Bald eagle nest site and nest tree characteristics in select biogeoclimatic zones of the 100 Mile House Forest District, British Columbia

Abstract

Bald eagle (Haliaeetus leucocephalus) nest site and nest tree characteristics were studied in the Sub-Boreal Spruce (SBS), Interior Cedar–Hemlock (ICH), Sub-Boreal Pine–Spruce (SBPS), and interior Douglas-fir (IDF) biogeoclimatic zones in the 100 Mile House Forest District, British Columbia. Dominant or codominant Douglas-fir (Pseudotsuga menziesii) containing large trunk forks or multiple forks of the trunk comprised 85% of 121 bald eagle nest trees. Black cottonwood (Populus trichocarpa) comprised 11% of known nest trees, and trembling aspen (Populus tremuloides), lodgepole pine (Pinus contorta), Ponderosa pine (Pinus ponderosa), and hybrid white spruce (Picea glauca x engelmannii) each contained 1% of known bald eagle nests. Tree height and diameter at breast height (DBH), nest height, and distance of nest to fish-bearing water were less for island nests compared to non-island nests. The mean distance of nests to fish-bearing water, by biogeoclimatic zone, was 78 m in the SBS, 104 m in the ICH, 241 m in the SBPS, and 368 m in the IDF. Ground slope and aspect were not factors in nest site location. The bald eagle nest trees studied were generally of low economic value to the forest industry as they contained less recoverable lumber than similar-sized trees with better form. To maintain bald eagle nesting habitat, large diameter, dominant or codominant trees containing large trunk forks, or multiple forks or leaders of the trunk and (or) large limbs should be identified and retained in groups, patches, or forest stands.