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Factors Affecting Juvenile Survival in House Sparrow Passer domesticus
Thor Harald Ringsby, Bernt-Erik Sæther and Erling Johan Solberg
Journal of Avian Biology
Vol. 29, No. 3 (Sep., 1998), pp. 241-247
Stable URL: http://www.jstor.org/stable/3677106
Page Count: 7
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We studied how variation in different reproductive traits (hatching date, clutch number and clutch size) in addition to mass, size and condition of the fledgling influenced its probability of survival until recruitment in a House Sparrow population living on islands off the coast of northern Norway in 1993 and 1994. Twenty-three and 21% of the fledglings were recorded alive in the population the year after hatching, respectively. Most mortality occurred just after fledging. In both years larger-sized fledglings survived better than smaller ones. Juvenile survival was independent of clutch size. Multiple logistic regression analyses showed that in both years juvenile survival increased with body size (expressed as tarsus length). In addition, in 1993 fledglings in high body condition survived better, whereas in 1994 hatching day explained a significant proportion of the variation in juvenile survival. However, this last year both body condition and size increased significantly with hatching date, suggesting that juvenile survival rate may have been dependent on body condition also in this year. These results demonstrate that losses of juveniles during the non-breeding season are strongly influenced by factors during the breeding season that affect the size and condition of the fledglings.
Journal of Avian Biology © 1998 Nordic Society Oikos