Growth of nestling sage sparrows and Brewer's sparrows

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From 1980-1984, we characterized Sage Sparrow (Amphispiza belli) and Brewer's Sparrow (Spizella breweri) nestling growth and evaluated proximate factors potentially influencing growth in a southeastem Idaho shrubsteppe community. Increase in mass and tarsus length of both species was best explained by a logistic equation. For Sage Sparrows, all growth parameters we estimated varied significantly among years; 1983 seemed especially favorable for growth. Sage Sparrow mass growth rate and tarsus length at age 8 days declined significantly later in the breeding season, and tarsus growth rate varied inversely with brood size. In general, daily maximum temperature was negatively correlated with Sage Sparrow growth; weather seemed to have more effect early in the nestling period than later. Infestations of fresh fly larvae (Sarcophagidae) on Sage Sparrow nestlings were associated with reduced tarsus Iength near fledging. Little variation in Brewer's Sparrow nestling growth was explained by the variables we measured. Mass growth rate varied significantly among years and throughout the breeding season. Mass attained by age 7 days was greater in larger broods, but this effect was confounded by interactions among brood size, year, and seasonal effects.

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Reference Code: A86PET02IDUS

Full Citation: Peterson, K. L., L. B. Best, and B. M. Winter.1986. Growth of nestling sage sparrows and Brewer's sparrows. Wilson Bulletin 98(4): 535-546.

Location: ANIMAL EF: BIRDS