Treesearch

The world is warming. Over the last 100 years, the global average temperature has increased by approximately 0.7°C. The United Nations Intergovernmental Panel on Climate Change projects a further increase in global mean temperatures of between 1.4° - 5.8° C by the year 2100. How will climate change affect Neotropical migrants? Models of changes in the breeding distributions of North American birds predict that most species will undergo some shift in their ranges. In parts of northern Minnesota and southern Ontario, this could lead to an avifauna with as many as 16 fewer species of wood...

This study presents a protocol developed to rapidly assess ectoparasite prevalence and intensity. Using this protocol during a mist-netting project in two different coffee agroecosystems in Chiapas, Mexico, data were collected on ectoparasitic chigger mite larvae (Acarina: Trombiculidae) found on resident and migratory birds. Surprisingly high infestation rates were found for some long-distance migrants, as high as 73 percent for Swainson’s Thrush (Catharus ustulatus), while many species remained uninfested. During the study, 17 of 26 species of long distance migrants and 24 of 44 resident...

Lake Texcoco was reported as almost dry in the late 1960s, and as a consequence the aquatic life has been considered gone since then. However, the government undertook a reclamation/restoration project in the area beginning in 1971 to help alleviate some of the environmental problems of Mexico City. Although Lake Texcoco was not completely dry in that period, the basin containing the lake had already lost the local forms of the Clapper Rail (Rallus longirostris), American Bittern (Botaurus lentiginosus) and Black-polled Yellowthroat (Geothlypis speciosa). With the restoration project an...

Sport hunting for Northern Bobwhites (Colinus virginianus) is the reason that approximately 300,000 acres of semi-wild lands still exist in the Red Hills region of north Florida and south Georgia. Use of fire for management and relatively large (400 to 4,000 ha), contiguous land ownerships permitted populations of bobwhite and Red-cockaded Woodpecker (Picoides borealis) to persist in the Red Hills as regional populations of these two species declined precipitously. Three factors play important roles in the habitat shared by these species: canopy cover, canopy tree species composition, and...

In the second half of the nineteenth century, driven by the cultural mandate of manifest destiny and economic expansion, the North American west was rapidly settled and permanently altered by hundreds of thousands of residents from the eastern United States, Canada, Central Mexico and Europe. The first region to fill up with new arrivals was the Great Plains, a “sea of grass” that stretched uninterruptedly, from the prairies of southern Canada across the middle of the United States, to the arid grasslands of Northern Mexico – an area of both stunning continuity and biological complexity...

The population size and distribution of the two species of sage-grouse (Greater – Centrocercus urophasianus and Gunnison – C. minimus) populations have become greatly reduced throughout western North America because of habitat changes. Threats are ongoing to the remaining sagebrush (Artemisia spp.) shrub steppe areas due to current land-use patterns. The proposed North American Sage-Grouse Management Plan, if implemented, could help manage existing sagebrush habitats used by sage-grouse and other sagebrushdependent avifauna, restore degraded habitats, and rehabilitate habitats no longer...

Migratory birds suffer considerable human-caused mortality from structures built to provide public services and amenities. Three such entities are increasing nationwide: communication towers, power lines, and wind turbines. Communication towers have been growing at an exponential rate over at least the past 6 years. The U.S. Fish and Wildlife Service is especially concerned about growing impacts to some 836 species of migratory birds currently protected under the Migratory Bird Treaty Act of 1918, as amended. While mortality estimates are often sketchy, and won’t be verified until nationwid...

Recent analyses and modeling of avian pesticide field studies have led to the conclusion that bird kills are regular and frequent in insecticide-treated fields. Unfortunately, data are seldom adequate to quantify this mortality. Also, mortality is expected to be highly variable in response to varying bird presence in and around treated fields. Studies reporting kills of birds in cornfields treated with granular formulations of carbofuran provide a good example of the types of calculations that are needed to estimate direct bird losses in farm fields. Several studies provide the means to...

Seabirds, a variety of related waterfowl species, and some wading birds and shorebirds (hereafter, “waterbirds”) are accidentally captured, entangled, injured or killed in active or derelict fishing gear. Accidentally or intentionally lost or discarded gear can also continue to “ghost fish,” often until the gear sinks or washes ashore. Seabirds are most affected by set and drifting gillnets and longlines – both the focus of this paper – while seines, trawls, traps, pots, and related equipment can capture and kill waterbirds. While estimates of local population mortality from site-specific...

Since 1966, many species of grassland and shrubland birds have declined substantially in New England (Askins 2000). The extent of grassland and shrubland habitat in New England has changed dramatically over the past 400 years. Presently, grassland and shrubland habitat in New England are created and maintained primarily as a result of four types of habitat management: mowing, livestock grazing, clear-cutting, and prescribed burning.