Apomorphine as an emetic for insectivorous songbirds: effectiveness and post‐release effects on survival and mass change

Emetics can be used to obtain food samples from birds, but they can harm birds during or after treatment. Studies to date suggest that apomorphine is a safe emetic for songbirds, but information is needed about possible post‐release deleterious effects. From March to July 2012, we collected food samples from insectivorous songbirds using apomorphine. We treated 67 Moustached Warblers (Acrocephalus melanopogon), 56 Reed Warblers (Acrocephalus scirpaceus), 15 Great Reed Warblers (Acrocephalus arundinaceus), and 12 Savi's Warblers (Locustella luscinoides). Effectiveness in inducing regurgitation was high (76.7%) and varied among species, being significantly more effective with Reed Warblers (91.1%). No birds died during treatment. To check for possible post‐release negative effects, we considered 53 treated Moustached Warblers and 37 treated Reed Warblers and selected an equal number of untreated individuals (simply captured, banded, and measured). We found no support for differences in survival or recapture probabilities between treated and untreated birds of either species within 21 d after administering apomorphine. We calculated body mass changes of all Moustached Warblers subsequently recaptured (within 21 d) and found no difference between treated (N = 8) and untreated (N = 22) birds, suggesting normal foraging activity after release. Our results suggest that apomorphine is a safe emetic, with no negative effect on survival at least in the short term. The effectiveness of apomorphine with insectivorous songbirds in our study contrasts with the results of some previous studies and confirms the differences in effectiveness among different taxa of songbirds. As with differences in effectiveness among species in our study, this variability in sensitivity to the emetic could be caused by morphological and physiological differences among different taxa.     

Cold weather events provoke egg ejection behaviour in open‐nesting passerines

We analysed 25 conspecific egg ejection events from a large sample of nests (n = 762) of three passerine species. In two species, most of the events could not be explained by intraspecific brood parasitism or nest sanitation behaviour. At least some of these cases were behavioural responses to unfavourable weather conditions in the spring of 2017. We conclude that clutch size adjustment through egg ejection may be more widespread among passerines than previously thought.     

Modeling and Mapping Abundance of American Woodcock Across the Midwestern and Northeastern United States

ABSTRACT We used an over-dispersed Poisson regression with fixed and random effects, fitted by Markov chain Monte Carlo methods, to model population spatial patterns of relative abundance of American woodcock (Scolopax minor) across its breeding range in the United States. We predicted North American woodcock Singing Ground Survey counts with a log-linear function of explanatory variables describing habitat, year effects, and observer effects. The model also included a conditional autoregressive term representing potential correlation between adjacent route counts. Categories of explanatory habitat variables in the model included land-cover composition, climate, terrain heterogeneity, and human influence. Woodcock counts were higher in landscapes with more forest, especially aspen (Populus tremuloides) and birch (Betula spp.) forest, and in locations with a high degree of interspersion among forest, shrubs, and grasslands. Woodcock counts were lower in landscapes with a high degree of human development. The most noteworthy practical application of this spatial modeling approach was the ability to map predicted relative abundance. Based on a map of predicted relative abundance derived from the posterior parameter estimates, we identified major concentrations of woodcock abundance in east-central Minnesota, USA, the intersection of Vermont, USA, New York, USA, and Ontario, Canada, the upper peninsula of Michigan, USA, and St. Lawrence County, New York. The functional relations we elucidated for the American woodcock provide a basis for the development of management programs and the model and map may serve to focus management and monitoring on areas and habitat features important to American woodcock.