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Birdhouse Predators - Protecting Nesting Birds

Starlings and House Sparrows

Starlings and house sparrows are two bird species introduced from Europe that can be classified as a predator as they bully and kill other cavity nesting birds. An entrance hole of 118" or less should be used to exclude sparrows if they are not wanted. If an entrance hole of 1" is used, chickadees, nuthatches and titmice will be too large to enter, leaving wrens as the only possible occupant.

If you are interested in having both house sparrows and other songbirds, it is good to have several birdhouses with larger holes just for sparrows and a couple of birdhouses with smaller holes to ensure smaller songbirds are guaranteed a place to nest.

House sparrows will feed insects to their young and therefore are beneficial to have around your yard. They are not as advantageous as smaller, native songbirds and are considered not as valuable to many people.

Cats, Raccoons & Opossums

If you think these animals will be a problem, they can be discouraged by added sheet-metal shields or baffles around posts to prevent them from climbing up the post. A bio-friendly grease can also be added to metal posts to make climbing more difficult for these animals.

Black and Grey Squirrels

Squirrels often chew out entrance holes of birdhouses trying to get inside. Birdhouses can make a great shelter for them to raise their own family if the interior is large enough. They can make entrance holes larger to gain access to a birdhouse because it can provide shelter from the elements. Squirrels target birdhouses ~900cm3 or greater because they provide enough room for squirrels to fit comfortably. Birdhouses for any birds other than chickadees, nuthatches, titmice and wrens must be over ~900cm3 and therefore a predator guard around the entrance hole is a good solution.

Predator guards, (seen in section below) keeps squirrels from enlarging the birdhouse entrance hole. They can be made from metal washers or even hardwoods such as oak. Some predator guards are plastic pipes that extend the entrance hole out from the birdhouse 2-3". While these solutions are not as aesthetically pleasing, they can provide a solution to an often daunting problem.

Birdhouses with an inner volume under ~900cm3 are overlooked by squirrels because they are too small. This is why there is a lack of a predator guard on the hexagonal birdhouse.
Grey squirrel with a pine cone looking down from a tree branch
Measuring the interior dimensions

Red Squirrels and Chipmunks

A metal predator guard can be used to deter squirrels and chipmunks from eating out / chewing the  entrance hole and making it larger
Metal predator guard
These creatures are small enough to fit inside smaller volume birdhouses and can chew out entrance holes and even enter through reinforced entrance holes of larger birdhouses. One solution is to sprinkle cayenne pepper on the birdhouse roof or other areas where the red squirrels go before they enter the birdhouse. If done properly, this can teach these guys to leave the birdhouse for the birds.

Predator guards can also be used to ensure the entrance holes aren't made larger by these creatures. Pictured to the left is a metal washer style predator guard.

Mice and Rodents

Sometimes birdhouses become nests for other creatures such as mice and other rodents. If this happens there could be a number of factors that are making the birdhouse unfavourable for birds and attractive to mice.

The birdhouse may smell. Clean the birdhouse interior with 1 part bleach and 9 parts water. Allow to air dry before re-mounting.

The birdhouse may have too large of an interior and too small of an entrance hole. Small songbirds don't want to fill the interior cavity with copious amounts of nesting material, and larger birds are unable to get in because the entrance hole is too small. Making the nesting area smaller or entrance hole larger is a viable solution.

To avoid rodents altogether, mount the birdhouse on a metal post which mice are unable to climb.

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