interplay between habitat choices and consequences. This approach promises to improve our understanding of the process of habitat selection and how it affects population distribution, abundance, and dynamics. Approaching habitat ecology in this way will encourage us to identify the times of year when habitat choices are made, the information that is available to birds and used at that time, and the individual fitness and population consequences of those choices. (PsycINFO Database Record (c) 2012 APA, all rights reserved)

Avian point counts for population monitoring are often collected over a short timespan (e.g., 3-5 years). We examined whether power was adequate (power >or= 0.80) in short-duration studies to warrant the calculation of trend estimates. We modeled power to detect trends in abundance indices of eight bird species occurring across three floodplain habitats (wet prairie, early successional forest, and mature forest) as a function of trend magnitude, sample size, and species-specific sampling and among-year variance components. Point counts (5 min) were collected from 365 locations distributed among 10 study sites along the lower Missouri River; counts were collected over the period 2002 to 2004. For all study species, power appeared adequate to detect trends in studies of short duration (three years) at a single site when exponential declines were relatively large in magnitude (more than -5% year-1) and the sample of point counts per year was >or= 30. Efforts to monitor avian trends with point counts in small managed lands (i.e., refuges and parks) should recognize this sample size restriction by including point counts from offsite locations as a means of obtaining sufficient numbers of samples per strata. Trends of less than -5% year-1 are not likely to be consistently detected for most species over the short term, but short-term monitoring may still be useful as the basis for comparisons with future surveys.

A dense canopy above the Strix occidentalis roost, and north-facing slopes were characteristic of all sites. The combined physical features created a microclimate that was 1-6oC cooler than that of more open areas. The owls showed signs of heat stress when temperatures reached and exceeded 27-31oC. The owls' apparent intolerance to high temperatures was, at least in part, related to their having plumage as thick as that of boreal-zone owls. Such plumage appears to be an adaptation for enduring periods of winter stress. Selecting cool summer roosts may be a behavioral adaptation to compensate for the owls' inefficiency in dissipating body heat. -from Author

Movement of forest songbirds among isolated forest patches following breeding represents an important but poorly understood component of landscape ecology and metapopulation theory. Using radio-telemetry, we followed 44 male Ovenbirds (Seiurus aurocapillus) during the post-fledging period to determine if movement patterns differed in landscapes dominated by agriculture versus those dominated by forest. No differences in home-range size, mean distance moved per day, or maximum distance moved were observed for males captured in a forested landscape vs. those captured in forest fragments in an agriculturally dominated landscape. Male Ovenbirds observed with young moved less than males without young and rarely crossed open gaps. Individuals that failed to breed moved more extensively than successful breeders, possibly in an effort to find new territories for use in future breeding seasons.

Environmental conditions during the neonatal period can affect the growth, physiology, behavior, and immune function of birds. In many avian studies the nestling environment includes investigator handling of young, which may be stressful. While neonatal handling is known to affect the adult phenotype in rats, the effects of handling on development have rarely been examined in wild birds. We examined the effect of short, repeated periods of neonatal handling on avian growth and immune system development. We subjected American Kestrels (Falco sparverius) and European Starlings (Sturnus vulgaris) to 15 min of daily investigator handling throughout the nestling period, while controls remained undisturbed. Immediately prior to fledging we assessed cutaneous immunity, humoral immunity, mass, and degree of fluctuating asymmetry. Daily handling did not significantly affect any of these measurements. We also addressed the possibility that treatment differences would appear only when birds were challenged with a more substantial stressor by bringing birds into captivity for 24 hr. Captivity did not affect mass, but significantly lowered the cutaneous immune response, although this was independent of treatment. Therefore, brief periods of investigator handling did not appear to affect immune or morphological development in these species, whereas 24 hr of captivity resulted in suppressed cutaneous immune responses.

Thesis (M.S.)--University of New Mexico. Bibliography: l. 38-41.

