Winter Philopatry of Harlequin Ducks in Prince William Sound, Alaska

Abstract

We used capture-mark-recapture data to assess winter philopatry by Harlequin Ducks (Histrionicus histrionicus) in Prince William Sound, Alaska, during winters 1995–1997 and 2000–2001. Philopatry was quantified using homing rates, which were estimated as the proportion of birds recaptured at their original site out of all recaptured birds. Between-year homing rates of 0.95 (95% CI: 0.87–1.00) and 1.00 (0.92–1.00) were estimated for females and males, respectively, at three locations on Montague Island. Similar homing rates were measured in western Prince William Sound, where estimates were 0.92 (0.80–0.98) for females and 0.96 (0.79–1.00) for males, with a scale of detected movements for all recapture birds ranging from 3–52 km. Our results indicate that wintering aggregations may be demographically independent at a much finer spatial scale than genetic data indicate, and that conservation efforts should recognize this degree of demographic separation among population segments. Filopatría Invernal de Histrionicus histrionicus en Prince William Sound, Alaska Resumen. Utilizamos datos de marcaje y recaptura para determinar la filopatría de Histrionicus histrionicus en Prince William Sound, Alaska, durante los inviernos de 1995–1997 y 2000–2001. La filopatría fue cuantificada utilizando la tasa de retorno, estimada a partir de la proporción del total de aves capturadas que se recapturaron en su sitio original. Las tasas de retorno entre años, estimadas en tres localidades en la isla Montague, fueron de 0.95 (95% IC: 0.87–1.00) y 1.00 (0.92–1.00) para hembras y machos, respectivamente. En Prince William Sound se midieron tasas de retorno similares, donde las estimaciones fueron 0.92 (0.80– 0.98) para las hembras y 0.96 (0.79–1.00) para los machos, y para todas las aves recapturadas se detectó una escala de movimiento entre 3 y 52 km. Nuestros resultados indican que las agrupaciones de invierno pueden ser demográficamente independientes a una escala espacial mucho más fina de lo que los datos genéticos indican, y que los esfuerzos de conservación deberían reconocer este grado de separación demográ fica entre segmentos de poblaciones.

Annual Winter Site Fidelity of Barrow's Goldeneyes in the Pacific

“…Goldeneyes wintering along the Pacific north coast showed a high degree of inter‐annual and intra‐annual fidelity to their coastal wintering sites based on satellite telemetry data. Inter‐annual fidelity observed in goldeneyes were similar to those observed in some other sea ducks, geese, and swans whereby individuals express relatively high degrees of fidelity to winter habitats in successive years (Limpert , Robertson and Cooke , Petersen and Flint , Iverson et al ). For goldeneyes, we observed slight differences in site fidelity between sex and age classes, and among coastal regions, but overall goldeneyes had a low propensity to change wintering locations between or within years, similar to other waterfowl species (Robertson and Cooke ).…”

Site fidelity and the demographic implications of winter movements by a migratory bird, the harlequin duckHistrionicus histrionicus

“…This deficiency limits our ability to formulate effective area‐specific conservation strategies for wildlife populations. Given the high degree of philopatry exhibited by both male and female harlequin ducks to molting sites in Prince William Sound (Iverson et al 2004), and the rates of within‐winter site fidelity documented in this study, it is clear that spatial structure exists at a fine spatial scale among female harlequin ducks during the non‐breeding season. Our data indicate that at the site scale (16.7 ±1.5 km 2 ), which we defined as distinct bays, inlets, groups of islets, or continuous sections of coastline where female harlequin ducks were captured and released, approximately one in four birds emigrated over the course of the winter period.…”

“…Pacific harlequin ducks are short distant migrants that spend a vast majority of their annual cycle on wintering areas and do not undertake extensive molt or spring staging migrations (Robertson and Goudie 1999, but see Brodeur et al 2002). Both males and females are known to exhibit extremely high rates of between‐year site fidelity to specific molting/wintering areas (Cooke et al 2000, Robertson et al 2000, Regehr 2003a, Iverson et al 2004), and pair bond formation occurs during winter (Bengtson 1972, Gowans et al 1997, Robertson et al 2000). Additionally, harlequin ducks are long‐lived, exhibit low annual productivity, and there is some evidence that post‐fledglings accompany their mothers to coastal areas during winter (Regehr et al 2001).…”

“…These traits make the survival and movement patterns of breeding age females particularly influential from a population dynamic perspective. Finally, due the large number of individuals that were radio tracked over an extensive study area, and an extensive body of previous research documenting population‐specific distributions (Esler et al 2000b), between year homing rates (Iverson et al 2004), and survival rates (Esler et al 2000a, Peterson et al 2003), we believe this study is uniquely suited to address the demographic implications of individual patterns of site fidelity and movement by a migratory bird.…”

Harlequin Duck population injury and recovery dynamics following the 1989 Exxon Valdez oil spill

“…Dispersal.-Harlequin Duck movements in Prince William Sound were evaluated using mark-recapture (Iverson et al 2004) and radio telemetry (Iverson and Esler 2006). We used these estimates to derive transition probabilities between oiled and unoiled areas, as well as the probability of emigration from Prince William Sound as a whole during the 1995-1997 and 2000-2003 monitoring periods (Table 3).…”