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Browsing Researcher Spotlights by Author "Boyd, W.S."
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Item Open Access A comparison of the Characteristics and Fate of Barrow's Goldeneye and Bufflehead Nests in Nest Boxes and Natural Cavities(University of California Press, 2002) Evans, M.R.; Lank, D.B.; Boyd, W.S.; Cooke, F.Abstract. Barrow's Goldeneye (Bucephala islandica) and Bufflehead (B. albeola) are cavity-nesting waterfowl that have received considerable attention in studies using nest boxes, but little is known about their nesting ecology in natural cavities. We found larger clutch size, lower nesting success, and different major predators for Barrow's Goldeneyes nesting in boxes versus those nesting in natural cavities, but few differences for Bufflehead. These differencesa re attributedt o the location and physical differencesb etween Barrow's Goldeneyen est boxes and naturalc avities that affect theirc onspicuousnesst o predatorsa nd conspecific nest-parasitizingfe males. Goldeneyeb oxes were concentratedin highly visible locations such as trees at water or forest edge. Natural cavity nests, on the other hand, were often abandoned Pileated Woodpecker (Dryocopus pileatus) cavities, which were more dispersed throughout the forest interior and concealed under dense canopy cover. Bufflehead natural cavity nests were typically closer to edges, which may account for their similarity with boxes. We conclude that in some respects, studies of Barrow's Goldeneye that use nest boxes may not be representativeo f birds nesting in naturalc avities, whereast hose of Bufflehead are more likely to be so.Item Open Access Long-term pair bonds in Harlequin Ducks.(University of California Press, 2000-02) Smith, C.M.; Cooke, F.; Robertson, G.J.; Goudie, R.I.; Boyd, W.S.We documented the frequency of pair reunion in Harlequin Ducks (Histrionicus histrionicus) on breeding streams in Alberta, and at a molting/wintering area in southwestern British Columbia. As long as their mate is alive, Harlequin Duck pairs reunite on the wintering area and return to the breeding stream together. Pairs reunite even if the female is unsuccessful at breeding the previous season, which suggests that reuniting with the same mate year after year is important. Some males that have lost their mate and fail to re-pair on the wintering area show fidelity to their former breeding site.Item Open Access Molt and the basic plumage of male Harlequin Ducks.(University of California Press, 1997-02) Cooke, F; Robertson, G.J.; Goudie, R.I.; Boyd, W.S.Using observations on 28 individually marked male Harlequin Ducks from mid-June until late November, we describe plumage changes which occur as individuals proceed from the alternate plumage through basic to the return of the new alternate plumage. We also describe the timing of these events, at the individual and population level. Conspicuous white tertial feathers which become visible early in the period of the basic plumage present a challenge to existing theories to explain the function of the drab basic plumage. We hypothesize that these feathers act as a badge of quality and are used as a sexual signal to other birds. Intra-sexual competition among males to assess the quality of rival males prior to subsequent pair formation is a proposed function of this feather badge.Item Open Access Spacing Patterns, Mating systems, and winter Philopatry in Harlequin ducks.(University of California Press, 2000) Gregory, J.R.; Cooke, F.; Goudie, R.I.; Boyd, W.S.Many species of waterfowl form pair bonds during the nonbreeding season, yet current descriptions of mating systems and patterns of philopatry in waterfowl focus on the breeding grounds. We studied wintering Harlequin Ducks (Histrionicus histrionicus) in southwestern British Columbia to examine mating systems and philopatric behavior outside of the breeding season. The number of males at our study area was far more variable than that of females. Males that were unsuccessful in obtaining a mate were observed over a larger area than were paired males. Habitat use overlapped considerably among paired males, and no territorial boundaries were formed. Annual return rates to the nonbreeding grounds were high for both sexes (62% for females, 77% for males). Individuals not only returned to the general study area, but also to specific sections within the study area. Males that did not pair in the previous year returned to the study area in the subsequent year with the same frequency as males that had obtained mates; however, they tended to leave the study area prior to courtship. Therefore, it is possible that males return to the same wintering grounds each year to reunite with a previous mate. High levels of philopatry by both sexes allow pairs to reunite in fall, potentially increasing the benefits of philopatry for both sexes.Item Open Access Survival, emigration and winter population structure of Harlequin Ducks.(University of California Press, 2000-02) Cooke, F.; Robertson, G.J.; Smith, C.M.; Goudie, R.I.; Boyd, W.S.A population of individually marked Harlequin Ducks (Histrionicus histrionicus) at White Rock, British Columbia, Canada was examined to measure the degree of population differentiation among birds which pair during the winter months. This required an understanding of the patterns of emigration among wintering sites in different segments of the population. Some juveniles arrived at the wintering grounds accompanied by their mothers, thus initially arriving into the same winter population as their parents. Young males were more likely than young females to disperse during the first two years of life. Adult males had higher local survival than adult females during the summer months, probably because of the greater mortality risks to nesting females. During the nonbreeding seasons, local survival was the same in both sexes. Paired males had a local survival of more than 90%, suggesting both high survival and strong philopatry. Unpaired males had a lower local survival rate, suggesting they have higher mortality and/or emigration rates. Young females had the same local survival rate as adult females, suggesting that they did not disperse during the winter. These winter philopatry patterns are similar to the general pattern of breeding philopatry in waterfowl, with females showing stronger philopatry than males, and paired adults stronger philopatry than unpaired and young birds. The dispersal of young males makes local population differentiation unlikely in this species.Item Open Access The Timing of Pair Formation in Harlequin Ducks.(University of California Press, 1998-08) Robertson, G.J.; Cooke, F.; Goudie, R.I.; Boyd, W.S.The timing of pair formation varies within and among species of ducks. In this study we documented the chronology of pair formation in a population of wintering Harlequin Ducks (Histrionicus histrionicus) in southwestern British Columbia. Harlequin Ducks began forming pair bonds in October and over half of the females were paired by December. This timing is much earlier than other ducks of similar size. A segment of this population was individually marked, and we documented the reunion of mates in subsequent years. In all cases where both members of the pair returned to their wintering grounds they reunited in the fall. New pair bonds, involving young males and females, were formed in the spring. We suggest that pair reunion in this species reduces the costs of courtship and pair bond maintenance and allows males to pair early in the nonbreeding season, compared to other species.