Marsh Wrens (Cistothorus palustris) destroyed Yellow-headed Blackbird (Xanthocephalus xanthocephalus) eggs presented on wren territories and probably disrupted at least 10 of 189 yellowhead nesting attempts. Male yellowheads discriminated among Marsh Wren, Song Sparrow (Melospiza melodia), and Common Yellowthroat (Geothlypis trichas) songs, with the greatest proportion of aggressive approaches in response to broadcast Marsh Wren songs. The proportion of aggressive approaches by male yellowheads to Marsh Wren playbacks beside yellowhead nests was 27% and did not change with the stage of the nest; but the proportion of aggressive responses by females did vary, and was highest (53%) in response to playbacks beside nests containing eggs. Male responses are interpreted as reflecting territorial defense against Marsh Wrens, and female responses as a localized nest defense against egg predators.

Clutch sizes of North American woodpeckers exhibit strong positive latitudinal gradients. There is no overall effect of either estimated first egg date or proximity to the coast on clutch size. However, mean clutch size varies inversely with an index of winter productivity and estimates of breeding densities of all woodpecker species combined; clutch size is uncorrelated with summer productivity. These results support Ashmole's hypothesis that geographic trends in fecundity are determined, at least in part, by seasonality of resources.

In nature, the ability to defend against predators is fundamental to an animal's survival. From the giraffes that rely on their spotted coats to blend into the patchy light of their woodland habitats to the South American sea lions that pile themselves in heaps to ward off the killer whales that prey on them in the shallow surf, defense strategies in the animal kingdom are seemingly innumerable. In Antipredator Defenses in Birds and Mammals, Tim Caro ambitiously synthesizes predator defenses in birds and mammals and integrates all functional and evolutionary perspectives on antipredator defenses that have developed over the last century. Structured chronologically along a hypothetical sequence of predation—Caro evokes a gazelle fawn desperate to survive a cheetah attack to illustrate the continuum of the evolution of antipredator defenses—Antipredator Defenses in Birds and Mammals considers the defenses that prey use to avoid detection by predators; the benefits of living in groups; morphological and behavioral defenses in individuals and groups; and, finally, flight and adaptations of last resort. Antipredator Defenses in Birds and Mammals will be of interest to both specialists and general readers interested in ecological issues.

We investigated the departure, transient movement, and local settlement stages of natal dispersal in a population of Northern Goshawks (Accipiter gentilis) on the Kaibab Plateau of northern Arizona. The study included 614 color-banded juveniles produced at 555 nests during 1991-2003, 89 of which were radio-marked during 1998-2001. Radio-marked juveniles initiated dispersal between 71 and 103 days posthatching, and spent between 33 and 66 days in the natal territory after fledging. Our best-fitting proportional hazards models predicted the timing of dispersal as a function of annual differences in the density of primary bird and mammal prey species, weather conditions, and natal brood size. Once dispersal was initiated, most juveniles moved into the more open habitats that surrounded the study area and few eventually returned to breed; first-year fidelity to the local natal population was 28%, and only 69 (11%) color-banded juveniles had entered the territorial population by 2004. Median natal dispersal distance on the Kaibab Plateau was 15.0 km (range = 0.1-58.1 km), a distance equivalent to about four times the diameter of an average breeding territory (3.8 km). Local settlement behavior of Northern Goshawks appeared to be driven by a combination of intraspecific competition for a limited number of breeding opportunities and inbreeding avoidance. However, much of the natal dispersal process operated at broad spatial scales beyond our study population, indicating a potentially high level of demographic connectivity among naturally fragmented breeding populations in the American Southwest.

