VOL. 58, NO. 1 (MARCH 2005) P. 55–65

Shorebird and Passerine Abundance and Habitat Use at a High Arctic Breeding Site: , PAUL B. LATOUR,1,2 CRAIG S. MACHTANS1 and GERARD W. BEYERSBERGEN3

(Received 29 September 2003; accepted in revised form 24 June 2004)

ABSTRACT. Shorebirds and passerines were surveyed at Creswell Bay, Somerset Island, in the High Arctic Ecozone (Canadian Arctic Islands) during the breeding season (June and July, 1995–97) and in August 1995 (post-breeding). The study area, situated on the north and south sides of Creswell Bay, consisted of sedge marsh and sedge wetland in the lowest areas, with shrub tundra dominated by Dryas spp. or Cassiope spp. and sparse herbaceous tundra over more upland areas. Surveys were carried out on 400 × 400 m plots distributed among the vegetation types according to their relative amounts within the study areas (34 plots in 1995; 33 plus 56 new plots in 1997). Eleven shorebird and three passerine species were observed during the surveys. Densities of breeding shorebirds were similar in 1995 and 1997 (37.3 and 33.1 birds/km2), while in 1996 a late spring with heavy snow cover resulted in reduced numbers of birds and no breeding. Shorebirds and passerines were much more numerous in sedge marsh and sedge wetland. White-rumped sandpiper (Calidris fuscicollis) and red phalarope (Phalaropus fulicarius) were the most abundant shorebirds breeding at Creswell Bay, and Lapland longspur (Calcarius lapponicus) was the most abundant breeding passerine. White-rumped sandpiper and sanderling (Calidris alba) were the most numerous species present after the breeding period. American golden-plover (Pluvialis dominica), red phalarope, and white-rumped sandpiper showed significant habitat preferences. An estimated 10 341 (± 6596; 95% CI) shorebirds were on the north area in 1995 and 14 840 (± 10 744) on both areas in 1997. The estimated maximum numbers over both years of white-rumped sandpiper (6769 ± 3725) and buff-breasted sandpiper (Tryngites subruficollis) (908 ± 1169) at Creswell Bay were more than 1% of the species’ estimated national populations (1.5% and 5.1%, respectively). This abundance, along with the relatively high species diversity at this high-latitude site, warrants its continued status as a Canadian Wildlife Service “key habitat site,” and every possible effort should be made to ensure its long-term protection. Key words: Creswell Bay, High Arctic, Nunavut, shorebirds, passerines, density, numbers, habitat, species diversity, protection

RÉSUMÉ. Les oiseaux de rivage et les passereaux ont fait l’objet d’une étude menée à la baie Creswell, dans l’île Somerset située dans l’écozone de l’Extrême-Arctique (archipel Arctique canadien) durant la saison de nidification (juin et juillet, 1995–97) et en août 1995 (période post-reproductrice). La zone d’étude, située sur les rivages nord et sud de la baie Creswell, consistait en des cariçaies de terrains marécageux et humides dans les terres les plus basses, avec une toundra arbustive dominée par Dryas spp. ou Cassiope spp. et une toundra herbacée clairsemée dans les terres plus hautes. L’étude a été effectuée sur des parcelles carrées de 400 m de côté réparties dans les divers types de végétation selon l’importance relative de ces derniers dans les zones d’étude (34 parcelles en 1995; 33 parcelles plus 56 nouvelles en 1997). On a observé 11 espèces d’oiseaux de rivage et trois espèces de passereaux durant l’étude. Les densités des oiseaux de rivage qui nidifiaient étaient semblables en 1995 et en 1997 (37,3 et 33,1 oiseaux/km2), alors qu’en 1996, un printemps tardif accompagné d’un important couvert nival a fait que le nombre des oiseaux a diminué et qu’aucun nid n’a été construit. Les oiseaux de rivage et les passereaux étaient beaucoup plus nombreux dans les cariçaies de ter