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Agricultural waste grains are significant for providing nutrients for wintering waterfowl in California. Rice and corn comprise 56% of their nutrient needs in the Central Valley and changes to agricultural practices, such as postharvest treatments, could impact these food resources. Currently, limited data exist on how postharvest treatments in rice and corn fields affect the abundance of waste grain, yet these data are essential to determine the carrying capacity of agricultural lands for wintering waterfowl. To address this knowledge gap, we estimated the abundance of waste grain (kg/ha) using dry field transects, dry field soil cores, and flooded field (wet) soil cores. In 2016 and 2017, we sampled 84 rice fields and 47 corn fields. Our results indicate that the abundance of waste rice varied significantly among postharvest treatments. Fields that received no postharvest treatment (stubble left standing; no incorporation of straw) had the greatest amounts of waste rice, whereas fields that were disced, disced and rolled, or burned provided the least amount of waste rice. The average abundance of waste rice across all postharvest treatments was 320 kg/ha in dry fields (arithmetic mean; geometric mean = 228 kg/ha; soil core samples). Estimates of waste rice in flooded fields averaged only 169 kg/ha (geometric mean 98 kg/ha; soil core samples), significantly lower than in the same fields prior to flooding. Variation in the abundance of waste corn was greater than that of waste rice. Fields that did not receive any postharvest incorporation had the greatest abundance of waste corn, 233 kg/ha on average (arithmetic mean; geometric mean = 72 kg/ha), whereas fields that were incorporated (disced or disced and rolled) contained significantly lower abundance of waste corn, averaging 50–60 kg/ha (arithmetic mean; geometric mean = 5–10 kg/ha). The average, across all postharvest treatments, was 159 kg/ha of waste corn (geometric mean = 25–34 kg/ha). Our results suggest that postharvest practices affect the abundance of waste grain in rice and corn fields; changes in these practices could impact food availability for wintering waterfowl. Our results also indicate that the method of sampling waste grain can influence estimates of residual grain abundance.

Environmental contamination is widespread and can negatively impact wildlife health. Some contaminants, including heavy metals, have immunosuppressive effects, but prior studies have rarely measured contamination and disease simultaneously, which limits our understanding of how contaminants and pathogens interact to influence wildlife health. Here, we measured mercury concentrations, influenza infection, influenza antibodies and body condition in 749 individuals from 11 species of wild ducks overwintering in California. We found that the odds of prior influenza infection increased more than fivefold across the observed range of blood mercury concentrations, while accounting for species, age, sex and date. Influenza infection prevalence was also higher in species with higher average mercury concentrations. We detected no relationship between influenza infection and body fat content. This positive relationship between influenza prevalence and mercury concentrations in migratory waterfowl suggests that immunotoxic effects of mercury contamination could promote the spread of avian influenza along migratory flyways, especially if influenza has minimal effects on bird health and mobility. More generally, these results show that the effects of environmental contamination could extend beyond the geographical area of contamination itself by altering the prevalence of infectious diseases in highly mobile hosts.

The black-headed duck (Heteronetta atricapilla) of South America is the only known avian obligate brood parasite with precocial offspring. In Argentina, it relies on two species of coots as primary hosts, which typically reject 35–65% of duck eggs. We show that environmentally driven increases in host egg rejection behavior lead to substantial reductions in the reproductive success of the brood parasite. Episodes of flooding and vegetation loss caused dramatic shifts in host egg-rejection behavior, resulting in rejection (85–95%) of almost all duck eggs. Coots respond to fluctuating water levels by building up their nest, raising their own eggs but leaving duck eggs behind. Coots can apparently recognize parasitic duck eggs, but large-scale rejection is triggered only when hosts must actively make a choice. We use a simple population model to illustrate the unique demographic challenges that black-headed ducks face with their parasitic lifestyle and to explore the potential impact of environmentally induced escalation of egg rejection. Using the best available estimates for key vital rates, we show that obligate parasitism may provide a demographically precarious existence for black-headed ducks, even under benign environmental conditions. Environmentally mediated increases in egg rejection rates by hosts could impact significantly the viability of this enigmatic species of brood parasitic duck. Our results demonstrate that egg rejection rates are not fixed properties of host populations or individuals but are strongly influenced by social and ecological factors. Shifts in these environmental drivers could have important and unforeseen demographic consequences for brood parasites.

Research into plumage ornaments and plumage signals of individual state has focused primarily on males, while variation among females has received far less attention. White patches of plumage around the eye (eye patches) are a female-specific plumage trait in the wood duck, Aix sponsa, a sexually dimorphic species of cavity-nesting waterfowl in North America. We observed considerable variation in the size of these patches among females and sought to evaluate whether this trait might indicate individual quality (‘quality cost hypothesis’) or the influence of stress or past investment (‘stress indicator hypothesis’). We measured the area of female eye patches in five populations of wood ducks during three breeding seasons and examined whether eye patch area varied in relation to age, nest success, future breeding, activity and/or body condition. Eye patch area was highly variable among individuals but repeatable within individuals, varied across years and study sites, correlated strongly with age but weakly with an index of body condition. For individuals greater than 4 years of age, eye patch area was negatively related to the likelihood of returning to breed in the following year. Eye patch size was positively correlated with nest initiation date and this was more pronounced in older birds, but there was no correlation of eye patch area with clutch size or hatch success. Our results suggest that this unique female-specific plumage trait reflects individual age and future reproduction potential. Larger eye patches in older females may be an indicator of senescence or terminal investment, and we hypothesize that eye patch size could act as a signal of individual state or social status in this species.

