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Birdaday Field Notes

Nest box reference

When to clean out birdhouses

The cleaning itself is simple; the timing is what matters. A nest with eggs or young is protected by federal law, and the published guides disagree on whether to clean between broods, in fall or just before spring. This page sets out what each source says, what the U.S. Fish and Wildlife Service (USFWS) says about nests, and a cleaning routine built from the published steps.

Quick read

Never while the nest is in use. USFWS: it is illegal to destroy a nest that has eggs or chicks in it, or one that young birds still depend on.

After the young leave: clean only when there is "absolutely no sign of breeding activity in the box"; if you are not sure, wait another day (NestWatch).

At least once a year: at the end of the season (e.g. September) or right before the next one (e.g. February), as Sialis.org puts it. Sources prefer different ends of the winter.

House Sparrows and European Starlings: the Migratory Bird Treaty Act (MBTA) does not apply to them (USFWS list, 2020). State and local rules can differ.

When the sources say to clean

"—" means the source does not address that point.

Source Between broods End of season Before the next season
NestWatch FAQ (Cornell Lab) Leave the nest; the parents may raise another brood. Some monitors clean after every brood. Remove the nest, scrub with mild detergent and water —
NestWatch Eastern Bluebird page Clean out "as soon as a brood fledges" for a second attempt — —
All About Birds (Cornell Lab) — Suggested (citing NestWatch), but not required; birds often clean the box themselves —
Sialis.org Prefers right after fledging; leave Tree Swallow nests 1–2 weeks At a minimum, e.g. September Or right before, e.g. February; again if mice moved in
North American Bluebird Society (NABS), monitoring sheet (rev. 2007) Remove the nest once nesting ends Leave the last nest in so jewel wasps can overwinter —
Clemson Extension (HGIC 2908, 2023) Remove all nesting material after fledging — Clear debris from boxes left up over winter
Maryland DNR (2018) — Clean out once nesting season is over Repair in winter: owl boxes in January, kestrel and bluebird boxes by mid-February, most songbird boxes by the first week of March
Bexar County Master Gardeners (Texas, 2026) — Clean at the end of each season… …"preferably in late winter/early spring"

Where the sources disagree

A nest-box year, with the example cleaning and repair dates the sources give, numbered 1 to 6A January to December timeline. 1 January: repair owl boxes. 2 February: clean before the season and have boxes up in the south; kestrel and bluebird boxes ready by mid-February. 3 March: songbird boxes ready by the first week of March and northern boxes up by mid to late March. A long shaded band from spring through summer marks the nesting season, when in-use nests are left alone; its timing varies by species and region. 4 Dashed lines inside the band mark the gaps between broods, when sources disagree about cleaning. 5 September: end-of-season cleaning. 6 A band from late fall through February marks winter, when birds may roost in boxes and mice may move in. A nest-box year: example dates from the sources roosts, mice roosts, mice Nesting season leave in-use nests alone (timing varies by species and region) JFMAMJJASOND 123456 Schematic: months are examples from the sources; your birds' dates differ. Not to scale.
  1. January: inspect and repair owl boxes (Maryland DNR).
  2. February: pre-season cleaning, e.g. February (Sialis.org); boxes up by February in the south (NestWatch); kestrel and bluebird boxes ready by mid-February (Maryland DNR).
  3. March: most songbird boxes ready by the first week of March (Maryland DNR); boxes up by mid to late March in northern regions (NestWatch).
  4. Between broods (dashed red lines): clean right after fledging (NestWatch bluebird page, Sialis.org, Clemson, NABS) or leave the nest until the season ends (NestWatch FAQ).
  5. September: end-of-season cleaning, e.g. September (Sialis.org).
  6. Winter: boxes may hold roosting birds, mice or squirrels (NestWatch); mice move in from late fall through winter and their nests should come out before spring (Maryland DNR).
Drawing: Birdaday Field Notes, following the NestWatch, Sialis.org, NABS, Clemson Extension and Maryland DNR pages cited below. The nesting band is schematic. Not to scale.

What federal law says about nests

This is a summary of USFWS and state agency guidance, not legal advice. When in doubt, ask your state wildlife agency before removing a nest.

