Chimney Swift Monitoring 2024

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What are they?

Chimney Swifts are small, dark birds that are present in London from late April to early October. Often first detected by their twittering, swifts fly high above buildings and treetops, snatching insects from the air. Tiny twig-and-saliva nests are placed well down inside old chimneys, one nest per shaft. During spring and fall migration, groups of swirling swifts make spectacular dives into chimneys to spend the night.

Non-breeding swifts roost together in chimneys. Sometimes there is an active nest in a chimney at the same time.

Where and when can we see them?

As soon as you hear their twittering, look for them zooming overhead. Once you learn their sound you will notice them in areas with old chimneys in southern Ontario.

A pair of swifts waste no time before entering a chimney – blink and you could miss them.

Dozens of swifts may be seen around a chimney with a large roost. They may make several approaches before entering.

Why monitor?

Nature London shares its data with the provincial database maintained by Ontario SwiftWatch. Our information helps inform conservation decisions and contributes to the knowledge of swift numbers in Ontario.

When do we monitor?

In 2024, we plan to monitor on Tuesday evenings, but fewer of them than in past years. See the schedule below. The dates of the National Chimney Swift Roost Monitoring Program of Environment and Climate Change Canada involve 4 nights that are only 4 days apart.

May 7, 22 (Wed), 26 (Sun), 30 (Thur); June 3 (Mon), 18; July 9, 30; August 13, 27; September 10, 24; October 8.

During August and September, we may monitor the busiest chimneys on behalf of out-of-town wildlife rehabilitators who specialize in raising orphaned Chimney Swifts. It is important to identify optimal release sites.

How do we monitor?

On a typical night, you spend a pleasant hour near sunset, making observations and contributing to citizen science. The goal is for everyone to stay safe and healthy. We also hope you enjoy the swifts and the monitoring sessions.

Before a night of monitoring, read the parking tips and recommended monitoring positions for your assigned location. Report any corrections. We maintain the details for each chimney location in a password-protected area of the Nature London website.

Start monitoring 30 minutes before sunset until 30 minutes after (or it is too dark). Sunset time is included with each monitoring assignment.

If it is cold (<13º), cloudy or rainy, start monitoring 45-60 minutes before sunset. You may choose to monitor on a subsequent night when conditions are better and your partner is available. For some locations, you can monitor from inside your car, even in heavy rain.

Always bring the following:

  • Printed field data recording form for each chimney to be monitored
  • Pencils, clipboard, timepiece, swift business cards

Consider bringing the following:

  • Lawn chair, seasonal clothing, water, insect repellent, phone, buddy, binoculars.

Fill in preliminary data on the form: date, location, observer(s), sunset time, weather codes, start time, and whether you are video recording.

For locations with two chimneys, complete a separate form for each chimney, deciding in advance which monitor is responsible for monitoring and recording at each chimney.

To the nearest minute, record times and numbers of swifts entering and exiting a chimney. For big numbers, record estimates and approximate time intervals.

To complete the form, record your stop time, times of first and last entries by swifts, plus any other notes of interest.

How do we report our observations?

Use the link on the website to access the online data entry form.

Each chimney monitored must be reported separately.

Personal safety

Here are some suggestions for your comfort and safety.

  • Always monitor with a partner
  • Carry a phone.
  • Remain aware of the surrounding area.
  • Place lawn chairs in an area of high visibility or monitor from a vehicle.
  • Respect private property and pedestrian traffic.
  • If you are uncomfortable, leave immediately.
  • Carry swift cards to give to curious passersby, but don’t be distracted.

Monitoring tips

One monitor should be watching the top of the chimney at all times.

Record the times and numbers of all swifts entering or leaving the chimney.

Try to avoid counting near misses.

If many swifts enter at nearly the same time, switch to counting/estimating by 5s or 10s.

If you are the only monitor at a chimney, minimize the time your eyes are off the chimney. You could try to make voice memos instead of manually recording the numbers of swifts.

Record any interesting swift behaviour, possible predators, and other observations.

To estimate the number of swifts inside the chimney for the night, subtract exits from entries.

If at any time during the evening, you find your number of exits is greater than your number of entries, there were swifts in the chimney before you arrived or you missed an entry.


There is one point of contact for all members of the Chimney Swift Monitoring Committee (Glenn, Susan, and others):

Glenn is looking after the scheduling. He prepares and circulates monitoring assignments for each night of monitoring. For orientation, he matches new monitors with experienced monitors. He makes every effort to accommodate preferred monitoring partners, preferred chimney locations, and personal schedules (including last-minute changes).

A summary of monitoring results will be available after each monitoring date.