Chimney
A chimney is a hollow tree with better ventilation.
Chimney Swifts, raccoons, and grey squirrels all use flues, and the right response is different for each.
An unlined masonry flue is a vertical cavity with a rough surface, protected from weather and predators. Chimney Swifts nest on the inner wall and are federally protected while doing so; raccoons use the smoke shelf as a den; squirrels fall in and cannot climb out of a slick metal liner.
What you are hearing
Chittering and a mechanical twittering that rises and falls is a swift brood, and it lasts about two weeks before they fledge. Scrabbling that continues at all hours, with silence in between, is an animal trapped on the damper. Heavy movement above a closed damper at dusk is a raccoon leaving to forage.
What to do
- 01Keep the damper closed and the fireplace doors shut while you work out what you have.
- 02If it is a swift brood, wait. They fledge within a fortnight and leave for the season.
- 03If something is trapped on the damper, hang a knotted rope or heavy towel down the flue at dusk and leave the room. Most animals climb out overnight.
- 04For a raccoon in a den, wait for the young to be mobile, then fit a one-way door at the top and cap the chimney once it is empty.
- 05Have the flue inspected before the next fire. Nest material is a fire hazard.
What not to do
- Do not light a fire to drive anything out. It kills the animals and can set the flue alight.
- Do not remove an active swift nest. They are protected under the Migratory Bird Treaty Act.
- Do not open the damper to look. Animals enter the room and the situation gets much harder.
Stopping it happening again
- Fit a stainless steel cap with a spark arrestor once the flue is confirmed empty — never during nesting season.
- Have the chimney swept annually. A clean, capped flue is not attractive to anything.
- Consider leaving one unused flue capped with mesh that still admits swifts if you want to keep them; their numbers are falling.
When to call someone licensed
Any raccoon in a flue, any animal you cannot see, and all capping work. Chimney work is height work.
Find a rehabilitatorUnderstand the animal
Chimney Swifts lost their original habitat — hollow old-growth trees — and moved into masonry. Their decline is partly a story about capping chimneys.