Birdhouse Competition

by Dick Lamster, March 2004

This is a difficult article for me to write. I love birds and especially cavity nesting birds. There are over 40 cavity nesting birds in Oregon and many of us build and maintain birdhouses for local species that will nest in artificial bird boxes. I have been building and maintaining birdhouses for over 20 years. Currently, Maeve (Sowles) and I have 40 birdhouses on our property, and last year our houses had 37 successful nests resulting in 148 fledged birds. The five species that used our birdhouses last year were: western bluebirds, tree swallows, violet-green swallows, black-capped chickadees and chestnut-backed chickadees.

After analyzing my own experience, reading articles on this topic and conversing extensively with birding friends, professional biologists and other birdhouse "keepers", I have come to the following realizations:

#1. If you maintain birdhouses that are being used by ropean starlings or houses sparrows (also called English sparrows), for the sake of our native birds, you must destroy the nest and eggs. These two species are not protected by law since they are classified as non-native by the State of Oregon. You should watch your birdhouses and check frequently (once a week) to see which species are using them. If starlings or house sparrows are nesting in your birdhouse, then open the house and remove the nest and any eggs that are present. If they return a second or third time, it would be best to take the house down. A birdhouse that allows starlings and house sparrows to breed is very harmful to native birds and ecosystems, and it is best to remove it.

#2. In most cities, only starlings and house sparrows will nest in the birdhouses that people maintain. So, in sum, I am discouraging you from trying to maintain birdhouses in many parts of town.

#3. The correct hole size for the typical cavity nesting small birds we will attract here in the Willamette Valley is 1 1/2 inch. This size is suppose to keep out starlings, but house sparrows can squeeze through a 1 1/2 inch hole. A 1 1/4 inch hole will allow chickadees, nuthatches, wrens and possibly downy woodpeckers to pass through, but is too small for western bluebirds, swallows and house sparrows. If you have birdhouses for larger woodpeckers, wood ducks, American kestrels, barn owls, northern flickers, screech owls and other species that require entrance holes larger than 1 1/2 inch, then you will be providing houses for starlings. Again, you must monitor your big bird houses and if starlings are nesting there, you should remove the nest and eggs and take the house down if the starlings return.

#4. If you have decorative birdhouses in your yard that are the incorrect size for Willamette Valley birds, please cover the entrance hole so they are not used by birds. Birdhouses that have the incorrect interior dimensions, including depth of the cavity below the entrance hole, will frequently expose the nesting birds to predators (such as cats or raccoons) or result in overcrowding of the young inside the house. Of course, incorrect entrance hole sizes of decorative birdhouses create the same problems discussed above. Birdhouses should not have perches below the entrance hole. These perches actually hinder the cavity nesting birds from using the house. Obviously, natural holes in trees that cavity nesting birds normally use do not have perches below each hole. Almost all cavity nesting birds have strong legs and feet for gripping the edge of a hole and some even have specially adapted tail feathers that assist in supporting the bird on the edge of a flat, vertical surface.

I have two more pieces of advice. Please be sure to clean out your birdhouses every fall after the birds have left. Remove the old nest and scrape out the bird "doo doo" and any insects such as wasps that have invaded the house. Then, clean the house with a mild bleach solution. Do not spray the inside or outside of the house with insecticides. Leave the door open for a couple of days and then close it and leave the house up all winter. Some birds may roost in the houses at various times during the winter and you can enjoy them again. I also recommend placing your birdhouses on metal posts rather than wooden posts or in trees. Smooth, round metal posts will prevent predators such as cats, raccoons and snakes from climbing the post and raiding the birdhouse.

Please feel free to call me at 343-8664 to discuss anything about cavity nesting birds. I have good birdhouse plans that I will send to you free, courtesy of Lane Audubon, which will increase your chances of providing an inexpensive birdhouse that will assist our native cavity nesting birds. This will, in turn, allow you the pleasure of watching them and enjoying their company.

Dick Lamster is a past president of Lane Audubon.