BY SSI CONSERVANCY
Old-timers on Salt Spring may remember the western bluebird, once a common breeding bird in southwestern British Columbia.
Populations began declining in the 1950s and they disappeared from Vancouver Island and the Gulf Islands in the early 1990s. Experts suspect that loss of Garry oak meadows, cutting down of old trees used for nesting, climate change, declines in their insect prey due to pesticides and competition for nest holes with the introduced house sparrow and European starlings all contributed to the declines.
Seventeen years ago, western bluebirds were reintroduced onto San Juan Island, and 10 years ago, several more were released in and around the Cowichan Garry Oak Preserve near Maple Bay. Since then, small breeding populations have established. However, it was not until late October last year that western bluebirds were seen again on Salt Spring. A group of seven individuals, that were colour-banded near Maple Bay, was spotted foraging in farmland and investigating some nest boxes. This is exciting news that bodes well for the recovery of the species on our island.
The Salt Spring Island Conservancy works to conserve many of our declining bird species. In 2009, the conservancy started erecting nest boxes throughout the southern part of the island in Garry oak and farmland habitats, in recognition that adding nest boxes has reversed some bluebird population declines in Oregon, Washington and the interior of B.C. Our primary goal was to provide nest boxes for bluebirds that might disperse here from reintroduced populations. Our secondary goal was to provide boxes for other native species such as violet-green swallows, tree swallows and house wrens. All these species use cavities in trees, created by woodpeckers, to nest, but will nest readily in boxes. Swallows, which take their insect prey on the wing, are part of a group of birds called aerial insectivores. This group declined by 59 per cent between 1970 and 2016 in Canada.
Volunteers now monitor over 200 nest boxes on private land and in conservation areas from the slopes of Mount Tuam and Mount Maxwell to the Fulford and Beaver Point valleys. So far, we have not had any bluebirds nesting in them. The boxes are used primarily by violet-green and tree swallows and house wrens.
Unfortunately, we have observed some disturbing long-term trends that reflect the noted widespread decline in aerial insectivores: the occupancy of our nest boxes by swallows declined from 42 per cent in 2009 to 25 per cent in 2022. In addition, during the heat dome in late June of 2021, breeding success plummeted from an average of 66 per cent of nests fledging young, to only 49 per cent. Many of the chicks overheated and died in the nest. SSIC is researching methods to help nest boxes stay cooler, such as reorienting the direction the box faces, painting the box white or shading the box with a larger lid.
We are looking for volunteers to assist in monitoring and cleaning nest boxes. This is done in the fall and volunteers must be fit (some boxes are on steep slopes) and interested in a long-term commitment. If you are interested, please contact Debra Cobon at debra@saltspringconservancy.ca.