Helping Birds Nest
In the spring, male birds establish their domain, choosing a favorite post, pole, branch, or spot along the roof-line as the dais from which they will survey and protect their territory. They advertise the desirability of their domain with frequent singing. Rival males are driven away with a loud show of bravado. Females, even though they assume a submissive posture, are greeted somewhat the same. Nesting will begin soon after females enter the territory.
Nesting is a springtime activity, but helping birds to nest is a year-round obligation. Monitoring, protecting, and cleaning nest boxes is not for absentee hosts. There are several types of nest boxes and bird houses:
Gourd nests— Drill a l¼-inch hole in a dried gourd and hang it by heavy wire from a tree. Hollowed coconuts, pipes, and even flower pots serve in the same way.
Nesting shelves, cones, and platforms— Shelves appeal to larger birds like Phoebes, Doves, and Robins that would normally nest in the crotch of a tree. Inverted nesting shelves are great for Barn and Cliff Swallows. A nesting cone, positioned in a branch crotch, can serve the same species. Larger nesting platforms (for Owls, Eagles, Ospreys, Hawks, fowl, and other water birds) are more ambitious structures involving boards and wire construction.
Nesting house— This style of bird house draws cavity-nesting birds that may be hard-pressed for cavities in an urban environment. About 50 species will use bird houses, and of that number over 30 regularly do so. Many birds will use a perch just outside the port.
Multi-nesting apartment— Colonial birds like Purple Martins will occupy this style bird house with many ports. While not so well insulated as a timber house, numerous gourd nests, hung next to each other, make a popular multi-nest establishment. Native Americans of the Southeast originated this technique.
Bird House Construction
Whether homemade or purchased, a few rules apply to bird house construction:
Stick to nesting boxes made of natural, not synthetic, materials. Synthetic boxes require less maintenance but don't ventilate properly.
Wood for wooden houses should be at least a half-inch thick.
Houses with removable or hinged roofs and floors are easier to care for and clean.
Roofs should be sloped to avoid flooding.
Bird houses need ventilation. If there are no ventilation holes around the top of the house, drill a few.
To avoid flooding, be sure there are drainage holes in the floor and that the roof extends at least 3 inches beyond the front of the house.
You can stain or paint the outside of the house in a natural color, but leave the inside natural. Don't use creosote or lead-based paints.
Bird House Proportions
Different-sized ports and house dimensions attract different birds. The accompanying table indicates birds and the dimensions of bird houses to which they gravitate. The port measurements are precise—to discourage other birds such as House Sparrows, Common Grackles, and Starlings. These birds are intelligent and adaptable and therefore abundant, particularly in urban areas. Unfortunately, they make pushy neighbors and easily take over houses intended for other birds.
Port dimensions of less than 1½
Rich Aquatic Gravy
It is not just fish and larger marine life that make up the diet of ocean-going birds and waders. They also eat tiny Zooplankton that have fed on even more infinitesimal phytoplankton. It is difficult if not impossible to distinguish the individual creatures in this Zooplankton stew. However, copepods, amphipods, ostracods, krill, pteropods, and larval gastropods are some of the popular ingredients.
In the spring, hang a wire basket filled with short pieces of twigs, string, yarn, and even hair and chicken feathers out in the yard. Do not include synthetic fibers. These “construction” materials help birds prepare their nests. Some birds will make use of sticky mud which you can keep in a shallow pan.
Available materials will allow birds to build their own nests or speed up birds’ acceptance of any nest boxes you install in your garden. Placing a few wood chips or shavings (not sawdust) in the box will help get the bird started on its nest.
Positioning Bird Houses
Bear in mind the habits of the birds you wish to attract. Read about your sought-after species’ general routines. Birders in your area can share techniques that have worked for them. Where you position a bird house will influence the type of bird it attracts and whether or not it attracts any.
For example, Robins like evergreen trees and shrubs, Wrens like brushy thickets, and Phoebes build near running water. There can be stiff competition between species that nest in the same habitats, and the nesting box site may be a strong determinant in the species that settles there.
Choose a site in early fall. The house will have time to weather, and birds will be accustomed to it by the time spring and breeding season arrive. Find a secluded part of the yard that is protected from the elements, facing away from the direction of storms in your area. It should be neither too sunny nor too cool. Baby birds need some sunshine. In early fall there are still leaves, so be sure the site is not too shady. Most birds want easy access from flight.
