EXTRA MALE PARENTAL BEHAVIOR - EVIDENCE FOR AN ALTERNATIVE MATING STRATEGY IN THE MOUSTACHED WARBLER ACROCEPHALUS-MELANOPOGON

Until recently, the Moustached Warbler was considered strictly monogam ous, However, in our study we observed males other than the pair male incubating, feeding and defending nestlings. This additional care was far less extensive than that provided by the breeding male. Parental c are by extra males seems to facilitate their later forming of a pair w ith the female for a subsequent brood. This is suggested by the follow ing results: intrusions at foreign nests were strongly male-biased; hi gh rates of non-aggressive encounters between intruders and pair femal es; helping behaviour occurred mostly in the presence of females; in s ubsequent second broods, two documented cases of mate switching at nes ts with extra male care in contrast to two cases of mate fidelity at n ests where extra males did not help.