A DNA test to sex most birds.

Model Selection And Multimodel Inference

Global increases in environmental noise levels – arising from expansion of human populations, transportation networks, and resource extraction – have catalysed a recent surge of research into the effects of noise on wildlife. Synthesising a coherent understanding of the biological consequences of noise from this literature is challenging. Taxonomic groups vary in auditory capabilities. A wide range of noise sources and exposure levels occur, and many kinds of biological responses have been observed, ranging from individual behaviours to changes in ecological communities. Also, noise is one of several environmental effects generated by human activities, so researchers must contend with potentially confounding explanations for biological responses. Nonetheless, it is clear that noise presents diverse threats to species and ecosystems and salient patterns are emerging to help inform future natural resource-management decisions. We conducted a systematic and standardised review of the scientific literature published from 1990 to 2013 on the effects of anthropogenic noise on wildlife, including both terrestrial and aquatic studies. Research to date has concentrated predominantly on European and North American species that rely on vocal communication, with approximately two-thirds of the data set focussing on songbirds and marine mammals. The majority of studies documented effects from noise, including altered vocal behaviour to mitigate masking, reduced abundance in noisy habitats, changes in vigilance and foraging behaviour, and impacts on individual fitness and the structure of ecological communities. This literature survey shows that terrestrial wildlife responses begin at noise levels of approximately 40 dBA, and 20% of papers documented impacts below 50 dBA. Our analysis highlights the utility of existing scientific information concerning the effects of anthropogenic noise on wildlife for predicting potential outcomes of noise exposure and implementing meaningful mitigation measures. Future research directions that would support more comprehensive predictions regarding the magnitude and severity of noise impacts include: broadening taxonomic and geographical scope, exploring interacting stressors, conducting larger-scale studies, testing mitigation approaches, standardising reporting of acoustic metrics, and assessing the biological response to noise-source removal or mitigation. The broad volume of existing information concerning the effects of anthropogenic noise on wildlife offers a valuable resource to assist scientists, industry, and natural-resource managers in predicting potential outcomes of noise exposure.

https://www.wildliferesearch.co.uk/Wildlife_Research/Publications_files/A%20synthesis%20of%20two%20decades%20of%20research%20documenting%20the%20effects%20of%20noise%20on%20wildlife%20Shannon.pdf

A synthesis of two decades of research documenting the effects of noise on wildlife

Note for ornithologists who plan to use drones or model aircraft to study or monitor birds in the United States: The Airborne Hunting Act may prohibit the use of drones to study or monitor wildlife in the United States, except for state and federal agency personnel or their agents (i.e., someone who is working under contract to or in collaboration with state or federal agencies) or under a permit issued by one of those agencies. However, the USFWS will not issue such permits and only four states allow the use of drones for research. The Ornithological Council has asked the Office of the Solicitor of the Department of the Interior to determine if the use of SUA to study wildlife is subject to the AHA. Anticipating that the Solicitor will determine that the AHA does apply, The Ornithological Council has also filed a petition for rulemaking asking the USFWS to issue permits. Read more on this situation on OrnithologyExchange.org.