Give your bird residents ample opportunity to locate the nesting box, but move it if no bird takes up residence once nesting season is well under way. Once birds nest, leave the nest in place (since many species raise more than one brood) or another family may claim it.
Nests are not just “for the birds.” Communities of tiny parasites move in to scavenge on food scraps, feathers, and sometimes the birds themselves. In small quantities, feather lice and red mites are not too problematic. Blowfly larvae are the most pernicious. Adult blowflies lay eggs on newly hatched nestlings. The eggs hatch and the larvae attach themselves to soft parts of the nestlings. Since larvae wiggle to the bottom of the nest during the day to keep out of sight, a wire mesh platform (cut to the floor dimensions) on the bottom of the house will diminish their number.
Nematodes are smooth-skinned worms, some of which are parasitic and fatal in birds. The gapeworm can attach itself to the trachea in fowl and obstruct their throat. The crop worm also irritates and obstructs the windpipe and esophagus in many types of birds. Another destructive nematode is the spiral stomach worm. Birds with these worms exhibit an unsteady gait and have trouble breathing. They become emaciated and usually die.
Protecting Bird Houses Against Predators
Nesting boxes can leave eggs and hatchlings even more vulnerable to predators than feeders. Most cavity-nesting species have young that are born helpless and unable to defend themselves against squirrels, cats, snakes, and, most wily of all, raccoons.
If the house is post-mounted, wrap the post with sheet metal or stovepipe, or coat it with automotive chassis grease. If the house is in a tree, attach a collar or cone of galvanized metal around the trunk. Houses that are at least 5 feet off the ground are safe from cats as long as there is nothing for the cat to climb. You can also increase the thickness of the port by adding another inch-thick board drilled to the same dimensions. This keeps paws and larger birds’ beaks out of the nest.
In some areas, wasps and ant colonies overtake boxes before birds can move in. If you find ants and wasps in the spring when you check and clean boxes, spray a dose of pyrethrum into the box at night when most of the insects will be inside. Plug the port with a rag. Most of the insects will be dead by morning. (Pyrethrum, originally made from dried chrysanthemum flower heads, is now artificially synthesized. Although highly toxic to insects, it does not harm birds. Its effect is of short duration.) A greasy pole will also disabuse ants of climbing to the box.
To avail fresh nesting sites to your amorous bird residents, take the box down and clean it in early spring. By waiting until late spring, you preserve the habitat of a blowfly predator, the chalcid wasp. Strew old nesting material away from the nest rather than burning it unless it has a lot of lice and mites.
After removing the nesting material, fumigate with pyrethrum if necessary. Nest boxes with very high insect infestations need thorough scrubbing with washing soda and several applications of scalding water. You can spray the box interior with gamma benzene hexachloride at ten-day intervals to counter serious infestations.
Creating a Bluebird Habitat
One of the most beloved species in the United States is the Eastern Bluebird. As a cavity nester, its population has much suffered from urbanization because there are fewer dead trees and fewer old wooden fence posts.
House Sparrows (also cavity nesters) compete aggressively with Bluebirds for nesting spots. For this reason, Bluebird lovers must plan their gardens and nest placement carefully. Bluebirds feed on insects picked up from the ground and need a good view with sparse or low vegetation, like mowed lawns or fields. They benefit from a perch such as a crossbar nailed to two tomato stakes pounded into the ground. Put a birdbath nearby so Bluebirds can first bathe, then preen and dry off on the perch.
Sometimes positioning the Bluebird house as low as 3 feet off the ground will dissuade sparrows. Bluebirds may also nest in smaller houses than Sparrows, and they prefer a port farther off the floor. Check the dimensions recommended for bluebird houses in the table on p. 215. Face the nest box toward trees or shrubs that are 25 to 100 feet away. If you install more than one box, keep them 100 feet apart to correspond to territorial needs.
They will be attracted to suet feeders and mealworms. Bluebirds use fine dry grasses and pine needles in their nest-building.
Once Bluebirds locate a desirable nesting area, they usually return year after year. Write to the North American Bluebird Society for more information.