Extent of parental care, such as food provisioning to offspring, can vary widely between sexes in socially monogamous birds. The determinants of the sex-specific provisioning behaviors remain unclear as they could be associated with individual condition, as well as mate contribution and quality. In a population of Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha), we tested the good parent hypothesis, the reproductive compensation hypothesis, and the differential allocation hypothesis among 29 nesting pairs during the breeding season. Using multivariable linear regression, we examined the relationship of offspring food provisioning rate, a measure of parental care, with each parent's own demographic (sex, age), morphological (tail length, wing chord, tarsus, mass, body fat, and cloacal protuberance), and physiological (hematocrit and infection status) characteristics, as well as crown-white, a reliable status signal in this species. In male birds, feeding rate was positively correlated with partner crown-white (0.31 [95% CI: 0.18, 0.44] times hour−1 per 1% crown-white), and inversely associated with partner mass and body fat (mass: (−0.42 [95% CI: −0.80, −0.05] times hour−1 per 1 g; body fat: −1.74 [95% CI: −2.58, −0.90] times hour−1 per 1-unit increment in body-fat score). These findings suggest that mate quality is a predictor of food provisioning behavior in males but not females, thus providing some sex-specific support for the differential allocation hypothesis. On the other hand, we did not find conclusive evidence for the good parent or reproductive compensation hypotheses.
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Vol. 132 • No. 4