Abstract
This study investigates the use of paper birch (Betula papyrifera) by cavity nesters at two sites in the Interior Cedar-Hemlock biogeoclimatic zone of Arrow Forest District The type and extent of this use is compared to the use of other tree species and between stand types containing a birch component. Data on the relative use of birch was obtained from a two-year data set on wildlife tree use in the Deer Creek watershed. Nesting cavities and woodpecker feeding sign were assessed on trees located in 85 random plots and 68 plots centred around active nest trees. Variables quantified for all tree species in 0.04 ha plots included: tree species, diameter at breast height (dbh), height, decay class, tree defects (e.g., broken tops or trunks), presence of visible conks, number of old and new nesting and feeding cavities, species of cavity nester, and type of feeding (e.g., excavations or sapsucking). These same variables were quantified for all birch trees on 20 x 100 m transects located in a mixed riparian stand at Deer Creek, and in a mixed and a pure upland stand in the Pend d'Oreille Valley. All birch retained on a 15 ha portion of an upland cutblock in the Pend d'Oreille Valley were also assessed.
At Deer Creek, paper birch constituted only 7% of the sampled tree species, yet over 30% of birch had old and/or new nest cavities in them, compared to 0-13% of conifers. Six cavity-nesting species were observed nesting in birch; relatively large trees (20-50 cm dbh and 5-20 m height) with heart rot and broken tops or trunks were selected. Birch ranked fifth out of seven species in the proportion of trees with feeding sign and at least five cavity-nesting species were observed feeding in birch. Trees in the <20 cm dbh class and the 5-20 m height class were preferred.
The proportion of birch trees used for nesting and feeding differed in the four stand types. The mixed riparian stand had the highest proportion of trees with nests (10.8%), followed by the upland clearcut (4.7%), mixed upland (3.3%), and pure upland (0.8%) stands. Use of birch for feeding was highest in the upland clearcut (36%), followed by the mixed upland (26%), mixed riparian (20%), and pure upland (5.8%) stands. Our results emphasize the importance of mixed stands (riparian and upland) as nesting and feeding habitat for cavity nesters and the value of retaining birch during harvesting. Management recommendations to retain birch during harvest planning are put forward.
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Updated April 12, 2007
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