We modeled the relationship between egg flotation and age of a developing embryo for 24 species of shorebirds. For 21 species, we used regression analyses to estimate hatching date by modeling egg angle and float height, measured as continuous variables, against embryo age. For eggs early in incubation, we used linear regression analyses to predict hatching date from logit-transformed egg angles only. For late incubation, we used multiple regression analyses to predict hatching date from both egg angles and float heights. In 30 of 36 cases, these equations estimated hatching date to within four days of the true hatching date for each species. After controlling for incubation duration and egg size, flotation patterns did not differ between shorebirds grouped by mass (¿100 g or <100 g) or taxonomy (Scolopacidae versus Charadriidae). Flotation progressed more rapidly in species in which both adults incubate the clutch versus species in which only one adult incubates the clutch, although this did not affect prediction accuracy. We also pooled all continuous data and created a generalized regression equation that can be applied to all shorebird species. For the remaining three species, we estimated hatching date using five float categories. Estimates of hatching date using categorical data were, overall, less accurate than those generated using continuous data (by 3%-5% of a given incubation period). Our equations were less accurate than results reported in similar studies; data collected by multiple observers and at multiple sites, as well as low sample sizes for some species, likely increased measurement error. To minimize flotation method prediction error, we recommend sampling in early incubation, collecting both egg angle and float height data in late incubation, and developing site- and species-specific regression models where possible

The Picui Dove (Columbina picui) has been considered sexually monochromatic, with females slightly duller than males. This assessment has been based on colors perceived by the human eye. However, birds possess an additional, near-ultraviolet photoreceptor and thus are sensitive to wavelengths humans are not. Measurements of reflectance using spectroradiometry permit an objective determination of the coloration of the birds' plumage and of color differences between the sexes. We here show that the plumage coloration of the Picui Dove is clearly sexually dimorphic. Males were overall brighter than females, and several body regions showed a significant sex difference in spectral shape. These results imply that studies of sexual selection in this and related species should measure sexual dichromatism objectively, and should not rely on human color perception. Determinación Objetiva del Dicromatismo Sexual del Plumaje en Columbina picui Resumen. La especie Columbina picui ha sido considerada sexualmente monocromática, siendo las hembras levemente más opacas que los machos. Esta conclusión ha sido basada en la percepción humana del color. Sin embargo, las aves poseen un fotorreceptor adicional en el ultravioleta cercano y son, por lo tanto, sensibles a longitudes de onda que los humanos no perciben. La medición de la reflectancia por medio de la técnica de espectrofotometría permite una determinación objetiva del color del plumaje y de las diferencias de color entre los sexos. En este estudio mostramos que C. picui es claramente sexualmente dicromática, siendo los machos más brillantes que las hembras y presentando en algunas regiones del cuerpo diferencias en el espectro de las longitudes de onda reflejadas. Estos resultados demuestran que la determinación de dicromatismo sexual no debería basarse en la percepción humana y tiene, además, implicancias para los estudios de selección sexual en esta especie y especies relacionadas.

We examined seasonal variation in the hatching sex ratio of Audouin's Gull (Larus audouinii). This species is sexually size dimorphic (males are 20% larger than fe- males at fledging); it has a modal clutch of three eggs, which vary in size (the third egg is the smallest) and hatch asynchronously. These sex, egg size, and hatching patterns generate substantial within-brood differences in chick size that interact with the food provisioning of the parents to influence chick survival. Parental provisioning capacity depends on both parental quality and environmental conditions, both of which are known to decline with season. Consequently, the optimal brood composition is likely to vary within a season. Using molecular markers to sex newly hatched chicks, we found that offspring sex was influenced by an interaction between hatching date and hatching order, with the proportion of males among third-hatched chicks initially increasing and then decreasing later in the season.

Birds show quite distinct changes in both external and internal appearance. An evolutionary interpretation of these cyclic life-history phenomena would benefit from a system of description aimed at mapping shared ancestries of arguably the ‘‘easiest’’ of traits: the molts and seasonal plumage changes. By 1959, Humphrey and Parkes had already provided the basis of such a system, but its development and application, especially with regard to the confusing first plumage cycle, by Howell et al. (2003), adds considerably to its power. I hope this leads to an upsurge of evolutionary studies of molt and plumage cycles that in turn provide the basis for analyses of other aspects of the flexible phenotype of birds. With such an increase, the study of molts and plumages could once again be at center stage of avian biology.

