The “cycle of violence” hypothesis implicates child abuse as a cause of later violent behavior via social transmission between generations. It has received mixed support from human research and has prompted the study of nonhuman models with comparable abuse behaviors. The underlying biology of child abuse remains a controversial subject, perhaps partly because in nonhuman animals similar behavior occurs relatively rarely in wild populations. The Nazca Booby (Sula granti), a colonial seabird, provides a nonhuman model in which maltreatment of nonfamilial young is widespread under normal living conditions. Essentially all adults show social attraction at some point in their lives to the offspring of other parents, often with a sexual and/or aggressive motivation. Here, we show a correlation between the degree to which a young bird is targeted by such adults and its own infliction of maltreatment later in life. The results provide the first evidence from a nonhuman of socially transmitted maltreatment directed toward unrelated young in the wild.

We investigated territory-level habitat use patterns of 132 color-banded male Ovenbirds (Seiurus aurocapilla) over a 12-year period at Hawk Mountain Sanctuary in eastern Pennsylvania. Our primary goals were to test hypotheses concerning selection behavior as well as to describe territory fidelity of an area-sensitive Neotropical migrant by quantifying year-to-year movements of individuals over a period equivalent to several generations. Furthermore, we tested whether returns and territory shifts were associated with prior reproductive success and bird age. We measured occupancy as the number of birds that occupied 60-m grid cells that covered two 18-ha study sites over the 12-year period and similarly calculated rates of reproductive success within each grid cell. Rates of reproductive success were generally high (>60%) and were not correlated with occupancy rates. Return rates also were high, and birds rarely moved far from their first territory (mean = 68 m) during their lifetimes. There was no relationship between site fidelity and past reproductive success, but shift distances decreased with age. Our results differed from past studies that found a relationship between breeding dispersal and past reproductive success for species in a number of habitats. High territory fidelity regardless of past reproductive performance may represent a general case for songbirds breeding in homogeneous, high-quality habitats in which sources of failure are infrequent and unpredictable. In such cases, the potential benefit of moving may not outweigh the costs, and being able to obtain and maintain a territory may be of prime importance.

Energy gain is thought to play a central role in prey selection by most foragers, but it may conflict with food theft avoidance and be constrained by undeveloped foraging skills. We investigated predation by the Glaucous-winged Gull (Larus glaucescens) on the ecologically important Ochre Sea Star (Pisaster ochraceus). We tested the hypothesis that Pisaster size selection by gulls was based on energetic profitability, defined as energy provided per unit handling time. We then examined the degree to which profitability interacts with intraspecific kleptoparasitism risk and age-related foraging efficiency (i.e., energy intake rate, prey capture success) to produce the patterns of prey choice observed in a natural setting. Behavioral observations of free-living gulls revealed moderate to high (32.5–91.6%) occurrences of Pisaster in gull diets. We used handling time data and bomb calorimetry to determine the relationship between Pisaster size and energetic profitability, which informed prey offer experiments that allowed us to test hypotheses regarding gull prey choice. We found that gulls readily distinguished between Pisaster sizes on the basis of energetic profitability, selecting the most profitable individual in 60% of trials. Prey discrimination ability did not differ between gull age classes and thus did not contribute to the reported reduced foraging efficiency of juveniles. However, gulls exhibited a significant nonlinear decrease in preference for highly profitable Pisaster with increasing kleptoparasitism risk.

Seasonal and annual variation in food availability during the breeding season plays an influential role in the population dynamics of many avian species. In highly dynamic ecosystems like wetlands, finding and exploiting food resources requires a flexible behavioral response that may produce different population trends that vary with a species' foraging strategy. We quantified dynamic foraging-habitat selection by breeding and radiotagged White Ibises (Eudocimus albus) and Great Egrets (Ardea alba) in the Florida Everglades, where fluctuation in food resources is pronounced because of seasonal drying and flooding. The White Ibis is a tactile “searcher” species in population decline that specializes on highly concentrated prey, whereas the Great Egret, in a growing population, is a visual “exploiter” species that requires lower prey concentrations. In a year with high food availability, resource-selection functions for both species included variables that changed over multiannual time scales and were associated with increased prey production. In a year with low food availability, resource-selection functions included short-term variables that concentrated prey (e.g., water recession rates and reversals in drying pattern), which suggests an adaptive response to poor foraging conditions. In both years, the White Ibis was more restricted in its use of habitats than the Great Egret. Real-time species—habitat suitability models were developed to monitor and assess the daily availability and quality of spatially explicit habitat resources for both species. The models, evaluated through hindcasting using independent observations, demonstrated that habitat use of the more specialized White Ibis was more accurately predicted than that of the more generalist Great Egret.

