Workshop Proceedings

This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. ALPINE BIRD COMMUNITIES OF WESTERN NORTH AMERICA: IMPLICATIONS FOR MANAGEMENT AND RESEARcH!/ Clait E. Braun Wildlife Researcher Colorado Division of Wildlife, Research Center, 317 West Prospect Street, Fort Collins, Colorado 80526 ABSTRACT The avifauna of alpine regions of western North America is notably depauperate. Average community size is normally 3 to 4 although 5 species may consistently breed and nest above treeline. Only 1 species is a year around resident and totally dependent upon alpine habitats. Seasonal habitat preferences of the breeding avifauna are identified and the complexity of the processes and factors influencing alpine regions are reviewed. Management problems are discussed and research opportunities are identified. KEYWORDS: alpine ecosystem, habitat, avifauna, management, western North America. INTRODUCTION Alpine ecosystems occur in most of the high mountain cordilleras of western North America. Alpine, as used in this paper, refers to the area above treeline where habitats are characterized by short growing seasons, low temperatures and high winds. The term "tundra" is frequently used to describe these habitats but is more properly used in connection with arctic areas north of the limit of forest growth (Hoffmann and Taber 1967). While use of the terms "alpine tundra" and "arctic tundra" is common in designating above treeline (alpine) and northern lowland areas (arctic), the terminology of Billings (1979) is preferred. Likewise, lumping of alpine and arctic ecosystems into the "tundra biome" (see Kendeigh 1961) is not really feasible because of the extreme differences in radiation, moisture, topography, photo period, presence or absence of permafrost, etc. (Billings 1979). Long term ecological studies of vertebrates breeding or resident in alpine ecosystems are lacking. Most studies have been done on a single species for a short 1/ - Paper presented at The Workshop: Management of Western ForestsandGrasslands for Nongame Birds, Sale Lake City, Utah, February 11-14, 1980. 280 duration (usually 1 or 2 field seasons) at a single location. During a long term study (1966 to present) of the population ecology of white-tailed ptarmigan (Lagopus leucurus)at a number of sites~ opportunities were available for observations of other avian species seasonally dependent upon the alpine ecosystem. Through observation, the habitat requirements of the alpine avifauna became apparent. This paper identi fies the important breeding birds of alpine habitats in western North America and their habitat preferences. GEOGRAPHICAL DISTRIBUTION OF ALPINE HABITATS In western North America alpine habitats occur from Alaska, Yukon Territory, British Columbia, and Alberta into the contiguous United States as far south as Arizona and New Mexico. The principal mountain ranges involved south of Canada are the Rocky Mountains on the east and the Sierra Nevada-Cescade Mountains on the west. Numerous small, isolated areas exist between these 2 great north-south systems with the east-west trending Uinta Mountains being the largest. Isolated outlying mountain ranges with small areas of alpine habitat occur east of the major cordillera in Montana and Wyoming. The 2 major mountain systems tend to merge in Canada but separate northward into Alaska. Treeline decreases from south to north from about 3,500 meters in New Mexico, Colorado and Arizona to about 2,000 meters in northern Montana. In Alaska, treeline occurs at less than 1,000 meters. The total expanse of this area is unknown but approximately 3 million hectares of alpine habitats are estimated to occur in the contiguous western United States (Brown et al. 1978). CHARACTERISTICS OF ALPINE HABITATS Land Forms The alpine landscape is rugged with steep mountains, cliffs and talus slopes being abundant. Gentle benches and slopes do occur along with many glaciated valleys originating from cirques. Frequently alpine areas are rocky, especially near morainal deposits, although large expanses of relatively smooth terrain with few apparent rocks are not uncommon. Patterned ground, rock streams and solifluction terraces caused by freezing and thawing and downslope movement of saturated soils frequently occur where moisture is sufficient. Soils on steeper slopes are shallow, weakly developed, coarse and well drained. Poorly drained bog soils occur on sites with gentle relief (Retzer 1956, Nimlos and McConnell 1962 and 1965). Climate The climate in alpine habitats is characterized by high winds, low temperatures, low effective moisture and short growing seasons (Marr 1961 and 1967, Judson 1977, Billings 1979). Wind is exceedingly important as it directly affects snow deposition and distribution of plant communities. Maximum wind speeds occur from November through April with occasional extremes in excess of 160 km/hr (Marr et al. 1968a and b, Judson 1977). Wind speed in summer is less with July being the calmest month (~ 10 km/hr) (Marr et al. 1968a and b). Temperatures inalpine habitats fluctuate widely from day to day and season to season resulting in short growing seasons of up to 60 to 90 days (Billings and Mooney 1968). Some growing seasons do not exceed 45 days as night time temperatures may drop below 0°C inlate July and early August (Marr et al. 1968a and b). Mean daily temperatures are highest from mid-June to early September and lowest from late Novem ber into March (Marr 1961). 