Sunday, September 27, 2020

Behaviour and patterns of attendance of non-breeding birds at the breeding colony in a Buller's albatross Thalassarche bulleri population at The Snares

TitleBehaviour and patterns of attendance of non-breeding birds at the breeding colony in a Buller's albatross Thalassarche bulleri population at The Snares
Publication TypeJournal Article
Year of Publication2006
AuthorsStahl, JC, Sagar, PM
JournalNotornis
Volume53
Issue4
Pagination327-338
Type of Articlearticle
Keywordsalbatrosses, breeding season, colony attendance, known-age, prebreeder, Thalassarche
Abstract

Colony attendance and behaviour of non-breeding Buller’s albatrosses Thalassarche bulleri were studied at 2 Snares Is colonies in 2000-2004. Non-breeders comprised 31-32% of birds ashore in Mar-May (incubation to early chick-rearing), 44% in Jul (late chick-rearing), and 51% overall. Among non-breeders, the proportion of adults that had been recorded breeding in previous years decreased from 47% in Mar to 4% in Jul, with prebreeders (known-age birds that had not been observed breeding) dominating the composition overall (80%). The percentage of surviving birds seen ashore was 59% among prebreeders aged 6 years (modal age of first return), 88% among experienced prebreeders (birds that had been recorded ashore in >1 breeding season), 86% among remating (widowed or divorced) adults, and 63% among sabbatical (birds that had been recorded breeding in previous years, but were not breeding in the year of observation) adults. Colony attendance period was shortest among inexperienced prebreeders (latest birds to arrive), longest among 3rd year (i.e. known-age birds recorded ashore for the 3rd year) prebreeders (early arrival, late departure), and intermediate among last-time prebreeders and former breeders (early arrival, departure in mid-season). Failed breeders attended for up to 3 months, but departed after May irrespective of failure date. Birds stayed ashore for longer and at sea for shorter periods as they gained experience; the percentage of days ashore increased up to the 3rd prebreeding year, and was higher in males than females. Movements between colonies and subcolonies were most frequent during the first 3 prebreeding years. Prebreeders frequently joined display groups during their first 2 years (34% of observations in May), and associated with a nest site in May-Jul of their 3rd year. Among remating adults, displaying was most frequent in females and early in the season (Mar); their behaviour converged towards that of paired adults by May. Attendance patterns and behaviour were broadly similar to those of other albatrosses, except for earlier departure during the last prebreeding year not previously reported in an annually breeding species.

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