Australasian gannets demonstrate population-level flexibility in migration strategy

• Main Authors: 3rd World Seabird Conference 2021, Green, Jonathan
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Underline Science Inc. 2021
• Subjects: Animal Biology; Animal Science; Ornithology; Antarctic; Deakin; Dee; Queensland; Antarc*; British Antarctic Survey
• Online Access: https://dx.doi.org/10.48448/wp4n-gd56; https://underline.io/lecture/34671-australasian-gannets-demonstrate-population-level-flexibility-in-migration-strategy

Abstract: Studies of seasonal migration within and between species help us to understand the drivers of this behaviour, why a diversity of strategies is observed and what might happen in the future under environmental change. Seabirds demonstrate the full range of non-breeding movement strategies from remaining fully resident to undertaking some of the longest recorded migrations. We investigated movement, behavioural time budgets and subsequent energetic costs during three winter non-breeding periods of a population of Australasian gannets (Morus serrator) breeding in southern Australia. We observed a novel strategy of facultative dispersal migration, not previously described in seabirds. In two years (2015 & 2016), gannets showed partial migration, similar to congeneric species, with some individuals travelling up to 2500 km while others remained resident. However in 2003, no individuals undertook a substantive migration and all remained close to their breeding colony throughout the winter. One consequence of this flexibility was an 8% increase in daily energy expenditure (DEE) at the population level in years with partial migration. This was driven by an increase in the time spent on water by migrating individuals, rather than an increase in the time spent in energetically costly flight. DEE for all strategies was greater during the winter than during the summer breeding period. We conclude that pressure for nesting space in their breeding colony, coupled with adequate locally available prey resources during winter means that for some individuals and in some years, migration is not advantageous or necessary. However the high DEE and observation of periodic partial migration suggests that in some years local resources are not enough to support the entire population, necessitating a dispersive migration in some individuals. Further work will investigate the nature of these localised drivers and whether this flexibility may provide resilience to environmental change. Authors: Jonathan Green¹, Norman Ratcliffe², Ashley Bunce³, John Arnould⁴ ¹University of Liverpool, ²British Antarctic Survey, ³University of Queensland, ⁴Deakin University