Thesis (M.S.)--Michigan State College of Agriculture and Applied Science. Dept. of Zoology, 1956. Includes bibliographical references (leaves 70-72).

Our aim in this study was to survey the communities of bacteria found in the cloacae of adult and nestling Tree Swallows (Tachycineta bicolor), determine if there were familial patterns of prevalence, and determine if there were relationships between bacteria loads and nestling size when 12 days old and fledging success.

We examined the vocal and behavioral responses of free-living male Brown-headed Cowbirds (Molotharus ater) to playbacks of Eight whistles (FWs) from local, near-foreign, and distant-foreign dialects. Full, partial, and reverse FWs were broadcast to solitary males. Test males responded with their own FWs and approached playbacks of FWs significantly more than playbacks of control heterospecific vocalizations. This suggests that all three dialects were recognized as conspecific. The strongest responses were elicited by playbacks of local FWs, and there was little behavioral evidence that males distinguished between the near-foreign and distant-foreign dialects. Males responded to playbacks of partial or complete local FWs primarily with the next or missing part of the FW. That is, they avoided matching the playback. The FW responses to playbacks of near-foreign and distant-foreign EWs were not consistent. Males presumably use matching-avoidance within a FW dialect to initiate social interactions with particular conspecific males.

Golden-fronted Woodpeckers (Melanerpes aurifrons) and Red-bellied Woodpeckers (M. carolinus) are sympatric from southwestern Oklahoma to eastern Texas. Earlier studies found no evidence of hybridization (Selander and Giller 1963). However, in the recent past the area of range overlap between these two species has increased, thereby increasing the opportunity for hybridization. I investigated the possibility of hybridization by analyzing morphological and electrophoretic characteristics. Twenty-five (15.8%) individuals with intermediate morphologies were collected within the area of overlap and were identified as putative hybrids. Electrophoretic analysis of 12 liver and muscle proteins revealed a close genic affinity between the two species. Individual genic complements within the zone of overlap indicate that some individuals are intermediate. The intermediate morphology and mixed genic composition of some individuals within the zone of overlap supports the conclusion that Red-bellied and Golden-fronted woodpeckers hybridize.

Thesis--(M.S.)--University of Georgia, Athens, 1961. Bibliography: leaves 31-33.

We conducted a study of the breeding biology of the Thorn-tailed Rayadito (Aphrastura spinicauda) in secondary forests on the continental island of Chiloe (42degreesS), southern Chile. Rayaditos are small insectivorous furnariids inhabiting the south-temperate forests of Chile and Argentina. We followed the reproduction of rayadito pairs breeding in nest-boxes. Rayaditos build their nests mainly of rhizomes and stems of epiphytic vines, grasses, and hairs during periods of at least a week, and show a marked population asynchrony in laying dates of more than two months (October-December). Rayaditos lay clutches of 3-6 eggs with a mode of 4 and laying occurs on alternate days. Eggs are 50% larger and hatchlings are 30% larger than expected from allometric equations. Most broods hatch synchronously. Nestling growth curves adjust well to logistic functions and at 2 weeks nestlings attain masses similar to asymptotic values. Nestling growth, which occurs over 3 weeks, is 27% slower than expected from allometry. Fledglings attain adult size with respect to tarsus length, but have less developed plumage and higher body mass than adults. Rayaditos exhibit clutch and brood reduction, suggesting possible food limitation. The protracted breeding periods may preclude second breeding attempts for most pairs in Chiloe. There is evidence for declines in parental quality with season. The low seasonal fecundity, large eggs, and prolonged dependence periods of a truly south-temperate species like the Thorn-tailed Rayadito reflect a 'slow' life history similar to that of tropical passerines.

