47 research outputs found
Collateral damage: Anticoagulant rodenticides pose threats to California condors
Anticoagulant rodenticides (ARs) are widespread environmental contaminants that pose risks to scavenging birds because they routinely occur within their prey and can cause secondary poisoning. However, little is known about AR exposure in one of the rarest avian scavengers in the world, the California condor (Gymnogyps californianus). We assessed AR exposure in California condors and surrogate turkey vultures (Cathartes aura) to gauge potential hazard to a proposed future condor flock by determining how application rate and environmental factors influence exposure. Additionally, we examined whether ARs might be correlated with prolonged blood clotting time and potential mortality in condors. Only second-generation ARs (SGARs) were detected, and exposure was detected in all condor flocks. Liver AR residues were detected in 42% of the condors (27 of 65) and 93% of the turkey vultures (66 of 71). Although concentrations were generally low (\u3c10 ng/g ww), 48% of the California condors and 64% of the turkey vultures exposed to ARs exceeded the 5% probability of exhibiting signs of toxicosis (\u3e20 ng/g ww), and 10% and 13% exceeded the 20% probability of exhibiting signs toxicosis (\u3e80 ng/g ww). There was evidence of prolonged blood clotting time in 16% of the free-flying condors. For condors, there was a relationship between the interaction of AR exposure index (legal use across regions where condors existed) and precipitation, and the probability of detecting ARs in liver. Exposure to ARs may complicate recovery efforts of condor populations within their current range and in the soon to be established northern California experimental population. Continued monitoring of AR exposure using plasma blood clotting assays and residue analysis would allow for an improved understanding of their hazard to condors, particularly if paired with recent movement data that could elucidate exposure sources on the landscape occupied by this endangered species
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Social Cues and Environmental Conditions Influence Foraging Flight Distances of Breeding Wood Storks (Mycteria americana)
The influence of both environmental conditions and social cues on the distance flown to foraging
sites was examined for breeding Wood Storks (Mycteria americana) in the Florida Everglades, USA. Adult Wood
Storks (n = 73) were followed in a small plane from their nesting colony to their foraging locations during the time
when adult Wood Storks were incubating and feeding chicks. On average, foraging sites were close to the nesting
colony (mean = 9.6 km ± 1.1), and in shallow water (mean = 9.9 cm ± 0.7) that was receding at a moderate rate
(-0.36 cm/day ± 0.13). Wood Storks landed at foraging sites already occupied by other white wading birds 99% of
the time, with a mean flock size of 64 ± 14 birds. Model selection identified flock size and water recession rate as
the most important variables that influenced Wood Stork foraging flight distances. Distances flown to foraging sites
increased with increasing flock sizes and decreased with increasing recession rates (increasing by 39% and decreasing by 18% across the observed range of data, respectively) while accounting for colony location and water depths.
These findings are particularly important because they demonstrate that both social and environmental factors
play critical roles in the foraging site selection process Wood Storks use during the breeding season. Further, these
results in part can be linked to management activities because at least in the case of water recession rates, managers
can actively influence recession rates across much of the Everglades landscap
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Stability of Avian Fecal Corticosterone Metabolite Levels in Frozen Avian Feces
Fecal corticosterone metabolites are commonly used in avian ecology as a measure of response to stress. Recent research on
mammals suggested that the manner in which samples are stored could be critical to alleviating any storage handling bias. Cross-reacting metabolites can increase glucocorticoid metabolites even after samples are frozen and, thus, result in an overestimation of hormone levels as the time increases between when samples were collected and when levels are measured. We examined effects of sample storage time on fecal corticosterone metabolites for 2 avian species across 165 days. We observed no change in fecal corticosterone metabolites across the sampling periods in either fulvous whistling-ducks (Dendrocygna bicolor) or white ibis (Eudocimus albas). Results suggest that avian fecal corticosterone metabolite levels do not change when samples are frozen for long periods of time and that there were no differences in the response between the 2 species we compared. This study demonstrated that avian fecal corticosterone samples are accurate even after freezing and, thus, studies that seek to address conservation questions may rely on these data. Studies of additional bird species are needed to generalize our findings to other avian taxa
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Potential for successful population establishment of the nonindigenous sacred ibis in the Florida Everglades
The nonindigenous sacred ibis (Threskiornis aethiopicus) was first discovered breeding in the
Florida Everglades in 2005 in the Arthur R. Marshall
Loxahatchee National Wildlife Refuge. Prior to this,
sacred ibises were seen periodically throughout South
Florida since the mid 1990s, with occasional confirmed breeding occurrences in Miami-Dade and Palm
Beach counties. We used a logistic regression model
developed by Allen (Biol Invasions 8:491–500, 2006)
to predict the probability of successful establishment
of sacred ibis in the Florida Everglades ecosystem.
