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Chick growth and survival in northern lapwings Vanellus vanellus indicate that secondary females do the best of a bad job

Authors


G. Grønstøl, Univ. Museum of Bergen, Univ. of Bergen, Allégt. 41, PO Box 7800, NO-5020, Bergen, Norway. E-mail: gaute.gronstol@um.uib.no

Abstract

The polygyny threshold model predicts that monogamous and secondary females on average settle at the same time and have similar reproductive success. This is not generally found. Incorporating varying female competitive strength into the model, changes the predictions to state that secondary females should breed later and show a reduced success compared to that of monogamous and primary females. We examined if this was the case by investigating growth and survival in chicks of northern lapwings Vanellus vanellus from mothers of monogamous, primary and secondary mating status. Chicks where monitored from hatching to the age of 15–18 d. Growth and survival in secondary chicks was lower than in monogamous and primary chicks. Primary chicks survived significantly better than secondary chicks. Survival of monogamous chicks was comparable to primary chicks and close to significantly higher than in secondary chicks (p = 0.086). Among surviving chicks, daily weight gain in monogamous chicks was significantly higher than in secondary chicks. Growth rates of primary chicks were comparable to monogamous chicks and tended to be higher than in secondary chicks (p = 0.11). Monogamous and primary females both bred significantly earlier than secondary females, and chick survival and body-mass growth decreased significantly with hatching date. Given the premium on early breeding in lapwings, secondary females appeared to do the best of a bad job, and their later onset of breeding could have been caused by poorer condition and/or lower breeding experience. Additional costs might also have accrued from sharing breeding resources with primary females that presumably were stronger competitors.

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