Breeding Ecology of House Sparrows: Spatial Variation

Abstract

Geographic differentiation in breeding ecology of house sparrows [Passer domesticus] between Calgary, Alberta [Canada] and Lawrence, Kansas [USA] is limited primarily to differences in nesting phenology and probability that clutches will be successfully incubated. Breeding begins later but at cooler temperatures in Calgary than in Lawrence. Annual variation in initiation of breeding activities indicates that breeding is not strictly cued to photoperiod or temperature. Breeding continues later in summer in Calgary, ceasing when temperatures start to decline. Cessation of egg laying in Lawrence appears to be associated with high temperatures and dry conditions of mid-summer. General aspects of most study sites, particularly in Calgary, were similar. Yet variation within localities (among farms) was high. These productivity differences probably reflect microenvironmental variation in diversity and abundance of insect prey since variation among farms was particularly high for fledging success. Nest site effects were high only for egg weight. Variation in reproductive output among box-nesting house sparrows could not be attributed to the microenvironment of the nest itself. Geographic patterns in onset and duration of the breeding season and clutch size have been rapidly established since house sparrows were introduced to North America a little over a century ago.