Bats, while extremely ecologically beneficial (they are insectivorous, important pollinators, and are a food source for large raptors), bats can become a nuisance and a human health threat when pressed out of their natural habitats and into closer contact with humans/into roosting in man-made structures. Bats hibernate during colder months and, while they often do so in caves, rock crevices and tree cavities, they will also hibernate in human-built structures, preferably those which hold to temperatures between 32-41 degrees Fahrenheit. If able, they will return to the same roosts every year.
Always work with a specialist when dealing with bats for two important reasons: 1) because of regulations: most species are protected, and 2) because of human health and safety concerns. Bats can carry and transmit disease and ectoparasites, such as rabies, histoplasmosis (spread via bat guano), and bat bugs,* which are very similar to bed bugs (*If you believe that you have “bed bugs” but have experienced recent bat activity, have an inspection to rule out bats/bat bugs. Such an inspection can save time and money by preventing recurring “bed bug” treatments when in fact the problem-causing pests are bat bugs).
Bats are most likely protected in your locality and it is probably illegal to kill bats in your area. Even the timing and process of removal is likely regulated. If bats are encountered with white nose syndrome during inspection, that should be reported to the proper authorities before removal, in case they want to retrieve specimens and/or track cases. Many species are federally and/or locally protected. Be sure to work with the appropriate pest or wildlife removal company to ensure that you follow legal guidelines in dealing with vertebrate pests.
There are many bat species in North America, many of them legally protected. One of the most common varieties is the Big Brown Bat, which is found in virtually every American habitat. Big brown bats weigh between ½ and ¾ of an ounce with wingspans from 13 to 16 inches. Their fur is longish and somewhat oily and brown, while their broad snouts, short ears, and wing membranes are black.
Signs of Infestation
- You see bat guano (bat droppings) around the home or workplace buildings
- You see oily streaks around certain parts of your home or buildings
- You hear sounds in the attic
- You see a bat in your home or inside a building
- Your attic has a strong pungent odor (bat urine smells like ammonia)
- You see bats flying to and from your home or structures
- Your pet brings home a bat
- You see stains on the ceilings
- You see dead bats in or around the property
- You see piles of black droppings on attic insulation
Control and Treatment
Bat removal is always a job for professional pest control operators – try to find one who specializes in bats and understands pertinent bat-related regulations. While removal can be costly, there is one fairly simple thing that you can undertake on your own: observation. If you can undertake an evening “stake out” and observe from where bats are entering/exiting a building, then alert your pest professionals to the locations of bat activity, you save having them perform this step. If you can not identify the sources of the bat activity, the pest professionals should be able to – sometimes even using camera systems to detect breaches.
Exclusion is the main control tool used in bat management.
The most common and straightforward way to exclude bats is using a one way device. This is usually achieved through the use of a custom fitted, semi-rigid wire mesh that allows bats to squeeze out to exit the structure, but restricts access and confuses them when they try to re-enter.
There are specific periods during the year, generally during gestational and rearing periods, when bat exclusion is NOT permitted at all. Your removal specialist should know and abide by these legal restrictions. Rare exceptions may be made for health reasons and usually require approval from a government agency.
Remember to be on the look out for bat bugs once removal and exclusion is completed. Bat bugs can travel in search of new hosts after bats are removed.
Contracting a pest control professional to erect bat-specific artificial roosts (bat boxes) is another good option for keeping bats out of homes and buildings. Installing bat boxes near homes and buildings, in addition to providing bats with a better roosting space, encourages natural insect control and bats’ pollination activities. Make sure that they are properly installed (at the right height: 10-20 feet above ground, and in the right places: where they get approx. 7 hours/day of sunlight, etc).
Bats like to eat beetles, moths, mosquitoes, and more.
Pigeons and English Sparrows (aka House Sparrows, English House Sparrows, or Moineau Domestique) are two of the more troublesome pest birds for institutions in urban environments and in small rural communities.
These birds adapt well to man-made environments where they are able to nest and roost. Nesting materials along roof edges can clog gutters, downspouts and air intakes. Clogged gutters and downspouts can, in turn, cause moisture problems in buildings, attracting other destructive pests, like termites and silverfish. And birds’ nests alone, even those which aren’t causing blockage issues, are known to harbor many museum pests such as: psocopterans, beetles (especially Dermestidae), mites, and moths (including clothes moths). All of these pests will feed on museum specimens!
Bird fecal droppings can deface and damage buildings and statues, and the fecal droppings of particular species may carry diseases such as histoplasmosis, encephalitis, pigeon ornithosis, Newcastle disease, crytococosis, toxoplasmosis, pseudo-tuberculosis, pigeon coccidiosis, and salmonella food poisoning. Further, some of the ectoparasites of pigeons, such as chewing lice, fleas, ticks and mites, can transfer to people. While a live bird’s presence and activities pose immediate threats to collections and building interiors/exteriors, bird carcasses are also highly problematic, as they can trigger still more pest infestation (by, for example, webbing clothes moths or dermestids, like carpet beetles). This Case Study shared by Christina Cain from the Denver Museum of Art illustrates what can happen when an infestation derived from a bird carcass strikes.
Visit Cornell’s All About Birds online bird guide for more information on specific bird species, their habitats, behaviors, and identification tips.
Many species of birds are federally and/or locally protected. Be sure to work with the appropriate pest or wildlife removal company to ensure that you follow legal guidelines in dealing with avian pests.
Signs of Infestation
Often the first signs of infestation are the birds themselves. Many species (and often the nestlings especially) are very vocal throughout the day and are conspicuous in their habits. Noisy nesting birds may even be heard through interior walls.
Signs that birds may be nesting in the nooks and crannies of building may include:
- Nesting materials (for example, feathers, twigs, grasses, scraps of paper, mud, etc.) tucked around discrete spots on the exterior of the building, for example: along ledges, roof edges, or soffits
- Concentrated areas of fecal material on the ground around or on the sides of buildings
- Entrance holes where birds can be seen entering and exiting cavities
- Birds seen transporting nesting materials to and fro
Control and Treatment
The most effective control and treatments rely upon exclusion techniques – especially for deterring nesting birds. As part of any exclusion plan, existing nests should be removed and any holes or crevices in external building structures should be filled or closed off. Control is most effective when preventing birds’ access to safe/easy nesting spots in and on buildings.
Various bird deterrents are commercially available. These deterrents operate in several different ways, and researching which methods work best for which type of birds, or birds of your area may prove prudent.
- Chimney caps, dampers, and mesh gutter covers discourage nesting and bird activity.
- Bird spikes can help as a landing/nesting deterrent, but they require maintenance (such as removing nesting material that may be deposited on top of the spikes). Spikes may not entirely eliminate bird dropping issues. Most pest companies will not install spikes without a maintenance contract attached to the installation of these spikes. Potential locations for spike installation may include parapet walls, roof lines, ledges, sills, eaves, etc.
- Bird deterrent wires are a sleek almost invisible way to prevent birds from perching/nesting. These cost more upfront, but are more effective than spikes and present a much cleaner/more minimal aesthetic. These should not require a service maintenance contract.
- Sound, air, or water delivery devices are available. These are, however, rarely used near museum settings, and certain birds can become inured to these methods of deterrence.
- Ultrasonic bird control devices properly mounted can be useful in loading dock situations to run birds out of large spaces.
While many birds eat seeds, berries, and insects, others like the House Sparrow and Pigeon have adapted to eat almost any grain product and will thrive on handouts of bread, crackers, and snack foods. Posting signs for patrons to NOT feed birds is another possible control technique.
Created 2017, Updated 2022