Silvicultural practices following clearcutting in boreal forest may encourage the creation of monospecific, single-aged stands having less vegetation heterogeneity and diversity than original stands. We conducted point counts in central Saskatchewan, Canada, 1993-1995, in pure and mixedwood stands dominated by black spruce (Picea mariana), jackpine (Pinus banksiana), trembling aspen (Populus tremuloides), or white spruce (Picea glauca). Mixedwood stands supported more individuals and more species than pure stands. Higher abundance in mixedwood stands relative to pure stands was consistent among nesting guilds and migration strategies. Rarefaction revealed similar patterns, although pure trem- bling aspen stands were predicted to support more species than aspen-dominated mixedwood stands. Increased avian diversity in mixedwood stands was not solely the result of the mixing of bird species associated with coniferous or deciduous forest types. Chipping Sparrow (Spizella passerina), Pine Siskin (Carduelis pinus), White-winged Crossbill (Loxia leucop- tera), Red-breasted Nuthatch (Sitta canadensis), Swainson's Thrush ( Catharus ustulatus), and Tennessee Warbler (Vermivora peregrina) were more abundant in mixedwood stands than pure stands. Black-throated Green Warbler (Dendroica virens), Magnolia Warbler (D. magnolia), and Blackburnian Warbler (D. fusca) were abundant in stands dominated by white spruce but were absent from jackpine or black spruce. Other species such as American Redstart (Setophaga ruticilla) and Chestnut-sided Warbler (D. pensylvanica) relied exclu- sively on pure trembling aspen, particularly stands with dense shrub cover. Several bird species in the boreal forest will be adversely affected by forestry practices that target mature to old aspen and white spruce mixedwoods and promote reduction in mixedwood compo- sitions of regenerating stands.

Maximizing reproductive output often entails a trade-off between energy spent on current breeding attempts and that saved for future reproductive opportunities. For species with biparental care, energy spent on the current breeding attempt represents not only a trade-off with future breeding opportunities but also an interaction with the energetic effort of one's mate. In most songbird species, the female typically invests the most in the early stages of breeding. Consequently, the male's contribution to provisioning young may free the female from this energetically costly activity and aid her ability to attempt a second brood. We investigated parental provisioning in the Black-throated Blue Warbler (Dendroica caerulescens) to see if males and females altered their provisioning rates with respect to first and second broods. Using parental provisioning rates from 239 nests from three study sites over 6 years, we show that females provisioned young of first broods at a rate lower than that for second broods, while males' provisioning rate did not differ. Males' provisioning rate was inversely associated with that of females, with males increasing their provisioning when the number of young in a nest increased while females' provisioning decreased. Consequently, we believe our results highlight both the trade-off in energy females spend on current and future reproduction and the role of males' care in helping to maintain reproductive output through increased effort when conditions for feeding are difficult.

Typescript. Thesis (M.A.)--University of Montana. Bibliography: leaves 83-93.

We examined changes in body composition of Red Knots (Calidris canutus islandica) following arrival on their High Arctic breeding grounds at Alert, Ellesmere Island, Canada. Knots arrived in late May and early June with large fat and muscle stores. In the next two weeks, fat and protein stores (pectoral muscles) declined, while increases occurred in gizzard, proventriculus, gut length, heart, liver, and possibly gonads. Most stores were used before egg laying occurred and were therefore not available for egg formation. Early development of ova in some females suggests that body stores may be incorporated into the earliest eggs. While stores may be used for survival when conditions are difficult after arrival, their rapid loss and the concomitant increase in other organs suggests that a major function may be to facilitate a transformation from a physiological state suitable for migration to one suitable, and possibly required, for successful breeding.

"This book is well worth buying for its detailed summaries of the 25 studies, many of which are classic long-term projects, and for its insights into the factors determining reproductive success."—William J. Sutherland, TREE "A must read for anyone interested in evolution, mating/social systems, and population ecology."—John L. Koprowski, IJournal of Insect Behavior

Thesis (M.A.)--University of California, June 1949. "Literature cited": p. 28.

