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Swallowville: Pop. 200

Issue 6NatureNature Issue 6Species

The travellers who arrive here come from as far away as Panama and Colombia to this spot in the spring, where over thirty nest boxes stand. Welcome to Swallowville, home of up to two hundred Tree Swallows from May to June. Walk down the Lakeshore Lookout trail at Mountsberg Conservation Area around this time and you’ll see the lively flock swooping and diving and flying this way and that, socializing, plucking prey, and nesting.

Early in the nesting season, staff ecologists will toss a handful of feathers early in the nesting season to a great rush of excitement while the birds rush to collect the best ones. Tree Swallows line their nests and cover their eggs with white feathers. Staff use pillow feathers because there are fewer mites. Even if no one offered feathers to the swallows, the birds would find leftover feathers down at the reservoir. It’s believed that the birds use white feathers to hide their white eggs from predators. It’s difficult for staff to do an egg count because of all the white feathers curving over the eggs. Some swallows will steal feathers from their neighbours if they’re too lazy to find their own. Tree Swallows also use the feathers for play–at least from what we can see. Males, especially, perform with the feathers in grand displays. A male bird will fly up, up high into the sky, drop the feather, and then swoop around the feather all the way down until the bird finally catches it again. Some swallows will attempt to take the feather from it’s owner as it floats down. When Mountsberg has visiting school groups, interpretative staff will give children white feathers to throw so that the swallows catch the feather in mid-air. Some Tree Swallows have become bold in previous years and will come right up to your hand and pluck the feathers from your fingers.

Tree Swallow. Photo by Jim Aikenhead.

Tree Swallows need somewhere to stow their white feather nests and progeny, and prefer to nest in cavities; they need a sheltered hole to make their home. In the wild, they’ll make their homes in carved-out holes by the carpenters of the forest, woodpeckers. Tree Swallows are not finicky and will readily move into nest boxes made by humans, provided that the location is right. They prefer open fields or beaver meadows because they have room to fly and there is enough room in open spaces for the whole flock to move in. Tree swallows are very social and like to visit with their neighbours and family and friends, but they like to have their own allotted space. Tree Swallows are the suburbanites of the bird world: they prefer space between their detached homes. If two nest boxes are too close together, only one family will move into a nest box. Other prospecting families will find the other nest box too close for comfort.

While it may seem appealing to build a nestbox in your own backyard, there are a few reasons we do not recommend that the public erect nest boxes. Exceptions to this rule are farmers or landowners who own large rural areas with open space because they are the most likely to attract a flock of tree swallows. Suburban and urban nest boxes on the other hand will attract the non-native European House Sparrows which are abundant in these areas. European House Sparrows cannot co-exist with other species; in fact, they will destroy eggs, and kill nestlings and adult birds. You wouldn’t want to invite the vicious European House Sparrows into your backyard.

We have not seen European House Sparrows at Mountsberg, and the Tree Sparrows do share the space with more amenable neighbours. Wrens will sometimes take over a nest box or two placed near the shrubs, albeit, they are grumpier then the amiable Tree Swallows and will fill surrounding nest boxes with sticks to prevent new neighbours from moving into their backyard. We’ll often see a pair of Eastern Bluebirds take a box on the very far edge.

Photo by Karlee May

Wrens are only the beginning of neighbours who settle in Swallowville. A busy community full of wild flowers and pollinators thrives underneath the nest boxes even after the Tree Swallows have left in late June. Stand on the edge of Swallowville and you’ll see Black-eyed Susans, Wild Carrot, Wild Grape, Red Clover, Goldenrod, Chicory, and Daisies. Don’t wander in because Poison Ivy grows amidst the tangles. Since so many plants beloved of pollinators grow here, you’ll see an array of damselflies, dragonflies, and butterflies, besides many other insects buzzing and floating around the field of flowers. Swallowville is home to a plethora of flora and fauna, and is a living example of biodiversity in our watershed.

As pretty and serene as Swallowville is now, we could lose it in the future. Due to climate change, the warm weather means that plants are blooming, and the bumper crops of insects are out before the Tree Swallows have returned home. The birds miss out on a much needed feast before nesting. Tree Swallows are areal insectivores meaning that they catch insects in the air during flight. They are not considered a species of concern but all areal insectivores have been experiencing declines in their populations. Areal insectivores are increasingly missing out on the best meals because of the asynchrony between insect populations and migration time. Another part of the problem is the use of insecticides, because then there are even fewer insects around for areal insectivores to eat. Another concern is the unusual cold spells during the breeding season or very rainy weather. Our population at Swallowville, for now, seems stable, but to the east and the north of us, many Tree Swallow populations are in steep decline.

Thank you to  Brenda Van Ryswyk, Natural Heritage Ecologist for her contributions.

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Last modified: September 11, 2017

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