Population genetics and relatedness in a critically endangered island raptor, Ridgway’s Hawk Buteo ridgwayi

Many island avian populations are of conservation interest because they have a higher risk of extinction than mainland populations. Susceptibility of island birds to extinction is primarily related to human induced change through habitat loss, persecution, and introduction of exotic species, in combination with genetic factors. We used microsatellite profiles from 11 loci to assess genetic diversity and relatedness in the critically endangered hawk Buteo ridgwayi endemic to the island of Hispaniola in the Caribbean. Using samples collected between 2005 and 2009, our results revealed a relatively high level of heterozygosity, evidence of a recent genetic bottleneck, and the occurrence of inbreeding within the population. Pair relatedness analysis found 4 of 7 sampled breeding pairs to be related similar to that of first cousin or greater. Pedigree estimates indicated that up to 18 % of potential pairings would be between individuals with relatedness values similar to that of half-sibling. We discuss our findings in the context of conservation genetic management suggesting both carefully managed translocations and the initiation of a captive population as a safeguard of the remaining genetic diversity.     

Extraterritorial forays and male parental care in hooded warblers

Extrapair paternity is common among many songbird species yet few studies have quantified male extraterritorial foray (ETF) effort and examined potential trade-offs. One potentially important constraint for males is the need to provide parental care. Current models of male extrapair mating tactics propose that males reduce extraterritorial foray effort later in the breeding season because they face a trade-off between feeding nestlings versus pursuing extrapair matings. However, detailed field studies examining the trade-off between paternal care and male extraterritorial forays are lacking. We used radiotelemetry to quantify male extraterritorial foray effort in hooded warblers, Wilsonia citrina, to test the widely held predictions that: (1) males make significantly fewer and shorter forays during the nestling stage relative to other stages (i.e. fertile and incubating stages); and (2) male extraterritorial foray effort is negatively correlated with parental effort. Males made 0.87+/-0.09 forays/h and spent on average 12.2% of their time foraying off territory. Results were equivocal; some data suggested male foray effort decreased in relation to parental care, while other data suggested otherwise. Pairwise tests controlling for (1) extrapair mating opportunity among males and (2) male, territory and social mate quality revealed a possible trade-off between the mean duration and percentage of time in extraterritorial foray versus providing parental care. Conversely, results also revealed (1) no difference in foray rate, foray duration or percentage of time spent off territory over the various stages of the breeding season, (2) no relationship between male foray effort and male feeding rate, and (3) no difference in foray rate in pairwise comparisons, controlling for variability in extrapair mating opportunity and male quality. Overall, the trade-off between providing male parental care and pursuing alternative mating tactics may not be as strong for male hooded warblers as once hypothesized because males dedicated relatively little time to seeking extrapair copulations off territory. Copyright 2000 The Association for the Study of Animal Behaviour.     

Comparison of the mating systems and breeding behavior of a resident and a migratory tropical flycatcher

ABSTRACT.   Little is known about the genetic mating systems of tropical passerines and how they vary among species. We studied the Lesser Elaenia ( Elaenia chiriquensis ) and the Yellow-bellied Elaenia ( E. flavogaster ) near Gamboa, Panama. These species breed in the same habitat, but Lesser Elaenias are intratropical migrants with seasonal territories and Yellow-bellied Elaenias are permanent residents that remain paired and defend territories throughout the year. Lesser Elaenias exhibited greater breeding synchrony (15–18 %) than Yellow-bellied Elaenias (9–10%). For Lesser Elaenias, 10 of 15 (67%) nests contained extra-pair young and 14 of 38 (37%) young resulted from extra-pair fertilizations (EPFs). In contrast, only one extra-pair nestling (4%, N = 24 nestlings) was found in 13 Yellow-bellied Elaenia nests. Neither species exhibited strong mate guarding. The higher rate of EPFs in Lesser Elaenias is consistent with the hypothesis that year-round territorial tropical passerines with low breeding synchrony have little or no extra-pair behavior compared with species that breed seasonally. Although the low singing rates of Lesser Elaenias (7 songs/h) suggest that this not an important cue for female extra-pair mate choice, the role of conspicuous male dawn song remains to be investigated. Further studies of tropical passerines are needed to help disentangle the effects of synchrony, density, and other ecological and behavioral factors that have influenced the evolution of extra-pair mating systems in passerines.