Climate as a driver of phenological change in southern seabirds (6535)
On a global scale, seabirds are one of the most threatened bird groups and, overall, their conservation status is rapidly deteriorating. Southern Hemisphere countries are over-represented in the numbers of species of conservation concern (8 of 10 countries with the highest numbers of seabird species of conservation concern are south of the Equator). Long-term phenological data on seabirds in the Southern Hemisphere are limited compared to the Northern Hemisphere. In order to improve seabird management and conservation status, a better understanding of the implications of changes in marine and terrestrial environments to seabird species is required. As a first step in this process, we conducted a meta-analysis of the drivers of phenological changes among Southern Hemisphere seabirds.
Overall, there was a general trend towards phenological events occurring later over time (67% of all significant trends; 34% of all data series, n=84), although the magnitude, and sometimes the direction of the trend varied by taxa and location. Seabirds breeding in the Australian region exhibited the strongest trends towards later events, particularly the Laridae (gulls, noddies and terns), as did migratory southern polar species. In contrast, earlier events were more often observed for breeding Antarctic and subantarctic seabirds, and for Spheniscidae (penguins). The drivers of phenological change in southern seabirds varied, but were generally associated with changes in oceanographic conditions; sea-ice playing an important role for the more southerly species. Anticipated responses under a warming climate varied. For some species at some locations, higher land surface temperatures may impact on seabird productivity through increased competition for nesting sites. While for other locations and species, such as the Little Penguin Eudyptula minor in south-eastern Australia, higher ocean temperatures are expected to correspond to increased productivity, at least in the short-term, manifested through earlier breeding, heavier chicks, and an increased chance of double brooding.
Climate change adaptation options for Southern Hemisphere seabirds have been most highly studied for Australian species, particularly in the case of the Little Penguin. Due to their relative ease of implementation, most of the suggested adaptation options are land-based, with few being developed for marine environments. Changes in the timing of important life-cycle events, such as breeding and moult, have the potential to either increase or decrease the exposure of seabirds to extreme temperatures and other extreme events such as storm surges. We provide examples that illustrate effective management responses for dealing with heat stress in surface- and burrow-nesting seabirds.