Factors Affecting Clutch Size in Arctic Passerines

• Published in: Ecological Monographs
• Main Author: Hussell, David J. T.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1972
• Subjects: Arctic; Canada; Devon Island; Plectrophenax nivalis; Snow Bunting; Subarctic; Lapland
• Online Access: http://dx.doi.org/10.2307/1942213; http://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2307%2F1942213; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2307%2F1942213; https://onlinelibrary.wiley.com/doi/pdf/10.2307/1942213; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.2307/1942213

Clutch size and related aspects of breeding biology were investigated in the Lapland Longspur (Calcarius lapponicus) and Snow Bunting (Plectrophenax nivalis) in the North American Arctic, and in allied temperate and subarctic species. Evidence was sought to test Lack's hypothesis that the increase in clutch size with latitude is related to the length of daylight available for the adults to collect food for their young, and that clutch size is ultimately determined by the average maximum number of young for which the parents can find food. The arctic species were studied mainly at 76° N on Devon Island; some additional data were collected elsewhere. Increase in clutch size with latitude was correlated with a decrease in the adults' night rest period from 7 hr at 50° N to 3—5 hr in the Arctic. In the Lapland Longspur in Canada clutches were larger at high latitudes and at localities with early breeding seasons. Clutch size and latitude were not significantly related for those localities where activity of adults attending nestlings is not restricted by daylength. Differences in clutch size were not attributable to geographic or interspecific variation in hatching asynchrony, hatching success, or growth of the young. Hatching of Lapland Longspur and Snow Bunting clutches on Devon Island corresponded closely with the emergence of the adult insects which predominate in the nestlings' diet, but other factors may also influence the timing of the breeding season. The decline in clutch size in these single—brooded species as the season progressed apparently was not related to changes in the environmental food supply. In the multiple—brooded Chestnut—collared Longspur (C. ornatus) in Saskatchewan clutch sizes changes little during the season. Annual differences in clutch size were demonstrated in the Snow Bunting, but their significance is unknown. Although Snow Bunting clutches of seven are rare on Devon Island, more young were fledged from experimental broods of seven than from smaller broods, but the young averaged ...