The hormonal response to a spectrum of intrasexual social stimuli was studied in captive Brown-headed Cowbirds (Molothrus ater). Males were housed in individual cages in one of four conditions: (1) in a semicircle with other males (= visual + vocal stimuli), (2) in acoustic chambers with visual access to a devocalized companion (= visual stimuli only), (3) in chambers in which a tutor tape was played daily (= vocal stimuli only), and (4) in acoustic chambers with no other input (neither visual nor social stimuli). Blood samples were taken at 2-week intervals throughout the spring and early summer and assayed for testosterone. The results indicate that the greatest increase in testosterone was in the birds receiving visual plus vocal stimuli and in those receiving only visual stimuli; males receiving only vocal stimuli had a muted endocrine response, and those receiving no social stimulation exhibited the briefest response. The relatively small response to vocal stimulation is consistent with the absence of a behavioral response to simulated territorial intrusions (i.e., song playbacks) that has been shown in previous studies in male cowbirds.

To explore age-class variation in Brown Pelican (Pelecanus occidentalis) hunting success, three behavioral aspects of foraging (dive height, dive angle, and head orientation) were examined in detail. Adults had greater foraging success than birds in three younger age classes. Success improved linearly with age, but was generally lower than reported in previous studies. Both dive height and dive angle varied significantly as a function of age. Adult mean dive height was higher than that of juveniles and first-year birds, but did not differ from that of subadults. Adults, subadults, and juveniles relied more on steep dive angles and less on flat dive angles than first-year birds. Results indicated a significant positive correlation between dive height and dive angle, suggesting that refraction is important when birds are hunting prey that are relatively deep in the water. Pelicans appeared to minimize surface glare by orientating away from the sun while diving.

Thesis (M.A. in Zoology)--University of California, Berkeley, Sept. 1957. Includes bibliographical references (leaves 78-82). Microfilm. s

We studied the summer habitat ecology of 12 Northern Spotted Owls (Strix occidentalis caurina) in two areas of northwestern California. Spotted Owls used mature or old-growth conifer forests significantly more than expected relative to their availability within their home ranges. In contrast, Spotted Owls used forests of intermediate and young age significantly less than expected relative to their availability within their home ranges. Eighty four percent of 616 Spotted Owl radiotelemetry locations were recorded in mature or old-growth forests. Spotted Owls used forests of complex structure and old age. There were significant differences in habitat structure (e.g., canopy closure, shrub cover, herb cover, old-growth conifer basal area, and hardwood tree density) among habitats used for frequent foraging, infrequent foraging, and roosting. In addition, male and female owls appeared to select habitats with different structure for foraging. Male owls which are smaller than female owls foraged in habitats which had higher tree density than female owls. The mean summer home-range size was 413 ha (SD = ± 196 ha) with males having smaller mean home-range size than females (338 ha and 538 ha, respectively).

Thesis (Ph. D. in Zoology)--University of California, Berkeley, Jan. 1960. Bibliography: leaves 73-78.

Thesis (M.S.)--University of Arizona. Includes bibliographical references.

Thesis (Ph. D. in Zoology)--University of California, Berkeley, Sept. 1960. Bibliography: leaves 51-53.

Eruptive movements of the Clark's Nutcracker (Nucifraga columbiana) were observed during the late summer and fall of 1977, 1978 and 1979 in northern Utah and adjacent states. Over 2,000 emigrating nutcrackers were seen during these periods. Eruptions began in mid to late August, about the time nutcrackers began foraging on developing conifer cones, and continued until early October. Nearly all nutcrackers traveled in small, loose flocks (x = 10.1 individuals). During 1977-1978, most emigrating nutcrackers appeared to winter in p&on-juniper woodlands of Utah and adjacent states and no nutcrackers were reported outside their normal breeding range. A northward movement of nutcrackers, presumably the same population observed emigrating southward in fall 1977, was noted in summer 1978. Evidence for breeding of nutcrackers on their wintering areas is presented. A compartmental model summarizes current knowledge on the temporal and spatial aspects of nutcracker emigration. Journal Article

