Demography of White-Crowned Sparrows (Zonotrichia-Leucophrys-Nuttalli)

From Pubwiki

[edit] Author(s)

• Baker, M. C.
• Mewaldt, L. R.
• Stewart, R. M.

[edit] Journal

Ecology 62.3 (1981): 636-44.

[edit] Keywords

demography life table population biology reproduction sex ratio survivorship zonotrichia leucophrys

[edit] Abstract

Analysis of a White-crowned Sparrow population in coastal California resulted in estimate\ of the magnitude of variation in longevity (a) among cohorts in the same breeding heason. (b) between sexes. and (c) between years. Mean longevity calculated from early juvenile life averaged =13 mo whereas mean longevity calculated from the egg stage was -6 mo. Survival of fledglings to I January wa\ generally lower and more variable among cohorts than survival beyond January as adults. Reproductive information from a sample of known-age female\ indicated that clutch size and number of nestling5 increased with female age. Age-specific longevity and clutch size were combined to calculate the net reproductive rates of two female cohorts. These were 1.042 and 1.025, respectively. A combination of survival information from five cohorts and information on the numbers of males and females in reproductive condition suggested an effective sex ratio of one male per 1.2 females. This departure from strict monogamy reduces the genetically effective population sire by 10%.

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