Environmental drivers of penguin phenology: Divergent phenological responses of the Adélie penguin
Shifting environmental conditions around the Antarctic continent are giving way to changes in snow and ice dynamics, which affect both access of Adélie penguins to suitable breeding habitat as well as the spatio-temporal distribution of their prey-base. The timing (phenology) of these organism-environment interactions is critical for ecosystem functionality in highly seasonal environments such as those inhabited by the Adélie penguin in Antarctica. Breeding and migratory behaviors are tightly linked to the timing of these seasonal cycles, and any phenological mismatches (an uncoupling of events such as peak food requirements of young and peak food availability) could have significant impacts on the functionality of the ecological community.
This work uses long-term time series of breeding phenology collected from eight sites around Antarctica to determine which environmental processes drive and constrain Adélie penguin phenology. Multivariate regression and model selection are used to disentangle the effects of proposed environmental drivers. While many environmental variables (such as air temperature and snow depth) exhibit significant correlations, a unique set of metrics exists for each of the proposed processes driving these phenological patterns.
Adélie penguins exhibit divergent phenological responses across the Antarctic continent. Along the Antarctic Peninsula, clutch initiation (egg lay) dates are advancing (trend to earlier egg lay). No trend is apparent in the Ross Sea while a trend towards delayed breeding phenology is present in Eastern Antarctica. These birds likely time their breeding events to maximize reproductive output – clutch initiation dates too early or too late in the breeding season may result in nest failure.
We propose that these divergent phenological responses are driven primarily by access to snow-free nesting territory, colony access (via sea ice extent), and/or prey availability. The distinct cues used to determine optimal breeding periods and potential factors constraining breeding events will be discussed, as will the importance of local vs. large-scale environmental processes in driving phenological patterns in the Antarctic.
This work represents a unique opportunity to examine physical forcing of ecological processes over the circumpolar range of a widely distributed Antarctic meso-predator and key indicator species. Conclusions drawn from this work have significant implications for developing a more complete understanding of ecosystem dynamics in the Southern Ocean as well as more broadly applicable insights into other high latitude environments.