The nominate subspecies of Rock Sandpiper (Calidris p. ptilocnemis; hereafter ptilocnemis) numbers about 20,000 birds and winters primarily in upper Cook Inlet, Alaska (61°N, 151°W). This is the most-northerly site to host nonbreeding shorebirds in the Pacific Basin, and is also the world’s coldest site that regularly supports shorebirds in winter. Cook Inlet’s cold temperatures impose high energetic demands on ptilocnemis and create unique foraging hurdles due to the annual formation of extensive sea and shore-fast ice. We experimentally compared the metabolic output and foraging-related behaviors of ptilocnemis to individuals of another subspecies (C. p. tschuktschorum) that winters at more benign, southerly locations along the Pacific coast of northwest North America. The two subspecies exhibited similar metabolic responses to cold temperatures, but ptilocnemis displayed differences in foraging abilities that yielded higher rates of energy intake and food-waste processing compared to tschuktschorum. This was likely due to physiological differences between the two subspecies in digestive capacity and not differences in feeding behaviors or prey finding abilities. In the wild, ptilocnemis increases the size of its gizzard and liver to increase digestive capacity, and accumulates high fat stores to help endure periods of low food availability. In addition to these physiological adjustments, the winter occupancy of upper Cook Inlet by ptilocnemis is further facilitated by an abundance of unusually high-quality food resources, the bivalve Macoma balthica. Taken together, these unique behavioral, physiological, and environmental factors permit ptilocnemis to exploit the seemingly inhospitable conditions along Alaska’s frozen edge.
|Translated title of the contribution||Op de bevroren rand: ecologische en fysiologische beperkingen in de levensloop van een noordelijk overwinterende steltloper|
|Qualification||Doctor of Philosophy|
|Publication status||Published - 2014|