University Of Western Ontario Researchers State Breeding At-risk Species Could Be Template For Future
Somewhere in the southwest corner of Western’s campus is a site which could be a template for the conservation of bird species at risk in North America.
The barn swallow structure is a wooden installation designed to resemble a barn, with one noticeable difference: it does not have a floor. Its intended occupants do not need it. The structure was built in the fall, under the leadership of Brendon Samuels, PhD candidate in biology. The project is being supported by WWF-Canada, University Students’ Council, the Society of Graduate Students, the Advanced Facility for Avian Research and Bird Friendly London/Nature London.
The ’barn’ provides an alternate location for barn swallows to breed without interference from humans or predators, and its success will mark a solution to a problem which took years to be fully understood.
A small insectivorous bird, the barn swallow is the most common species of swallow, and is found in many countries around the world. In Canada, however, it is a ‘species at risk’: between 1970 and 2019, its numbers declined 68.6 per cent to 6.4 million, and continue to fall. The reason is human.
“Before colonization, the birds would use old, dead tree trunks upon which to build nests. Since colonization, most of these trees have been removed. Also, now there are a lot of pests like raccoons and squirrels, so even if the birds find a tree, their eggs might get eaten up. So the birds pretty quickly adapted to nesting on buildings, and barns were quite common till a few decades ago,” said Samuels.
These nests would be located towards the top of the walls, near the roof of the barn.
“A big reason for the decline in their numbers is loss of habitat. A lot of the barns, which replaced the trees, were replaced by other types of structures. Also, insect populations have declined a lot because of the use of pesticides. So, one way in which we can help stabilize their numbers is to replace the structures in which they used to build their nests,” said Samuels.
Attempts have been made to accommodate the birds affected by habitat loss. From 2015 onwards, the Ontario ministry of transportation put up barn-like structures along highways built over the birds’ habitat, like wetlands. These structures, however, have not been very successful at attracting the swallows. The reasons are being studied.
The structure has ledges to provide support for nests. (Brendon Samuels)
Meanwhile, the Western campus appears to offer swallows several favoured spots in buildings, culverts and tunnels, where they build their nests each season. The birds occur in high numbers at Western because of the habitat available here including wetlands, grasslands, old growth forest and the Medway Valley Heritage Forest which has been designated an environmentally significant area.
“The nests are made of mud and twigs. The swallows have to make hundreds of trips and build them with saliva. It’s quite labour intensive and although the birds do not re-use nests, they do return to the same approximate location each nesting season,” said Samuels, who has meticulously documented and mapped hundreds of barn swallow nesting sites around campus.
“In some cases, they like building nests in a particular spot on the wall of a campus building because it is stable and supports the nest, while being far away from predators,” the researcher said.
Biologists now have a much clearer idea of the swallow’s declining numbers, habitat and food source loss, and nesting requirements. The new breeding structure is a secluded spot on campus, and its precise location is a closely-guarded secret to give some peace and quiet to the birds, which can get protective and territorial during nesting season.
The structure has ledges in different shapes and sizes, located near the roof, allowing the birds to choose a suitable, stable spot for a nest. The legs supporting it have conical sleeves to prevent predators from climbing up the walls. It is also surrounded by spots teeming with insects to serve as food source for the birds and their hatchlings.
Going forward, project members will monitor the birds’ use of the structure. Successful nests would mean the construction features of the barn and its location could be used to create design standards for similar structures elsewhere, in a continuing effort to stabilize the species’ population. And saving the barn swallow could show the way for conservation groups to bring together better understanding of urban spaces, design and ecology to protect other species.