Birds Western Colorado

BIRDS . Ill WESTERN COLORADO by William A. Davis prepared for the Colorado Field Ornithologists CONTENTS General Topography of Western Colorado •• 1 H~it~s • • • • • • • 2 Explanation of text 6 Acknowledgements and references •••••••••••••••• ·7 BIRDS IN WESTERN COLORADO 8 through 37 Trips and Special Birds • • • • • • • 38 Black Canyon of the Gunnison National Monument ••••• 39 Colorado National Monument • • • • • • • • • • • • • • • 40 De Beque Canyon • • • 43 The Grand Mesa • • 44 Hanging Lake •• 46 Hart's Basin . o •• o ••••••••• 47 Highline Lake and Mack-Mesa Reservoir • 48 Mesa Verde National Park •••••••• 49 Rifle Gap Reservoir, Falls and Fish Hatchery ••• 50 Rock Creek Bird Nesting Area ••••• • • 51 The San Juan Mountains • • • • • 52 Sweitzer Lake 55 Black Swifts • 56 Gray Vireo, Burrowing Owls • • • • • • • •••• 56 & 57 White-tailed Ptarmigan, Rosy Finches • • 57 & 58 Empidonax Flycatchers • • • • • • • • • • • • • • • • • • 58 I Western Colorado is Colorado west of the Continental Di vide. It has an area of about 38, 000 square miles and consti tutes about one third of the state. Much of it is wild or sparse ly inhabited, and unreachable by paved roads. It is rich in num bers of species of birds, some of which are unknown in most parts of the country. Yet it is relatively unexplored ornitho logically. Bailey and Niedrach's "Birds of Colorado" has few records from the western side of the state and notes " that there has been comparatively little field work in the counties west of the Continental Divide". This booklet has two purposes. One is to present a pre liminary fi'e1d list of the birds of Western Colorado which will be increased, improved and corrected by future observers. The list shows when the different species are present, their usual habitat and an indication of the ease with which they may be found. The other purpose is to provide visiting bird-watchers with an introduction to the area and suggest trips to see birds. General Topography Western Colorado is high dry country. The days are us ually sunny, the nights cool, and the air clear. The Rocky Mountains on the eastern side are massive and jagged with many peaks over 14, 000 feet high. Timberline is at about 11, 500 feet so the higher mountain tops are bare rock or thinly cover e d with a dense coniferous forest down to an altitude of about 8,000 feet. Snow falls deep on the mountains in winter. The many streams fed by the melting snows rush down the mountainsides cutting valleys through the rock. In their higher reaches these valleys are narrow and moist. The stream beds are edged with willow and alder while the steep sides are covered with aspen and blue spruce as well as the conifers found on the mountain side. Westward the mountains fall off into the Colorado Plateau, cut up by many deep canyons and river valleys. This high pla teau descends gradually to the west into Utah and south into Ari zona and New Mexico with an average elevation of about 6,000 feet at the state lines. Because the land slopes downward to the west from the high Rockies, western Colorado is commonly called the ''western slope". Characteristic vegetation of the dry plateau and its canyons is a thin growth of Rocky Mountain jun iper and pinyon pine, 1 • The rivers of western Colorado flow in a westerly direc tion; all become part of the Colorado River. In some p 1 aces the river gorges are steep rocky walls. In many places, how ever, the valleys are wide with a nearly level floor of open fields. Such open valleys or plains are called "parks", a term that is used for any open grassy area in this land of arid and desert-like. Their characteristic vegetation is sagebrush, wil low and tamarisk at the water's edge as well as occasional marshy places with cattails. Though the general topography of western Colorado f o 1- lows a simple pattern, with the Rockies on the east run n in g north and south and the plateau with its rivers falling off grad ually to the west, the pattern is so broken up that it is not ap parent at first. The crinkling of the earth's crust which creat ed the mountains has been irregular. The San Juan Range to the south and the Elk Mountains in the center are we 11 to the west of the main ranges. The Uinta Mountains of Utah extend eastward into the northwest corner of Colorado. The Grand Mesa, situated in central western Co 1 or ado, has an enormous lava cap lying over the sedimentary rocks which constitute the plateau. Flat topped, with an elevation of 10, 800 feet, it has more than 200 lakes and reservoirs scat tered through its forest. The annual precipitation on the Grand Mesa is about 30 inches; most