Obligate brood parasites depend entirely on other species to raise their offspring. Most avian obligate brood parasites have altricial offspring that require enormous amounts of posthatching parental care, and the large fecundity boost that comes with complete emancipation from parental care likely played a role in the independent evolution of obligate parasitism in several altricial lineages. The evolution of obligate parasitism in the black-headed duck, however, is puzzling because its self-feeding precocial offspring should not constrain parental fecundity of a potential brood parasite in the way that altricial offspring do. We used an experimental nest predation study to test the idea that high nest predation rates played a role in the evolution of brood parasitism in this enigmatic duck. Experimental duck eggs in untended nests suffered massive rapid predation, while eggs in tended nests of the three main hosts, all aggressive nest defenders, had very high success, illustrating the benefits of parasitizing these 'bodyguard' hosts.

Interspecific hybridization is recognized as an important process in the evolutionary dynamics of both speciation and the reversal of speciation. However, our understanding of the spatial and temporal patterns of hybridization that erode versus promote species boundaries is incomplete. The endangered, endemic koloa maoli (or Hawaiian duck, Anas wyvilliana) is thought to be threatened with genetic extinction through ongoing hybridization with an introduced congener, the feral mallard (A. platyrhynchos). We investigated spatial and temporal variation in hybrid prevalence in populations throughout the main Hawaiian Islands, using genomic data to characterize population structure of koloa, quantify the extent of hybridization, and compare hybrid proportions over time. To accomplish this, we genotyped 3,308 double-digest restriction-site-associated DNA (ddRAD) loci in 425 putative koloa, mallards, and hybrids from populations across the main Hawaiian Islands. We found that despite a population decline in the last century, koloa genetic diversity is high. There were few hybrids on the island of Kaua'i, home to the largest population of koloa. By contrast, we report that sampled populations outside of Kaua'i can now be characterized as hybrid swarms, in that all individuals sampled were of mixed koloa × mallard ancestry. Further, there is some evidence that these swarms are stable over time. These findings demonstrate spatial variation in the extent and consequences of interspecific hybridization, and highlight how islands or island-like systems with small population sizes may be especially prone to genetic extinction when met with a congener that is not reproductively isolated.

Modern genetic parentage methods reveal that alternative reproductive strategies are common in both males and females. Under ideal conditions, genetic methods accurately connect the parents to offspring produced by extra-pair matings or conspecific brood parasitism. However, some breeding systems and sampling scenarios present significant complications for accurate parentage assignment. We used simulated genetic pedigrees to assess the reliability of parentage assignment for a series of challenging sampling regimes that reflect realistic conditions for many brood-parasitic birds: absence of genetic samples from sires, absence of samples from brood parasites and female kin-structured populations. Using 18 microsatellite markers and empirical allele frequencies from two populations of a conspecific brood parasite, the wood duck (Aix sponsa), we simulated brood parasitism and determined maternity using two widely used programs, cervus and colony. Errors in assignment were generally modest for most sampling scenarios but differed by program: cervus suffered from false assignment of parasitic offspring, whereas colony sometimes failed to assign offspring to their known mothers. Notably, colony was able to accurately infer unsampled parents. Reducing the number of markers (nine loci rather than 18) caused the assignment error to slightly worsen with colony but balloon with cervus. One potential error with important biological implications was rare in all cases-few nesting females were incorrectly excluded as the mother of their own offspring, an error that could falsely indicate brood parasitism. We consider the implications of our findings for both a retrospective assessment of previous studies and suggestions for best practices for future studies.

Birds may use a variety of cues to select a nest site, including external information on habitat structure and nest site characteristics, or they may rely instead on social information obtained directly or indirectly from the actions of conspecifics. We used an experimental manipulation to determine the extent to which a California population of the wood duck (Aix sponsa) used social information gleaned from visual cues inside nest boxes that might indicate the quality or occupancy of that site. Over two nesting seasons, we manipulated the contents of newly installed boxes to simulate one of three states: (1) presence of wood duck eggs, indicating current use of a nest site; (2) presence of down and shell membranes, indicating a previously successful nest; and (3) control nests with fresh shavings indicating an unused box. In addition, we measured habitat characteristics of the area surrounding each box to assess the use of external, non-social information about each nest site. We found no evidence that females laid eggs preferentially, or that conspecific brood parasitism was more likely to occur, in any of the treatments. In contrast, nest site use and reproductive traits of wood ducks did vary with vegetation cover, and orientation and distance of the box from water. Our results suggest that personal information, not social information, influences initial nest site selection decisions when females are unfamiliar with a site. Social cues likely become increasingly important once nest sites develop their own history, and a population becomes well established. In selecting a nest site, birds may use many types of information, including habitat characteristics, their own previous breeding experience, or social cues inadvertently provided by other individuals of the same or different species. We examined information use in a Californian population of wood ducks by experimentally manipulating the visual cues within nest boxes and found that females did not use internal box cues to direct their nesting behaviors, appearing to rely on key habitat characteristics instead. These results contrast with previous studies of this system, suggesting that females may change the cues they use depending on their prior experience with a particular area. In the nest site selection literature, there appears to be a divergence between research on passerines versus waterfowl, and we advocate unifying these perspectives.