Song Sparrows (Melospiza melodia) provide one of North America’s best examples of geographic variation in phenotype, with approximately 26 described subspecies recognized. However, researchers have found inconsistent signals when making comparisons between subspecies and genetic markers. We examined seven microsatellite loci from 576 Song Sparrows of 23 western North American populations representing 13 recognized subspecies. We assessed the level of concordance between microsatellite genotypes and subspecies. We found that in some, but not all, instances neutral genetic structure corresponded to recognized phenotypic structure. However, some populations not currently recognized as subspecies were found to be genetically differentiated from all other populations that are considered to be the same subspecies. We suggest that a combination of phenotypic characters, behavioral traits, and multiple loci be used when assessing geographic variation in birds, and that sampling should be conducted in more than one location within broadly distributed subspecies.

Most of the Great Skuas ( Stercorarius skua ) breeding at Hermaness, Shetland, exhibit dietary specialization: a small proportion feed almost exclusively upon seabird prey, a small proportion feed as generalists, and most feed on fishery discards. We investigated the foraging dynamics, reproductive performance, and survival of Great Skuas that specialized in depredating other seabirds compared with those feeding predominantly on fish. Around half of the specialist bird predators defended combined breeding and feeding territories that included a section of seabird colony; the remainder of the predatory skuas foraged away from breeding territories. Specialist bird predators retained their feeding habit and, if present, feeding territory, across years, Time budgets revealed that specialist bird predators spent less time foraging than skuas feeding predominantly on fish. Results of radio-telemetry indicated that bird-specialist skuas have smaller home ranges than other birds. In a comparison of reproductive performance, specialist bird predators consistently hatched earlier among years. They also showed larger clutch volumes and improved chick condition, but these were subject to annual variations. Hatching success and fledging success for specialist bird predators and specialist fish predators were similar. Specialist bird predators showed similar annual survival compared with fish-feeders over the same period. Specializing as a bird predator may be limited to the best birds in the population, but their poorer than predicted breeding success reveals the need for further study into the relationship between diet and reproductive success in this species.

Egg temperature (Tegg) of Zonotrichia leucophrys oriantha was measured throughout incubation and under natural variations in environmental conditions at high altitude. Information on Tegg, air temperature (Ta), nest placement and attentiveness patterns was integrated in order to elucidate adaptive forms of incubation behaviour. Despite wide daily variations in ambient conditions, incubating females were able to maintain mean Tegg between 34-38oC. Large oscillations in Tegg (17.8-43.0oC) occurred when females were foraging, especially during early morning and late afternoon when Tas were low. Low and fluctuating temperatures were not detrimental to embryo development. High Teggs did not occur because females prevented exposure of eggs to solar heating by remaining on the nest during critical periods. Mean Tegg was significantly higher in ground in aerial nests. Habitat availability seemed to be of major importance for selection of nest height. Orientation of nests with respect to the vegetational mass in which they were built was non-random and was probably related to prevailing winds or to sun exposure.-Authors

At Boundary Bay, British Columbia, Canada, Peregrine Falcons (Falco peregrinus) captured 94 Dunlins (Calidris alpina) in 652 hunts. The two main hunting methods were open attacks on flying Dunlins (62%) and stealth attacks on roosting or foraging Dunlins (35%). Peregrines hunted throughout the day, yet the kill rate per observation hour dropped 1¿2 hr before high tide and peaked 1¿2 hr after high tide. The drop in kill rate coincided with the departure of the mass of Dunlins for over-ocean flights lasting 2¿4 hr. The peak in kill rate occurred just after the tide began to ebb and the Dunlins returned to forage in the shore zone. The hypothesis that closeness to shoreline vegetation is dangerous for Dunlins is supported by three converging lines of evidence: (1) the high success rate (44%) of peregrine hunts over the shore zone compared to the rate (11%) over tide flats and ocean; (2) the high kill rate per observation hour at high tide; and (3) the positive correlation of kill rate with the height of the tides. Seven of 13 Dunlins killed by Merlins (Falco columbarius) and all five Dunlins killed by Northern Harriers (Circus cyaneus) were also captured in the shore zone.