/pdf/guidelines-to-the-use-of-wild-birds-in-research-nt8fr62toe.pdf

Guidelines to the use of wild birds in research

Summary
Many aspects of the social environment affect hypothalamic-pituitary-adrenal (HPA) axis function and increase circulating glucocorticoid concentrations. In this review, we examine the relationships between the social environment and the function of the HPA axis in vertebrates.
First, we explore the effects of the social environment on glucocorticoid secretion in territorial (primarily non-social) species, with an emphasis on the effects of variation in population density, as modified by environmental factors such as predation risk and food availability. In general, high population density or frequent territorial intrusions are associated with increased glucocorticoid secretion in a wide range of taxa, including mammals, birds, fish and reptiles, although there is considerable variability across species.
Second, we consider the effects of social interactions and dominance rank on glucocorticoid secretion in social species, mostly in birds and mammals. We review studies that have detected an association between social status and glucocorticoid levels – sometimes with higher glucocorticoid levels in low-ranking individuals, and sometimes with higher glucocorticoid levels in dominant individuals. The relationship between dominance and glucocorticoid levels varies among species, populations and years, in a manner that depends on the stability of the social hierarchy, environmental conditions, the type of breeding system, and the manner in which high rank is obtained and maintained.
Finally, we discuss the concept of allostasis and consider interactions between social effects and other environmental factors, noting that there is relatively little research on these interactions to date. For both non-social and social species, we identify priorities of future research. These priorities include more complete descriptions of HPA function that move beyond measurements of basal glucocorticoid concentrations (which will generally require field experiments), to studies that examine organizational effects of social stressors, that directly test the relationship between HPA function and fitness, and that examine how glucocorticoid responses affect population dynamics.
Although several lines of evidence suggest that glucocorticoid responses can affect the fitness of individuals and therefore can alter the dynamics of populations, the effect of glucocorticoid responses on population dynamics remains essentially unstudied.

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The ecology of stress: effects of the social environment

A long-standing question in animal communication is whether signals reveal intrinsic properties of the signaller or extrinsic properties of its environment. Alarm calls, one of the most conspicuous components of antipredator behaviour, intuitively would appear to reflect internal states of the signaller. Pioneering research in primates and fowl, however, demonstrated that signallers may produce unique alarm calls during encounters with different types of predators, suggesting that signallers through selective production of alarm calls provide to conspecific receivers information about predators in the environment. In this article, we review evidence for such ‘functional reference’ in the alarm calls of birds based on explicit tests of two criteria proposed in Macedonia & Evans’ (Ethology 93, 1993, 177) influential conceptual framework: (1) that unique alarm calls are given to specific predator categories, and (2) that alarm calls isolated from contextual information elicit antipredator responses from receivers similar to those produced during actual predator encounters. Despite the importance of research on birds in development of the conceptual framework and the ubiquity of alarm calls in birds, evidence for functionally referential alarm calls in this clade is limited to six species. In these species, alarm calls are associated with the type of predator encountered as well as variation in hunting behaviour; with defence of reproductive effort in addition to predators of adults; with age-related changes in predation risk; and with strong fitness benefits. Our review likely underestimates the occurrence of functional reference in avian alarm calls, as incomplete application and testing of the conceptual framework has limited our understanding. Throughout, therefore, we suggest avian taxa for future studies, as well as additional questions and experimental approaches that would strengthen our understanding of the meaning of functional reference in avian alarm calls.

On the Meaning of Alarm Calls: A Review of Functional Reference in Avian Alarm Calling

Field observations and model-presentation experiments have shown that yellow warblers (Dendroica petechia) produce “seet” calls preferentially in response to brood-parasitic brown-headed cowbirds (Molothrus ater). In this study, we investigated whether seet calls are functionally referential alarm calls denoting cowbirds by determining whether female warblers responded appropriately to seet calls in the absence of a cowbird, whether alarm calling by warblers varied with response urgency, and how warblers in a population allopatric with cowbirds responded to cowbird and avian predator models and seet playbacks. As a control, we presented “chip” calls, which are elicited by nest predators as well as by non-threatening intruders, but are not strongly associated with cowbirds. Yellow warblers responded differently to playbacks of seet than chip calls. To seet playbacks, almost 60% of females gave seet calls and rushed to sit in their nests, responses typically elicited by cowbirds, whereas these responses were given infrequently in response to chip calls. Yellow warblers seet called equally in situations that simulated low, medium and high risk of parasitism, which suggests that these calls did not vary with response urgency. In a population allopatric with cowbirds, seet calls were rarely produced in response to cowbird or avian nest predator models and never to seet playbacks. These results suggest that seet calls are functionally referential signals denoting cowbirds and that cowbird parasitism was a strong selective pressure in the evolution of functional referentiality in the seet call of yellow warblers.

