How to translate text using browser tools
1 July 2004 ANNUAL SURVIVORSHIP OF THE SEDENTARY RUFOUS-CROWNED SPARROW (AIMOPHILA RUFICEPS): NO DETECTABLE EFFECTS OF EDGE OR RAINFALL IN SOUTHERN CALIFORNIA
Scott A. Morrison, Douglas T. Bolger, T. Scott Sillett
Author Affiliations +
Abstract

The Rufous-crowned Sparrow (Aimophila ruficeps) is a nonmigratory passerine that displays an area-sensitive distribution pattern of abundance in fragmented coastal sagescrub habitat of southern California. To determine if habitat fragmentation negatively affected adult survival, we used Cormack-Jolly-Seber models to compare annual survival probabilities of adult sparrows breeding in habitat adjacent to urban-developed edges to those of birds breeding in the interior of large habitat expanses in San Diego County, 1997–2000. During that period, an El Niño event brought heavy rainfall to the study area, and a La Niña event brought drought. Annual survival probabilities were relatively high for a small passerine (females: 0.69 ± 0.05 SE; males: 0.74 ± 0.04 SE) but, given our data, did not differ between habitat types or with rainfall. Annual resighting probabilities for the birds were strongly associated with variation in rainfall, being high in the wet year and low in the dry year. Mate- and site-fidelity were apparently high, and surveys during the nonbreeding season documented that the sparrows stayed paired and on territories year-round. We hypothesize that the high apparent survivorship of this species is related to its nonmigratory habit and its tendency to curtail reproductive effort during periods of food scarcity. Although our survivorship analysis suggests that the urban-wildland interface does not adversely affect survival of territorial Rufous-crowned Sparrows, our power to detect an effect of habitat edge on survival was low. Thus, we urge caution in concluding that edge effects do not have an ecologically important influence on survival rates in this species.

Scott A. Morrison, Douglas T. Bolger, and T. Scott Sillett "ANNUAL SURVIVORSHIP OF THE SEDENTARY RUFOUS-CROWNED SPARROW (AIMOPHILA RUFICEPS): NO DETECTABLE EFFECTS OF EDGE OR RAINFALL IN SOUTHERN CALIFORNIA," The Auk 121(3), 904-916, (1 July 2004). https://doi.org/10.1642/0004-8038(2004)121[0904:ASOTSR]2.0.CO;2
Received: 10 February 2003; Accepted: 28 March 2004; Published: 1 July 2004
RIGHTS & PERMISSIONS
Get copyright permission
Back to Top