Habitat Fragmentation Effects on Birds in Grasslands and Wetlands: A Critique of our Knowledge
نویسندگان
چکیده
Habitat fragmentation exacerbates the problem of habitat loss for grassland and wetland birds. Remaining patches of grasslands and wetlands may be too small, too isolated, and too influenced by edge effects to maintain viable populations of some breeding birds. Knowledge of the effects of fragmentation on bird populations is critically important for decisions about reserve design, grassland and wetland management, and implementation of cropland set-aside programs that benefit wildlife. In my review of research that has been conducted on habitat fragmentation, I found at least five common problems in the methodology used. The results of many studies are compromised by these problems: passive sampling (sampling larger areas in larger patches), confounding effects of habitat heterogeneity, consequences of inappropriate pooling of data from different species, artifacts associated with artificial nest data, and definition of actual habitat patches. As expected. some large-bodied birds with large territorial requirements, such as the northern harrier (Circus cyaneus), appear area sensitive. In addition, some small species of grassland birds favor patches of habitat far in excess of their territory size, including the Savannah (Passerculus sandwichensis), grasshopper (Ammodramus savannarum) and Henslow's (A. henslowii) sparrows, and the bobolink (Dolichonyx oryzivorus). Other species may be area sensitive as well, but the data are ambiguous. Area sensitivity among wetland birds remains unknown since virtually no studies have been based on solid methodologies. We need further research on grassland bird response to habitat that distinguishes supportable conclusions from those that may be artifactual.
منابع مشابه
Habitat suitability modeling of water birds and waders in Hamun wetland by by Maximum Entropy model
Climate change and human activities have increased negative pressure on natural ecosystems. Wetlands are such ecosystems that widely affected by these negative changes. Birds as a part of wildlife in a wetland have damaged by destruction of wetlands, so, a large group of them, are at risk of extinction. Habitat destruction in wetlands in arid and semi-arid areas has more negative effects on the...
متن کاملRelationship between habitat area and the distribution of tidal marsh birds
—To assess the relationship between marsh area and relative abundance of tidal marsh bird species, we surveyed birds on 86 circular plots in 40 salt and brackish tidal marshes in Connecticut. We measured marsh area in two ways: the amount of contiguous marsh vegetation not interrupted by broad barriers (.500 m of open water or .50 m of upland habitat) and by narrow barriers (.30 m of open water...
متن کاملConservation Implications When the NestPredators Are Known
Conservation and management of passerines has largely focused on habitat manipulation or restoration because the natural communities on which these birds depend have been destroyed and fragmented. However, productivity is another important aspect of avian conservation, and nest predation can be a large source of nesting mortality for passerines. Recent studies using video surveillance to identi...
متن کاملLack of South Caspian Habitat Conservation Network, A Serious Threat on Biodiversity
Iran, a 4-season land in the world, is located in semi-arid part of Asia. There are several geographical climates in this country, which are the main causes for the existence of diverse ecological conditions. In the north, where the Caspian Sea meets the land, there are three provinces. One of these, Guilan province, (the studied area) is located in the southwest of the Caspian with different g...
متن کامل