As global climate changes, there is increasing need to understand how changes in the frequencies of environmental variability affect populations. Age-structured populations have recently been shown to filter specific frequencies of environmental variability, favoring generational frequencies, and very low frequencies, a phenomenon known as cohort resonance. However, there has been little exploration of how changes in the spectra of environmental signals will affect the stability and persistence of age-structured populations. To examine this issue, we analyzed a likely example to show how changes in the frequency of an influential climate phenomenon, the El Nino-Southern Oscillation (ENSO), could affect a marine bird population. We used a density-dependent, age-structured population model to calculate the transfer function (i.e., the frequency-dependent sensitivity) of Brandt’s cormorant (Phalacrocorax penicillatus), a representative marine bird species known to be influenced by ENSO. We then assessed how the population would be affected by ENSO forcing that was doubled and halved in frequency. The transfer function indicated this population is most sensitive to variance at low frequencies, but does not exhibit the sensitivity to generational frequencies (cohort resonance) observed in shorter-lived species. Doubling the frequency of ENSO unexpectedly resulted in higher mean adult population abundance, lower variance, and lower probability of extinction, compared to forcing with the historical or reduced ENSO frequency. Our results illustrate how long-lived species with environmentally driven variability in recruitment, including many species of marine birds and fish, may respond in counterintuitive ways to anticipated changes in environmental variability.

Changes in climate, vegetation, and land use are recognized as important drivers of changes in the distribution and abundance of wildlife. However, the behavioral and demographic mechanisms through which these changes affect populations have received less attention. Identifying these mechanisms is an important component of predicting the impacts of increasing environmental change. We used 30 yr of nest monitoring data at a study site where White-crowned Sparrow (Zonotrichia leucophrys) breeding density declined 85% to evaluate factors influencing habitat selection and reproductive success. Rapid secondary plant succession occurred at our study site, but the rate of change was faster in some areas than others. White-crowned Sparrows exhibited strong patterns of nest site selection, preferring open shrub vegetation and avoiding forest. As a result, many parts of the study area that were used for nesting early in the study period were no longer occupied by the end of the study period. Over the cours...

The North American Waterfowl Management Plan (NAWMP) has established a model for wildlife conservation planning over the last 3 decades. Management at a continental scale, leveraged funding, regional partnerships, and a strong science basis have been notable features. Periodic updates to the NAWMP occurred since implementation in 1986; however, a fundamental revision was accomplished in 2012 after extensive stakeholder engagement. An explicit fundamental goal for waterfowl conservation supporters was added in 2012, complementing existing goals for sustainable populations and sufficient habitat found in previous updates. We present a synopsis of progress toward implementation of the 2012 NAWMP and challenge the waterfowl management community to continue with meaningful steps toward achieving NAWMP goals. Adding goals and objectives for supporters increases potential relevance of NAWMP; however, it also presents a level of complexity that was not entirely anticipated. Additionally, the 2012 NAWMP recognized that traditional support from waterfowl hunters alone will not be sufficient to support waterfowl conservation in the future. Simultaneous consideration of multiple objectives, although implicit before, now is a specific focus for habitat and harvest management affecting hunters and other users of the waterfowl resource. The waterfowl management community is faced with revisiting objectives and management actions related to harvest regulations, landscape priorities, habitat conservation, and public engagement to garner broader support. These persistent management challenges are tangible and relevant candidates for greater integration. Ultimately, the structures and processes supporting waterfowl management also will need to be reconsidered. © 2017 The Wildlife Society.

Waterfowl monitoring, research, regulation, and adaptive planning are leading the way in supporting science-informed wildlife management. However, increasing societal demands on natural resources have created a greater need for adaptable and successful linkages between waterfowl science and management. We presented a special session at the 2016 North American Duck Symposium, Annapolis, Maryland, USA on the successes and challenges of linking research and management in waterfowl conservation, and we summarize those thoughts in this commentary. North American waterfowl management includes a diversity of actions including management of harvest and habitat. Decisions for waterfowl management are structured using decision analysis by incorporating stakeholder values into formal objectives, identifying research relevant to objectives, integrating scientific knowledge, and choosing an optimal strategy with respect to objectives. Recently, the consideration of the value of information has been proposed as a means to evaluate the utility of research designed to meet objectives. Despite these advances, the ability to conduct waterfowl research with direct management application may be increasingly difficult in research institutions for several reasons including reduced funding for applied research and the lower perceived value of applied versus theoretical research by some university academics. In addition, coordination between researchers and managers may be logistically constrained, and communication may be ineffective between the 2 groups. Strengthening these links would help develop stronger and more coordinated approaches for the conservation of waterfowl and the wetlands upon which they depend. © 2017 The Wildlife Society.

One of the fundamental decisions foragers face is how long an individual should remain in a given foraging location. Typical approaches to modeling this decision are based on the marginal value theorem. However, direct application of this theory would require omniscience regarding food availability. Even with complete knowledge of the environment, foraging with intraspecific competition requires resolution of simultaneous circular dependencies. In response to these issues in application, a number of approximating algorithms have been proposed, but it remains to be seen whether these algorithms are effective given a large number of foragers with realistic characteristics. We implemented several algorithms approximating marginal value foraging in a large-scale avian foraging model and compared the results. We found that a novel reinforcement-learning algorithm that includes cost of travel is the most effective algorithm that most closely approximates marginal value foraging theory and recreates depletion patterns observed in empirical studies.

Recent declines in sea duck popula- tions have highlighted the need for additional basic research across the life cycle of these long-distance migratory birds. A lack of basic ecological information on Surf Scoters (Melan- itta perspicillata), including the linkage between wintering and breeding areas and description of their nesting areas, is a major impediment to determining factors contributing to their decline. We marked 415 Surf Scoters with radio and sat- ellite transmitters at four wintering areas along the Pacific coast to describe their breeding syn- chrony, sympatry, philopatry, and nesting areas selection in the northern boreal forest (NBF). Their primary breeding region was located in the western NBF centered on the Great Slave and Great Bear Lakes in the Northwest Ter- ritories, Canada, and their mean settling date (31 May) was remarkably synchronous (0.9 d). We developed a nearest-neighbor statistic C to examine nesting areas of individuals from dif- ferent wintering areas and found that they were not clustered (C 0.031, P 0.15), but nests of eight individuals found in successive years were highly philopatric and within 1.2 0.2 km of their previous locations. Finally, we compared nesting areas and random locations with step- wise selection in a second-order Akaike Infor- mation Criterion (AIC c ) analysis to identify the best models. Key landscape features included distance to snowline, elevation gradient, num- bers of lakes, distance to treeline, and latitude. A nonparametric classification and regression tree (CART) showed that nesting areas were in an arc of habitat near snowline (218 km), in lower elevation gradients (14 m/km), and in areas with 3-6 lakes within 2 2 km. Climate change is predicted to have the greatest effects on more northern ecosystems, and NBF species like Surf Scoters with relatively inflexible breeding ecol- ogy may be adversely affected if they are unable to adapt quickly to rapidly changing conditions.

