Adoption or infanticide: options of replacement males in the European starling |
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Authors: | H G Smith L Wennerberg Torbjörn von Schantz |
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Institution: | (1) Ecology Building, Department of Animal Ecology, Lund University, S-223 62 Lund, Sweden, SE |
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Abstract: | The behaviour of a male bird towards a potential mate and her clutch may depend both on his expected paternity and on the
likelihood that she will produce a replacement clutch if he commits infanticide. In this study we evaluate the choices made
by replacement male European starlings Sturnus vulgaris. By removing males before and during laying, we induced other males, mainly neighbours, to mate with the reproductively active
females. When the original male was removed before laying, a new male adopted the subsequent clutch in 14 out of 15 cases.
When ten females were widowed during their laying period, replacement males never adopted their clutches. The paternity of
replacement males was a function of when they replaced the former male. When replacement occurred more than 3 days before
egglaying, the new male fathered nearly all offspring; when it occurred the day before laying, the new male still fathered
more than every second young. When the original male was removed during his mate’s laying period, in five out of ten cases
a replacement male committed infanticide by throwing out the eggs, but this only occurred in one out of 15 cases when removal
took place before laying. The evidence for infanticide actually being committed by the replacement male was circumstantial.
Four out of six of the females affected by apparent infanticide produced replacement clutches in which the male presumably
had higher paternity than in the original clutch. In all cases, the male adopted the replacement clutch. In five cases when
the original male was removed during laying, the neighbours neither adopted the brood nor committed infanticide, although
they sometimes were seen courting the widowed female and copulating with her. These cases occurred later during laying than
those were males comitted infanticide. The time from infanticide to the laying of the replacement clutch tended to increase
as infanticide was committed later in the laying sequence. We conclude that strategies of potential replacement males are
influenced by their expected paternity in the current brood and the probability that the female will produce an early replacement
clutch.
Received: 10 March 1995 / Accepted after revision: 28 October 1995 |
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Keywords: | Adoption Infanticide Sturnus vulgaris Paternity Male investment |
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