Breeding habitat selection by Barrow's goldeneye and Bufflehead in the Cariboo-Chilcotin region of British Columbia: Nest sites, brood-rearing habitat, and competition

Barrow's Goldeneye and Bufflehead are secondary cavity-nesters that rely heavily on nest sites created by primary cavity excavators. For these species, reproduction and recruitment of offspring may be highly dependent on at least these three factors: (1) the availability of nest cavities for females to lay eggs, (2) the quality and availability of brood-rearing habitat and its effect on the growth and survival of ducklings, and (3) the influence of intra- and interspecific competition on settlement patterns and breeding success. I examined these three factors, and provided recommendations aimed at sustaining Barrow's Goldeneye and Bufflehead populations in areas of intensive land management.; Barrow's Goldeneye used primarily abandoned Pileated Woodpecker cavities located in aspen trees with a diameter at breast height greater than 35 cm. Active nest sites were typically higher above ground, had relatively larger entrance diameters and floor areas, and the bottom of the canopy was higher than unused cavities. Bufflehead used abandoned Northern Flicker cavities in aspen trees with diameters larger than 25 cm. Bufflehead cavities had larger entrance diameters than unused cavities, and smaller floor areas. More than 90% of all cavities used by both species were located within 200 m of a body of water. The nesting ecology of Bufflehead was similar in natural cavities and nest boxes, but Barrow's Goldeneye had greater nest success in natural cavities than in boxes.; Wetland selection by Barrow's Goldeneye and Bufflehead was influenced by a complex of factors including the lake's physical characteristics, water chemistry, food supply, and to a lesser degree, aquatic vegetation. I found positive correlations between invertebrate abundance within a wetland and Barrow's Goldeneye duckling masses at day 40, prefledging survival, and first year return rates, but not recruitment as breeders.; Experimental removal of goldeneye nest sites did not result in a decrease in the number of goldeneye breeding pairs in the treatment area, suggesting habitat saturation prevented dispersal to new sites. The number of goldeneye broods declined, but this did not result in increased brood survival for other species. These results suggest that either, (1) goldeneye do not have a direct effect on other species' brood survival rates, or (2) the ecological interactions between these species are complex and changes in response variables, such as reproductive success of subordinate species, may not be detected in such a short term study, or (3) there are other costs of coexistence that were not measured in this study.; Forest management should protect primary cavity-nesting species, by leaving mature and old aspen. Conserving aspen stands close to rich brood-rearing wetlands, will help maintain nest sites for cavity-nesting waterfowl in central British Columbia, and aid in the production and survival of their young.