Studies of avian nest success often focus on examining influences of variation in environmental and seasonal factors. However, in-depth evaluations can also incorporate variation in individual incubation behaviour to further advance our understanding of avian reproductive ecology. We examined these relationships in colonially nesting Black-crowned Night-Herons Nycticorax nycticorax using intensive video-monitoring methods to quantify incubation behaviours. We modelled nest survival as a function of both extrinsic factors and incubation behaviours over a 3-year period (2010–12) on Alcatraz Island, USA. Model-averaged parameter estimates indicated that nest survival increased as a function of greater incubation constancy (% of time spent incubating eggs within a 24-h period), and average daily precipitation throughout the nesting stage. Common Ravens Corvus corax are the only known nest predator of Night-Herons on Alcatraz Island, as on many other coastal Pacific islands. We also investigated the effects of heterospecific nesting of California Gulls Larus californicus and Western Gulls Larus occidentalis in a mixed-species colony with Night-Herons, based on nesting proximity data collected over a 2-year period (2011–12). This second analysis indicated that, in addition to incubation behaviours, nesting heterospecifics are an important factor for explaining variation in Night-Heron nest survival. However, contrary to our original expectation, we found that Night-Herons experienced increased nest survival with increasing distance from gull colony boundaries. These results may apply to other areas with multiple colonial nesting species and similar predator communities and climatic patterns.

Parental incubation behavior largely influences nest survival, a critical demographic process in avian population dynamics, and behaviors vary across species with different life history breeding strategies. Although research has identified nest survival advantages of mixing colonies, behavioral mechanisms that might explain these effects is largely lacking. We examined parental incubation behavior using video-monitoring techniques on Alcatraz Island, California, of black-crowned night-heron Nycticorax nycticorax (hereinafter, night-heron) in a mixed-species colony with California gulls Larus californicus and western gulls L. occidentalis. We first quantified general nesting behaviors (i.e. incubation constancy, and nest attendance), and a suite of specific nesting behaviors (i.e. inactivity, vigilance, preening, and nest maintenance) with respect to six different daily time periods. We employed linear mixed effects models to investigate environmental and temporal factors as sources of variation in incubation constancy and nest attendance using 211 nest days across three nesting seasons (2010–2012). We found incubation constancy (percent of time on the eggs) and nest attendance (percent of time at the nest) were lower for nests that were located < 3 m from one or more gull nest, which indirectly supports the predator protection hypothesis, whereby heterospecifics provide protection allowing more time for foraging and other self-maintenance activities. To our knowledge, this is the first empirical evidence of the influence of one nesting species on the incubation behavior of another. We also identified distinct differences between incubation constancy and nest attentiveness, indicating that these biparental incubating species do not share similar energetic constraints as those that are observed for uniparental species. Additionally, we found that variation in incubation behavior was a function of temperature and precipitation, where the strength of these effects was dependent on the time of day. Overall, these findings strengthen our understanding of incubation behavior and nest ecology of a colonial-nesting species.

Edge effects on nesting success have been documented in breeding birds in a variety of contexts, but there is still uncertainty in how edge type and spatial scale determine the magnitude and detectability of edge effects. Habitat edges are often viewed as predator corridors that surround or penetrate core habitat and increase the risk of predation for nearby nests. We studied the effects of three different types of potential predator corridors (main perimeter roads, field boundaries, and ATV trails within fields) on waterfowl nest survival in California. We measured the distance from duck nests to the nearest edge of each type, and used distance as a covariate in a logistic exposure analysis of nest survival. We found only weak evidence for edge effects due to predation. The best supported model of nest survival included all three distance categories, and while all coefficient estimates were positive (indicating that survival increased with distance from edge), 85% coefficient confidence intervals approac...

Speciation is regarded primarily as a bifurcation from an ancestral species into two distinct taxonomic units, but gene flow can create complex signals of phylogenetic relationships, especially among different loci. We evaluated several hypotheses that could account for phylogenetic discord between mitochondrial DNA (mtDNA) and nuclear DNA (nuDNA) within Hawaiian duck (Anas wyvilliana), including stochastic lineage sorting, mtDNA capture and widespread genomic introgression. Our results best support the hypothesis that the contemporary Hawaiian duck is descended from an ancient hybridization event between the mallard (Anas platyrhynchos) and Laysan duck (Anas laysanensis). Whereas mtDNA clearly shows a sister relationship between Hawaiian duck and mallard, nuDNA is consistent with a genetic mosaic with nearly equal contributions from Laysan duck and mallard. In addition, coalescent analyses suggest that gene flow from either mallard or Laysan duck, depending on the predefined tree topology, is necessary to explain contemporary genetic diversity in Hawaiian ducks, and these estimates are more consistent with ancient, rather than contemporary, hybridization. Time since divergence estimates suggest that the genetic admixture event occurred around the Pleistocene-Holocene boundary, which is further supported by circumstantial evidence from the Hawaiian subfossil record. Although the extent of reproductive isolation from either putative parental taxon is not currently known, these species are phenotypically, genetically and ecologically different, and they meet primary criteria used in avian taxonomy for species designation. Thus, the available data are consistent with an admixed origin and support the hypothesis that the Hawaiian duck may represent a young hybrid species.

