Testing abiotic and biotic drivers of nomadic movement in a cold-adapted species
Temperate winters are predicted to change rapidly in the next decades, and cold-adapted species are on the frontlines of this environmental change. My current postdoctoral work uses an Arctic-breeding, temperate-wintering, extreme-cold specialist to understand if and how animals can flexibly adjust to changes in temperature and precipitation regimes through movement behaviour.Snow Buntings (Plectrophenax nivalis), as a cold-adapted Holarctic-breeding species, can act as a ‘canary in the coal mine’ to understand climate change effects on temperate and Arctic ecosystems. Snow buntings are nomadic during winter but the drivers and consequences of these movements are not known. This lack of information on their winter movement ecology is currently impeding estimates of abundance, since it is not clear if birds have now moved north of the range where winter survey efforts occur or are actually in serious decline. To date, we have documented sex-biases in winter distributions related to the effects of body size on cold tolerance. I also found that the date of spring migration initiation, speed and number of stopover days were important predictors of migration performance in this species. These factors in turn, are likely affected by the consequences of conditions and behaviour of individuals during the winter via seasonal carry-over effects. Preliminary winter movement data obtained by using the Motus Wildlife Tracking System have shown that individuals are roaming over hundreds of kilometres in winter. My next steps are to examine three main hypotheses for drivers of these nomadic movements: 1) abiotic (climate) variation, 2) internal physiological state (hormone levels), 3) external biotic factors such as presence of predators.
Tracking migration of a boreal forest stewardship species, the Connecticut Warbler (Oporornis agilis)
There is widespread recognition that understanding the mechanisms driving population trends of migratory birds measured at breeding sites necessitates full-life cycle information on potential limiting factors, including threats at winter sites and on migration (Faaborg et al. 2010; Marra et al. 2015). Full-life cycle study also requires integrative research approaches, for example, combining tracking technology, physiological measures of individuals, and remote sensing of habitat (Bowlin et al. 2010). For small migratory species, such as the many boreal-forest breeding warblers, tracking technology has only recently become available that will allow researchers to locate migration routes and wintering sites for these declining species (North American Bird Conservation Initiative Canada 2012). One such species is the little-studied Connecticut Warbler (Oporornis agilis), which migrates from the boreal forests of Canada to unknown wintering sites in South America (Pitocchelli et al. 2012). As a forest species dependent upon large patches of breeding habitat (Lapin et al. 2013), this bird is likely sensitive to the extensive tropical deforestation documented in the Amazon region (Hansen et al. 2013), where anecdotal reports suggest that it spends the winter (Pitocchelli et al. 2012). Long-term population declines in Connecticut Warblers, both across the range and specifically in their core breeding range in Manitoba (Fig.1) (Sauer et al. 2012), may be in part owing to winter habitat loss, or carry-over effects from poor-quality winter habitat. It has also been speculated, based on patterns in occurrence during fall migration (i.e. ebird records, occasional migratory fallouts on Bermuda), that Connecticut Warblers undergo a trans-oceanic migration, similar to that of the Blackpoll Warbler (Setophaga striata) (DeLuca et al. 2015). This type of extreme migration (nearly 3000km nonstop, over water) could put this species at particular risk from poor quality migratory stopover habitat, or severe weather events in fall. Confirming whether Connecticut Warblers show this pattern is important for starting to identify such potential threats.