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UBC Theses and Dissertations

Foraging ecology of Endangered Williamson’s Sapsuckers in Canada : multi-scale habitat selection in two biogeoclimatic zones St-Amand, Julien


Williamson’s Sapsuckers are Endangered woodpeckers in Canada that breed in montane forests only in British Columbia and require protection of their critical habitat. While there is reasonable knowledge of their distribution and nesting habitat requirements, there are knowledge gaps regarding foraging habitat of Williamson’s Sapsuckers. I investigated the selection of foraging habitat in managed forest at the foraging substrate and patch scales using visual observations of foraging behaviour of 27 radio-tagged Williamson’s Sapsuckers in the two biogeoclimatic zones where they are found in Canada, the Montane Spruce and Interior Douglas-fir. The characteristics of foraging trees differed with foraging mode and nesting status, but not with bird gender or age. Williamson’s Sapsuckers preferred large live Douglas-fir (> 22.5 cm dbh) for gleaning and sap feeding in both biogeoclimatic zones, while trees used for pecking were mostly large dying western larch in the Montane Spruce zone and large dead ponderosa pine in the Interior Douglas-fir zone. At the foraging patch scale, Williamson’s Sapsuckers did not prefer any stand-level characteristics in the Montane Spruce zone, while in the Interior Douglas-fir zone, they selected foraging patches with higher densities of their preferred foraging substrate (i.e., large live Douglas-fir). Areas of open habitat and single trees were avoided during foraging trips in both biogeoclimatic zones and this habitat type was found in significantly lower proportions in the Montane Spruce than in the Interior Douglas-fir zone. Williamson’s Sapsuckers showed no significant preferences for within-stand configuration characteristics (retained groups, forest edges, open stands and closed stands) in the Montane Spruce zone, but they preferred foraging along forest edges and in closed stands in the Interior Douglas-fir zone. I used foraging trip distances to recommend nest reserve (no-logging; 0-140 m from the nest) and nest management zones. For the nest management zone, I recommend only partial harvesting with retained groups of trees extending from 140-340 m in the Montane Spruce zone and from 140-410 m in the Interior Douglas-fir zone. My study on Williamson’s Sapsuckers is the first to provide a comprehensive representation of foraging habitat requirements for the species.

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