A study of a cuckoo species that usually shows cooperative nesting behaviour, but sometimes cheats at parenthood by laying eggs in others’ nests, reveals the benefits that have shaped the evolution of this parasitic tactic. How a cheating tactic evolved in cooperatively breeding cuckoos.

The impacts of the El Nino Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) on the ecology of the northeast Pacific are well known. However, recently there has been a shift in the dominance of El Nino events from the eastern Pacific (canonical) El Nino, to the central Pacific (Modoki) El Nino, concurrent with a strengthening of the North Pacific Gyre Oscillation (NPGO). Our examination of ocean conditions and seabird reproductive success in central California shows that the way these physical factors affect the pelagic food web is also changing. Reproduction of Cassin's auklet Ptycoramphus aleuticus and Brandt's cormorant Pha- lacrocorax penicillatus, species that forage at different trophic levels, responded primarily to ENSO variability from the 1970s to the 1990s. By 1995, however, NPGO had become the dominant variable determining Cassin's auklet reproductive success. Eventually, NPGO also became corre- lated with Brandt's cormorant success but in the opposite direction to Cassin's auklet. Thus, during the mid-1990s, the correlation between the reproduction of these 2 species weakened and even- tually became inversely correlated. This shift from coherent reproduction, presumably bottom-up driven, to an inverse relationship between the 2 species suggests that the structure of the local marine food web changed as the equatorial forcing changed. This non-stationary response of sea- birds to physical forcing is cause for concern since predictions of future ecosystem productivity and effects of climate change rely on the assumption that a species' response to environmental conditions is consistent over time.

Wide-ranging marine birds rely on multiple habitats for wintering, breeding, and migrating, and their conservation may be dependent on protecting networks of key areas. Urbanized estuaries are critical wintering and stopover areas for many declining sea ducks in North America; however, conservation measures within estuaries are difficult to establish given lack of knowledge about habitat use by these species and the variety of competing human interests. We applied hierarchical modeling to evaluate resource selection of sea ducks (surf scoters, Melanitta perspicillata) wintering in San Francisco Bay, California, USA, a large and highly urbanized estuary. We also examined their distribution, home range, and movements with respect to key habitat features and regions within the estuary. Herring roe was the strongest predictor of bird locations; however, eelgrass, water depth and salinity were also highly-ranked, with sea ducks using deeper areas of higher salinity associated with herring roe and eelgrass presence during mid-winter. Sea ducks were also strongly associated with ferry routes, suggesting these areas may contain resources that are too important to avoid and emphasizing the need to better understand water traffic effects. Movements and home range size differed between males and females in early winter but became more similar in late winter. Birds traveled farther and used several sub-bays in early winter compared to mid-winter when herring roe availability peaked in the Central Bay. Our findings identified key environmental variables, highlighted core use areas, and documented critical periods for consideration when developing conservation plans for sea ducks in urbanized estuaries.

Density-dependent population regulation is observed in many taxa, and understanding the mechanisms that generate density dependence is especially important for the conservation of heavily-managed species. In one such system, North American waterfowl, density dependence is often observed at continental scales, and nest predation has long been implicated as a key factor driving this pattern. However, despite extensive research on this topic, it remains unclear if and how nest density influences predation rates. Part of this confusion may have arisen because previous studies have studied density-dependent predation at relatively large spatial and temporal scales. Because the spatial distribution of nests changes throughout the season, which potentially influences predator behavior, nest survival may vary through time at relatively small spatial scales. As such, density-dependent nest predation might be more detectable at a spatially- and temporally-refined scale and this may provide new insights into nest site selection and predator foraging behavior. Here, we used three years of data on nest survival of two species of waterfowl, mallards and gadwall, to more fully explore the relationship between local nest clustering and nest survival. Throughout the season, we found that the distribution of nests was consistently clustered at small spatial scales (∼50–400 m), especially for mallard nests, and that this pattern was robust to yearly variation in nest density and the intensity of predation. We demonstrated further that local nest clustering had positive fitness consequences – nests with closer nearest neighbors were more likely to be successful, a result that is counter to the general assumption that nest predation rates increase with nest density.

Few studies have quantitatively projected changes in demography in response to climate change, yet doing so can provide important insights into the processes that may lead to population declines and changes in species distributions. Using a long-term mark-recapture data set, we examined the influence of multiple direct and indirect effects of weather on adult and juvenile survival for a population of Song Sparrows (Melospiza melodia) in California. We found evidence for a positive, direct effect of winter temperature on adult survival, and a positive, indirect effect of prior rainy season precipitation on juvenile survival, which was consistent with an effect of precipitation on food availability during the breeding season. We used these relationships, and climate projections of significantly warmer and slightly drier winter weather by the year 2100, to project a significant increase in mean adult survival (12-17%) and a slight decrease in mean juvenile survival (4-6%) under the B1 and A2 climate change scenarios. Together with results from previous studies on seasonal fecundity and postfledging survival in this population, we integrated these results in a population model and projected increases in the population growth rate under both climate change scenarios. Our results underscore the importance of considering multiple, direct, and indirect effects of weather throughout the annual cycle, as well as differences in the responses of each life stage to climate change. Projecting demographic responses to climate change can identify not only how populations will be affected by climate change but also indicate the demographic process(es) and specific mechanisms that may be responsible. This information can, in turn, inform climate change adaptation plans, help prioritize future research, and identify where limited conservation resources will be most effectively and efficiently spent.

