Establishment of pair and breeding site bonds by young known-age adelie penguins (Pygoscelis adeliae)

Abstract In marked contrast to adult ‘established’ breeding Adelie Penguins, young breeders (3, 4, 5, 6 and 7 years of age) exhibit only minimal faithfulness to mate and territory. Studies of large numbers of young birds show a sequence of steps in the establishment of the more rigid bonds found in experienced breeders. We have documented some aspects of this behaviour in young Adelie Penguins, and have outlined the first steps taken by the adolescent Adelie towards modal adult behaviour. The extended period of such behaviour seems adaptive in that it provides a flexible breeding reservoir for the population, as well as lending some limited flexibility to the highly stereotyped behaviour of the population as a whole. We have shown that: 1. (1) Early wandering by young Adelies is at first wide and narrows toward the time of first breeding. 2. (2) Site of first breeding is likely to be near the site of hatching. Forty per cent of first breeders breed within the natal colony (contiguous group), 66 per cent within the natal area (200 m). Fifty-eight per cent of first breeders have visited the vicinity of the nest during their pre-breeding years. No young bird has yet been confirmed to have bred in a different colony after first breeding. 3. (3) Mate at first breeding probably is a matter of chance availability at the time of breeding and is little dependent on previous temporary pairings. Only two of thirteen young birds bred with a former ‘keeping-company’ partner, and both had bred before. 4. (4) First breedings of females are most common at 4 years of age. The mode for males is 5 years of age. 5. (5) Mortality of young breeders and their mates probably exceeds that of established breeders. Forty per cent of pairs with one young partner returned the season following breeding versus 60 per cent of presumed established pairs. Twenty-one per cent (versus 5 per cent adults) of pairs had neither partner return. 6. (6) Breeding incidence in successive years is significantly lower in young breeders (71 per cent) and their mates (58 per cent) than in established breeders (99·7 per cent). 7. (7) Mates of young breeders are probably among the less fit individuals in the population, as suggested by 5 and 6 above. Perhaps they are also youngsters, or older, senescent birds. 8. (8) Young breeders change nest-site and mate significantly more frequently (44 per cent change mate, 50 per cent site) than do established breeders (16 per cent change mate, 22 per cent site) when both of a pair return. 9. (9) Asynchrony of partners' arrival at the rookery is a likely cause for the dissolution of some young birds' pair- and site-bonds. 10. (10) Young birds change mate and site during a single breeding season, as well as between seasons. 11. (11) The oldest known-age adelies studied (7-year-olds) have not yet reached the population norms in faithfulness to site or mate.