Empirical data collected from several sacred ibis nests
and chicks were used to validate those findings. The
probability of successful establishment was estimated
to be 73%. The physiological condition of nestlings
suggested that this species was able to fledge chicks in
good condition, thus adding to the potential to increase
their breeding population. Exponential population
growth rates and expanding distribution of the nonindigenous sacred ibis in France demonstrate this
species’ potential for becoming invasive in Florida.
We suggest that the most prudent and effective
management strategy is eradication of the few pioneering individuals that are nesting in the Everglades
as well as the urban source population
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Avian Radio-transmitter Harness Wear and Failure
Although investigators have compared radio-transmitter attachment devices and their likelihood of failure before the end of a study, few have directly evaluated the harness materials and fastening methods that are to be shed by a bird after the research period is over. We compared the likelihood of effective detachment after transmitter life of four harness materials (7-mm- and 9-mm-wide polyester rib- bon tape and polyester-coated rubber elastic) and three fastening methods (polyester thread, cotton thread, and Gorilla Super Glue™) using dummy transmitters exposed to the elements for >1.5 years. Both polyester ribbon and polyester-coated rubber elastic materials resulted in similar physical wear and remained intact for longer than a typical field seasonal, but fastening harnesses using Gorilla Super Glue™ resulted in the earliest and most consistent harness failure. Polyester ribbon material and glue fastening resulted in the earliest failure; mean failure time for 7-mm- and 9-mm-wide polyester ribbon tape with glue fastening was 408 days ±30 SE, and 249 days ± 29 SE, respectively. Failure times for both 7-mm- and 9-mm-wide polyester- coated rubber elastic and Gorilla Super Glue™ fastening treatments were in excess
of one year (438 days ± 14 SE and 438 days ± 13 SE, respectively). All harnesses with sewn thread fastening treatments lasted a minimum mean of 456 days, and i the case of both 7-mm-wide polyester ribbon and polyester-coated rubber elastic neither treatment ever failed over the period of study. Results suggest that using Gorilla Super Glue™ as a fastener maximized the likelihood of eventual harness failure, whereas transmitters fastened via sewing showed minimal signs of wear an were unlikely to be shed by a bird during a period of time less than two years. Additional experimental studies are warranted to examine alternative harness material types, fastening methods, and harness styles to maximize the potential of successful radio transmitter shedding
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The Role of Stress Proteins in the Study of Allostatic Overload in Birds: Use and Applicability to Current Studies in Avian Ecology
Stress proteins offer a measure of stress in birds at the cellular level that are an
alternative to the glucocorticoids. Stress proteins are not biased by handling stress, the
increase in stress proteins lasts longer than with other measures (e.g., corticosterone),
and, therefore, they may be a more appropriate measure of long-term or chronic stress.
However, caution should be practiced when using stress proteins because the level of
stress needed to elicit a response may be higher than with corticosterone. Stress
proteins have only recently been used to measure the response to competition, food
limitation, growth, and parasitism in birds. In other taxa, the stress proteins have been
used to measure genetic stress, temperature, toxins, UV radiation, and physical activity.
Stress proteins increase the options available to avian ecologists for understanding how
avian species respond to changes in the environment
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Multiple Nest-Tending Behavior in an Adult Female White Ibis
A non-breeding adult female White Ibis (Eudocimus albus) was observed tending multiple nests during
the 2006 wading bird breeding season in the Florida Everglades. This is the first known case of adult multiple
nest-attending breeding behavior documented for the Ciconiiformes order