Egg viability in birds declines with increasing length of the delay in the start of incubation (i.e., incubation delay) and may be influenced by microbial infection and exposure of eggs to temperatures above physiological zero (>24°C). Onset of incubation during egg laying results in developmental asynchrony of embryos but may help to maintain viability of early-laid eggs. We manipulated incubation delay of Wood Duck (Aix sponsa) eggs and tested for effects of incubation delay and ambient temperature on egg viability and microbial infection. We also examined onset of incubation by egg-laying females. Hatching success declined slowly with increasing length of incubation delay and was very weakly affected by increasing exposure to temperatures >24°C. On average, females began incubation at night 7 days after nest initiation, but egg viability had declined only 8.6% (95% confidence interval: 4.3–15.2) by day 7. Microbial infection of eggshells was not related to length of incubation delay or mean daily temperature of the exposure period. Clutch size declined as the breeding season progressed, and nocturnal incubation began earlier in the laying sequence with declining clutch sizes. Laying females, regardless of clutch size, incubated for 3 nights before starting full incubation. We suggest that early onset of incubation may be more important in reducing incubation period and predation risk than in maintaining viability of early-laid eggs.

The Imperial Woodpecker (Campephilus imperialis) of Mexico—the largest woodpecker in the world—probably became extinct in the late 20th century, without known documentation of the species in life. We describe a recently discovered 16-mm color film of an Imperial Woodpecker taken in 1956 by William L. Rhein. The film documents climbing strides, launches, flights, and foraging of one female Imperial Woodpecker. For perches and foraging the woodpecker used dead or recently dead Durango Pines (Pinus durangensis). Trunks of perch and foraging trees were of the largest diameters available in this tree species. After allowing for possible inaccuracies in the frame speed of the film, we found that the Imperial Woodpecker had slow climbing strides and a fast wingflap rate compared with other woodpeckers. Following landmarks documented during the 1956 expedition, we identified and surveyed the film site in 2010. The site was in coniferous forest in lightly undulating terrain at 2,700–2,900 m elevation. In 1956, the area was oldgrowth forest with abundant large and dead trees. By 2010, the area had been logged multiple times. Interviews with local people indicated that Imperial Woodpeckers had disappeared from the region by 1960 and that they were killed by hunting and perhaps through poisoning instigated by logging interests. Human persecution and the logging of large pines for timber and of dead trees for pulp were likely principal factors in the extinction process of the Imperial Woodpecker.

Many birds have colorful plumage ornaments that utilize carotenoid pigments, and these are often displayed in signaling contexts. Researchers in behavioral ecology have focused on examining carotenoids in general, and red carotenoids in particular, because they may be an honest index of individual condition or quality. However, few studies have examined the evolutionary changes in carotenoid-based coloration across a phylogeny. We used reflectance spectrometry to examine carotenoid-based coloration across the New World blackbirds (Icteridae). We scored discrete character states based on these measurements and mapped them onto the icterid phylogeny. Our results indicate that red coloration has been gained six times in the blackbirds from a common ancestor that exhibited yellow ornamentation. This result was supported by both parsimony and likelihood methods of ancestral state reconstruction and by each of three different scoring methods. Thus, multiple lineages of icterids have convergently evolved red patches from a common ancestor that most likely used yellow. Several other studies have observed repeated gains of red coloration, which suggests that our observations may reflect a directional trend common among avian clades.