The Black-headed Duck (Heteronetta atricapilla) is unique among obligate avian brood parasites because its highly precocial young leave the host nest shortly after hatching and impose no post-hatching costs on their hosts. Accordingly, we might expect host-parasite interactions in this parasite to differ strikingly from those of other brood parasites — they should be able to parasitize a broad diversity of hosts and be highly successful with these hosts. We conducted the second detailed study ever completed on patterns of host use in Black-headed Ducks. Based on four years of system- atic searches of multiple marshes in Argentina, we found no evidence that Black-headed Ducks ever had nests of their own, confirming the previous conclusion that Black-headed Ducks are, indeed, true obligate brood parasites. Contrary to expectation, however, we found that Heteronetta is ecologically dependent on a surprisingly small number of host species — two species of coots and a gull — all of which are widespread and locally abundant species. Other species are numerically less important as hosts either because they are relatively uncommon, or because they are avoided by the ducks. In the three main host species, hatching success of the duck eggs was also surprisingly low (≤ 28%), based on expectations for a precocial parasite, mainly due to host rejection or neglect. Mortality due to predation on host nests, in contrast, was low for all three primary host species. These observations corroborate Weller's observations from a single-year study. The combination of a dependence on few primary hosts and a relatively low hatching success are inconsistent with some previous hypotheses for the evolution of obligate brood parasitism in Heteronetta. Instead, our observations, and those of Weller, suggest that intense nest predation in Austral wetlands, coupled with an abundance of a few common host species that aggressively defend their nests and obtain high nest success rates, may have been an important factor in the evolution of obligate parasitism in this enigmatic duck.

Conspecific brood parasitism (CBP) resembles interspecific brood parasitism, except that parasitic females lay eggs in the nests of conspecifics. CBP is a female alternative reproductive behavior, and understanding its evolution requires a life history approach. We review studies that investigate life history aspects of CBP. One or more life history components have been examined for 56 species, 49 of which are relevant to the adaptive basis of CBP. Various approaches have been used to detect CBP, but there is increasing reliance on molecular methods. Molecular methods are not always foolproof, and false exclusions are incorrectly interpreted as CBP; future studies should employ multiple lines of evidence. Two types of parasites have been documented, often in the same species: non-nesting females without their own nest in a given year and nesting females that lay some of their eggs parasitically. There is no evidence for lifelong professional brood parasites; non-nesting females apparently adopt parasitism to make the best of a bad job, although we lack a clear understanding of the specific constraints that prevent these females from nesting or the costs that make restraint a better option. Parasitism by nesting females is common, surprisingly so in the precocial waterfowl, and is only rarely associated with breeding interruption or nest loss. Nesting females appear to use parasitism to enhance their reproductive output, but for most species it is not clear why females don’t lay the additional eggs in their own nest. A full understanding of this form of brood parasitism will require a better understanding of clutch size constraints.

We evaluated the contribution of interspecific interactions, intraspecific processes, and environmental forcing to variation in speciessa' abundance in a habitat undergoing rapid successional change. We applied a Bayesian hierarchical approach to a 29‐yr time series of territory density of seven landbird species at a site in coastal California where secondary plant succession has occurred. We found that interspecific interactions were the least important driver in our system, explaining between 0% and 5% of variation. The combined effects of vegetation and rainfall variation explained 6% to 30% of variation in species trends. Intraspecific processes explained between 0% and 39% of variation. Between 27% and 90% of variation was attributed to unexplained variation. Our results demonstrate that in the system studied, interspecific interactions among landbirds are relatively unimportant. These results suggest that in some cases it may be valid to model projections of individual populations to predict community responses to future conditions; however, this conclusion should be interpreted with caution because interspecific interactions in our community did not include novel interactions that could result from distributional shifts in species ranges.

We studied the association between space sharing and kinship in a solitary rodent, the dusky-footed woodrat (Neotoma fuscipes). Genetic relatedness was inversely correlated with geographic distance for female woodrats but not for males, a pattern consistent with female philopatry and male dispersal. However, some female neighbors were unrelated, suggesting the possibility of female dispersal. Relatedness of female dyads was positively correlated with overlap of their home ranges and core areas, indicating that females were more likely to share space with relatives, whereas males showed no correlation between relatedness and the sharing of either home ranges or core areas. However, some females that shared space were not close relatives, and some closely related males shared space. House sharing was exhibited both by close relatives and by distantly related or unrelated woodrats, and was not correlated with relatedness. The kin structuring we describe likely resulted from a pattern of female philopatry and male dispersal, but also may have resulted from kin-directed behaviors by females.

