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Mercury (Hg) is a ubiquitous environmental contaminant that affects avian reproduction and condition, in both aquatic and terrestrial species. Because Hg binds strongly to the keratin of growing feathers, molt is an important avenue for Hg elimination. We investigated the rate of depuration of Hg from songbird blood and organs (brain, kidney, liver, muscle) as a function of molt. We exposed 2 species of captive songbirds, European starling (Sturnus vulgaris) and zebra finch (Taeniopygia guttata), to environmentally relevant dietary Hg (1.2-1.5 mg/kg wet wt) for extended periods of time and then allowed them to depurate on a Hg-free diet for 20 wk. Depuration occurred either while birds were regrowing new feathers or when there was little to no molt occurring. Both species quickly eliminated Hg from blood and reduced Hg concentrations in other tissues by more than 90% over 20 wk. The rate of depuration was more rapid than previously reported in the literature, but depuration in small-bodied songbirds has rarely been studied. Molting birds depurated Hg from their blood more rapidly than nonmolting birds. The effect of molt on Hg retention in other tissues was more difficult to resolve, because by the time we sampled organ tissue, depuration was nearly complete. Our results confirm that molting expedites depuration and raises mechanistic questions about how songbirds depurate Hg stored in their tissues. Environ Toxicol Chem 2017;36:3120-3126. © 2017 SETAC.

In migratory birds, the ability to depart wintering grounds at the appropriate time is an important determinant of fitness. Understanding the regulation of this timing will be essential for predicting whether timing of bird migration keeps up with global climate change. We examined whether the timing of the late-winter molt, in which white-throated sparrows (Zonotrichia albicollis) replace head and body feathers in advance of mating, may constrain the timing of northward migratory departure. In an observational study, we found a significant correlation between timing of molt and the date on which free-living male white-throated sparrows disappeared from our study site during migration. The following year, we tested whether experimentally manipulating molt date by advancing photoperiod during temporary captivity would subsequently advance disappearance date once the birds were released. Sparrows that were experimentally induced to molt early disappeared from the wintering site before controls. However, the captive control birds also molted and disappeared from the site earlier than free-living controls, suggesting that the diet during captivity had played a role. In the third winter we completed the study by advancing or delaying molt using only dietary manipulation. Together, these results show that the ability to molt early in spring is related to early disappearance from the wintering site. Early molt likely has carry-over effects on reproduction and the requirements of molt may prevent populations from adjusting migration timing in response to global climate change. J. Exp. Zool. 321A: 586–594, 2014. © 2014 Wiley Periodicals, Inc.

Mercury can disrupt the endocrine systems of mammals and fish, but little is known about its effects on avian hormones. The authors employed an experimental manipulation to show that methylmercury suppresses the stress-induced corticosterone response in birds, an effect previously unreported in the literature. Corticosterone regulates many normal metabolic processes, such as the maintenance of proper blood glucose levels during stressful daily fasting; an inability to increase corticosterone levels in response to stressors renders a bird less able to face a wide array of environmental challenges. The authors studied reproductively mature zebra finches that had been exposed to 0.0 µg/g, 0.3 µg/g, 0.6 µg/g, 1.2 µg/g, or 2.4 µg/g (wet wt) dietary methylmercury throughout their life (i.e., from the egg onward). In contrast to some field studies, the present study found no significant change in baseline plasma corticosterone concentrations attributable to chronic methylmercury exposure. However, a comparison between the baseline corticosterone levels and levels after 30 min of handling stress revealed that the ability of birds to mount a stress response was reduced with increasing blood total mercury concentration. These results are consistent with adrenal corticoid disruption caused by chronic mercury exposure and mirror a similar study on free-living nestling songbirds exposed to environmental mercury. Environ Toxicol Chem 2014;33:1072–1076. © 2014 SETAC

