Bat Exclusion Blackout Dates: Colorado and Neighboring States

If you just found out you have bats, your first question is usually simple.

When can we fix this?

You might also hear scary sounding phrases like blackout dates, maternity season, and protected wildlife. That can feel frustrating, especially when bats are living in your home right now.

This article explains how bat exclusion timing works, with a strong focus on Colorado. We will also cover the states that border Colorado, since people in northern Colorado often have family, cabins, or rentals across state lines.

You will learn:

• What blackout dates really mean

• Why maternity season matters and what Colorado Parks and Wildlife recommends

• What nearby states recommend

• How pros plan a project so bats leave safely

This is educational only. We are not a government agency and we are not giving legal advice. Rules can change, and some situations involve special protections. When in doubt, we recommend checking with the state wildlife agency for your location.

Quick Definitions

What is bat exclusion?

Bat exclusion is the process of:

• Letting bats leave on their own

• Blocking them from getting back in

• Sealing the structure so they cannot move to a different gap

It is different from extermination. Ethical exclusion is about letting bats exit alive and safely.

What are blackout dates?

Blackout dates are time windows and specific laws when exclusion should not happen because:

• Baby bats might be inside and cannot fly

• Sealing the entry points can trap pups

• Trapped bats may end up in living spaces trying to escape

Some states publish clear seasonal laws while most simply provide seasonal guidance. Other states leave it as best practice guidance rather than a strict calendar. Either way, the biology is the same.

What is maternity season?

Maternity season is when female bats form maternity colonies and give birth. The pups are flightless for a period of time.

During that flightless period:

• The mothers leave at night to feed

• The pups stay behind

• If you seal the home, the mothers cannot return

• The pups cannot follow

That is why timing matters.

Colorado: What the State Recommends

Colorado Parks and Wildlife explains that bats can be excluded humanely by sealing access points, but warns that timing is important to avoid killing bats and their pups. CPW specifically says to avoid sealing bats out of buildings during pupping season, which can range from June to August.

What that means in real life

In Colorado, a simple, practical way to think about timing is:

• Spring, Mid to Late Summer, and fall are usually the best windows

• Summer is doable, but requires extra some caution because of pups

• Winter work depends on weather access and what the bats are doing

Colorado weather also matters. Even if a calendar says it is allowed, safe work still depends on:

• No snow or ice on roofs

• Safe ladder and roof access

• Materials adhering properly in cold conditions

Safety comes first for the homeowner and the technician.

Why bats are protected

Bats are protected and managed because they matter.

• They eat huge numbers of insects

• They reproduce slowly, usually one pup per year

• Many bat populations are under pressure from disease and habitat loss

When you understand that bats are slow to replace, the idea of protecting maternity colonies makes more sense.

This is also why bat work is not like general pest control.

The part homeowners care about

Can we do exclusion in Colorado most of the year?

Often, yes.

But the correct answer is:

• We can do exclusion when it is safe for bats

• We can do exclusion when it is safe for the crew

• We can do exclusion when the structure can be sealed correctly

Colorado is not a one size fits all state. A mountain cabin and a front range ranch home do not behave the same.

What we do during maternity season

If a home has bats during maternity season, professional options usually include:

• Inspection to confirm activity and entry areas

• Identifying whether pups are present

• Planning and scheduling exclusion accordingly

• Understanding that most bat-proofing preparation and sealing work can be completed during maternity season, with only the installation of one-way exclusion devices needing to wait until pups are able to fly.

• Helping you reduce risk inside living spaces

The goal is to avoid a rushed decision that creates a bigger problem.

Colorado Border States: Published Guidance and Common Timing

Colorado borders seven states:

• Wyoming

• Nebraska

• Kansas

• Oklahoma

• New Mexico

• Arizona

• Utah

States vary a lot in how clearly they publish seasonal guidance for homeowners. Below is what we could confirm from official sources at the time of writing.

