Chimney swifts are federally protected under the Migratory Bird Treaty Act, which means it is illegal to remove or disturb them, their nests, eggs, or young during breeding season. If swifts are already nesting in your chimney, you cannot legally evict them. The good news: they leave on their own every fall, and once they’re gone, you can permanently prevent them from returning with a chimney cap.
Why You Can’t Remove Them Right Now
Chimney swifts migrate to North America from Peru each spring and typically nest and raise young from late June through mid-August. Fall migration runs from mid-August through early October. During the entire time birds are present, federal law prohibits removing or disturbing them. Violations of the Migratory Bird Treaty Act can result in fines.
If you’ve called a chimney sweep, they should know this. Texas Parks and Wildlife recommends rescheduling any chimney cleaning for at least six weeks after eggs are laid, or at least four weeks after young hatch. The safest and simplest approach is to wait until late fall, after the swifts have migrated south for the winter, before doing any work on your chimney.
Managing the Noise While You Wait
The chirping of baby swifts begging for food is the main complaint most homeowners have, and it gets louder as the chicks grow. You won’t have to endure it for long. The entire nesting cycle from eggs to fledging takes roughly six weeks, and the young typically leave the chimney within two to three weeks of hatching.
In the meantime, close your fireplace damper completely and pack insulation material into the area below the damper and above the firebox. This can substantially reduce the noise that travels into your living space. It also helps block any odor from droppings. A white noise machine or fan near the fireplace can mask whatever sound gets through.
Install a Chimney Cap After They Leave
Once the swifts have migrated in the fall (typically by mid-October at the latest), a chimney cap is the permanent solution. Caps are protective metal coverings that sit on top of the flue, usually made of stainless steel or copper mesh. A stainless steel cap with a stainless steel spark guard will essentially last forever and requires no maintenance.
The mesh openings should be about 3/4 of an inch across. This is small enough to keep birds, squirrels, and raccoons out while still allowing proper ventilation and preventing ember escape. Common cap sizes for masonry chimneys include 8×8, 8×13, 13×13, 8×17, and 13×17 inches, but you’ll want to measure your flue or have a chimney professional measure it.
Schedule the installation for late fall or early winter. Most homeowners don’t think about their chimney until cold weather arrives, and by then chimney companies are backed up with inspection and repair requests. Booking ahead gives you a better chance of getting it done before the next heating season.
Do Not Light a Fire to Drive Them Out
This is both dangerous and illegal. Starting a fire while swifts are nesting can kill the birds (a federal violation) and poses a real fire hazard. Swift nests are small, bracket-shaped structures made of twigs glued to the chimney wall with saliva. They can break loose and fall into the firebox, or smoldering material can ignite creosote buildup on the chimney walls. Never use smoke, fire, or chemical repellents to try to force swifts out.
Consider Building a Swift Tower Nearby
If you want to keep chimney swifts off your property altogether, a cap alone does the job. But if you enjoy the birds (they eat thousands of flying insects daily) and just don’t want them in your chimney, you can redirect them to a purpose-built nesting tower.
A swift tower is essentially an artificial chimney. It needs to be at least eight feet deep with a minimum internal diameter of fourteen inches. Larger and deeper towers are more attractive to swifts because they also serve as communal roosting sites during migration. The interior surface must be rough so the birds can cling to the walls. A good material choice is 5/8-inch textured T1-11 plywood siding, installed with the rough side facing inward and the grooves running horizontally to create footholds.
Construction details matter. An air space between the inner chamber and outer wall, filled with rigid insulation board, prevents overheating, which is a common problem with smaller towers. The bottom should have a grid of 3/8-inch ventilation holes spaced one inch apart to keep the interior dark and appealing. A “sun collar” on the top north-facing edge protects eggs and young from direct sunlight. Paint or stain the outside a light color to reflect heat, but leave the inside unfinished so the texture stays rough.
Place the tower on the north or east side of a building where it stays cooler in summer. The top should extend four to six feet above the roofline of any nearby structure so swifts can spot it easily. A 24-inch band of metal flashing around the top acts as a predator guard against raccoons and opossums. Freestanding towers on legs work well too, but they need a concrete foundation: 36x36x6 inches for an 8-foot tower, or 48x48x8 inches for a 12-foot tower, reinforced with rebar.
Timeline for Getting Your Chimney Back
Here’s a realistic schedule. If swifts arrived in spring and you’re hearing nesting activity now, expect them to stay through late summer. By mid-October, the last stragglers have migrated south. Schedule a chimney sweep for late October or November to clean out any leftover nest material, droppings, and debris. Have the cap installed at the same time, and your chimney will be swift-free and ready for the heating season. Once the cap is in place, swifts will not return to that flue.