Читать книгу A Parliament of Owls - David Tipling - Страница 9

THE FIRST EUROPEAN SETTLERS TO MAKE IT across the Atlantic could have been forgiven for thinking “New World, same old owls.” Although connected by land to South America, North America shares many features of its natural environment with Europe, including some of its owls.

The explanation lies in geological history. South America was once part of the ancient southern supercontinent Gondwana, splitting from Africa some 135 million years ago, whereas North America was part of the northern continental landmass Laurasia, and was therefore once connected to Europe, sharing its recent glaciation history. Indeed, it was only three million years ago that North and South America came together at the Isthmus of Panama, and they now constitute separate biogeographical regions, each with its own evolutionary history.

Nowadays, North America is the world’s third-largest continent, extending all the way from the Canadian Arctic to southern Mexico and covering approximately 9.5 million square miles (24.7 million sq km). At least thirty-eight owl species are found there, although a significant proportion occurs only in the extreme south of the region, where biodiversity is boosted by the influence of tropical Central America. Indeed, Mexico is home to a greater number of bird species in general (± 1,040) than the United States and Canada combined, including typical Central American families such as toucans, motmots, and trogons that are thought to have originated in South America and subsequently extended their range northward.

While the first settlers may have brought with them their European ideas about owls, the indigenous peoples of North America already had a rich heritage in which owls figured prominently. The Cherokee, whose name for the Great Horned Owl—tskili—means “witch,” considered owls to be the embodiment of ghosts and as a result dreaded their nocturnal hoots as omens of evil. Others had more positive associations. For example, Sierra Nevadan Indians believed that the Great Horned Owl transported the souls of the dead to the afterlife, whereas Newuk Indians believed that after death the brave would become a Great Horned Owl but the wicked would become a Barn Owl. Pima Indians gave owl feathers to the dying, perhaps to help ease their passage into the afterlife where the owls awaited their souls. Tlingli warriors even hooted like owls as they charged into battle.

As in Eurasia, many of North America’s owls are adapted to, and thus largely restricted to, particular biomes. These follow a series of broad north to south bands. The northernmost is the Arctic tundra, which carpets much of Alaska and northern Canada, including Baffin Island, Victoria Island, Ellesmere Island, and the rest of the Canadian Arctic Archipelago. This harsh, largely treeless terrain, blanketed with snow and ice in winter, is home to the Snowy Owl, a true Arctic specialist, whose circumpolar range also extends across Eurasia. Although this largely white bird is supremely adapted to its snowy environment, it may move south during winter according to the fluctuation of its food supply, chiefly rodents such as lemmings.

South of the Arctic are the boreal forests, which cover much of Canada’s northern and mountainous regions. Species here include the Boreal Owl, Great Gray Owl (Strix nebulosa), and Northern Hawk Owl (Surnia ulula), all of which also occur in the boreal forests of northern Eurasia. As these forests extend further south across the continent, with a greater variety of forest types, more species occur, including the diminutive Northern Saw-whet Owl (Aegolius acadicus) of largely deciduous forests, the Western Screech Owl of the Rockies and west coast, and its eastern equivalent the Eastern Screech Owl (Megascops asio). The rapacious Barred Owl has a penchant for moist and swampy forest, including the Everglades and bayous of the south. Perhaps the rarest of North America’s owls, the Spotted Owl, finds refuge in the old-growth temperate rain forests of the Pacific Northwest.

Other habitats support specialized owls. A significant amount of the prairies—the great grassland plains that once covered much of central North America—has been lost to agriculture, but the pockets that remain harbor the Burrowing Owl, one of the world’s most charismatic and distinctive species, whose ecology is closely tied to that of the prairie dogs and other burrowing mammals with which it cohabits. Further south and west, in the arid regions, the diminutive Elf Owl has adapted to life in the desert, finding perfect nest holes among towering saguaro cacti. Further south still, into Mexico, a greater variety of owls reflects the tropical influence of Central America, which is responsible for a broader general biodiversity. These include pygmy owls (Glaucidium) and South American species such as the Spectacled Owl and Crested Owl, which extend a toehold into the region.

Two Boreal Owl fledglings near their forest nest.

A young Elf Owl peers from its cactus nest in a desert.

North America’s landscapes, like those of Europe, have been heavily modified by human activities. Some species have shown an impressive adaptability: the Great Horned Owl, for example, is not only the continent’s most rapacious species but also among its most common and widespread, finding aperfect niche in suburbia, where it terrifies the neighborhood cats and dogs when they venture too close to its nest. Screech owls, both Western and Eastern, also readily adapt to human habitation and are easily encouraged to stick around if suitable nest boxes are provided. The American Barn Owl (Tyto furcata), now recognized by some authorities as a separate species from the Common Barn Owl, also finds a home in farming landscapes, providing that they are not managed too intensively and still provide enough rough pasture and old buildings for hunting and breeding.

Nonetheless, the ongoing loss of habitat is taking its toll on some species. The best known of these is, perhaps, the Spotted Owl, whose conservation became a cause célèbre during U.S. elections in the 1990s, when the needs of the owl were pitted against those of the loggers who believed that their livelihoods depended upon felling precious old-growth forests. Today, a variety of conservation groups, both local and national, are working to protect owls wherever they occur.

A Burrowing Owl fledgling tries out new perspectives on the world outside its burrow.

A Snowy Owl’s bill is almost completely hidden by its feathers.