Hybrid zones between different plumage morphs are common in birds. These zones can be maintained by (1) divergent selection pressures on either side of the zone or (2) some restriction to mating between the forms that limits gene flow from one side to the other. In eastern Australia, there is a distinct hybrid zone between two plumage forms of the Australian Magpie (Cracticus tibicen), with black-backed birds in the north, white-backed birds in the south, and both forms plus intermediates in a zone ∼100 km wide. On the basis of social groups, there is no evidence of assortative mating in the hybrid zone. However, extrapair fertilizations (EPF) occur in other Australian Magpie populations and, thus, may also occur in the hybrid zone. We examined evidence of EPFs in the hybrid zone to test for either (1) positive assortative mating or (2) preference for the brighter plumage form. Although there were significant levels of EPFs of ∼30%, there was no evidence for positive assortative mating or preference for the brighter white-backed males. Other explanations for the current distribution of the hybrid zone and its maintenance will need to be investigated.

The Barred Owl (Strix varia) is a common nonmigratory owl distributed across southern Canada, south to California in the west, and to Texas and Florida in the east, with isolated populations in central Mexico. We examined the genetic structure of Barred Owl populations throughout their range using 500–600 base pairs each of one nuclear and three mitochondrial genes. In 75% of the shortest trees and 64% of the bootstrapped trees, Barred Owls were not monophyletic; rather, S. v. sartorii of Mexico was separated from the remaining taxa of S. varia by S. fulvescens of Central America. Consequently, the Barred Owls of Mexico are a species-level taxon. There was a large component (32%) of genetic variance distributed among population samples from the United States and Canada because of the occurrence of two clades of haplotypes (4.8% sequence divergence) with differing geographic distributions. One clade was predominant along the Atlantic Coast and the second in the south-central United States. The two clades co-occurred from the central Gulf Coast to the Upper Midwest, and across Canada to the Pacific. Nucleotide diversity was greatest where the clades overlapped in occurrence; mismatch distributions possessed the signatures of population expansion from the southern and eastern states to northern and western locations. These results suggest two Pleistocene refugia for northern populations of Barred Owls. Diversity within populations and divergence between haplotype clades varied by an order of magnitude among the three mitochondrial genes, but each recovered the overall phylogeographic pattern. The nuclear sequences showed much less variation and differentiation.

Climate change is predicted to increase the frequency and severity of extreme climate events, and it is important that we understand how this might affect natural systems. We examined the effects of extreme climate events on adult survival rates in three species of auks breeding on Triangle Island, British Columbia: Cassin's Auklet (Ptychoramphus aleuticus), Rhinoceros Auklet (Cerorhinca monocerata), and Tufted Puffin (Fratercula cirrhata). Our 15-year study period (1994–2008) included two extreme climate events: a strong El Niño event in 1997–1998 and an atmospheric blocking event in 2005. Neither event had any detectable effect on the annual adult survival rate (± 95% confidence interval) of either Tufted Puffins (females: 0.96 ± 0.05; males: 0.91 ± 0.06) or Rhinoceros Auklets (0.86 ± 0.02 in both sexes). By contrast, the adult survival of female Cassin's Auklets was halved during both extreme climate events (from a background rate of 0.84 ± 0.05 to 0.44 ± 0.10), whereas survival of males was low, but constant through time (0.75 ± 0.03). Our results, combined with those of previous studies, suggest that the major ongoing decline in the Cassin's Auklet population on Triangle Island is driven by negative effects of climatic variation on both reproductive success and the survival of adult females. Climate change may result in continued Cassin's Auklet population declines at this and more southerly colonies. By contrast, the relative stability of Rhinoceros Auklet and Tufted Puffin populations is likely attributable to the resiliency of adult survival rates to climatic conditions.

Widespread decline of Neotropical migrant songbirds requires better understanding of the mechanisms driving juvenile mortality. We used mark—resight encounter histories of 3,990 banded fledglings (1998–2002) to test whether late breeding or large brood size negatively affected apparent annual and migration—wintering survival probability of juvenile Purple Martins (Progne subis). We estimated apparent annual juvenile survival (φ;_a, fledging to 1 year old) by resighting individuals as adults at regional breeding colonies and at a premigratory roost. We tested for carryover effects of fledge week and brood size on migration—wintering survival (φ;_m, premigratory roost to 1 year old) using two encounter occasions per season (premigratory roost, breeding colony) to partition annual survival into premigration versus migration—wintering survival. Annual survival (± SE) was 0.27 ± 0.027 and the best model (model weight = 0.93) included week of fledging and brood size, with survival probability decreasing with increasing fledge date and brood size. Apparent fledgling survival probability to premigratory roosts (φ;_r) was 0.87 ± 0.03 and migration—wintering juvenile survival (φ;_m) averaged 0.32 ± 0.04 (range: 0.25–0.46 among years). The best model included an effect of fledging week (model weight = 0.99) on migration—wintering survival but little support for brood size effects. Late-fledged young that survive to begin migration may incur higher subsequent mortality because of less foraging time and experience before migration. Telemetry of 15 fledglings in 2007 also revealed high premigration survival to the premigratory roost (0.73). Most (81%) juvenile mortality occurred after the onset of migration. Juvenile recruitment and population dynamics are likely closely linked to migration and wintering ground threats.

