Spatio-temporal patterns of ptarmigan occupancy relative to shrub cover in the Arctic

Polar Biology
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Abstract

Rock and willow ptarmigan are abundant herbivores that require shrub habitats in arctic and alpine areas. Shrub expansion is likely to increase winter habitat availability for ptarmigan, which in turn influence shrub architecture and growth through browsing. Despite their ecological role in the Arctic, the distribution and movement patterns of ptarmigan are not well known, particularly in northern Alaska where shrub expansion is occurring. We used multi-season occupancy models to test whether ptarmigan occupancy varied within and among years, and the degree to which colonization and extinction probabilities were related to shrub cover and latitude. Aerial surveys were conducted from March to May in 2011 and April to May 2012 in a 21,230 km2 area in northeastern Alaska. In areas with at least 30 % shrub cover, the probability of colonization by ptarmigan was >0.90, indicating that moderate to extensive patches of shrubs (typically associated with riparian areas) had a high probability of becoming occupied by ptarmigan. Occupancy increased throughout the spring in both years, providing evidence that ptarmigan migrated from southern wintering areas to breeding areas north of the Brooks Range. Occupancy was higher in the moderate snow year than the high snow year, and this was likely due to higher shrub cover in the moderate snow year. Ptarmigan distribution and migration in the Arctic are linked to expanding shrub communities on a wide geographic scale, and these relationships may be shaping ptarmigan population dynamics, as well as rates and patterns of shrub expansion.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Spatio-temporal patterns of ptarmigan occupancy relative to shrub cover in the Arctic
Series title Polar Biology
DOI 10.1007/s00300-014-1504-z
Volume 37
Issue 8
Year Published 2014
Language English
Publisher Springer
Contributing office(s) Alaska Science Center Biology WTEB
Description 10 p.
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Polar Biology
First page 1111
Last page 1120
Country United States
State Alaska
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