Williamson’s Sapsucker (Sphyrapicus thyroideus) nest productivity in relation to tree densities in British Columbia

Les W. Gyug1, S. Wilson2, Chris Steeger3, and I. Penny Ohanjanian4

1Okanagan Wildlife Consulting, 3130 Ensign Way, Westbank, B.C. V4T 1T9 Canada; e-mail: les_gyug@shaw.ca
2EcoLogic Research, 406 Hemlock Avenue, Gabriola Island, B.C. V0R 1X1 Canada; e-mail: steven.wilson@ecologicresearch.ca
3Pandion Ecological Research Ltd., 532 Park Street, Nelson, B.C. V1L 2G9; e-mail: csteeger@netidea.com
44481 LD Ranch Road, Kimberley, B.C. V1A 3L4; e-mail: pohanj@xplornet.com

Abstract: We examined the relationship between nest productivity (number of young fledged per nest) and the density of live trees ≥ 18-cm dbh at 160 Williamson’s Sapsucker nests in southern British Columbia from 2006–2008. Mean nest productivity was 3.24 ± 0.11 (SE) and did not vary significantly from year to year or between the three regions where Williamson’s Sapsucker breed in B.C. Nest productivity did not vary significantly between open seed tree cuts (150 trees/ha) but 94% of nests in seed tree cuts were within 160 m of forests, well within the observed adult foraging ranges from nests. Nest productivity was significantly lower where average tree densities were <85/ha in the breeding territory (225-m radius surrounding a nest). Nest productivity was not affected by tree densities in the nest stand (within 60 m of the nest) but was significantly lower when tree densities were <85/ha in the foraging territory (60-225 m from the nest). Habitat targets during timber harvesting within Williamson’s Sapsucker breeding territories should retain an average of about 100 trees/ha with this target expected to be met for each breeding territory, but not necessarily at every location within each territory. The target of 100 trees/ha should maintain the average tree density well above the minimum of 85 trees/ha below which nest productivity is reduced.

Key words: Williamson’s Sapsucker, Sphyrapicus thyroideus, nest productivity, British Columbia

PDFicon Gyug, L.W., S. Wilson, C. Steeger, and P. Ohanjanian. 2010. Williamson’s Sapsucker (Sphyrapicus thyroideus) nest productivity in relation to tree densities in British Columbia. British Columbia Birds 20:9-15.


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