Functional reference in an alarm signal given during nest defence: seet calls of yellow warblers denote brood-parasitic brown-headed cowbirds

Blood sampling is often critical for answering a variety of questions about wild birds. However, it is important to assess the impacts, if any, of blood collection on wild birds. Here, we examined the effects of blood sampling on adults or nestlings in three species of free-living birds. First, we examined the effects of blood collection on annual survival and reproductive success in adult buff-breasted wrens Thryothorus leucotis in Panama. In adult wrens, blood collection from the brachial vein during the breeding season had no effect on annual survival or reproductive success. Second, we examined whether blood collection influenced mass gain in developing smooth-billed anis Crotophaga ani in Puerto Rico. In developing anis, blood collection from the femoral or jugular veins had no effect on mass gain of nestlings. Third, in developing European starlings Sturnus vulgaris in British Columbia, Canada, blood collection from the brachial vein had no effect of body condition. Blood collection from the jugular vein had a transient effect on body condition during the first week post-hatch, but this effect disappeared by the second week of age. Lastly, we present an extensive up-to-date review of the literature on the effects of blood collection on free-living avian species. Taken together, these data show that blood collection has no major negative effects on developing or adult birds in the wild.

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Effects of blood collection on wild birds: an update

Yellow warblers (Dendroica petechia) were exposed to taxidermic mounts of a brood parasite (brown-headed cowbird, Molothrus ater), avian nest predator (common grackle, Quiscalus quiscula) and control (fox sparrow, Passerella iliaca) during their laying and nestling stages to determine whether nest owners distinguish between the threats of brood parasitism and predation. Yellow warblers responded more intensely to the cowbird at the laying stage, performing two unique behaviours (seet calling and nest-protection behaviour) in response to this threat. By contrast, yellow warbler responses to the grackle were greater at the nestling stage, consisting largely of alarm calls (chip, metallic chip and warble calls). The sparrow model infrequently elicited aggressive behaviour from nest owners at either stage. These responses support the hypothesis that yellow warblers discriminate between threats of brood parasitism and nest predation. Yellow warblers may perform specific behaviours to cowbirds because defensive behaviours used against predators may be incompatible with cowbird deterrence. Female nest owners responded more frequently than males at the laying stage, and more intensely than males at both nesting stages. The distance that females and males approached the models and several aggressive behaviours were positively correlated. The greater responsiveness of females may be because they dominate their mates and because females are more experienced with intruders near the nest.

Nest Defence By Yellow Warblers: Recognition of a Brood Parasite and an Avian Nest Predator

Testosterone promotes aggressive behaviour in male vertebrates during the breeding season, but the importance of testosterone in female aggression remains unclear. Testosterone has both beneficial and detrimental effects on behaviour and physiology, prompting the hypothesis that selection favours an association between aggression and testosterone only in certain contexts in which intense or persistent aggression may be beneficial. We tested this hypothesis in a year-round territorial female buff-breasted wrens (Thryothorus leucotis), by exposing free-living females to experimental intrusions in different social (either single female or male, or paired decoys) and seasonal (pre-breeding or breeding) contexts. Females responded more aggressively to intrusions by females and pairs than to males. However, female intrusions elicited stronger responses during pre-breeding, whereas responses to pair intrusions were more intense during breeding. Territorial females had elevated testosterone levels after female intrusions and intermediate levels after pair intrusions during pre-breeding, but the levels of testosterone remained low after these intrusions during breeding. These results demonstrate seasonal differences in circulating testosterone following territorial aggression in female buff-breasted wrens and are suggestive of differences according to social context as well. Context-dependent elevation of testosterone implies that selection acts directly on female vertebrates to shape patterns of testosterone secretion.

/pdf/context-matters-female-aggression-and-testosterone-in-a-year-4a9c307u89.pdf

Sharon A. Gill

Papers

On the Meaning of Alarm Calls: A Review of Functional Reference in Avian Alarm Calling

Functional reference in an alarm signal given during nest defence: seet calls of yellow warblers denote brood-parasitic brown-headed cowbirds

Effects of blood collection on wild birds: an update

Nest Defence By Yellow Warblers: Recognition of a Brood Parasite and an Avian Nest Predator

Context matters: female aggression and testosterone in a year-round territorial neotropical songbird (Thryothorus leucotis)