Important note:

• Most states have guidance rather than strict legal blackout dates

• Federal protections can apply to certain bat species or roost sites

• Local rules, permits, or protected structures can add requirements

Utah

Utah Division of Wildlife Resources advises that excluding bats is best done in the fall and says to never seal bats out when there are pups in the roost. Their published guidance notes pups can be present May through August. (wildlife.utah.gov)

Practical takeaway:

• Avoid sealing during May through August when pups are present

• Fall is often ideal

Kansas

Kansas Department of Wildlife and Parks guidance for bats in houses gives clear seasonal recommendations.

They state that bat exclusion and removal is not recommended:

• May through late June

• November through February

They also note that the best months are September through October, and that July through October is generally the most common time bats are noticed. (ksoutdoors.com)

Practical takeaway:

• Late summer and early fall are the main window

• Avoid early summer when young may be present

• Avoid winter when bats may be inactive

Arizona

Arizona Game and Fish provides very direct guidance on the maternity period.

They say:

• Never exclude bats during the summer months of May to September because this is the maternity period and young bats could be trapped inside and separated from their mothers (azgfd.com)

They also note bats can squeeze into holes as small as 3/8 inch, which is one reason exclusion has to be detailed. (azgfd.com)

Practical takeaway:

• May through September is treated as a no exclusion window

• Plan for fall work when possible

Oklahoma

Oklahoma Department of Wildlife Conservation has published homeowner guidance for bats in attics.

They warn that if you seal the attic when you first notice bats you may trap young inside. They recommend waiting until about late July, when the young are old enough to fly, to exclude bats from the attic. (wildlifedepartment.com)

Practical takeaway:

• Late July and later is often the first safer window

• Early action should focus on not trapping pups

Wyoming, Nebraska, and New Mexico

For Wyoming, Nebraska, and New Mexico, we did not find a clearly published statewide homeowner calendar for exclusion blackout dates on official state wildlife pages during our research for this article.

That does not mean there are no rules.

It usually means one of these is true:

• The agency relies on general best practice guidance

• Rules are handled through permits for specific situations

• Guidance is spread across multiple documents or programs

Practical takeaway:

• Assume late spring and early summer can be risky due to pups

• Contact the state wildlife agency for the most current guidance if you are scheduling work across state lines

How long are pups flightless?

Homeowners often ask for an exact number of weeks.

In reality, it varies by species and conditions, and that is one reason agencies give broader windows rather than a single date.

A safe way to think about it:

• Pups are born in late spring through midsummer

• There is a period when they cannot fly

• Exclusion should wait until young are capable of leaving with the adults

This is why an inspection matters. When a colony is active, we are not guessing. We are looking for signs that help us time the project correctly.

Why people think exclusion can only happen in winter

This myth is common.

People hear that bats leave in winter, so they assume:

• Wait until winter

• Seal everything

• Problem solved

The reality is more nuanced.

• Some bats migrate

• Some bats hibernate

• Some use buildings as temporary shelter

• Winter access and weather can be a dealbreaker in Colorado

In the mountains, you can lose safe roof access quickly once snow and ice settle in. That can turn a good plan into a long delay.

The Colorado approach we recommend

If you are in Colorado, here is a calm, practical approach that protects bats and still solves your problem.

Step 1: Inspection and planning

An inspection can be done anytime it is weather safe, and answers:

• Where are they getting in

• How widespread are the gaps

• Are there signs of pups or a maternity colony

• What is the safest exclusion window

Step 2: Choose the best safe window

In Colorado, many homes are best handled:

• In spring before pupping season ramps up

• In mid to late summer and fall after young are volant and activity settles

Step 3: Do it once, do it right

The biggest time risk for homeowners is paying for a partial solution. If you seal only one area but leave other gaps, bats do what bats do. They keep searching. That is why full structure exclusion is usually the only approach that lasts.

Conclusion

Blackout dates are not about red tape. They are about biology.

In Colorado, state guidance is clear that you should generally avoid sealing bats out during pupping season.

Nearby states publish different windows, with some treating most of summer as a no exclusion period.

The best path is simple:

• Confirm what is happening with an inspection

• Plan exclusion for a safe window

• Complete a full, detailed seal so bats cannot shift to a new gap

That is how you protect bats, protect your home, and avoid repeating the same problem next year.