Habitat selection and nest success of the Upland Sandpiper (Bartramia longicauda) in Ivvavik National Park, Yukon, Canada

Résumé

The Upland Sandpiper (Bartramia longicauda) is a grassland shorebird species associated primarily with prairie habitats in central North America. A disjunct and poorly studied population also occurs in Yukon, Canada, and Alaska, United States. We studied habitat selection of nesting Upland Sandpipers in Ivvavik National Park, Yukon, at the scales of microhabitat (1-m radius around nest) and putative home range (11.3-m radius plots at nests and within 50 m of nest). At the microhabitat scale, the Upland Sandpiper selected nest sites with lower visibility from above than that of their home range (median 91.5%, range 70–98% versus median 99.0%, range 85–100%) and less-variable composition of vegetation than at random sites within the home range. Vegetation adjacent to the nest in the eastern quadrat was significantly shorter (mean ± standard error: 10.6 ± 1.55 cm) than that in other directions around the nest (> 13 cm); nest sites and microsites within home ranges were more often hummocky than random sites in the park. At the mesohabitat scale, Upland Sandpipers selected sites within home ranges with fewer trees than random sites within the park (10.3 ± 3.0 trees per 11.3-m-radius plot around nest versus 32.9 ± 5.9 trees per 11.3-m-radius plot in the park) and greater herbaceous cover (70.7% ± 3.0% versus 56.2% ± 3.7%). Despite the disproportionate use of sites with fewer trees, more herbaceous cover, and lower vertical visibility, these factors did not relate to nest success in our sample. Of the 24 nests found in 2010 and 2011, 22 contained four eggs and 2 contained three eggs. Upland Sandpipers at this high latitude site had a nesting success rate of 0.85 ± 0.01 and 0.56 ± 0.01 in 2010 and 2011, respectively, for a 21-day incubation period. Further assessment of the selected characteristics of nesting sites will improve our ability to predict the effects of northward shrub and tree encroachment on this grassland species.