TIMING OF COPULATIONS AND MATE GUARDING IN THE CHAFFINCH FRINGILLA-COELEBS

Copulation behaviour and mate guarding among radio-tagged male Chaffin ches were studied in conifer-dominated forest in southern Finland in 1 990-1991. Pair copulation rate was highest (one copulation hour-1) abo ut 1 to 3 days before egg laying and thereafter decreased. Neighbourin g males attempted to obtain extra-pair copulations during the presumed fertile period of the female. Both intra-pair copulations and EPC-att empts were observed throughout all daylight hours. Males guarded their mates by close following and guarding was most intensive in the popul ation of high breeding density. Mate guarding began several days befor e egg laying and continued until the start of incubation in high densi ty population but not in the low density. As eggs are fertilized durin g a short insemination window after laying and sperm transferred just after laying most probably fertilizes the following egg, males would b e 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 di fferences in intra-pair copulations or mate guarding intensity either prior to or during the days when eggs were fertilized. Another explana tion is that they have to spread out their copulations to decrease the risk of cuckoldry. Intensive mate guarding until the start of incubat ion seems to be important due to continuous threat of EPC-seeking male s especially in high breeding density. This may be most likely in coni ferous habitat where extra-pair males are able to inconspicuously appr oach females and guarding males may easily lose contact with their mat es.