Demography of an alpine population of Savannah Sparrows |
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Authors: | Michaela Martin Alaine F. Camfield Kathy Martin |
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Affiliation: | Centre for Applied Conservation Research, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada;, Canadian Wildlife Service, 5421 Robertson Road, RR1, Delta, British Columbia V4K 3N2, Canada |
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Abstract: | ABSTRACT. Although Savannah Sparrows ( Passerculus sandwichensis ) have been well studied across their North American range, few data are available for populations that breed in high-elevation habitats. We collected data over six years on the demography of a population of Savannah Sparrows ( P. s. anthinus ) breeding in alpine tundra and sub-alpine meadows in northern British Columbia, Canada. The mean duration of the breeding season at our site was 45.5 d, and pairs produced a maximum of one brood per season. Clutch sizes varied annually (mean = 4.37, range = 3.90 – 4.71 eggs). Nest fate also varied among years (range = 33 – 92%) due to variation in abiotic (weather) and biotic (predators) conditions. Uncorrected return rates of banded birds were 68% for adults and 17% for juveniles ( N = 22 and 102, respectively). However, when resighting probability was taken into account, apparent annual survival was 75% for adults and 34% for juveniles. Compared to populations at lower elevations, Savannah Sparrows in our study had shorter breeding seasons, fewer broods per season, larger clutches, and higher adult and juvenile return rates. Our results suggest that Savannah Sparrows that breed in high-elevation habitats have adopted a low fecundity, high survival life history strategy that enables their persistence in these challenging environments. |
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Keywords: | apparent survival clutch size high elevation life history reproductive potential return rates songbird |
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