In general, predation and disease do not seem to be important factors limiting 

 bird populations in coastal Maine. Ground nesters are more subject to 

 predation than species nesting above ground or in cavities. Common predators 

 on birds in coastal Maine include hawks, crows, ravens, blue jays, red 

 squirrels, chipmunks, raccoons, foxes, coyotes, weasels, and domestic pets. 



Human Related Factors Affecting Abundance 



Human activities in coastal Maine affecting the distribution and abundance of 

 terrestrial birds include habitat alteration, use of pesticides and 

 herbicides, accidental mortality caused by collisions with automobiles or 

 buildings, and hunting. Although the extent to which these factors effect 

 bird populations in coastal Maine is not known, the general ways birds are 

 affected are summarized below. 



Habitat alteration . Any activity that alters the composition and 

 structure of a plant community also affects the relative abundance and species 

 composition of the bird populations. Humans induce changes through logging 

 (clearcutting or partial cutting), fire, herbicidal application, highway 

 construction, transmission line construction, brush clearing, cull removal, 

 and urban or suburban development. 



Extensive studies on the effects of clearcut logging on bird populations were 

 conducted recently in northern Maine (Burgason 1977; Titterington 1977; and 

 Titterington et al. 1979). Total densities of breeding birds decreased by 

 half immediately after clearcutting, but increased to precut levels within 7 

 years. Species composition also was affected, since species preferring forest 

 habitats were replaced by edge species and species preferring early 

 successional stages. 



Clearing for highway and transmission line corridors effects bird populations 

 in a manner similar to that of clearcutting. Densities of breeding birds in a 

 highway right-of-way decreased from 7 birds/acre (17 birds/ha) to 3 birds/acre 

 (8.5 birds/ha; Ferris 1977). The association of birds replacing forest 

 inhabiting species was mostly edge species and ground feeding birds. Unlike 

 succession following clearcutting, the right-of-way association persists 

 indefinitely because natural vegetation succession is arrested by mowing, 

 herbicides, and brush clearing. An indirect effect of highways on bird 

 populations results from increases in cowbird and starling populations along 

 highways. Cowbirds are brood parasites and reduce the nesting success of 

 other birds nesting in the right-of-way and adjacent forest habitat. 

 Starlings use natural cavities as nesting sites and successfully outcompete 

 native bird species for the limited number of natural cavities. 



Herbicides are used to control hardwood tree species in spruce-fir areas. 

 This affects bird populations by altering habitat structure and species 

 composition (Best 1972; Dwernychuk and Boag 1973; and Beaver 1976). The birds 

 most affected include those utilizing immature deciduous forests (birch-aspen- 

 red maple forest type) and early successional habitats (many edge species). 

 Ruffed grouse are adversely affected as their preferred food sources include 

 aspens, which are target species for herbicide treatments. 



Small alterations of habitats cause subtle changes in bird populations. The 

 clearing of brush or the removal of blowdown trees in forests may lower the 



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