Timing of copulations and mate guarding in the Chaffinch Fringilla coelebs

Abstrakti

Copulation behaviour and mate guarding among radio-tagged male Chaffinches were studied in conifer-dominated forest in southern Finland in 1990-1991 . Pair copulation rate was highest (one copulation hour') about 1 to 3 days before egg laying and thereafter decreased. Neighbouring males attempted to obtain extra-pair copulations during the presumed fertile period of the female. Both intra-pair copulations and EPCattempts were observed throughout all daylight hours. Males guarded their mates by close following and guarding was most intensive in the population of high breeding density. Mate guarding began several days before egg laying and continued until the start of incubation in high density population but not in the low density. As eggs are fertilized during a short insemination window after laying and sperm transferred just after laying most probably fertilizes the following egg, males would be expected to ensure paternity by copulating both with their own mates and other females during this time. However, male Chaffinches do not seem to recognise the insemination window, as there were no diurnal differences in intra-pair copulations or mate guarding intensity either prior to or during the days when eggs were fertilized. Another explanation is that they have to spread out their copulations to decrease the risk of cuckoldry. Intensive mate guarding until the start of incubation seems to be important due to continuous threat of EPC-seeking males especially in high breeding density. This may be most likely in coniferous habitat where extra-pair males are able to inconspicuously approach females and guarding males mayeasily lose contact with their mates .