Mammalian Dispersal Patterns examines the ways that social structure affects population genetics and, in turn, rates of evolution, in mammalian groups. It brings together fieldwork in animal behavior and wildlife biology with theoretical work in demography and population genetics. The focus here is dispersal—whether, how, and when individuals leave the areas where they are born. Theoretical work in population genetics indicates that such social factors as skewed sex ratios, restrictive mating patterns, and delayed age of first reproduction will lower the reproductive variability of a population by reducing the number of genotypes passed from one generation to the next. Field studies have shown that many mammalian species do exhibit many such social characteristics. Among horses, elephant seals, and a number of primates, the majority of females are inseminated by only a fraction of the males. In pacts of wolves and mongooses, usually only the highest-ranking male and female breed in a given season. Although socially restricted mating tends to lower genetic variability in isolated populations, it actually tends to increase genetic variability in subdivided populations with low rates of migration between subunits. Among some species there is little dispersal and thus little gene flow between subpopulations; other species travel far afield before mating. The contributors to this volume examine actual data from populations of mammals, the way patterns of dispersal correlate with the genetic structure of individuals and populations, and mathematical models of population structure. This interdisciplinary approach has an important bearing on work in conservation of both wildlife and zoo populations, for it shows that the home range and the population size needed to maintain genetic variability can differ greatly from one species to the next. The volume also offers a fruitful model for future research.

In male House Finches (Carpodacus mexicanus), the extent and color of plumage varies depending on access to carotenoid pigments. ''Colorful'' males exhibit extensive red pigmentation, while less colorful (i.e., ''drab'') males exhibit carotenoid pigmentation over a smaller percentage of their plumage, pigmentation of a color besides red (e.g., yellow, gold, orange, or pink), or both. One explanation for maintenance of plumage variation is that it reliably reflects social status, allowing males to correctly assess their status in relation to others and avoid or minimize costly fights. Social relationships may also be related to endogenous factors, such as circulating levels of the hormones testosterone and corticosterone. High levels of testosterone may promote or facilitate increased aggression, and stress associated with receiving aggression from individuals of higher status may increase adrenal activity and secretion of corticosterone. We examined the relationship between plumage variability, steroid hormones, and social status in captive male House Finches during the non-breeding period in: (1) groups of males in which individuals varied by age, size, and plumage, and (2) pairs (dyads) of males matched for several measurable parameters except plumage. Testosterone and social status were not related in males competing in either groups or dyads, and levels of testosterone were routinely low. Corticosterone and status were not related in groups but, in dyads where subordinate individuals had little chance of escaping aggression from more dominant birds, subordinates exhibited significantly greater levels of corticosterone. Although drab males tended to achieve higher status than colorful males in both experiments, which is consistent with previous studies on free-living individuals, we could not reject the null hypothesis that plumage and status were unrelated. We conclude that dominance relationships among male House Finches during the non-breeding season may not be related to testosterone, but they are reflected by levels of corticosterone in some circumstances. Additionally, colorful plumage appears to be a poor predictor of high social status among male House Finches during the non-breeding season.

We quantified the efficacy of using pellet numbers to estimate predation rates on Common Eider (Somateria mollissima) ducklings by Great Black-backed Gulls (Larus marinus) by using eider ducklings fitted with radio transmitters. Ducklings fitted with radiotransmitters were no more vulnerable to gull predation than were other ducklings. The recovery of radio-transmitters attached to eider ducklings and subsequently retrieved from Great Black-backed Gull pellets suggests that traditional methods of estimating the number of eider ducklings eaten by gulls from the remains found in pellets at gull nests and loafing areas underestimates the true number eaten by gulls by a factor of 5-17. Previous low estimates of eider duckling mortality on the Wolves Archipelago, Bay of Fundy cannot be explained by movements of broods to the mainland coast.