of this comes as snow which piles to depths of over 10 feet. The Grand Valley lies just west of the Grand Mesa. About 12 miles wide, its floor has an altitude of about 4600 feet and an average annual precipitation of about 9 inches. In it is the town of Grand Junction, so named because it lies at the junc tion of the Gunnison and Colorado Rivers. This valley was for merly a sage brush desert and parts of it still are. Much of the valley has now been developed into orchards or farms by irrigation. Habitats Western Colorado varies in altitude from about 4, 300 feet in the gorge of the Colorado River where it enters Utah to over 14, 300 feet on Uncompahgre Peak in the San Juan Mountains. It varies in contour from precititous cliffs to level river valleys, 2 in vegetation from dense coniferous forest to bare alkali waste and from busy cities to uninhabited open spaces. The result is a wide variety of habitats and a wide variety of birds. In some places the change from one habitat to another is sudden, as when a river flows through desert. In others, where the mountain slopes are gradual, plant associations overlap so there is no boundary between them. Though oversimplified, the f o 11 ow in g habitats will be used for reference. 1. Tundra (from a Russian word meaning c o 1 d desert.) Timberline is at about 11, 500 feet. Above it the mountain tops are treeless with bare rock or a thin covering of low w i 11 ow s and other plants related to those of the arctic tundra. This is the Arctic-Alpine zone of Merriam's life zone terminology. Characteristic nesting birds above timberline are White -tailed Ptarmigan, Water Pipits and Brown-capped Rosy Finches. 2. Mountain Forest. The highest part of the mount a i n forest, from about 11, 000 to 11, 500 feet, has a growth of trees stunted by wind. This is the Hudsonian zone or wind timber. Characteristic trees are limber pine, bristle-cone pine, sub - alpine fir, Engelmann spruce and willows. Breeding birds include White-crowned Sparrows, Wilson's Warbler and Pine Grosbeak. From about 8,000 feet to 11,000 feet the mountainsides have a dense forest of conifers--Engelmann spruce, sub-alpine fir and lodgepole pine--interspersed with stands of aspen. This is the Canadian zone. Though wet while the snows are melting in the spring, mountain forest dries out in the summer and has little undergrowth. Breeding birds include the Gray Jay, Clark's Nutcracker, Hermit Thrush, Mountain Chicadee, B 1 u e Grouse, Audubon's Warbler and Gray-headed Junco. 3. Transition Forest. Between the dense growth of the mountain forest and the sparse growth of pinyon pine and juni per which is found on the plateau and dry canyons are a num ber of different plant associations which make up the Transition Zone. fu general, these form a rather open forest. Highest up are quaking aspen, Douglas fir and lodgepole pine. Character istic birds are Steller's Jay, Williamson's Sapsucker, Bro ad - tailed Hummingbird, Black-capped Chicadee and Western Blue bird. Lower down are wide areas of scrub oak interspersed 3 I with ponderosa pine, Colorado hawthorn and serviceberry. Char acteristic birds are Scrub Jay, Poorwill, Solitary Vireo, Dusky Flycatcher, Virginia's Warbler and Green-tailed Towhee. There is much intermingling of the Transition forest and its bird life with the zones above and below it. 4. Pinyon pine and Juniper. The dry plateau with it s ridges and canyons has a sparse growth of Rocky mountain jun iper and pinyon pine. This pinyon-juniper habitat, part of the Upper Sonoran zone, covers large sections of western Colorado from about 5, 000 to 7, 000 feet in altitude. Interspersed, par ticularly at lower levels, may be sagebrush, rabbit brush and yucca but most of the pinyon-juniper habitat is open with a thin ly covered floor of grass. Characteristic birds are Pinyon Jay, Gray Vireo, Gray Flycatcher, Bewick's Wren, Plain Titmouse and Chipping Sparrow. 5. Sagebrush. The driest, lowest and hottest parts of the valleys are arid and desert-like. The vegetation is sparse, consisting of sagebrush, cactus, yucca, rabbit brush, grease wood, grass and other low plants. This is part of the Upper Sonoran zone and the same plants grow at higher altitudes among the junipers and pinyon pine but on the valley floors there are no trees. Birds are few for there is little food or water. The Sage 1hrasher, Horned Lark, Blue-gray Gnatcatcher and Sage Sparrow are characteristic. Sage Grouse are found in a few places where there are extensive stands of larger sage. 6. Cliffs. Precipitous cliffs and rocky hillsides are found throughout western.

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