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Recruitment and the Timing of Reproduction in Lesser Snow Geese (Chen caerulescens caerulescens)

Fred Cooke, C. Scott Findlay and Robert F. Rockwell
The Auk
Vol. 101, No. 3 (Jul., 1984), pp. 451-458
Stable URL: http://www.jstor.org/stable/4086598
Page Count: 8
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Recruitment and the Timing of Reproduction in Lesser Snow Geese (Chen caerulescens caerulescens)
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Abstract

Recruitment of offspring into a breeding population of Lesser Snow Geese (Chen caerulescens caerulescens) at La Perouse Bay, Manitoba was used as a measure of reproductive success to assess the relative fitness of females who hatched their clutches early, middle, and late in the breeding season. In three of seven seasons investigated, goslings from early-hatching clutches showed significantly greater recruitment rates than their middle- or late-hatching counterparts. No significant differences in recruitment rates were detected in the other four seasons, although early-hatching clutches showed numerically higher recruitment rates in three of these seasons. There is, therefore, some indication of directional selection for early breeding. This conclusion contrasts with that drawn by Cooke and Findlay (1982), who, using fledging success as a measure of reproductive fitness, showed that females whose clutches hatched in the middle period had the highest fitness and concluded that the population was being exposed to stabilizing selection for synchronization. The discrepancy between these results and those presented in this paper indicates that conclusions concerning the action of selection in natural populations depend heavily upon the stage of the life cycle during which reproductive success is estimated. As such, evolutionary biologists must be cautious of relying too heavily on measures taken too early in the life of the organism.

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