Although mercury (Hg) is a well-studied contaminant, knowledge about Hg accumulation in snakes is limited. The authors evaluated Hg bioaccumulation within and among four snake species (northern watersnakes, Nerodia sipedon; queen snakes, Regina septemvittata; common garter snakes, Thamnophis sirtalis; and rat snakes, Elaphe obsoleta [Pantherophis alleghaniensis]) from a contaminated site on the South River (Waynesboro, VA, USA) and two nearby reference sites. Total Hg (THg) concentrations in northern watersnake tail tissue at the contaminated site ranged from 2.25 to 13.84 mg/kg dry weight (mean: 4.85 ± 0.29), or 11 to 19 times higher than reference sites. Blood THg concentrations (0.03–7.04 mg/kg wet wt; mean: 2.24 ± 0.42) were strongly correlated with tail concentrations and were the highest yet reported in a snake species. Within watersnakes, nitrogen stable isotope values indicated ontogenetic trophic shifts that correlated with THg bioaccumulation, suggesting that diet plays a substantial role in Hg exposure. Female watersnakes had higher mean THg concentrations (5.67 ± 0.46 mg/kg) than males (4.93 ± 0.49 mg/kg), but no significant differences between sexes were observed after correcting for body size. Interspecific comparisons identified differences in THg concentrations among snake species, with more aquatic species (watersnakes and queen snakes) accumulating higher mean concentrations (5.60 ± 0.40 and 4.59 ± 0.38 mg/kg in tail tissue, respectively) than the more terrestrial species, garter snakes and rat snakes (1.28 ± 0.32 and 0.26 ± 0.09 mg/kg, respectively). The results of the present study warrant further investigation of potential adverse effects and will aid in prioritizing conservation efforts. Environ. Toxicol. Chem. 2013;32:1178–1186. © 2013 SETAC

Many bodies of water around the world are contaminated with mercury from historic industrial and mining activities or ongoing atmospheric deposition, resulting in numerous fish consumption advisories. However, concerns about mercury have only rarely led to consumption advisories on waterfowl. In contrast with fish, waterfowl frequently disperse long distances to new watersheds, so hunters and wildlife managers do not know whether waterfowl at a pristine site have spent time at a contaminated site elsewhere. We sampled tissue mercury concentrations of mallards (Anas platyrhynchos), wood ducks (Aix sponsa), and Canada geese (Branta canadensis) at a site contaminated with mercury, during the breeding and hunting seasons. We found that many mallards had bioaccumulated mercury to levels that had the potential to produce reproductive effects and exceeded consumption advisories set for fish by regulatory agencies, whereas this was true for only a few wood ducks and Canada geese. We also documented that mercury-exposed waterfowl from this contaminated site were harvested by hunters as far as 1,054 km away. Our results suggest the need for more proactive sampling of waterfowl for mercury, and likely other bioaccumulating contaminants, in order to allow hunters to make more informed choices about consumption of their harvest. © 2012 The Wildlife Society.

Mercury is a ubiquitous environmental pollutant that can negatively impact physiology and behavior of vertebrates, causing sub-lethal changes in condition and reducing fitness. Here we examine its effect on offspring sex ratio. Previous studies demonstrate the ability of environmental contaminants to skew sex ratios in wild populations toward the production of females, and research in humans has demonstrated a decrease in male births following mercury exposure. We therefore hypothesized that female birds inhabiting the floodplain of a mercury-contaminated river would produce broods more biased towards the production of females relative to birds from uncontaminated areas. We examined complete broods of three species: the aquatic-feeding belted kingfisher Megaceryle alcyon, the terrestrial-feeding eastern bluebird Sialia sialis, and the tree swallow Tachycineta bicolor, which feeds from both aquatic and terrestrial sources. Nestling sex ratios were shifted toward the production of females in all three species on mercury-contaminated sites when compared to uncontaminated reference sites. These results may be explained by endocrine disruption or the Trivers–Willard theory of sex allocation. Our study is the first to examine the impact of mercury on offspring sex ratios in birds, and therefore contributes to our understanding of the potential for this persistent biomagnifying contaminant to alter fitness and effective population size in wildlife.

Golf courses ostensibly offer green space in urbanized areas, but it is unclear how suitable these human-modified habitats are for wildlife populations. Golf courses are home to a variety of wildlife, but in particular they have been the focus of research on avian responses to urbanization. Although numerous reproductive and diversity studies have been conducted on birds of golf courses, no research exists on postfledging survival in this created landscape. In 2008 and 2009, we estimated survival of eastern bluebird (Sialia sialis) fledglings using radio telemetry on golf course and other developed sites in Williamsburg, Virginia. We used nest survival models in Program MARK set in an information theoretic framework to assess whether the golf course habitat predicted mortality along with other previously studied variables, such as fledgling age, year, site, body condition, fledging date, and transmitter weight. We found no evidence that inhabiting a golf course increased mortality during the fledgling period, but we did find support for both fledgling age and fledging date as predictors of survival. Mortality decreased for older fledglings and those that fledged later in the season. Cause-specific postfledging survival rates did not differ among sites. Fledgling bluebirds did, however, move into habitat that was significantly more forested and less grassy than their natal habitat. For managers of wildlife on golf courses and other urbanized sites, our study is the first to show that placing nest boxes in manicured habitat may attract birds to areas without suitable habitat for fledglings. 2011 The Wildlife Society.

