TREE SWALLOWS SEEK THE OPEN SPACES

NESTING MATERIAL VARIES

The wren builds the bulk of its nest of sticks, the bluebird uses grass, and the tree swallow gathers large chicken, duck or game bird feathers to line a shallow nest of grass and roots. Where Chickadees fill the house with moss and dog hair or other types of fur. Usually there is no lack of these materials in the wild, but we have encouraged tree swallows and wrens to use our boxes by placing nesting material near the boxes.

SPACE THE BOXES

Spacing of boxes is necessary because birds space themselves naturally during the nesting period. Some birds, such as purple martins, gulls, cliff swallows or ledge-nesting sea birds, will tolerate other nests at very close quarters. But others—hawks, owls, kingbirds, and even robins—cannot be crowded into small spaces, nor can you get wrens to nest together in a house like martins.

The spacing of nest boxes depends on the arrangement of the food and cover and the degree of isolation this arrangement affords. In general, the average city back yard or garden is large enough for one or perhaps two families of wrens. The large expanses required for tree swallows and bluebirds eliminates these birds from most city locations. In farm yards or in rural areas, a tree swallow box should be at least 30 feet away from any other box. Bluebird spacing is less critical than that for tree swallows, but a box every 150 feet should be adequate.

Put the bird boxes up by March 15 so they will be ready when the birds arrive from the South. Occasionally, unwanted birds like the English sparrow or European starlings take over boxes. You can discourage them by repeatedly removing their nests. A periodic check will tell you if you have desirable tenants to encourage or undesirable ones to evict.

It often takes several boxes placed in the most likely sites to attract one pair of birds.

BLUEBIRD NEST BOX DESIGNS

Several designs have proven successful in providing safe homes for bluebirds.  Use the plan that best fits your budget, available woodworking tools and woodworking skill. One—inch rough lumber is ideal as it is less expensive and provides better insulation than planed (3/4 inch) lumber or other materials.

Guidelines:

• Avoid painting boxes dark colors: they will absorb too much heat.

• Provide ventilation by drilling holes or leaving cracks at the top of the sides of houses (see house plans).

• Entrance holes should be 1 1/2 inches in diameter and near the top  for Bluebirds and tree swallows, And 1 1/8" for Chickadees and Wrens,

• Predator guards on poles or at entrance holes are strongly recommended.

• All boxes should have a side, top or front that swings open so boxes can be cleaned out when necessary.

• Put drainage holes in the floor of all houses.

PLACING YOUR BLUEBIRD NEST BOX

Nesting Failures

Raccoon: A predator of bluebirds that will eat the eggs, young, and adults. Raccoons can climb nearly anything, and can reach into the nest cavity to grab eggs or birds from the nest. Look for a nest that is disturbed. Claw scratch marks may be found on the nest box. Raccoons eat their food outside of the nest cavity, so look for coarsely broken eggshell fragments or feathers below the nest cavity entrance or near the nest box.

House wren: Most nest losses attributed to wrens occur in nests containing eggs. The eggs are punctured and left in the nest, or are removed after being punctured and either dropped beneath the cavity entrance or carried away. The puncture holes may be very small. Wrens may build their nest on top of these eggs, so check under wren nests built over active bluebird nests.

House sparrow: They destroy eggs, but frequently kill young and adult bluebirds by pecking at their scalps. Look for bluebirds with substantial damage to the scalp region. Feathers will be missing and blood will be found. House sparrows Fill the entire house full of grasses and frequently build their nest over the corpse of their victims. Avoid placing nest boxes in areas with house sparrows, for instance near farmyards and in towns.

Snakes: They take nestlings and adults, but most frequently eggs. It is very difficult to determine nest failures from this cause because snakes usually leave no sign of their visit. 

Wessels, Red and flying squirrels: Squirrels will enter the nest box, and unlike raccoons, squirrels eat the eggs inside the nest cavity. You should find small fragments of eggshell in the cavity. They can be a problem near pine trees.

Other: Other types of nest failure that are uncommon include human, wasps, house cats, and opossum.  Vandalism can sometimes be a problem.

Also remember to use 1/2" galvanized poles, and clean your houses out in the fall and leave open, Then recheck  and close them back up in March to await the early arrivals.

Heat: During extended periods of hot weather in Wisconsin part of or entire broods of both bluebird and tree swallow young may die in nest boxes from overheating. This type of nesting failure can only be proven when individual nest boxes are checked nearly every day. If you suspect that a brood may be suffering from heat you may want to check that box more frequently.

Blowflies: Nestling birds are often parasitized by blowfly larvae.  Adult blowflies lay their eggs in the bluebirds nest. After hatching, the larvae feed on the blood of the bluebird nestlings by attaching to their feet, legs, abdomen, bill, or wing and tail feather shafts. They feed mostly at night, and drop from the nestlings during the day, returning to the bottom of the nest box. Up to 85% of eastern bluebird nests may be parasitized by these larvae. Artificial nest boxes appear to contain more larvae than natural cavities, with larvae more numerous during the late summer nesting period. A single nest may contain as many as 200 blowfly larvae. When heavy parasitism occurs, the nestlings are weakened and sometimes killed. To determine if there are larvae in the nest box, gently lift the nest material and look for the larvae on the bottom of the nest box and in the nest material. If larvae are found, Remove the larvae by scraping them from the bottom of the box.