The MBTA is "the primary legislation protecting native birds in the United States," and it covers native birds that do not migrate, such as chickadees (Maryland DNR). USFWS set out its current nest policy in a permit memorandum dated January 15, 2025 (MBPM-2-02), which replaced its 2003 and 2018 nest memos:

Nest What USFWS says
In use: holds viable eggs or nestlings, from the first egg until the young fledge and no longer depend on it Destroying it requires MBTA authorization. Permits are rare and usually only for a human health or safety problem (USFWS Bird nests page).
Inactive: no viable eggs or nestlings (before the first egg, after fledging, or abandoned) Can be destroyed without a permit, as long as nobody keeps the nest or its contents. You are responsible for confirming it is inactive, and destruction that takes birds or viable eggs is still illegal.
Keeping or moving a nest Possessing a nest, even one found on the ground, needs a permit. Relocating any nest, in use or not, needs authorization.
Bald and Golden Eagles Nests protected at all times under the Bald and Golden Eagle Protection Act.
Endangered Species Act-listed birds Inactive nests may still be protected.
House Sparrow, European Starling The MBTA does not apply: the 2020 list names the families Passeridae (including House Sparrow) and Sturnidae (except species in the Japan treaty). Maryland DNR also lists the Rock Pigeon as not federally protected.

The memo counts a nest under construction, before the first egg, as inactive. Nest-box groups take a stricter line. NestWatch says "it is illegal to disturb the nest or eggs of any native bird species," and Sialis.org says never remove active nests of native birds. The memo itself recommends doing nest work outside the nesting season, because nesting behavior can make it hard to tell whether a nest is in use.

State and local law can add rules. The memo says inactive nests may also be covered by Federal, State, Tribal or local laws, which you must check first. Maryland DNR notes that a state permit may be needed on top of a federal one, and that Mute Swans are protected by Maryland law even though they are an introduced species. It lists MBTA penalties of up to six months in jail and fines of up to $15,000.

Know whose nest it is. Male House Wrens may fill every box in their territory with twig nests, and the female uses only one (NestWatch), so an unused-looking stick nest can still belong to a native bird. Sialis.org warns that Western Bluebird and titmouse nests have been removed by people who took them for House Sparrow nests. Our House Sparrow guide compares the nests and eggs.

How to clean a nest box, step by step

  1. Confirm the box is finished. No sign of breeding activity (NestWatch). For a nest that looks abandoned, Sialis.org waits at least the incubation period plus a few weeks: "When in doubt, wait it out." Leave unhatched eggs at least 72 hours after the last chick hatched (Sialis.org); Clemson removes eggs that have not hatched 3–4 weeks after laying.
  2. Identify the nest (see above). Remove only nests that are inactive or belong to House Sparrows or starlings.
  3. Protect yourself. Wear gloves (Clemson, Maryland DNR); Sialis.org suggests a NIOSH N95 mask and standing upwind. Never reach into a box you cannot see into; use a putty knife or paint stirrer (Sialis.org, Maryland DNR).
  4. Mouse nest? Soak it first. CDC says do not sweep or vacuum rodent nesting material; spray it until very wet with a fresh 1-to-9 bleach solution (about 1½ cups per gallon) and wait 5 minutes or as the label directs. Sialis.org soaks the nest and box and waits 15–20 minutes.
  5. Bag the nest (Sialis.org inverts a plastic bag over the hand; Clemson uses paper bags) and dispose of it in the trash or far from the box, where it will not draw predators (Sialis.org, Maryland DNR, NABS, Clemson).
  6. Scrape and brush the inside with a stiff brush, clear clogged drainage holes and remove wasp nests (Sialis.org, Maryland DNR). Maryland DNR rubs the inside of the roof with unscented bar soap or nonstick cooking spray to discourage wasps.
  7. Disinfect only if needed, then leave the box open for at least a day to air and dry (Sialis.org, Maryland DNR).
  8. Repair: tighten screws and hardware, fix predator guards (Maryland DNR), and take off any sparrow spooker or wren guard (Sialis.org). Our birdhouse plans page covers hinged sides, vents and drainage.
  9. Wash your hands with soap and water (Sialis.org, CDC, Clemson).
  10. Decide on winter. Leave the box up as a roost, seal it, or prop the door open (NestWatch). NestWatch's Carolina Wren page says to leave boxes up in colder climates for winter roosting (Carolina Wren nest box notes); Maryland DNR opens the front or side of songbird boxes until spring to keep mice out. Either way, have boxes ready by February in the south and mid to late March in the north (NestWatch).

Checklist

For box sizes by species, see birdhouse dimensions; for running a series of boxes, see the bluebird trail steps.

Sources