Nature Net’s Pre- and Post-Field Trip Materials

Subject: Birds

Adaptation: A change in an animal’s body or behavior that helps it survive in its environment. For birds, this is especially true of beaks and feet. For example, duck feet are webbed to help make them excellent swimmers. Their beaks are adapted as "scoops" to help them remove food from the water.

Camouflage: An adaptation that allows animals to blend into their environment. An example of bird camouflage is the coloration of females of most species. They are often dull in color, and tend to blend into their surrounding environments. It helps female birds hide their nests and their young from predators. In contrast, most males of these species are brighter in color and able to lead predators away from the nest.

Habitat: The location or environment in which a bird lives.

Seasonal migration: The pattern of flying north in the spring to eat and breed, and south in late summer and fall to spend the cold months in a warmer climate. Migration is advantageous for many reasons. Primarily, it enables birds to avoid the physiological stresses of a harsh climate in the tropics, while taking advantage of a short-term but rich food supply in northern latitudes. Different species migrate different distances and to different places. Some, like geese, stop often along the way to feed while others, like swifts and swallows, do not stop at all and feed in flight. Many bird species migrate every year to the same breeding and wintering sites (this is known as site fidelity).

Voice: Songs and calls are critical mechanisms of communication between birds of the same species. Calls are shorter in duration than songs, serve a specific function, are generally innate rather than learned, and sound similar among different species. An example is an alarm call. Songs, on the other hand, are either partly or entirely learned and are unique to each species of bird. (Not all birds have songs - only the "songbirds," a suborder of the passerines, or perching birds, can sing.) Males use song to define their territory and recognize neighbors, or to find and maintain a bond with a mate. Bird songs are often heard during their breeding season!

Preening: a bird’s careful cleaning, re-arrangement and oiling of feathers with its bill. Most birds have a "preen gland" at the base of the tail. A bird will typically squeeze the gland with its bill and then work the oil into its feathers. The oil helps keep the feathers flexible, waterproof, and free of pests.

Breeding: involves finding a mate, reproducing and making a nest, laying and incubating eggs, and finally caring for chicks. Migratory birds arrive in their northern breeding grounds well before food becomes abundant. They find a mate using song and displays. They also do the work of building a nest. Some birds require only rudimentary nests because hatchlings will not stay very long. Other birds, like the bald eagle, take the time to carefully build a nest that will last years because they mate for life and return each year to the same breeding ground, and their chicks remain in the nest for a long time. Birds will then incubate the eggs - this is usually the job of the female, particularly when she is less conspicuously colored than the male (as in the case of the cardinal and goldfinch). Hatching is usually timed for when food is abundant. Chicks of different bird species hatch at different levels of development. They may be born helpless, blind and naked and need intensive care from their parents (like most songbirds, owls and woodpeckers). Or, they may be born with down feathers and the ability to see (like turkeys, grouse, ducks and geese). Many birds hatch at a stage of development somewhere in between these two extremes.

Avian evolution: In the context of evolution we understand birds as the descendants of reptiles. Birds are thought to have diverged from reptiles about 200 million years ago, during the age of dinosaurs. At least two important characteristics of birds connect them to a common ancestry with reptiles: 1) their body structure, and 2) their habit of laying eggs out of water. Bird feathers are currently thought to have evolved from reptilian scales. Although it is basically undisputed that birds evolved from reptiles, there are no good hints in the fossil record that directly connect the two groups of animals. Bird fossils are relatively scarce because their bones are hollow and thus more fragile, and also because it is likely that few early birds lived in environments - like swamps and estuaries - where fossils are easily preserved. The battle over how birds evolved still rages!

Conservation: Birds are a very big part of our lives. We wake up in the morning to their songs, we see the "V" formations of geese in the sky in spring and fall, we try to fly like they do and we draw and paint them because they’re so beautiful. We eat them and their eggs, raise them as pets, and use their feathers to adorn ourselves and put in our pillows and warm winter coats. Birds are an important part of most ecosystems because they keep lots of ecological processes going. For instance, they spread seeds, they serve as both predators and prey, and some eat dead and decaying animals. Many birds are now threatened by different actions of human beings. Some of the effects are direct, others more indirectly impact birds. For instance, poaching and illegal bird trade directly affects birds. Other circumstances, like filling in a wetland to build a mall or a parking lot, eliminates bird habitat so that birds cannot make nests and reproduce. Agricultural pesticides such as DDT have caused many hawk and eagle populations to decline in the past 50 years. Although the ban on DDT in the U.S. has helped bird populations to increase again, this chemical is manufactured and sold to other countries that are wintering grounds for the birds and so it affects them there. Introduction of non-native bird species also affects local bird populations and decreases diversity of birds. The European starling and house sparrow, both introduced from Europe, have competed with native birds like the bluebird for nest habitat and food, and as a result have reduced the native bird populations.

Bird Watching for All Ages: Activities for Children and Adults. Hunken, Jorie. The Globe Pequot Press. 1992.

Ranger Rick's Nature Scope. Birds, Birds, Birds. National Wildlife Federation, Washington, D.C. 1988.