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Warblers

Conservation Of Warblers

Warblers are small, often colorful birds, and there are many species of both the Parulid and Silviid warblers. As a result, these birds are among the most avidly sought-after sightings by bird-watchers. Birding is a non-consumptive field sport rapidly increasing in popularity. Birding, in conjunction with related activities such as bird-feeding, has a very large economic impact, and gives great aesthetic enjoyment to many people. Unfortunately, populations of many of the small birds that are the object of these activities, including warblers, are becoming increasingly at risk from a number of human activities.

In spite of their small size, migrating Old World warblers are commonly hunted as food in the Mediterranean region. These days, they are mostly captured with nets or using sticky perches from which the birds cannot extricate themselves. Large numbers of migrating warblers are caught in these ways, and are eaten locally or are offered for sale as a delicacy at markets. Some of the catch, generally pickled, is even traded internationally. The use of warblers in this way is a quite uncontrolled, free-for-all exploitation, and represents a significant risk to the populations of these tiny birds.

One species of North American warbler apparently became extinct around the 1950s or 1960s. The Bachman's warbler (Vermivora bachmanii) used to breed in mature broad-leaf forests of the southeastern United States. This species has not been seen for decades even though there still seems to be sufficient breeding habitat, including intact stands where Bachman's warbler used to successfully breed. The extinction of this species was probably caused by the conversion of its wintering habitat on the island of Cuba to agriculture. Once the surviving numbers of Bachman's warbler decreased to below a critical threshold of abundance, potential mates were probably unable to locate each other in their relatively large breeding range, and the population collapsed to extinction.

Many other species of North American warblers are at risk from decreases in the area of their wintering and/or breeding habitat. This concern is especially acute for those warblers whose habitat is mature forest. Losses of natural habitat directly decrease the populations of birds that can be sustained on the landscape. In addition much of the remaining breeding habitat is fragmented into small woodlots. This means that much of the remaining forest habitat is ecologically influenced by proximity to an edge with younger habitat. This factor appears to expose warblers and other forest birds to more intense predation, and to the debilitating effects of nest-parasitism by the brown-headed cowbird (Molothrus ater). Many North American ornithologists feel that these factors are causing large declines in the populations of numerous species of migratory forest birds, including many species of warblers. The same environmental problem, along with hunting, is affecting populations of warblers and other small birds in Europe and elsewhere.

When patience and birding skills allow their close observation, warblers can be wonderfully charismatic. Unfortunately, like so many other creatures native to North America and other parts of the rapidly changing world, many species of warblers are at great risk from the environmental changes being caused by humans and their activities.


Resources

Books

Ehrlich, P.R., D.S. Dobkin, and D. Wheye. Birds in Jeopardy. Stanford, CA: Stanford University Press, 1992.

Forshaw, Joseph. Encyclopedia of Birds. New York: Academic Press, 1998.


Bill Freedman

KEY TERMS

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Convergence

—An evolutionary pattern by which unrelated species that fill similar ecological niches tend to develop similar morphologies and behavior. Convergence occurs in response to similar selection pressures.

Nest parasite

—A bird that lays its eggs in the nests of other species. The host raises the parasitic egg, and often fails to successfully raise any of its own babies.

Additional topics

Science EncyclopediaScience & Philosophy: Verbena Family (Verbenaceae) - Tropical Hardwoods In The Verbena Family to WelfarismWarblers - American Warblers, Old World Warblers, Conservation Of Warblers