densities of birds utilizing the ground and shrub layers. Removing dead and 

 diseased trees may reduce the number of hole-nesting species (McClelland 

 1977). Removal of hedgerows from agricultural and developed areas eliminates 

 nesting cover and song perches for many edge nesting species that feed in 

 fields or in hedgerow habitats (sparrows, certain warblers, blackbirds, 

 flycatchers, and American kestrels). Hedgerow removal in England, for 

 example, has been a major factor in the decline of species utilizing shrub 

 habitats (Murton and Westwood 1974). Sand and gravel removal in bank swallow 

 colonies during the breeding season results in swallow mortality. 



Habitat modifications can be beneficial to birds. Populations of edge species 

 and species breeding and foraging in open habitats increase as blocks of 

 forest are removed. Bird species benefiting from forest clearing include 

 bobolinks, meadowlarks, savannah sparrows, horned larks, blackbirds, mourning 

 doves, kestrels, and killdeer. Birds benefiting from herbicide treatments 

 include species utilizing young and old conifers because plant succession is 

 directed toward the rapid return of coniferous forests. Deciduous forest and 

 mixed deciduous forest serai stages are eliminated. In contrast to ruffed 

 grouse, spruce grouse benefit from this type of silvicultural treatment. 

 Chimney swifts, barn swallows, cliff swallows, purple martins, phoebes, 

 nighthawks, and rough-winged swallows benefit from nesting directly in or on 

 buildings, bridges, or other structures. Bank swallow colonies and kingfisher 

 burrows increased with the commercial excavation of gravel and sand deposits. 

 Three introduced species, starling, rock dove (pigeon), and house sparrow, are 

 so well adapted to developed environments they are considered pests in many 

 areas because of their habit of nesting in or on human dwellings. 



Chemical contaminants . The primary sources of environmental contaminants 

 that affect terrestrial birds in the characterization area are the chemicals 

 used in spraying programs for the control of forest and agricultural insect 

 pests. Secondary sources include heavy metal contamination , terrestrial oil 

 spills, and air pollution. These have minor regional effects but may be 

 significant locally. 



Prior to 1972, DDT and its derivatives (organochlorine compounds) were major 

 causes for the decline of certain terrestrial birds that eat fish or other 

 birds, especially osprey, eagles, and accipitrine hawks (Cooper's and sharp- 

 shinned) . These chemicals degrade slowly and concentrate in tissues of birds 

 high on the food chain. 



Since 1972 organophosphate and carbamate compounds have been used for the 

 control of insect pests in Maine. These compounds break down rapidly and do 

 not accumulate to toxic levels within food chains. Chemicals now used for the 

 control of spruce budworm are Sevin, Dylox, and Orthene . Sevin is used most 

 extensively on Maine's forest lands. Dylox is used primarily along the coast 

 (near blueberry barrens) because of its low toxicity to bumblebees which 

 pollinate blueberries, and Orthene is used near lakes, ponds, and rivers. 

 Other chemicals used in Maine (currently registered by the Maine Department of 

 Agriculture, Pesticide Control Board) include Fenitrothion, Phosphamidon, 

 Mexacarbate, Guthion, Lannate, and Matacil (currently in experimental use 

 only, but expected to be registered in 1980). Sevin, Dylox, Orthene, Lannate, 

 and Matacil do not cause acute damage to birds but may affect their behavior 

 and reproductive success (Moulding 1976). Acute damage to birds from the 

 spraying of Phosphamidon and Fenitrothion insecticides for spruce budworm 



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