Geographic Variation in the Bioenergetics of the House Sparrow

Abstract

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Energy Management in Passerine Birds during the Nonbreeding Season

“…However, indirect support (reviewed by Witter and Cuthill, 1993) comes from studies showing that heavier birds exhibit decreased maneuverability, which theoretically should increase their risk of predation (Witter et al, 1994;Hedenstrom, 1992;Norberg, 1990;Blem, 1975). Witter et al (1994) found that European Starlings (Sturnus vulgaris) with extra weight added experimentally were less maneuverable and had a lower angle of ascent, but did not differ from controls in flight speed.…”

Avian Adjustments to Cold

“…Pronounced winter fattening does not occur in all small birds (Blem and Pagels 1984), and in species that do fatten, the levels of fat accumulated are subject to a high degree of intra-and interspecific variability. This variation is apparently only broadly correlated with climate (Blem 1973;Dawson and Marsh 1986). For example, American goldfinches wintering in Michigan accumulate considerably more fat than individuals of this species wintering in southern California where winters are less severe.…”

Winter Fattening in the American Goldfinch and the Possible Role of Temperature in Its Regulation

“…before summarizing these, we should note the possibility that a portion of the apparent diversity may be a product of our attempting in some cases to infer trends in winter fattening by use of information on body mass.) In the case of house sparrows (Passer domesticus) in North America, a direct correlation exists between fat content of most winter individuals and latitude (Blem 1973 Our study was undertaken in hopes of gaining a general understanding of the role of environmental temperature in regulation of winter fattening in passerine birds. This is a complex task, for although the temperatures incorporated into meteorological records constitute a useful index of the severity of winter climates, other variables are involved.…”