The Fragmentation of Our Natural Habitats
Unfortunately, land use for residential, road corridors and farming purposes in Southern Ontario has created a fragmentation of our forest cover. Urban sprawl through the creation of pavement and buildings permanently results fragmentation. This permanent loss of habitat for many bird species that historically lived and reproduced in larger tracts of unbroken forests has, in turn, led to the decline of many songbirds. This fragmentation has also benefited many of the predator species such as the crows, squirrels, raccoons, domestic cats, sea gulls and blue jays, as the feeding opportunities for these species are increased through the prevalence of surrounding crops, urban bird feeders, and municipal dump sites. Consequently, it is not only the size of the woodlots themselves that come into play, but the nature and characteristics of the surrounding landscape.
The habitats created by the boundaries of these broken up wood lots then have a big impact on the abundance of species and their survival rates. These ‘edge’ or ‘boundary’ habitats vary widely in structure and function, resulting in increased nest predation and brood parasitism. Cowbirds, for instance, which are well adapted to remove the eggs of the host species from their nests and substituting their own eggs, are attracted to the open habitat of these shrubby areas. Further in from the forest edges towards the centers of any woodlot the insect populations are stabilized, unlike the boundary zones where their communities are negatively impacted by the warmer dryer conditions. This has a direct impact on the food reserves for these birds. Some species are however, better adapted to the boundary conditions. Others are more vulnerable.
The shape of a woodlot is very important, as this defines how much boundary habitat and how much interior habitat exists. Woodlots that are round or square in shape provide for larger interior areas than woodlots that are long and narrow. Because of this connectivity is important, however preserving the larger areas of woodlots- preferably 100 – 200 hectares, is important in order to sustain sensitive species. The amount of forest cover plays a critical role in determining the variety of bird species that are found in any one area.
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