Sabtu, 06 Agustus 2011

Rock Creepers

Having a low center of gravity and equipped with relatively large, sharp-toed feet, canyon wrens comfortably negotiate the steep walls of canyons and rock formations throughout the western U.S, southwest Canada and Mexico. There they creep across the surface, scouring crevices for insects with their flattened heads and long, thin bills.

Inconspicuous to the casual hiker, canyon wrens are more often heard than seen. Their melodious, cascading song frequently rings through the canyon but these hunters prefer the shadows and their rusty-brown plumage blends with the rocky habitat. Monogamous for the breeding season (and perhaps for a year or more), canyon wrens build a cup-shaped nest of twigs and dried vegetation which is placed within a rock crevice; 4 to 6 eggs are incubated by both parents who also share the feeding duties.

Unlike their cousin, the rock wren, these birds do not migrate south for the winter; rather, they descend to lower elevations or move to more sheltered areas during the colder months. Strict insectivores, they prefer canyons with perpetual streams, insuring a steady supply of prey; pupae, hibernating spiders and insect eggs provide sustenance in winter.

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