Great Blue Herons have been declining in the Columbia Basin in recent years based on periodic monitoring. A long-term study is currently underway in an attempt to determine reasons for the declines and develop potential mitigation measures to slow downward trends in the future. This basin-wide study is being conducted by Marlene Machmer of Pandion Ecological Research Ltd. It is funded by The Columbia Basin Trust and The Fish and Wildlife Compensation Program.
Over the last decade the study has identified important nest colonies in the Creston Valley, the Rocky Mountain Trench, at Revelstoke and in other wetland/riparian habitats. These colonies are being monitored and studied. Two factors have emerged as contributing to herons declines: habitat loss and disturbance around the nest sites, and Bald Eagle predation. Nesting sites are found in both large deciduous and coniferous trees and they can be fairly easy to locate when nesting colonially. Breeding sites may consist of a dozen or more bulky stick nests; which are particularly easy to find in deciduous trees before the trees leaf out in the spring. However, some herons nest as single pairs or in groups of two or three pairs. These nests are usually built in conifers and are much more difficult to locate.
In the Arrow Lake and Slocan Lake Valleys, no nests are known at this time. In the 1980s two or three pairs were nesting in the conifers at Box Lake, but none have been seen there since then. I have heard similar reports of former nesting at Bonanza Marsh. But do herons still nest in the region? And if so, where? I suspect that they do! Over the last few years, up to 15 immature herons have been congregating in the fall near the creek mouth at Burton. Where have they come from? I considered the possibility that they had flown down from the Revelstoke colony, but discussions with birders in Revelstoke suggest that the herons remain in that region well into the fall. I need your help! I am hoping that a few of my readers will commit to recording some data for us during the coming months. What we need you to do is keep your eyes open. Every time you see a heron, we need you to write down the following information: The date, the time of day, the location, how many herons you observed and a brief description of what the herons were doing. (i.e, . roosting on the shoreline, flying west toward the lake, etc.) It is hoped that if we get enough information from observers in the valley, we may get a better idea of where to look for those hard to find conifer nests. If you would like to help, or if you’d like some more information, please email or phone me: 250-265-4456, or firstname.lastname@example.org.