Individual study: Effect of entrance size on nest box selection by common goldeneye Bucephala clangula and hooded mergansers Mergus cucullatus at Long Lake and Mattagami and Muskego Rivers, Ontario, Canada
Lumsden H., Page R. & Gauthier M. (1980) Choice of nest boxes by common goldeneyes in Ontario. Wilson Bulletin, 92, 497-505
The use of nest boxes in an attempt to increase duck stocks has been practiced during the last decades in Europe and North America. However, few data exist in North America on the characteristics of boxes and natural cavities that appear attractive to common goldeneyes Bucephala clangula for nesting. A selection of experiments in which goldeneyes were presented with boxes with a variety of features was undertaken. The experiment summarised here compared the response of goldeneyes, and also hooded mergansers Mergus cucullatus, to three different entrance sizes of nest boxes.
Study area: The experiment was conducted during two breeding season (1974 and 1996) and was carried out on Long Lake (including Robillard, Kinogami and Kushog Lakes) near Charlton (47º48'N, 79º59'W), and the Mattagami and Muskego Rivers (49º17'N, 81º38'W), northern Ontario, Canada.
Nest box design: Boxes (21 cm x 24 cm base x 45 cm high) were made of 1.27 cm sheeting grade plywood and mounted in sets of three (the centre one aligned with the tree trunk) on horizontal supports nailed about 3 m from the ground to trees alongside the lake or river bank. The bottom of the entrance hole was 33 cm above the box base.
Entrance hole size: Choice by goldeneye and hooded merganser among sets of three boxes with large (13 cm wide × 10 cm high), medium (10.5 × 8 cm) or small (7.5 × 6 cm) oval entrance holes and dark (black painted) interiors (spaced 0.6-1.2 km apart), was compared. In the two study years, use by these ducks of 103 and 105 sets of boxes on Long Lake and 64 and 46 sets of boxes on the Mattagami and Muskego Rivers were recorded. The smaller hooded merganser nests in this area as well as the goldeneye and may compete for nesting cavities; the smallest entrances were large enough to admit hooded mergansers, but too small for goldeneyes.
Box use: It was considered that a box was used if a duck laid one or more eggs in it. The boxes were visited at intervals averaging about 4 days (1-10 days), beginning in late April or early May until June.
Both species of ducks showed a strong preference for large entrance holes. Goldeneyes used boxes with large holes in 32 cases, medium in three and were unable to squeeze through the small entrances. Hooded mergansers chose the large in nine cases and the medium in four, the boxes with a small entrance hole were never used.
The results suggested that that goldeneyes and hooded mergansers do not divide the cavity breeding sites in the study area on the basis of the size of the entrance hole.
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