WATCHERS AT A ROOST: Chimney Swifts in Peterborough
We are fortunate to have many of the swifts still living in Peterborough
Starting in early May, Peterborough residents especially those living or working downtown may see the chimney swift flying overhead looking like the proverbial “cigar with wings”. Some of them stay to nest locally in our city’s chimneys but others continue northward to nest in other chimneys or tree cavities.
Have you seen them? Have you ever wondered what they do at night? What we can we learn about their nesting and their numbers by watching them go to roost?
The chimney swift is a small aerial insect-eating bird found in eastern North America during the summer and in the Amazon River basin of South America in the winter, making it a long-distance migrant. During the day, it flies in the sky almost continuously, feeding on flying insects. Its chittering calls and somewhat jerky flight may attract your notice high above the downtown core.
At night in our area, it seeks out chimneys to roost in. Its unusual habits of being restricted to aerial food sources which are declining has led to its being labelled Threatened both nationally and provincially under species at risk legislation. These laws give swift roosts and nests, including the chimneys, habitat protection. Funds are available from a national bird conservation organization, Birds Canada, which can allow owners to repair of chimneys used by swifts. We are fortunate to have many of the swifts still living in Peterborough.
In Peterborough, many swifts roost communally, every evening, in a chimney in the George Street and Charlotte Street area. As part of a coordinated effort to monitor their numbers across Canada, other birders and I have conducted watches at the chimney on a commercial building there for over 15 years. The watches are done on five evenings four days apart in late May and early June. Other chimney roost sites across the chimney swifts range in Canada are also monitored on the same dates, so a total number of swifts can be obtained.
Birds Canada reports on May 25, 2022, a grand total of 10,769 Chimney Swifts were seen at 96 roosts across from Manitoba to the Maritimes. Some chimneys have remarkable roost numbers. The Toronto Moss Park Armory had 1,800 swifts enter their large chimney on May 22, 2019. Newsletters on the compilations are available on the Birds Canada website.
In 2023, Dan Williams and I — along with 16 naturalists from the Peterborough Field Naturalists — watched the swifts’ main roost in Peterborough from the top of the King Street parking garage and counted them entering the chimney. Sometimes a few swifts went into other nearby chimneys. Here I report on our results from 2023 for five set dates in May and June and two dates in August.
The highest number of swifts entered the roost on May 24 when 165 entered. This total was comprised of local nesting birds as well as migrants. The least number of swifts entering the roost occurred on May 28 when 82 dropped into the main roost chimney.
It took the swifts an average of 36 minutes to enter the chimney from the time the first entered until the last. Sometimes a large group of swifts will enter the roost all at once as happened on May 24 when 81 swifts entered in one minute in a “swiftnado”.
On other nights their timing is more spread out. The peak time when swifts entered the roost varied from seven minutes after sunset to 16 minutes after sunset. Fewer swifts were seen in August when 51 entered on Au. 21. I was surprised that fewer were seen in August than in May and June. I had thought that young-of-the-year would increase the totals. Perhaps many swifts had already migrated.
Some nights in May and June, two or three swifts would go into adjacent chimneys which indicates they may be planning to nest in them. May 24 was also the night we saw a high-flying flock of 80 large brown-gray shorebirds heading NW. It is likely that they were Whimbrels flying from their staging grounds on the Chesapeake Bay to their Arctic breeding grounds. A common nighthawk was also seen. On May 28, a merlin which is a predator on swifts flew around the chimney as the swifts were entering. Perhaps the swifts prefer to enter the chimney all at once after sunset to avoid merlin predation. The evenings always had something interesting to see.
The count that year (165 on May 24) was higher than any other year in the past eight years that I have been recording the totals in eBird, a birding conservation database. Does this mean the population is increasing? Perhaps, but the number of chimneys for them to nest and roost in is slowly decreasing as new buildings no longer use open chimneys as in the past, so we must use caution in suggesting an increase.
Twenty years ago, the swifts used to roost in the old Central School. Erica Nol remembers seeing hundreds with her Trent University students. The numbers entering the downtown chimneys have declined. National surveys of roost numbers show the numbers to be stable.
What about trees? Do they nest in trees as they once did historically? An encouraging note is found in a recent study by ornithologist Jeremie Tixier who found five active chimney swift nests in cavities in yellow birch and sugar maple trees in an old growth forest in Quebec. They were found by catching swifts at a roost, placing radio tracking tags on them and then following them to nesting trees. The study suggests that with proper protection and management, some of Canada’s forests can provide nesting habitat which would supplement that of our cities’ chimneys.
In August, the chimney swifts start to migrate south. Their numbers drop off sharply after the first week of September.
If you are interested in seeing the swifts go into their roost chimney, the best times are to go between mid-May and late August. The main roost chimney is visible if you look north from the top of the King Street parking garage. Start watching the sky for swifts about 15 minutes before official sunset, knowing that peak entry is a few minutes after sunset.
You’ll see them flying arcs in the sky, slowly gathering in numbers until right around sunset they start entering the chimney in a swirl. On clearer, warmer nights they seem to stay out a few minutes later as was seen in our August observations. The 2024 established national watch dates will be on May 18, 22, 26, 30 and June 3.