Just before sunset on a cloudy and unseasonably cool evening in early June, I headed out in search of a group of Chimney Swifts roosting near my neighbourhood in central Ottawa. Upon arrival at about 8:20pm, I saw a dozen Chimney Swifts circling and calling high above me.
As I listened I could hear the high pitched twittering of many more swifts than I could see, as they circled overhead. It was amazing to watch them whiz about above my head. Their flight seemed truly effortless reminding me more of a swarm of insects then a flock of birds. It was only a few minutes before the group doubled and then tripled in size. The way they were all calling at once made it seem as though they were catching up on the day’s gossip as they rejoined the group for the night.
Chimney Swifts fly constantly and are almost never seen perched. As members of the guild of aerial insectivores they have the specialized ability to catch insects in mid flight. They have a significant role to play in controlling insect populations as a single bird is capable of eating more than 1,000 insects in one day.
From where I stood only a block from the intersection of Somerset and Booth I could see the Ottawa River downhill. This section of the river all the way West to Innis Point makes up the Lac Deschênes – Ottawa River Important Bird Area, a site recognized globally for its significance to bird populations. The Chimney Swifts make the short trip from their roost every morning to the river to feed on the abundant insects found there.
It was about 8:45pm when the sun was setting and hundreds had gathered together. They were moving with the gusting wind and circling around the large brick chimney I knew had to be their roost. Each bird was constantly banking and turning. It may have been an illusion of the light, but their long-pointed wings seemed to blur in the air with their fast wing beats.
All at once one bird rushed into the chimney, followed by another, and then a few more. It was not a swarm all at once, but a constant stream as some flew into their roost and other swooped around one last time before calling it a night.
Chimney Swifts do not sit on perches like most birds, but instead cling to the walls of rough, vertical surfaces with their long claws. Before European settlement these birds would have roosted in caves and hollow tress. The construction of stone and brick chimneys provided the perfect alternative as much of their natural roost were removed by forestry. They thrived in urban areas and became common.
Today their numbers are suffering from changes in chimney design and the Chimney swift is listed as Threatened both federally and provincially in Ontario. Covered or narrow flutes make the chimney inaccessible, and updating chimneys with a smooth interior mean that there is nowhere for these birds to cling onto. At the same time, fewer buildings are being built with chimneys as a chimney’s function has become obsolete with advances in heating technology.
Watching this group funnel into the chimney it is easy to believe that Chimney Swifts nest in colonies. However this is not the case. Swifts will migrate into Ontario around early May and will roost together until about mid-June when pairs go off to build a nest by themselves. The nest is a construction of small twigs held together with saliva which acts as glue holding the cup like formation onto the inside wall of a chimney. Non-breeding swifts will still stay together in the summer, and are joined by the breeding pairs for the migration journey around the end of August. Chimney swifts breed in eastern north America and winter in north western south America.
By 9:10pm the sun had set and the last swifts had filed into the roost. The night was very peaceful after all the chatter a few hundred swifts produce had ended.
There are colonies like this one across the city and other cities in Canada, although there are fewer every year. I am excited to come back next spring and see how the swifts are doing.