We developed and evaluated the performance of a metapopulation model enabling managers to examine, for the first time, the consequences of alternative management strategies involving habitat conditions and hunting on both harvest opportunity and carrying capacity (i.e., equilibrium population size in the absence of harvest) for migratory waterfowl at a continental scale. Our focus is on the northern pintail (Anas acuta; hereafter, pintail), which serves as a useful model species to examine the potential for integrating waterfowl harvest and habitat management in North America. We developed submodel structure capturing important processes for pintail populations during breeding, fall migration, winter, and spring migration while encompassing spatial structure representing three core breeding areas and two core nonbreeding areas. A number of continental-scale predictions from our baseline parameterization (e.g., carrying capacity of 5.5 million, equilibrium population size of 2.9 million and harvest rate of 12% at maximum sustained yield [MSY]) were within 10% of those from the pintail harvest strategy under current use by the U.S. Fish and Wildlife Service. To begin investigating the interaction of harvest and habitat management, we examined equilibrium population conditions for pintail at the continental scale across a range of harvest rates while perturbing model parameters to represent: (1) a 10% increase in breeding habitat quality in the Prairie Pothole population (PR); and (2) a 10% increase in nonbreeding habitat quantity along in the Gulf Coast (GC). Based on our model and analysis, a greater increase in carrying capacity and sustainable harvest was seen when increasing a proxy for habitat quality in the Prairie Pothole population. This finding and underlying assumptions must be critically evaluated, however, before specific management recommendations can be made. To make such recommendations, we require (1) extended, refined submodels with additional parameters linking influences of habitat management and environmental conditions to key life-history parameters; (2) a formal sensitivity analysis of the revised model; (3) an integrated population model that incorporates empirical data for estimating key vital rates; and (4) cost estimates for changing these additional parameters through habitat management efforts. We foresee great utility in using an integrated modeling approach to predict habitat and harvest management influences on continental-scale population responses while explicitly considering putative effects of climate change. Such a model could be readily adapted for management of many habitat-limited species.

When nest predation levels are very high or very low, the absolute range of observable nest success is constrained (a floor/ceiling effect), and it may be more difficult to detect density-dependent nest predation. Density-dependent nest predation may be more detectable in years with moderate predation rates, simply because there can be a greater absolute difference in nest success between sites. To test this, we replicated a predation experiment 10 years after the original study, using both natural and artificial nests, comparing a year when overall rates of nest predation were high (2000) to a year with moderate nest predation (2010). We found no evidence for density-dependent predation on artificial nests in either year, indicating that nest predation is not density-dependent at the spatial scale of our experimental replicates (1-ha patches). Using nearest-neighbor distances as a measure of nest dispersion, we also found little evidence for "dispersion-dependent" predation on artificial nests. However, when we tested for dispersion-dependent predation using natural nests, we found that nest survival increased with shorter nearest-neighbor distances, and that neighboring nests were more likely to share the same nest fate than non-adjacent nests. Thus, at small spatial scales, density-dependence appears to operate in the opposite direction as predicted: closer nearest neighbors are more likely to be successful. We suggest that local nest dispersion, rather than larger-scale measures of nest density per se, may play a more important role in density-dependent nest predation.

Conspecific brood parasites lay their eggs in the nests of other females in the same population, leading to a fascinating array of possible ‘games’ among parasites and their hosts (Davies 2000; Lyon & Eadie 2008). Almost 30 years ago, Andersson & Eriksson (1982) first suggested that perhaps this form of parasitism was not what it seemed—indeed, perhaps it was not parasitism at all!Andersson & Eriksson (1982) observed that conspecific brood parasitism (CBP) was disproportionally common in waterfowl (Anatidae), a group of birds for which natal philopatry is female-biased rather than the more usual avian pattern of male-biased natal philopatry. Accordingly, Andersson (1984) reasoned (and demonstrated in an elegantly simple model) that relatedness among females might facilitate the evolution of CBP—prodding us to reconsider it as a kin-selected and possibly cooperative breeding system rather than a parasitic interaction. The idea was much cited but rarely tested empirically until recently—a number of new studies, empowered with a battery of molecular techniques, have now put Andersson’s hypothesis to the test (Table 1). The results are tantalizing, but also somewhat conflicting. Several studies, focusing on waterfowl, have found clear evidence that hosts and parasites are often related (Andersson & Ahlund 2000; Roy Nielsen et al. 2006; Andersson & Waldeck 2007; Waldeck et al. 2008; Jaatinen et al. 2009; Tiedemann et al. 2011). However, this is not always the case (Semel & Sherman 2001; Anderholm et al. 2009; and see Poysa 2004). In a new study reported in this issue of Molecular Ecology, Jaatinen et al. (2011a) provide yet another twist to this story that might explain not only why such variable results have been obtained, but also suggests that the games between parasites and their hosts—and the role of kinship in these games—may be even more complex than Andersson (1984) imagined. Indeed, the role of kinship in CBP may be very much one of relative degree! Table 1. A summary of recent studies that have tested for evidence of relatedness between hosts and parasites in avian conspecific brood parasites Species Evidence of host–parasite relatedness? Evidence of local kin structure? Relatedness > expected spatially r Host–Parasite r Population Costs or benefits measured? Method Source CBP, conspecific brood parasitism. Common moorhen (Gallinula chloropus) Mixed Some parasitism between relatives Yes Limited dispersal of both sexes No Not greater than expected — — No (but discussed) DNA minisatellite fingerprints McRae & Burke (1996) Common goldeneye (Bucephala clangula) Yes Number of parasitic eggs also increased with relatedness Not tested; high female philopatry Yes 0.132 — No Protein fingerprints 50 bands Andersson & Ahlund (2000) Wood duck (Aix sponsa) No (parasites avoid relatives) Not tested; high female philopatry No Significantly less likely to parasitize local kin — — No Behavioural observation Semel & Sherman (2001) Common goldeneye (B. clangula) No Relatedness unlikely to explain CBP Not tested Not measured — — Yes Field measures Poysa (2004) Wood duck (A. sponsa) Yes (for primary parasites) No Yes (for primary parasites) 0.04 (all) 0.11 (primary parasites) 0.01–0.02 No 5 microsatellites Roy Nielsen et al. (2006) Common eider (Mollissima somateria) Yes No Yes 0.122 (all) 0.126, 0.162 (two colonies) −0.065 (neighbours 1–10 m) No Protein fingerprints 30 bands Andersson & Waldeck (2007) Common eider (M. somateria) Yes Number of parasitic eggs also increased with relatedness Yes Relatedness declined with distance Possibly Host–parasite relatedness > close neighbours in 1 of 2 analyses 0.18–0.21 0.09 (neighbours) No Protein fingerprints 51 bands Waldeck et al. (2008) Barnacle goose (Branta llucopsis) No Weak Females within 40 m more closely related No 0.04 −0.0008 No Protein fingerprints 28 bands Anderholm et al. (2009) Barrow’s goldeneye (Bucephala islandica) Yes Number of parasitic eggs increased with relatedness Weak Slight decline in relatedness with distance No Host–parasite relatedness similar to neighbours 0.08 −0.015 0.11 (neighbours) No 19 microsatellites Jaatinen et al. 2009 Common eider (M. somateria) Yes Interaction with parasite status No Yes 0.39 (mean) 0.48, 0.28 (different sites) 0.0 No 7 microsatellites Tiedemann et al. (2011)

