Moreover, early arriving geese were more successful than late arriving. Brood size in relation to age of marked bird. Experience of the parents was another factor of importance for the breeding result. For all lakes except Fj llfotasj n new breeders had an appreciably smaller brood size at fledging than experienced breeders. Besides experience there was also an age effect, the success rate increasing up to the age of four even for geese starting to breed at the unusual age of two years.
Social factors are also important for the breeding success.
Co-operation between the partners of a pair is another factor of importance. The death of a partner for some reason leads to a markedly smaller brood size of both small and fledged young for the surviving partner in a new relationship the following breeding season. In a number of cases, a separation and repairing was observed with the two former partners still alive and breeding in the same area. Divorcing pairs had a much lower mean brood size before the divorce than the population mean. The experience and age of the marked breeder have been noted as important factors behind much of the variation in the breeding result of Greylag Geese.