Accurate estimates of demographic rates are fundamental to understanding population dynamics and can provide insights into the ecology and conservation of a species. We used multistate mark—recapture models to estimate apparent annual survival, encounter probability, and life-stage transitions in Laysan Albatrosses (Phoebastria immutabilis) at Kaena Point, Hawaii, from 2003 to 2010. Four-state models of prebreeders, breeders, failed breeders, and skipped breeders overestimated survival by 1–3% and underestimated skipped breeding by 5–6%, but five-state models that included a state for unobserved skipped breeders performed better. Survival did not vary among years and was highest in prebreeders (mean ± SE = 0.996 ± 0.010) and lower in successful breeders (0.932 ± 0.023) than in failed breeders (0.963 ± 0.018), suggesting a cost to reproduction. Survival was similar in males and females among prebreeders, breeders, and failed breeders, but survival of males was lower among skipped breeders. Encounter probability was related to monitoring effort; more frequent visits and use of field-readable auxiliary bands and remote cameras resulted in higher encounter rates. With sufficient effort, all skipped breeders were observed at the colony even though they did not breed. Recruitment averaged 24% in females and 21% in males and varied among years. Breeding frequency averaged 0.807 ± 0.028 and varied among years. Successful breeders were more likely than failed breeders to skip the next breeding season. Estimates of all demographic rates except recruitment were similar to estimates for Laysan Albatrosses from Midway in the 1960s despite differences in methodology. This information can help measure population dynamics, breeding population sizes, population trends, and efficacy of conservation actions.

Brood size and hatching patterns in birds are widely believed to represent adaptations to food availability during the brood-rearing period. Experimental manipulations of brood size and hatching patterns have been widely employed to determine whether parents can raise larger or more synchronous broods, but concurrent manipulations of food abundance to test the supposed causal mechanism have been rare. I studied survival to fledging of 1,060 American Coot (Fulica americana) chicks from 99 broods for which brood size, hatching asynchrony, and food availability had been experimentally manipulated via inter-nest transfers of newly hatched young and provisioning of supplemental food. Survival of color-marked young was measured until 45 days posthatch using Cormack-Jolly-Seber mark—resighting models. Survival of offspring from unsupplemented broods declined linearly with experimental increases in brood size, and this decline was large enough to ameliorate any benefits to parents from larger broods. However, offspring survival was unaffected by experimental alterations of brood size in American Coots that received supplemental food, and supplemented pairs would have benefited from raising larger broods. Parents that produced larger clutches were more successful at raising large broods, consistent with the individual-optimization hypothesis. By contrast, observed hatching patterns were not optimal at promoting offspring survival, with both experimental increases and reductions in asynchrony leading to higher fledging rates. American Coot parents appeared to be adept at regulating food allocation among offspring with or without hatching asynchrony, which suggests that hatching patterns are most likely an artifact of selection for early onset of incubation.

