Yukon Swallow and Bats on Farmlands

“This story was written in March and depicts weather conditions in keeping with that time period. Maria Leung”

The thick blanket of snow covering the landscape would hardly suggest that spring is around the corner, but the lengthening daylight and the calls of the boreal owl tell me otherwise. When the last vestiges of snow are disappearing, we anticipate the return of our seasonal wildlife, the migratory birds and the bats.

For the past two years, our team has been studying a few of these species in and around farmlands in Yukon, namely Barn Swallow, Bank Swallow, Rusty Blackbird, and Little Brown Bat, with the support of local farmers and landowners. These species were selected because the Committee on the Status of Wildlife Species in Canada (COSEWIC) had identified them as species at risk. The three bird species have all seen drastic population declines of 70% or more in Canada. The Little Brown Bat has succumbed to white nose syndrome in other parts of its range, an imported fungus that results in massive bat mortalities in winter hibernacula.

Downward trends in insect populations and habitat degradation are among the threats facing these species. Currently, in Yukon, we find ourselves in an enviable situation. The nests of Barn Swallows that we followed were more often successful than not. In both years, a few pairs fledged two broods successively. We documented 37 active colonies of Bank Swallows along the 61 km stretch of the Takhini River ending at the Yukon River. We detected pairs of Rusty Blackbirds in the Takhini River Valley, the M’Clintock Valley, and close to the north end of Little Atlin Lake. Little Brown Bats and other bat species were found on all farms where we set up acoustic detectors, and over 75% of the bat boxes we installed saw some use by bats.

Unlike the agricultural landscapes of southern Canada where large cultivated fields abut each other and original forest and native grasslands are mostly small remnants, our Yukon farmlands are situated in a matrix of wildlands. Cultivated fields are intermixed with patches and borders of forest and wetlands. Many of the wetlands and ponds are still surrounded by native marsh, shrub and forest. For forest bats, such as the Little Brown Bat, tracts of forest provide roosting sites and safe cover for commuting to favoured wetland hunting areas. Similarly, the Rusty Blackbird nests in riparian forest and feeds along the shores of wetlands and ponds.

The cold wet summer of 2020, filled with mosquitoes, offers more insight as to what the Yukon is endowed with. Swallows are aerial insectivores, catching their insect prey in the air, and do not usually feed during rainstorms or when cold temperatures prevent the insects from flying. This would mean that the total time during which it was possible to feed was much reduced in 2020. However, the unusually high abundance of mosquitoes meant that finding prey was relatively easy when weather was agreeable. This could explain why we did not detect a drop in Barn Swallow nesting success compared to the sunnier summer of 2019, or fewer sites with bat activity despite the poor weather. Bats are also aerial insectivores although here in Yukon, they are known to glean insects and spiders from vegetation early in the growing season. Numerous insects for birds and bats to feed on also suggests that Yukon farmers use fewer insecticides than farmers in other parts of Canada. This is crucial, because declining populations of insects are implicated in the decline of these and many other species that depend on insect prey.

Compared to other parts of Canada, the Barn Swallow, Bank Swallow, Rusty Blackbird and Little Brown Bat appear to be doing relatively well here in Yukon

So, compared to other parts of Canada, the Barn Swallow, Bank Swallow, Rusty Blackbird and Little Brown Bat appear to be doing relatively well here in Yukon. We are fortunate that many farmers have kept native vegetation around their wetlands, and that many farmers care about the wildlife they can reasonably share their farmlands with. The benefits are often mutual, because swallows and bats consume insects that can be pests to people and crops. Our hope is that we can continue to see the birds, bats and insects thrive in Yukon, including in our agricultural landscape. Meanwhile, we continue to summarize our findings in a set of beneficial practices for farmers and land planners. 

Maria Leung is a wildlife biologist living in Whitehorse and a keen supporter of local food. She, along with Donald Reid (Wildlife Conservation Society Canada) and Brian Slough (Consulting Biologist), has been working on this project on species at risk on Yukon agricultural lands, supported by Environment Canada Habitat Stewardship Program, and by Weston Family Foundation.

Living With Wildlife – Steve Wilson

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