281 In alpine habitats most annual precipitation occurs in late winter and early spring (January through June) and occurs mainly as snow (Marr 1961). Fall and early winter are the driest periods and annual droughts are not uncommon. While total annual moisture may vary from 63 to 120+ centimeters (Marr et al. 1968a and b, Brown et al. 1978), not all is effective since constant winds blow much of what falls as snow from exposed areas. Some alpine habitats may be up to 70% snowfree in winter (Osburn 1963). Consequently windswept alpine habitats receive little effective mois ture while more protected sites may be seasonally irrigated from melting snowfields. Vegetation The vegetation of alpine habitats consists mostly of perennial grasses, sedges, forbs and low growing shrubs with prominent inclusions of lichens and mosses (Billings 1979). Annuals are not common (Bliss 1971) but are somewhat more widespread i~ the Sierra Nevada-Cascade Mountains (Chabot and Billings 1972). Plant communities in alpine areas may be complex and extremely variable within limited distances. Moisture is a major factor affecting plant distribution with graminoids (Poaceae and Cypera ceae) and low shrubs (Salicaceae and Ericaceae) being dominant in wetter sites and cushion plants and lichens being prominent in dry sites. Major plant communities at or above treeline vary depending upon location but can be generalized as Carex-Deschampsia meadow (Little 1941, Hanson 1953), Kobresia meadow (Marr 1961), Carex-Geum meadow, Carex-Trifolium turf, Geum turf, Salix-Carex wet meadow, cushion plant stand, Dryas stand and Krummholz (Picea-Pinus-Abies-Salix) (Daubenmire 1943, Marr 1961, and many others). AVIFAUNA Alpine habitats are unusually depauperate in numbers of breeding species. Typi cally no more than 5 species regularly complete their breeding and nesting activities above treeline. These are: white-tailed ptarmigan, horned lark (Eremophila alpes tris), water pipit (Anthus spinoletta), rosy finches (Leucosticte spp.) and white crowned sparrow (Zonotrichia leucophrys). Other species which may nest above treeline given proper circumstances are: prairie falcon (Falco mexicanus) (cliffs), common raven (Corvus~) (cliffs), robin (Turdus migrat~) (Krummholz), and mountain bluebird (Sialia currucoides) (old buildings). Other species have been occasionally documented or suspected of nesting above treeline but these isolated occurrences are poorly documented and exceptional. Few alpine habitats have more than 3 or rarely 4 of the 5 typical breeding species (Hoffmann and Taber 1959). Water pipits, horned larks and white-crowned sparrows are most widespread with rosy finches a close 4th· Major gaps occur in the distribution of white-tailed ptarmigan especially in the southern Cascade-Sierra Nevada Mountains and in isolated mountain ranges between the 2 major north-south cordilleras (Aldrich 1963, Braun and Rogers 1971). None of the isolated mountain ranges east of the Rocky Mountains is occupied by this grouse. In recent years suc cessful. transplants of white-tailed ptarmigan have occurred in the Sierra Nevadas (California), Wallowa Mountains (Oregon), Uinta Mountains (Utah) and Pike's Peak (Braun et al. 1978). The success of these transplants indicate that isolated alpine habitats are probably suitable for this species and that ecological barriers have been important in determining its present distribution. Habitat Preferences WHITE-TAILED PTARMIGAN Habitats seasonally used by white-tailed ptarmigan in Alberta, Montana and Colo rado have been described (Herzog 1977, Choate 1963, Braun 1971, Braun and Schmidt 282 1971, Braun et al. 1976). Winter habitats may be at or above treeline or in riparian zones some distance from alpine regions. Areas used are typically dominated by species of willows (Salix), alder (Alnus), and birch (Betula) which are used for food (Weeden 1967, May and Braun 1972) and clumps of dwarf or scattered conifers (Picea engelmannii, Abies lasiocarpa, Pinus spp.). In high snowfall

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