Reproductive schedules of Dusky Flycatchers (Empidonax oberholseri) at Tioga Pass, in the central Sierra Nevada of California, varied considerably among years. Dates of earliest laying ranged from 29 May to 1 July and varied with snow depth, melt dates, and other factors associated with snowpack. A small apparent advance in laying date over the course of the study (0.52 days year-¹ over 15 years) was associated with extremes in winter snowpack and spring melt that were related to wet—dry cycles in the Sierra Nevada. Spring snowpack acted on reproductive timing through direct and indirect effects of temperature, melt schedule, and phenological changes in habitat availability. The influence of these variables on laying dates was greatest on the first females to lay (most in early June) and declined through mid-July, when breeding terminated. Clutch size and fledgling production varied between years of heavy and light snowpack as a direct consequence of delayed egg laying in years of heavy snow. In years of light snowpack, females that laid eggs by mid-June produced larger clutches, fledged more young per nest, and were more likely to renest if nest failure occurred. Only two females attempted two broods in a single season, and both were among the first to breed. Seasonal declines in sensitivity to local environmental conditions may constrain the ability of Dusky Flycatchers to adjust breeding schedules to match phenological delays produced by changes in winter temperature, precipitation, and snowpack, and may limit range expansion to areas with arid winters and earlier spring melt.

Despite mounting evidence of mercury accumulation in terrestrial ecosystems, few data exist on how environmental mercury exposure affects reproductive success in free-living songbirds. From 2007 through 2010, we monitored reproductive success of Carolina Wrens (Thryothorus ludovicianus) breeding along the forest floodplain of two mercury-contaminated rivers in Virginia. Using an information-theoretic approach, we found a 34% reduction in nesting success of Carolina Wrens on mercury-contaminated sites when compared with reference sites. Blood mercury concentration of the attending female was a strong predictor of nest success. Birds nesting on contaminated sites were 3× more likely to abandon their nests than birds on uncontaminated reference sites. We report a range of effects concentrations associated with various levels of reproductive impairment; for example, a 10% reduction in nest success corresponded with 0.7 µg g^-1 mercury in the blood, 2.4 µg g^-1 mercury in body feathers, 3.0 µg g^-1 mercury in tail feathers, and 0.11 µg g^-1 mercury in eggs. This is the first field study to document the effect of specific adult songbird blood mercury concentrations on breeding performance; our results show that free-living songbirds can suffer negative reproductive effects at relatively low mercury concentrations.

Variation in mating success among individuals is the basis for sexual selection and the evolution of elaborate secondary sexual traits. In socially monogamous species, variation in mating success is generally thought to be small, but a skewed adult sex ratio, differences in female fecundity, and extrapair fertilizations that arise from matings outside the social pair bond can increase variance in reproductive success. We investigated how these factors generate the opportunity for sexual selection in the socially monogamous White-crowned Sparrow (Zonotrichia leucophrys pugetensis). We found a 38% increase in the standardized actual variance in reproductive success compared to the apparent standardized variance of males because of the contribution of extrapair fertilizations to total reproductive success. However, partitioning variance into within-pair and extrapair components showed that the majority of variance in male reproductive success was attributable to within-pair success and a skewed adult sex ratio. Finally, reproductive success increased significantly with the number of mates in males but not in females, which suggests a stronger potential for sexual selection in males than in females in this population. Our results confirm that social mating success may increase the variance in reproductive success more than extrapair fertilizations in some monogamous species. Thus, the evolution of sexual ornaments may be influenced equally or more by the number of available mates and their fecundity than by extrapair matings.

The phylogeny of spiderhunters (Nectariniidae: Arachnothera) was reconstructed by comparing mitochondrial and nuclear DNA sequences of all currently recognized species and with broad geographic sampling of two particularly variable species complexes, the Little Spiderhunter (Arachnothera longirostra) and the streaky spiderhunters (A. modesta and A. affinis). It appears to be a relatively old group, whose diversification was not caused by recent sea-level changes. However, the modern, highly sympatric distribution of the large species in the Sunda lowlands was probably a result of dispersal via recent land bridges. Within the highly variable A. longirostra group, there are substantially diverged taxa in the Philippines that should be considered different species. Within the A. affinis—modesta complex, there are three distinct species and a closely related fourth, which describe a clear allopatric distribution: A. affinis in Java, A. modesta in the rest of the Sunda lowlands (except Sabah), A. magna in the Malayan highlands and mainland Southeast Asia, and A. everetti in the Bornean highlands and Sabah. Depending on whether mitochondrial or nuclear genes were compared, monophyly of the genus was disrupted by a single outgroup sunbird (Hypogramma hypogrammicum) or by all outgroup sunbirds included in the study. The discrepancy between nuclear and mitochondrial results is probably a case of deep coalescence and will require additional markers for resolution.