Geoscience Reference
In-Depth Information
to be a very successful group of plants, which today includes some 250,000 species, compared with 550 con-
ifer species. Unlike gymnosperms, the angiosperms conceal their seeds inside an ovary. This strategy con-
ferred a number of advantages, protecting them from infections, drying, and insects. By the Early Tertiary (65
to 1.8 million years ago) deciduous forests virtually covered North America, and by the Late Miocene, 15 mil-
lion years ago, a number of modern tree families, such as beech and maple, had become established.
Conifers advanced and retreated with the glaciers and today are dominant at higher elevations of the Ap-
palachians. The largely deciduous forests of eastern North America evolved as an adaptation to winter but de-
veloped where growing seasons were relatively warm, long, and humid. A number of bird and mammal famil-
ies co-evolved with this highly successful plant group, including songbirds and deer, which continue to be im-
portant components of deciduous as well as coniferous forests.
The conifers, or evergreens, can thrive under the harshest conditions, but colorful deciduous forests now dominate the
woods of eastern North America.
THE NEWEST BIRD
ORNITHOLOGIST E.P.
Bicknell first identified “a hitherto unknown thrush” on Slide Mountain in New York's
Catskill Mountains in 1881. This songster was quickly consigned to taxonomic obscurity, however, when it
was classified as a subspecies of the more widespread gray-cheeked thrush, which breeds in the boreal forests
