The crazed, backyard homebuilder: There’s a plan

Written by Jack Sanders
Thursday, 20 May 2010 04:00

While it would seem a waste of time and energy to build two, three or four nests when only one is needed, various birds build several nests, and for different reasons. However, one species that can be prolific at nest building can also be a threat to more sensitive species.

Some birds use nests as part of the mating ritual. Each spring when it establishes its territory, the male House Wren builds several incomplete nest structures, made of twigs. These may be in cavities or sheltered places. Bluebird boxes are a favorite location.

When a female shows up, the House Wren begins wooing her by singing and hopping in and out of each nest — almost like an overly enthusiastic real estate agent showing off different homes. However, when the female picks one, she often tosses out the work of the male and builds her own nest. Sometimes, she finishes off the male’s work by lining it with soft grasses.

The leftover stick-filled cavities — holes in trees, foundations or nest boxes — may serve to define the territory of House Wren, discouraging other birds from using the locations for their own nests. It’s tough to fit a family in a cavity full of sticks.

This is a problem with the House Wren. For years I’ve had a bluebird box in the backyard, and many of those years, I’ve seen bluebirds starting to set up home therein. But soon after the bluebirds are settling in, the aggressive House Wrens show up from their winter grounds in the South, and chase them away.  The male then begins filling the bluebird box with sticks.  Right up to the top sometimes.

Ten years ago, when I was writing The Internet Guide to Birds and Birding for McGraw-Hill, I came across a fascinating account of one birder’s study of the House Wren. Althea R. Sherman wrote a paper presented to the Iowa Ornithological Union in 1924, causing an uproar — defenders of the little birds were distressed by her conclusions. She maintained that the House Wren is responsible for destroying many nests of other birds, damaging eggs and driving out other species. She wrote in 1925: “There is only one sin that causes constant mourning in sackcloth and ashes, that causes me to lie awake nights visioning the future condition of our country with its bird population consisting mainly of those undesirable aliens, the Starling, the English [House] Sparrow, together with the Grackles and the House Wrens:  That sin was the putting up of bird houses and allowing them to be occupied by House Wrens.”

Some species may build multiple nests to throw off predators. The more structures that look like nests that appear in an area, the less unusual the real nest looks in the eye of a potential enemy. These are called “dummy nests.”

Many human contractors build groups of houses together in order to save time and money on materials, equipment and labor. Some birds, such as the Prairie Warbler, may engage in the same kind of construction efficiencies. They build several nests at one time because they are in nest-building mode. Extra nests may be used for second or third broods after the first brood is raised.

Coming up

Spring bird walk, with author-naturalist Ed Kanze, Saturday, May 22, 7:30 a.m., free, meet at parking lot near nature center at Ward Pound Ridge Reservation, Route 124, Cross River, N.Y.

Birds in their Habitats, a birding class for all ages, Saturday, May 22, 9:30 to noon, $12/adults, youths free, Audubon Greenwich, 613 Riversville Road, 203- 869-5272 x230, Greenwich.audubon.org.

Annual Birdathon, count as many different bird species as possible in 24 hours while raising funds for Bedford Audubon Society’s Scholarship Fund, science and education projects — see bedfordaudubon.org, Saturday, May 22, 5 p.m. to Sunday, May 23, 5 p.m.  914-232-1999.

Spring migration bird walks, rain or shine, at 7 a.m., about 90 minutes, Wednesday, May 26, at Fairchild Garden, meet in parking area on North Porchuck Road; Saturdays, May 22, at Audubon Greenwich, meet in main parking area; Audubon Greenwich, 613 Riversville Road, 203- 869-5272 x230, Greenwich.audubon.org.

Early-Morning Spring Bird Walks with Bedford Audubon Naturalist Tait Johansson, Tuesdays and Thursdays in May, 7:30 to 9:30, email or call for locations, This e-mail address is being protected from spambots. You need JavaScript enabled to view it or  914-232-4806.

Saturday Morning Bird Walks with Luke Tiller; to register, sunrisebirding.com/walks.htm; 203-453-6724, This e-mail address is being protected from spambots. You need JavaScript enabled to view it

First Sundays, birding at Greenwich Point with Meredith Sampson of Wild Wings, and other guides, 203-637-9822.

Copyright 2010 by Jack Sanders. Send sightings or comments to: jackfsanders [at sign] yahoo.com, or to Bird Notes, Box 1019, Ridgefield, CT 06877; or call 203-438-1183, extension BIRD (2473), and leave a message with your report, spelling your first and last names and telling us your town. If you need help identifying a bird, try your local nature center. If you find an injured bird, call wildlife rehabilitator Darlene Wimbrow of Redding, 203-438-0618, Wildlife in Crisis of Weston, 203-544-9913, or Wild Wings of Greenwich, 203-637-9822. The columnist’s website is www. sandersbooks. com.