Gray-cheeked Thrush (Catharus minimus minimus) distribution and habitat use in a montane forest landscape of western Newfoundland, Canada

Once abundant, the Newfoundland Gray-cheeked Thrush (Catharus minimus minimus) has declined by as much as 95% since 1975. Underlying cause(s) of this population collapse are not known, although hypotheses include loss of winter habitat and the introduction of red squirrels (Tamiasciurus hudsonicus) to Newfoundland. Uncertainties regarding habitat needs are also extensive, and these knowledge gaps are an impediment to conservation. We investigated neighborhood and landscape scale habitat associations of Gray-checked Thrush in a 200-km[sup 2] study area in the Long Range Mountains of western Newfoundland, where elevations range from 300-600 m and land-cover was a matrix of old growth fir forest, 6- to 8-year-old clear-cuts, coniferous scrub, bogs, and barrens. Taken together, our results suggest selection for mixed habitats and sensitivity to both neighborhood and landscape-scale habitat. Finally, restriction of thrushes to higher elevations is consistent with the hypothesis that they have been impacted by squirrels, because squirrels were rare or absent at these elevations.Original Abstract: Autrefois abondante, la Grive a joues grises de Terre-Neuve (Catharus minimus minimus) a diminue de 95 % depuis 1975. La ou les causes sous-jacentes a l'effondrement de cette population sont inconnues, bien que les pertes d'habitat sur les aires d'hivernage et l'introduction de l'ecureuil roux (Tamiasciurus huclsonicus) sur l'ile de Terre-Neuve fassent partie des hypotheses avancees. Les incertitudes quant aux besoins en matiere d'habitat sont egalement considerables et representent des obstacles pour la conservation. Nous avons examine les associations de la grive avec l'habitat a l'echelle locale (c.-a-d. a l'interieurde 115 m [4,1 ha]) et a celle du paysage (c.-a-d. a l'interieur de 1 250 m [490.8 ha]) sur une aire d'etude de 200 km super(2) situee dans les monts Long Range dans l'ouest de Terre-Neuve. ou l'altitude varie de 300 a 600 m et le couvert forestier est constitue d'une matrice de vieilles forets de sapins, de coupes totales agees de 6 a 8 ans. d'arbustes coniferiens, de tourbieres ombrotrophes et de landes. Les grives etaient restreintes aux altitudes au-dessus de ~375 m et leur occurrence etait fortement associee positivement avec l'altitude. Leur occurrence etait aussi positivement associee aux peuplements de grands arbustes a l'echelle locale; a l'echelle du paysage, l'occurrence montrait des relations curvilignes avec la proportion de grands arbustes e