We evaluated predation on nests and methods to detect predators using a combination of infrared cameras and plasticine eggs at nests of American avocets (Recurvirostra americana) and black- necked stilts (Himantopus mexicanus) in Don Edwards San Francisco Bay National Wildlife Refuge, San Mateo and Santa Clara counties, California. Each technique indicated that predation was prevalent; 59% of monitored nests were depredated. Most identifiable predation (n 5 49) was caused by mammals (71%) and rates of predation were similar on avocets and stilts. Raccoons (Procyon lotor) and striped skunks (Mephitis mephitis) each accounted for 16% of predations, whereas gray foxes (Urocyon cinereoargenteus) and avian predators each accounted for 14%. Mammalian predation was mainly nocturnal (mean time, 0051 h 6 5 h 36 min), whereas most avian predation was in late afternoon (mean time, 1800 h 6 1 h 26 min). Nests with cameras and plasticine eggs were 1.6 times more likel yt o be predated than nests where only cameras were used in monitoring. Cameras were associated with lower abandonment of nests and provided definitive identification of predators.

Mammal species characterized by highly fluctuating populations often maintain genetic diversity in response to frequent demographic bottlenecks, suggesting the ameliorating influence of life history and behavioral factors. Immigration in particular is expected to promote genetic recovery and is hypothesized to be the most likely process maintaining genetic diversity in fluctuating mammal populations. Most demographic bottlenecks have been inferred retrospectively, and direct analysis of a natural population before, during, and after a bottleneck is rare. Using a continuous 10-year dataset detailing the complete demographic and genetic history of a fluctuating population of golden-mantled ground squirrels (Spermophilus lateralis), we analyzed the genetic consequences of a 4-year demographic bottleneck that reduced the population to seven adult squirrels, and we evaluated the potential “rescue effect” of immigration. Analysis of six microsatellite loci revealed that, while a decline in allelic richness was observed during the bottleneck, there was no observed excess of heterozygosity, a characteristic bottleneck signature, and no evidence for heterozygote deficiency during the recovery phase. In addition, we found no evidence for inbreeding depression during or after the bottleneck. By identifying immigrants and analyzing their demographic and genetic contributions, we found that immigration promoted demographic recovery and countered the genetic effects of the bottleneck, especially the loss of allelic richness. Within 3 years both population size and genetic variation had recovered to pre-bottleneck levels, supporting the role of immigration in maintaining genetic variation during bottleneck events in fluctuating populations. Our analyses revealed considerable variation among analytical techniques in their ability to detect genetic bottlenecks, suggesting that caution is warranted when evaluating bottleneck events based on one technique.

Conspecific brood parasitism (CBP) occurs in over 200 species of birds. Efforts to detect CBP have relied on either observational criteria, or more recently, on molecular methods. While molecular approaches are powerful, they are expensive, time consuming and may prove prohibitive for studies requiring estimates of CBP over large spatial and temporal scales involving hundreds of nests. We evaluated a series of observational methods that have been applied in previous studies to detect CBP, using two species of cavity-nesting ducks, the Barrow's goldeneye Bucephala islandica and common goldeneye B. clangula, as test species. We first describe a method based on differences in egg morphology and find it to be a reliable method to detect CBP in both species in British Columbia, Canada. The application of recursive partitioning analysis was especially effective in classifying parasitized and non-parasitized nests using differences in egg morphology. We then evaluated five additional observational criteria that have been used previously in several studies to detect CBP in birds. We show that considerable redundancy exists among all criteria, as expected, but no single method is effective at detecting all suspected cases of CBP. Subsets of criteria (2 or more eggs/d, eggs laid 2 or more days after incubation, and clutch sizes exceeding 12 eggs) were successful, in combination, in detecting 75% of parasitized nests for goldeneyes. Finally, we suggest that ecological and evolutionary analyses of the dynamics of CBP will require estimates of the frequency of the parasitic tactic in the population (rather than just the proportion of parasitized nests) and we provide a simple method to obtain such an estimate. Although our data are specific to goldeneyes, the techniques we used should have broad application to other studies of CBP.

Female Northern Pintails (Anas acuta) were sampled in California's three main Central Valley wintering regions (Sacramento Valley, Suisun Marsh, San Joaquin Valley) during September–October before most regional movements occur and microsatellite and mitochondrial DNA were analyzed to examine population structure and relatedness. Despite reportedly high rates of early-fall pairing and regional fidelity, both sets of markers indicated that there was little overall genetic structuring by region. Pintails from Suisun Marsh did exhibit higher relatedness among individuals and capture groups than in the Sacramento or San Joaquin Valleys, likely reflecting a sample comprised of a greater proportion of local breeders. The lack of genetic structuring among regions indicates that a high degree of movement and interchange occurs among pintails wintering in the Central Valley. Thus, although maintaining the existing distribution of pintails among Central Valley regions is important for other reasons, it doe...