Hunting and habitat loss represent an increasingly common anthropogenic impact. Available evidence suggests that defaunation is typically differential: medium/large mammals are most affected while small rodents are less affected, or even favored. In heavily impacted areas, such as Los Tuxtlas, the residual mammalian fauna is dominated by small rodents. We tested the expectation that if small rodents will preferentially attack small‐seeded species, large‐seeded species may escape predation in the absence of medium/large seed predators and that this may affect germination and, possibly, recruitment. Experiments with caged rodents (Heteromys desmarestianus) under laboratory conditions showed a preference for smaller seeds. A field experiment involving seeds of contrasting size showed that small, unprotected seeds experienced a predation risk 30‐times larger than protected seeds, while the effect of protection was not significant for large seeds. These patterns of predation led to significant differences in germination: protected small‐seeded species had a fourfold greater germination than unprotected small‐seeded species, while germination was not significantly different between exposed and protected large seeds. The observed contrasts in germination suggest that under heavy defaunation, small‐seeded species are likely to be penalized by the overabundance of small rodents, while large‐seeded species escape predation. Our results are consistent with the observation of dense seedling carpets dominated by large‐seeded species in the understory of Los Tuxtlas. We speculate that the patterns we uncovered may explain, at least partly, the impoverished diversity of the understory vegetation that characterizes heavily defaunated understories and that this has the potential to affect forest regeneration.

Lead poisoning occurs worldwide in populations of predatory birds, but exposure rates and population impacts are known only from regional studies. We evaluated the lead exposure of 1210 bald and golden eagles from 38 US states across North America, including 620 live eagles. We detected unexpectedly high frequencies of lead poisoning of eagles, both chronic (46 to 47% of bald and golden eagles, as measured in bone) and acute (27 to 33% of bald eagles and 7 to 35% of golden eagles, as measured in liver, blood, and feathers). Frequency of lead poisoning was influenced by age and, for bald eagles, by region and season. Continent-wide demographic modeling suggests that poisoning at this level suppresses population growth rates for bald eagles by 3.8% (95% confidence interval: 2.5%, 5.4%) and for golden eagles by 0.8% (0.7%, 0.9%). Lead poisoning is an underappreciated but important constraint on continent-wide populations of these iconic protected species.

Lead poisoning of scavenging birds is a global issue. However, the drivers of lead exposure of avian scavengers have been understood from the perspective of individual species, not cross‐taxa assemblages. We analyzed blood (n = 285) and liver (n = 226) lead concentrations of 5 facultative (American crows [Corvus brachyrhynchos], bald eagles [Haliaeetus leucocephalus], golden eagles [Aquila chrysaetos], red‐shouldered hawks [Buteo lineatus], and red‐tailed hawks [Buteo jamaicensis]) and 2 obligate (black vultures [Coragyps atratus] and turkey vultures [Cathartes aura] avian scavenger species to identify lead exposure patterns. Species and age were significant (α < 0.05) predictors of blood lead exposure of facultative scavengers; species, but not age, was a significant predictor of their liver lead exposure. We detected temporal variations in lead concentrations of facultative scavengers (blood: median = 4.41 µg/dL in spring and summer vs 13.08 µg/dL in autumn and winter; p = <0.001; liver: 0.32 ppm in spring and summer vs median = 4.25 ppm in autumn and winter; p = <0.001). At the species level, we detected between‐period differences in blood lead concentrations of bald eagles (p = 0.01) and red‐shouldered hawks during the winter (p = 0.001). During summer, obligate scavengers had higher liver lead concentrations than did facultative scavengers (median = 1.76 ppm vs 0.22 ppm; p = <0.001). These data suggest that the feeding ecology of avian scavengers is a determinant of the degree to which they are lead exposed, and they highlight the importance of dietary and behavioral variation in determining lead exposure. Environ Toxicol Chem 2020;39:882–892. © 2020 SETAC

Illegal killing of nongame wildlife is a global yet poorly documented problem. The prevalence and ecological consequences of illegal killing are often underestimated or completely unknown. We review the practice of legal recreational shooting and present data gathered from telemetry, surveys, and observations on its association with illegal killing of wildlife (birds and snakes) within conservation areas in Idaho, USA. In total, 33% of telemetered long-billed curlews (Numenius americanus) and 59% of other bird carcasses found with known cause of death (or 32% of total) were illegally shot. Analysis of spatial distributions of illegal and legal shooting is consistent with birds being shot illegally in the course of otherwise legal recreational shooting, but snakes being intentionally sought out and targeted elsewhere, in locations where they congregate. Preliminary public surveys indicate that most recreational shooters find abhorrent the practice of illegal killing of wildlife. Viewed through this lens, our data may imply only a small fraction of recreational shooters is responsible for this activity. This study highlights a poorly known conservation problem that could have broad implications for some species and populations of wildlife.

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Sources of lead exposure of many bird species are poorly understood. We analyzed blood lead concentrations from osprey (n = 244; Pandion haliaetus) and bald eagles (n = 68; Haliaeetus leucocephalus) and documented potential sources of lead they may encounter. Adult bald eagles had higher blood lead concentrations than did adult osprey. However, blood lead concentrations of nestlings were similar for both species. Although 62% of osprey had detectable lead concentrations (x¯ = 1.99 ± 4.02 μg/dL, mean ± standard deviation [SD]), there was no difference in the detection frequency or lead concentrations between osprey adults and nestlings. Likewise, we found no differences in the detection frequency or lead concentrations in osprey adults and nestlings from high‐ and low‐salinity areas. Of the bald eagle samples tested, 55% had detectable lead levels (x¯ = 6.23 ± 10.74 μg/dL). Adult bald eagles had more detectable and higher lead concentrations than did nestlings or pre‐adults. Among environmental samples, paint had the highest lead concentrations, followed by sediment, blue catfish (Ictalurus furcatus), and gizzard shad (Dorosoma cepedianum). There was no correlation between blood lead concentrations of osprey adults and their offspring. Our results indicate that, in the Chesapeake Bay region of Maryland and Virginia (USA), there are multiple sources by which piscivorous raptors may be exposed to lead. Environ Toxicol Chem 2019;38:862–871. © Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

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