As a birder I’ve been aware that populations of certain species of birds have been declining, but I was unaware of how dramatically the numbers of Barn Swallows (Hirundo rustica) had fallen until I heard Dick Cannings talking about it on CBC Radio’s BC Almanac (available in iTunes – episode 2011-08-23 at about the 14:20 mark). According to Cannings, Barn Swallows have experienced a 75% decline in numbers in the last 25 years, with close to 40% of that drop coming in the last 10 years.
It’s because of that rapid, unsustainable decline, that Barn Swallows were recently listed by COSEWIC as Threatened (May, 2011). They are also Blue Listed (species of Special Concern) in British Columbia. There is currently estimated to be around 3 million Barn Swallows in Canada during the breeding season.
The exact cause of the precipitous decline is unclear but has been linked to a number of different factors. Cannings intimated that climate change was probably a key factor. Long distance migrating birds still leave their wintering grounds at the same time as they always have because their departure is triggered by day length. When they arrive in North America, the insects that they feed on may have already hatched due to an earlier spring. There is evidence that overall populations of insects are also declining as a result of changes in climate.
The Vancouver Avian Research Centre is conducting ongoing research on aerial insects and foraging success of Barn Swallows and other species of swallows at Colony Farms. Derek Mathews with Vancouver Avian Research Centre also mentions climate change, citing both changes in temperature and precipitation as factors in reducing insect populations and the ability of flying insectivores to feed. Lost of nesting habitat, increased use of pesticides on fields, and light pollution may also have an impact on Barn Swallow numbers.
I haven’t seen many Barn Swallows this year, but I happened to be staying at Penfold Farm B&B for a couple of nights this week and was delighted to discover that there were still swallows nesting in the old barn on the property. Gary and Gwenyth told me that the number of birds nesting in the barn had declined from around a dozen to just a few. There appeared to be one active nest in the barn while I was there, and at least four young birds begging for food.
If you’re interested in doing your part to preserve some habitat for these swallows, the farm is actually for sale. It’s a delightful place to stay, and I hope that when it does sell that the new owners are as conscious of its ecological value as its current ones are!