Copulation behavior of a potentially double-brooded bird of prey, the black-winged kite (Elanus caeruleus)

FERRERO, J.J.; GRANDE, J.M.; NEGRO, J.J.

Journal of Raptor Research

Año: 2003 vol. 37 p. 1 - 7

Raptors show high copulation rates when compared to other birds. This fact has been generally attributed to sperm competition. However, copulation rates in raptors tend to be seasonally bimodal, with an early peak outside the female´s fertile period that cannot be explained by the sperm competition hypothesis. We studied the copulation behavior of the Black-winged Kite (Elanus caeruleus), that, unlike raptors previously studied, may raise two broods consecutively in the same breeding season. The first recorded copulation occurred 44 d prior to the onset of laying and the last one on d 66 after. We observed three seasonal peaks in copulation frequency. The first two peaks (40 and 10 d before egg laying, on average) correspond to the normal pattern in raptors. To explain the first peak, we propose three hypotheses: (1) pair bonding, (2) mate assessment, and (3) territorial signaling. Unfortunately, we have been unable to elaborate further predictions that would distinguish among these three hypotheses. The second peak, during the fertile period, may be attributed to sperm competition.. The third peak, previously unreported in raptors, occurred 50 d after the onset of laying, the mean time lag between first and second clutches in the area. These late copulations, which were also performed by pairs that laid one clutch, may reflect the propensity of the species to Jay second clutches (we recorded six replacement clutches and five second clutches out of 98 breeding attempts). This third peak of copulations may also have a fertilization function and may be related to sperm competition.