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Potential Problems and Solutions

Predators: 
Cats, raccoons, snakes and red squirrels are all predators. Evening raids on nest boxes by raccoons suggest that these animals may learn to use human scent as a guide for locating nests that contain eggs and young. The nests can be protected by using post baffles/guards and/or post coatings such as Tanglefoot. Predators may be thrown off your scent by walking indirectly to each nest site. When approaching a box, continue 8 to 10 feet beyond it and retrace your steps taking a last large step sideways to the box.

Other Cavity-Nesters:
Other unwanted birds may compete for the box, going as far as to destroy or puncture eggs. House (English) sparrows are the greatest threat. They are messy nest builders, using bits of plastic, string, and loose vegetation. Bluebirds on the other hand, make neat grass cups. If you discover a house sparrow nest, remove it from the box and take it out of the immediate area. Do not build a perch on the box as this encourages sparrows and is not necessary for songbirds. Trapping and eliminating English sparrows and European starlings is more effective than simply removing their nests. If you are uncomfortable with removing the nests or the birds, another option is to shake the sparrow or starling eggs and leave them in the nest so that they will not hatch. The adults will continue to incubate the eggs and not attempt to build another nest.

It is against the law to remove nests or eggs of birds other than sparrows or starlings. Monitors need to be positive of bird and egg identification before taking action to remove them. A brief description of different species' nests and eggs is included at the end.

Parasites:
Blowfly larvae attach themselves to the feet, legs, underside of wings and beaks of newly hatched fledglings and draw out blood and other fluids. The female blowfly will lay 50-200 eggs in a grass nest. If the infestation is severe, fledglings may be killed or seriously weakened. A wire mesh screen placed in the bottom of the nest box will prevent the larvae from travelling back up through the nest once they have fallen through the screen. Parasites can transfer from one nest to the next, and it is therefore essential that the old nest is removed after the young fledge. Wear gloves when removing infested nests.

Bad Weather:
Continued rain for several days may cause the nest to become very wet and young nestlings may die - especially if it is before their feathers develop. Native cavity-nesting songbirds have a very poor sense of smell, and therefore, will not object to the wet nest being removed and replaced with dry grass clippings from the area. Especially hot weather can also be detrimental to nesting success. It is important that nest boxes contain ventilation openings on the bottom as well as the top of the box. A new technique to improve air flow and protect the box from bad weather is placing a dark shingle on the lid of the box. The shingle absorbs heat, creating warmer conditions near the top of the box. This, in effect, creates an air flow from the bottom ventilation openings to the top openings. Certain sites have found this increased ventilation to be effective at combating extreme heat and humidity.

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