ADDIS, E.*; WACKER, D.; CLARK, A.; COVERDILL, A.; MEDDLE, S.; WALKER, B.; LANDYS, M.; RENEERKENS, J., WINGFIELD JC; Landys, M., Reneerkens J.; Univ. of Washington; Univ. of Washington; Univ. of Washington; Univ. of Washington; Univ. of Edinburgh; Univ. of Washington; Univ. of Washington; NIOZ, Univ. of Washington: Influence of habitat condition on breeding in Plectrophenax nivalis and Calcarius lapponicus
Arctic songbirds face unpredictable environmental conditions upon arrival at their breeding grounds. Mutable food supply, temperature, and precipitation may shorten an already brief breeding season. Thus, breeding in these areas requires early arrival and quick nesting. One major determinant of breeding commencement appears to be habitat condition. Snow cover, wind, temperature, vegetation, and moisture all influence the state of the habitat. Thule, Greenland (N 76° 32�, W68° 50�) is near the northern range limit of two Arctic breeding passerines: Snow bunting (SNBU), Plectrophenax nivalis, and Lapland longspur (LALO), Calcarius lapponicus. We hypothesized that the above variables influence choice of territory, nest site, and subsequently, date of first egg. We predicted that SNBUs would prefer different habitats from LALOs because the former are cavity nesters while the latter build nests in grass. While much of egg laying and nest building is controlled hormonally, timing is also influenced by the presence of suitable nest sites and food abundance. We plotted nest sites on GIS vegetation maps, and found that SNBUs prefer rocky areas and LALOs prefer moist, heavily vegetated areas. We also discovered for both SNBUs and LALOs, date of first egg corresponds with reduced snow cover; nests were established later in areas with lingering snow. In addition, while LALOs arrive later than SNBUs, their date of first egg ranges from earlier than (2004) to concurrent with (2001) SNBUs�. In future work, we hope to quantitatively measure snow cover reduction and food availability, correlate them with nest initiation, and further assess the role microhabitat conditions play in nest location.
