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BioLab 3
Exercise 1
Avian Engineers
Objectives:
- To explore biodiversity through the engineering accomplishments of birds as nest builders.
- To utilize the Internet as a tool to learn more about selected birds and their nests.
- To engage in nest building activities.
- To submit answers in writing to your instructor based on your observations and work.
Materials:
- A computer.
- Internet access through an Internet service provider (ISP),
and a browser such as Netscape Navigator.®
- Nesting materials - twigs, strips of paper, pieces of rope, a shoe box.
- Pen and paper.
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Background:
- Imagine designing and constructing a building with no concrete, no steel beams, no glass windows and no heating system. Impossible? No. Year after year, birds - avian engineers - do just that. Birds are master builders. They build nests to provide shelter and a safe, warm environment for their young. Nests must withstand predators, high winds, precipitation, and any environmental challenge. When you think about it, nests are amazing pieces of engineering. Using only materials available in their environment, birds build nests in trees, on cliffs, in sand, and even in our homes. The diversity of nest types is surpassed only by the number of species of birds.
A Yellow Hammer. Drawing by Patricia Fagerland of Long Beach, Washington.
- Nidification is the practice of nest building. It involves preparations for the deposition of eggs or young and their care. Species of mammals, reptiles, amphibians, fishes and invertebrates also build nests. We will focus on bird nest building in this exercise. Nesting is a seasonal activity occurring the same time each year. Hormones play a part in the control of this activity.
- Location selection is the first task in nest building. Two primary factors determine this decision: environmental conditions and the state of the young when they emerge.
- There are 4 general categories of nesting sites:
- Ground, cliffs, beaches
- Trees, shrubs, vines
- Aquatic habitat
- Cavities
Aves that use ground, cliffs or beaches on which to build their nests include game birds, such as quail, grouse, pheasants and turkeys. Some small birds, such as juncos, sparrows and warblers, build directly on or near the ground. And, not all birds construct nests. Some waterfowl and a few land birds lay eggs on bare rock or ground. Many raptorial birds nest on the ground in steppe or desert country. The nest may be placed on a rise or on a small pile of stones. On islands where there are few predators, birds of prey, such as ospreys, may nest on exposed shore.
Trees, shrubs and vines are popular locations for nest building. These are the preferred sites of many songbirds, such as orioles, robins, cardinals, mockingbirds, thrashers, kingbirds, hummingbirds and finches. Aquatic habitats, such as swamps and marshes, are favorite locations for nests of herons, ducks, gulls, egrets, blackbirds and some swallows. Cavity nesting birds include many familiar garden birds, such as bluebirds, chickadees, wrens, starlings, woodpeckers and flickers. These birds will also locate in bird houses if available. Flickers and starlings have curved bills to chip away spots softened by rot. Parrots and woodpeckers will use hollows in trees to deposit their eggs.
- Birds of prey (ex. eagles, ospreys) will build their nests almost anywhere since they can defend themselves and do not need to hide. They do select locations that are sheltered from wind, rain and hot sunshine. The best sites include sheltered rock ledges, holes in trees, small caves, in buildings or on the ground. Once location is decided upon, construction begins...
- Nesting materials and construction become the next order of business. When it comes to selecting building materials, again, the choices are diverse. Nests come in many shapes and sizes. Smaller species of birds make elaborate nests that are hidden or well-camouflaged so they are very hard to see. These may be built in hedgerows, bushes or on the ground as bowl-shaped structures. The nests are constructed of fine grass interwoven with horsehair, and may be masked by moss or lichens (ex. titmouse). Calliope Hummingbirds are great at camouflage. They often shape their nests to look like pine or spruce cones the size of walnuts, and build them adjacent to real cones. When complete, you can't see the nest.
In addition, it is lined with willow down or some other soft material for insulation. Some birds lay a foundation of clay or mud (ex. thrushes) and line the interior with decayed wood and cow dung. If you leave a tray out with dirt and water, it will assist robins and swallows with their nest building. A few species, such as the swallow tube and flamingo, use saliva as cement for mud-built nests. Swifts use saliva to glue small twigs to the inside of a chimney to form a tiny basket. Some species use yarrow, rue or thyme in constructing their nests, as these herbs are natural insecticides.
- Orioles build incredible nests. They weave hanging purses that are not hard to see, but are very hard to reach. The nest is constructed from top to bottom of long grass stems and plant fibers. It is suspended by a long fibrous strand or rope that is attached to a large tree branch. Toward the end of the rope there is an enlargement to form a spherical chamber. An entrance is placed at the top or in the side of the structure.
- Ostriches, Struthio camelus, from East Africa, only scrape a hole in the ground to construct their nests. Many birds will share a nest. See photos below:
- Birds of prey build nests that can become enormous structures by adding to existing ones year after year. A nest may be 17 feet deep and 5 feet across. An eagle's nest built in a tree may become so heavy that the branches may not be able to withstand the weight of the nest, and the tree will collapse. A nest 10 feet deep may contain a ton of sticks. A pair of bald eagles used the same tree in Ohio for over 35 years until it crashed to the ground, weighing about two tons! As long as these nests are not built on the top-most branches, they do have the advantage of providing shade. Can you find the eagle's nest in the photograph (taken in Alaska) below?
- Some birds in dry-lands build nests in large cactus-like plants with sharp spines and poisonous sap. These provide less danger from the ground, but, the tops are exposed to sun and are vulnerable to air attacks.
- Chicken-like (Gallinaceous)
birds make a shallow depression in the ground. The fowl-like megapodes
of New Guinea and Australia build a big mound of decaying vegetable
matter and lay eggs deep in the fermenting material. The heat
generated from decay hatches the eggs.
- The nest of the Cactus Wren
(Arizona) is easy to reach, but hard to enter. This bird builds
its nest among the spines of a cholla cactus. The bird is able
to move about in the nest without getting jabbed by the cactus
pines. Cliff Swallows pick up mud by the beakfull. Pairs
of swallows shape cave-like nests in the faces of cliffs one
pellet at a time.
- References
- Campbell, Neil A., Jane B. Reece and Lawrence G. Mitchell. 1999. Biology 5th Edition. Benjamin/Cummings - Addison Wesley Langman, Inc., New York.
- Encyclopedia Britannica. 1969. William Benton, Publisher, Chicago. Vol. 16.
- Lloyd, Glenys and Derek. 1971. Birds of Prey. Bantam Books, New York.
- Mahnken, Jan. 1994. Feeding The Birds. Wing Books, Avenel, New Jersey.
- Mader, Sylvia S. 1998. Biology 6th Edition. WCB McGraw-Hill, New York.
- Poole, Robert M. - Editor. 1983. The Wonder Of Birds. National Geographic Society, Wash., D.C.
- To read more on birds and their nests, go to the following web sites. Then return to this page and continue with the Methods section:
Bird Information Chart - Nests
Bird Nest Photos
Nests
Bird Nests in Winter - with a quiz to test your knowledge
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Methods:
- You can help birds with their nest building tasks. Go to the
Birds
and Nests and Birdhouses web site, and follow the instructions
to perform nest activities. Report your observations to your instructor
in writing via email.
Additional Links:
- Bird Families of the World
- The New Zealand Kiwi Bird
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