Environmental effects on movement and breeding of Australasian Gannets: insights from banding records

Abstract

ABSTRACT Banding has historically been the most efficient method of marking individuals to gather large datasets on bird movement, especially in seabirds which spend a large proportion of their life-cycle at sea. The Australian Bird and Bat Banding Scheme has gathered such long-term records, including for the Australasian Gannet (Morus serrator). Between 1954 and 2022, a total of 12,583 bands were deployed at seven breeding sites in Australia, of which 522 were recovered dead. An additional 325 individuals from four banding sites in New Zealand were recovered along the Australian coastline. The effects of broadscale environmental indices on movement (inferred from banding recoveries) during the post-breeding period were investigated at two colonies with the most banding effort (Pope’s Eye, Lawrence Rocks). Individuals >1 year old and those from Pope’s Eye were recovered closer to their banding site. There were negative effects of current-year Southern Oscillation Index (SOI) and 1-year lagged Southern Annular Mode (SAM) on recovery distances for Lawrence Rocks individuals, while 2-year lagged SAM positively and negatively affected recovery distance and direction, respectively, for Pope’s Eye individuals. The number of chicks banded (index of chick production) at Pope’s Eye was negatively influenced by 1-year lagged SAM and 2-year lagged SOI, while the likelihood of recoveries of first-year individuals was positively influenced by 1-year lagged SAM. The results of the present study revealed a potential effect of environmental conditions on post-breeding movement with seemingly contrasting effects between colonies, and on reproduction, highlighting the usefulness of long-term banding and recovery efforts.