Abstracts of Publications

Betz, William W. and Rogier Gruys 1995. Range extensions of the Snow Mountain Quail (Anurophasis monorthonyx) to the Oranje Mountains (Star Mountains, Irian Jaya). Science in New Guinea 21(2):69-72.

Abstract

On an expedition to the Oranje Mountains (Star Mountains, Irian Jaya) we observed two species of birds which were previously thought to be endemic to the Snow Mountains. We suggest that the lack of high altitude Snow Mountain birds in the Star Mountains is more likely due to a lack of surveys than to their physical absence.

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Gruys, Rogier C., and Susan J. Hannon 1993. Sex determination of hunter-killed and depredated willow ptarmigan using a discriminant analysis. J. Field Ornithol. 64(1):11-17.

Abstract

A method of determining the sex from remains (only wings, primaries and/or rectrices available) of adult and yearling Willow Ptarmigan that were killed by predators or hunters is described. Measurements of wing chord, and length of outer rectrix, and primaries 8 and 9 were taken from live birds of known sex and age in spring. A discriminant analysis using a model incorporating wing chord and rectrix length best separated the sexes in the reference collection. Models incorporating wing chord and length of primary 8, or rectrix length and length of primary 8 were less reliable. With all models, however, over 80 % of birds were correctly classified to sex. Similar results were obtained when the discriminant functions were used to classify birds of known sex and age that were killed by predators or hunters. Feather wear, however, as well as selective killing of large and small birds by hunters and predators, respectively, may affect accuracy of classification.

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Gruys, Rogier C. 1993. Autumn and winter movements of willow ptarmigan at Chilkat Pass, B.C. Arctic 46(3):228-239.

Abstract

I examined the causes and extent of differential movements by adult male and female willow ptarmigan (Lagopus lagopus alexandrae) during autumn and winter. Ptarmigan did not leave their breeding grounds immediately after the breeding season, but remained on or near their territories until December. After chicks fledged, part of the population moved uphill from their territories. Coincident with moult into winter plumage, ptarmigan moved farther from their territories. Both movements were probably to areas with better protection against predators. After moulting all tagged males and half of the tagged females returned to their territories, and males resumed territorial display. Ptarmigan remained on their territories until increasing snow cover depleted cover, forcing them to leave. Males left the breeding grounds later than females, and returned earlier in spring. In winter females moved farther than males, but segregation was not complete. Possible causes of sexual segregation are discussed.

Keywords Willow ptarmigan (Lagopus lagopus alexandrae), autumn territoriality, winter movements, sexual segregation, northern British Columbia.

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Gruys, Rogier C. 1991. Autumn and winter movements and mortality of willow ptarmigan at Chilkat Pass, B.C. Unpubl. M.Sc. Thesis, Univ. of Alberta, Edmonton, Canada.

Abstract

I studied the timing and extent of movements and mortality of adult willow ptarmigan at Chilkat Pass, B.C. during autumn and winter. Radio-tagged ptarmigan did not leave their breeding grounds immediately after broods broke up, but remained on or near their territories until December. After chicks fledged, part of the population moved uphill from their territories. In late September, coincident with molt into winter plumage, ptarmigan moved farther from their territories. Both movements were presumably to areas with better cover and/or food. Once they molted, all tagged adult males and half of the tagged females returned to their territories, and males resumed territorial display. Ptarmigan remained on their territories until increasing snow cover depleted food and cover, forcing them to leave. Males left the breeding grounds later than females, and returned earlier in spring. In winter females moved farther than males, but several males moved as far as females.

Natural autumn and overwinter mortality of adult males and females was similar in both years of the study. Adult females suffered most mortality during autumn raptor migration and on their wintering grounds. Adult males were killed during autumn and spring raptor migrations, as well as on the wintering grounds. Birds wintering in sub-alpine and forested habitats suffered similar mortality. During the breeding season female mortality ranged between 5 and 26%, mostly during incubation and after chicks hatched. In contrast, males suffered negligible mortality after they settled on their territories. Hence, differential mortality between the sexes occurred during the breeding season.

Hunting mortality of banded birds was less than 20% in each of ten years. Banded males and females suffered similar hunting mortality each year. Among unbanded birds, males predominated in the hunters' bags even when females were still in the areas frequented by hunters. Hence, sex and age ratios from hunters' bags are an inaccurate estimator of true population composition.

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