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Class: Aves
Birds
are two-legged vertebrates with feathers, a characteristic that distinguishes
them from all other animals. Modern birds lack teeth and acquire food
with a rigid protein structure known as abill. Some fossil birds, however,
had teeth and other characteristics of bipedal reptiles, the group from
which birds clearly evolved. The precise ancestry of birds has been a
subject of considerable debate. Some scientists believe that birds are
the direct descendants of dinosaurs, while others believe that birds originated
from a separate group of reptiles, more closely related to primitive alligators
and crocodiles.
Bird Diversity
Ornithologists (scientists who study birds) have described 9648 bird species, representing 15 orders, 187 families, and 2050 genera. More than half of these species belong to a single large category known as perching birds (Order Passeriformes). Songbirds represent a major group within this order. Although several new species have been discovered during the past decade most of the world's bird species are known and, next to mammals, birds are one of the best studied groups of organisms. The world's highest diversities of birds occur in the humid tropics, where spectacular groups like hummingbirds, toucans, hornbills, parrots, and birds-of-paradise are represented by many species. A 400 mi x 400 mi area in the United States, for example, typically contains about 120 to 150 breeding species, whereas the same area in Central or tropical South America usually contains more than 500 species (MacArthur 1969). Because birds are migratory, however, relatively high diversities occur in northern latitudes, and the Great Lakes region supports one of the richest bird faunas in North America (Price et al. 1995). Groups like thrushes, flycatchers, and warblers are particularly diverse here.
Importance of Birds
Birds have always been an important part of human subsistence, culture, art and, more recently, recreation. According to a survey conducted by the U.S. Census Bureau, 63 million Americans 16 years or older spent time birdwatching, photographing wildlife, or participating in some kind of non-consumptive wildlife-related activity during 1996. Total expenditures for these activities were $29 billion, up 39% from 1991. Birds are important elements of nearly every ecosystem on earth. Many plants depend on birds for pollination and seed dispersal. Specialized interactions between hummingbirds and flowering plants, for example, illustrate the vital role of birds in our environment. Fruit eating birds such as hornbills, toucans, birds-of-paradise, and representatives from many other groups are critically important for seed dispersal in tropical rain forests. In the Great Lakes Region, Blue Jays are the major long distance disperser of acorns, helping oak trees colonize new sites. Many other trees and shrubs produce fruits which ripen during fall movements of migratory birds like thrushes, tanagers, catbirds, grosbeaks, sparrows, and warblers. Finally, bird predation plays a significant role in regulating populations of insects, rodents, and other animals, some of which are serious human pests.
Wisconsin BirdsApproximately 230 bird species are known to breed in Wisconsin, and nearly 170 others have been seen as migrants or occasional visitors (Robbins 1990). Because it encompasses a transition between prairie and savanna regions of the Central Plains and mixed conifer-hardwood forests of the Noorthern Lake States, Wisconsin supports particularly diverse opportunities for birdwatchers. Grassland birds are especially diverse in southern Wisconsin, eastern deciduous forest birds occur throughout the state, and boreal species are present in the north. Wetland species are well represented in places such as lower Green Bay, Horicon Marsh, the Mississippi River floodplain, and Crex Meadows State Wildlife Area. The Wisconsin Breeding Bird Atlas, a landmark program sponsored by the Wisconsin Society for Ornithology, has developed comprehensive maps of breeding bird distributions in Wisconsin.
Biodiversity Topics: Introduction . Plants . Animals . Mammals . Birds . Reptiles & Amphibians . Arthropods . Spiders . Insects
© 2001-2004 The Cofrin Center
for Biodiversity and the University of Wisconsin Green Bay,
All Rights Reserved
Last
updated on
May 19, 2004