Some species of birds store food, often hoarding several hundreds of seeds over a period of just a few weeks. Field and laboratory studies have demonstrated that food-storing species have an impressive memory and an enlarged region of the brain, the hippocampal region. Lesion experiments have shown that the hippocampus is important in accurate retrieval of stored food. Taken together, these results have led to the hypothesis that the enlarged hippocampus is associated with the memory requirements of retrieving stored food. In this review, we discuss four areas of study: comparative studies of the brain, comparative studies of behaviour, developmental plasticity and seasonal changes in food storing and the hippocampus.

We investigate the scenario in which some amount of higher quality habitat is destroyed and is then replaced by some undetermined amount of lower quality habitat. We examined how much low-quality habitat would need to be created to maintain the equilibrium population abundance in the entire geographic area. Using a source‐sink model, we find that (1) the number of hectares of created habitat per hectare of destroyed habitat must equal the ratio of the high-quality habitat’s productivity to the low-quality habitat’s productivity, however, (2) if the created habitat is a sink, then there is a threshold fraction of destroyed high-quality habitat below which the initial population abundance cannot be maintained through the creation of habitat. We illustrate these results using data on Redwinged Blackbirds (Agelaius phoeniceus) in two different regions where high-quality habitat is being replaced by or converted into lower quality habitat.

We assessed adult reproductive and nesting success, and developmental instability, survival, and condition of nestling eastern bluebirds (Sialia sialis) breeding in nestboxes on and off golf courses. With this information we tested hypotheses predicting that nestboxes on golf-course habitat provided poor nesting and chick-rearing environments due to pesticide pollution or other factors. Contrary to our prediction, nestboxes on golf courses received 28% more bluebird eggs and produced 17% more fledglings than nestboxes on nongolf sites. Individual nests on golf courses appeared to have slightly reduced probabilities of survival during laying and incubation, but we found no depression in the overall Mayfield survival probabilities. Surprisingly, nestling bluebirds raised in golf-course boxes exhibited 39% less fluctuating asymmetry of their tarsus bones, possibly an indicator that nestlings that survived to fledge had been under less stress during development. This may have resulted from stronger selection against asymmetrical nestlings on golf courses, or it may indicate that golf-course nestboxes provide higher-quality habitat for bluebirds. Our results suggest that for this bird species, nestboxes on the golf-course habitat we studied can provide high-quality rearing environments and may serve as population sources. This may not apply to other species, including most birds of conservation concern, which do not nest in protected artificial cavities or forage directly on turfgrass habitat.

We surveyed the avian communities of 87 golf courses during the 2002 breeding season to determine whether golf courses provided significant habitat for birds of conservation concern in Virginia. We defined birds of conservation concern as those with breeding priority scores ≥16 in our region, as classified by Partners in Flight (2002). The species richness and relative abundance of birds on golf courses varied widely, but in general, courses supported few birds of conservation concern. We found that a typical course had 3 times as many species of conservation concern as others, we compared the land cover on the richest and most depauperate golf courses in an attempt to explain what attracted birds of conservation concern to some courses but not others. Proportions of forested land within the golf-course boundaries and within 1.5 km of the center of the course were the best predictors of a course's conservation value. Our results suggested that 1) regional planners should not expect typical golf courses to provide more habitat for birds of conservation concern than alternative land uses, including residential or agricultural uses; and 2) designers of golf courses in this region can increase the conservation value of courses by increasing the amount of forested land on the course.

We sought to determine whether early arrival was a determinant of contest outcome in loosely organized, non-breeding flocks of birds. In White-throated Sparrows (Zonotrichia albicollis) arrival date during autumn migration, i.e. within-year prior residence, was a significant determinant of contest outcome for those birds that were not present on the study site in previous years. To determine whether the advantage of early arrival was due to prior residence per se, as opposed to some correlate of arrival date (e.g. condition), we experimentally delayed the arrival of 60 migrants. We found a significant effect of the delay: the outcome of contests between naturally arriving (control) birds and experimentally delayed birds was significantly related to the difference between the control bird's natural arrival date and the experimental bird's delayed arrival date. Thus, prior residence per se, and not some correlate of arrival date, had a significant effect on a naive individual's ability to win contests. Interestingly, arrival date had no effect on contest outcome among birds that had wintered on the site in previous years. Because a prior residence advantage accumulates in a time-dependent manner, our results suggest that fighting ability or perceived resource value increases with site familiarity. Thus, there may be selection on arrival date and site-faithfulness as behavioral strategies to increase access to resources.