9 Springer-Verlag 1987 Male parental care and monogamy in snow buntings

Summary. We experimentally removed males from a random sample of 14 snow bunting (Plectro-phenax nivalis) pairs to determine the influence of male parental care on reproductive success. Wi-dowed females increased their rate of food delivery to nestlings by increasing their feeding visit rate but not their load size. However, Widows were only able to achieve 73 % of the food delivery rate of Control pairs and, as a result, they raised fewer offspring of lower quality (i.e. lower mass at fledg-ing). Total brood mass raised by Widows was only 55 % of that of Control pairs. Thus, in the year of our experiment, male parental care in the nest-ling period almost doubled the reproductive suc-cess realized from a brood. Our experiment, how-ever, was done in a year of poor food availability and data from the previous year, when food supply was higher, indicate that males may not always be so important. Since nestling food supply ap-pears to be unpredictable at the time of pair forma-tion, we suggest hat monogamy is a bet-hedging strategy in case of poor food availability. As a consequence the importance of male parental care in some years may explain why snow buntings are almost always monogamous