By Susan Thurn,
CNHM Director of Education
A pair of tree swallows has built their nest in the Museum’s bluebird nesting box. The Eastern phoebe is back again on the same nest at my house. The bald eagle is back roosting on the same tree on the Namekagon River, not far from its nest. Imagine the fragility of a nest, which often forces birds to build a new nest every year. However, nests that overwinter can harbor deadly numbers of pathogens or parasites that await the returning birds. What do birds do to cope with these issues?
Nests are often alive with invertebrates that feed on birds, their waste, or on each other. Flies, ticks, mites, fleas, and ticks or bacteria and fungi are discouraged by many different strategies birds use.
One of the most widely used methods is to remove the fecal sacs of the young. Some materials are selected by the parenting birds that help to sanitize the nest. For example, some hawk species continually add fresh leaves that contain pesticides such as hydrocyanic acid, which impacts parasites. Starlings can discriminate between leaves and choose the best to deter lice or bacteria which they include in their nests. Cedar bark is also used for its repellent properties. Nuthatches rub pine pitch and insects around the entrance to their cavity, relying on the defensive chemicals of the pitch and insects to protect them. Some birds of prey’s young defecate outside of the nest or in other birds, outside their nest hole opening. Some bird species put carnivore scat in their nests to repel smaller predators. The great-crested flycatcher puts a snake skin into its nest, which is believed to deter predators such as squirrels.
Birds definitely go to great lengths to protect their young. If heavy parasitism or infestation of a nest begins, birds will desert the nest, and in some cases, entire bird colonies have moved themselves to a new site. It is amazing the ingenuity that the bird world uses to survive!
Nature Watch is brought to you by the Cable Natural History Museum. For 40 years, the Museum has served as a guide and mentor to generations of visitors and residents interested in learning to better appreciate and care for the extraordinary natural resources of the region. The Museum invites you to visit its facility and new exhibit, On Lake Owen: The Art of Walter Bohl, in Cable at 13470 County Highway M or on the web at www.cablemuseum.org to learn more about exhibits and programs.