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ABSTRACT. This paper reports on the nesting phenology, breeding biology, and attrition rates at different stages of the breeding cycle of a population of rock ptarmigan (Lagopus mutus) at Windy Lake, Northwest Territories, from 1987 to 1989. By early May, males were on the study area, mostly in flocks numbering in the tens and hundreds. Females arrived two to three weeks later, about one week after males had dispersed and established territories. All males succeeded in establishing a territory, but only 83% were successful in attracting a mate. There were no unmated females. All but one male were monogamous. The initiation of laying was highly synchronous both within and between years, beginning shortly after ground snow cover receded below 50% (early June). Initiation of laying and clutch size were not correlated with either pre-incubation body weight or wing chord of females. The majority (71%) of hens that deserted or had their first nest depredated during laying renested. However, renesting was rare once incubation had commenced. Clutch size of first nests (mean = 8.7) was significantly larger than that of renests (mean = 5.0). In one year, adults laid larger clutches than yearlings; this did not result, however, in adults' fledging larger broods than yearlings that year. Pooling years, yearling females were as successful as adults: the proportion of first nests initiated that fledged was 0.56 for yearling hens and 0.55 for adult hens. Of all the hens that settled to breed at Windy Lake in 1988 and 1989, 57% were successful in fledging a brood. Predation was the major cause of complete nest failures. Predation of clutch caused most failures (72%), followed by depredation of the hen (24%) and brood predation (4%).Key words: reproduction, population attributes, rock ptarmigan, Lagopus mutus, Northwest Territories RÉSUMÉ. Cet article fait état de la phénologie de la nidification, de la biologie de la reproduction et des taux de réduction naturelle à différents stades du cycle reproducteur d'une population de lagopèdes des rochers (Lagopus mutus) à Windy Lake (Territoires du Nord-Ouest) de 1987 à 1989. Au début de mai, les mâles se trouvaient sur le site de l'étude, pour la plupart en volées regroupant des dizaines et des centaines d'individus. Les femelles arrivaient deux à trois semaines plus tard, environ une semaine après que les mâles se soient éparpillés et aient établi leur territoire. Tous les mâles ont réussi à établir leur territoire, mais seulement 83 p. cent ont réussi à attirer une partenaire. Il n'y a eu aucune femelle non fécondée. Tous les mâles sauf un se sont révélés monogames. Le début de la ponte s'est produit à peu près au même moment, au sein d'une même année et d'une année à l'autre, commençant peu après que la couverture de neige ait reculé de plus de 50 p. cent (début juin). Le début de la ponte et la taille des couvées n'étaient pas corrélés avec le poids corporel d'avant la couvaison ni avec la corde de l'aile des femelles. La plupart (71 p. cent) des femelles qui ont abandonné le nid,...

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We studied the extent to which male American Redstarts (Set&zuga ruticillu) share songs in their repertoires. Examining samples of songs from three locations in New Brunswick, Canada, we found significant heterogeneity in the frequencies of the different songs across the locations. The extent to which neighbors shared songs related to increasing repertoire size (mean 4.4 songs/adult male). In the relatively larger sample at St. Andrews, neighboring adult males shared significantly more song types (P < 0.05) than did adult males chosen at random. However, this result applied only to individuals with intermediate-sized repertoires (four songs). Subadult males at St. Andrews shared as much with neighboring adult males as did adult males among themselves. In the small, island population at Back Bay, adult males shared noticeably more songs than at St. Andrews. We attribute the difference in degree of song sharing to demographic aspects, including patterns of settlement, interacting with tendencies to copy songs. Therefore, any so-called "dialects" in songs of American Redstarts seem more as "epiphenomena" resulting from competiton between males rather than as indications of local adaptations of males.

The Migratory Bird Sanctuaries of the North Shore of the Gulf of St. Lawrence are important breeding grounds for many seabird species. The quinquennial censuses of seabirds in these sanctuaries have been carried out for 80 years (since 1925), in order to detect changes in the distribution and population levels of seabirds breeding on the North Shore. Between 1998-1999 and 2005, the most striking trends observed were the near doubling in numbers of Common Eiders in most sanctuaries, and the strong population growth rate of Razorbill. Unexplainable declines of Common Murre and Atlantic Puffin were observed at some of the larger colonies of these species. The last active colonies of Leach’s Storm-Petrel (Corossol Island) and Caspian Tern (Île à la Brume) on the North Shore seem on the verge of disappearing, with zero and three birds observed in 2005, respectively. Seabird populations in the larger, more accessible and disturbed sanctuaries are still markedly smaller than in historical times.Les refuges d’oiseaux migrateurs de la Côte-Nord du Golfe du Saint-Laurent constituent d’importants sites de nidification pour plusieurs espèces d’oiseaux marins. Des inventaires quinquennaux des oiseaux marins dans ces refuges sont effectués depuis 80 ans (depuis 1925), pour détecter les changements dans la répartition et les niveaux de population des oiseaux marins nichant sur la Côte-Nord. Entre 1998-99 et 2005, les tendances les plus marquantes étaient chez l’Eider à duvet, dont les effectifs ont pratiquement doublé dans la plupart des refuges, et chez le Petit Pingouin, dont les populations ont également connu une croissance rapide. Des déclins énigmatiques chez le Guillemot marmette et le Macareux moine ont été observés à plusieurs des colonies les plus importantes de ces espèces. Les dernières colonies actives d’Océanite cul-blanc (à l’île du Corossol) et de Sterne caspienne (à l’île à la Brume) sur la Côte-Nord semblent sur le point de disparaître, avec respectivement zéro et trois oiseaux observés en 2005. Les populations d’oiseaux marins demeurent à des niveaux bien endeça de ceux rapportés historiquement dans les refuges de grande superficie, davantage accessibles et sujets au dérangement.