By Susan Benson,
CNHM Director of Education
Birds’ nests – can you imagine making a home for your young with a beak? Many might think of a nest as something made by the bird itself, such as the mud and grass nest of the robin, or the more complex woven northern oriole. For some, the nest is simply a spot on the soil, or a knot-hold left by a broken branch, a chamber in a tree, or a mud cavity. A bird’s nest helps hide the parent bird when incubating the eggs and shelters the young. We have evidence that using a nest is critical for warmth, provided by birds near volcanoes or hot water streams lay on heated soil near those places, or by the fact that so many nests are lined with materials that have insulation values. This entire nesting process is truly fascinating.
Why do birds build such elaborate nests? Perhaps, as real estate agents exclaim, is it location, location, location. To get off the forest floor, a bird must build a base that mimics the ground. They need to consider how to keep the eggs warmer, and sine the tops of the eggs are warmer than the bottoms, birds can create a layer of air-trapping insulation between the nest floor and eggs to keep the eggs evenly heated.
Some small birds find protection in the lower parts of nests of larger birds. For example, American kestrels and western kingbirds will often nest in the stick nests of golden eagles, and common grackles and house sparrows will nest in the nests of ospreys. They get protection from the hawk as well as leftover scraps of food.
The nesting habits of birds are varied. Gulls lay eggs on bare ground or rocks. Woodpeckers hew out a deep nest in a rotten limb. The kingfisher digs one out of a sandy bank, while the cuckoo takes possession of the nest of some other bird. The northern oriole constructs a hanging nest of elaborate workmanship. Using thin plant fibers, they loop one around the branch, hold down the irregular spiral, poke a new piece of material into it, pull it through, and loop it around the branch. They sometimes double the new end back, making a knot, by accident. When finished with the exterior weaving, they line the nest, and after ten thousand insertions of material and weeks of effort, they are ready to lay eggs.
The largest nests on record in North America have been built by the bald eagle. One in Vermillion, Ohio had been occupied by eagles for 35 years and was estimated to weigh about two tons when it crashed to the ground. What a nest!
The cup of the nest built by songbirds rests on a foundation nest of twigs interwoven with grasses, weed stems or rootlets, and is lined with finer grasses, mosses, strips of bark, dead leaves, pine needles, feathers, and animal hairs.
Some birds use mud or leaf mold to hold the nest together. Other birds use saliva to cement together the nest materials. Hummingbirds use spider webs to construct their tiny nest. Some birds will use all sorts of man-made products including Kleenex, barbed wire, and strips of plastic.
Saying someone is bird-brained seems like a compliment to me. The effort and innovation that birds have used to design such a wide variation of methods to protect their young suggests a high level of intelligence. Keep your eyes out for birds’ nests and the activities birds do this time of year to care for their young. Please continue to Email any observations to firstname.lastname@example.org.
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 exhibits, the Curiosity Center and Brain Teasers 2, in Cable at 13470 County Highway M. Also find us on the web at www.cablemuseum.org to learn more about exhibits and programs.