Chimney Swift Monitoring 2024

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What are they?

Chimney Swifts are small, dark birds that are in London from late April to early October. Their chittering sounds (heard on the video) alert us to their presence. They fly high, snatching insects from the air. They build twig-and-saliva nests usually deep inside old chimneys, one nest per shaft. See nest-building in the video at the bottom of this page.

How can we see them?

As soon as you hear them, look up. They zig-zag as they hunt. When gliding, they look like fat cigars with boomerang-shaped wings. Once you learn their sound you will notice them in areas with old chimneys across southern Ontario.

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 less often than in past years. See the dates below. The dates of the National Chimney Swift Roost Monitoring Program of Environment and Climate Change Canada involve four non-Tuesdays that are four 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 monitor the busiest chimneys on behalf of out-of-town wildlife rehabilitators who specialize in raising orphaned swifts. They require a chimney with at least 75 swifts.

Monitoring procedure

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.

Before a night of monitoring, print sufficient copies of the field data recording form. Also, read the parking tips and recommended monitoring positions for your assigned location. Report any corrections for the next monitoring team. We maintain the form and 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 steady 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 are useful for identifying other animals.

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

Reporting observations

Use the link on the website to access the online data entry form. The fields of the online form are in the same order as the fields of the printed form.

Each chimney monitored must be reported separately.

Submit a report even when there are no swifts.

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. The QR code on the card links to this webpage.

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 alone, 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 the orientation of new volunteers, 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).

We publish a summary of monitoring results for each monitoring date.

A deeper dive

Previous version of this page.

Birds Canada prepared this video which features two of the chimneys in our program.