Breeding Bird Survey 



This nationwide survey samples bird populations along randomly selected 

 driving routes, each 25 miles (45 km) long. Birds are counted during 3-minute 

 stops every half mile along a route. By comparing only routes run in 

 consecutive years by the same person(s) (to reduce observer bias) trends in 

 species abundance can be determined. The survey is biased in favor of those 

 bird species found along secondary roads so comparisons of abundance between 

 species are not valid unless habitat availability along routes is determined. 



There are 17 breeding bird survey routes in the characterization area. Based 

 on general vegetation zones suggested by Kuchler (1964) and Peterson (1975), 

 these routes can be grouped into southern New England (4 routes in region 1), 

 northern hardwood (9 routes in regions 2 to 5), and spruce-hardwood (4 routes 

 in region 16) . 



The abundance of birds along survey routes is represented as either overall 

 abundance (birds per route) or frequency of occurrence (percent of the 50 

 stops on which a species occurs). The 20 most common species in each of the 

 three zones are summarized in table 16-6. Regions 1 to 5 show similar trends 

 in species abundance, but region 6 has some important differences. Hermit 

 thrushes, red-eyed vireos, Nashville warblers, and solitary vireos are more 

 common in region 6 than elsewhere, whereas wood thrushes, yellow warblers, 

 song sparrows, red-winged blackbirds, grackles , catbirds, and robins are less 

 abundant. These differences result from differences in habitat availability 

 due to changes in land-use patterns. Some of these changes are described in 

 chapter 9, "The Forest System" and chapter 10, "Agricultural and Developed 

 Land." 



Breeding bird surveys have also been used to detemine trends in the abundance 

 of individual species (table 16-7) . Significant long-term increases in wood 

 thrushes and rufous-sided towhees have occurred in the characterization area, 

 probably because of natural range expansion. Hermit thrushes have declined 

 perhaps because of interspecific competition with wood thrushes (Morse 1971b). 



The breeding bird survey documented severe reductions in songbird numbers 

 after spraying Phosphamidon and Fenitrothion for control of spruce budworm in 

 New Brunswick (Pearce et al. 1976). Reduced numbers of small insectivorous 

 songbirds were documented following severe cold springs in New Brunswick 

 (Erskine 1978). In Maine, declines of swallows following a cold spell in May, 

 1974, and the effect of the cold winter of 1976 on species such a winter wren, 

 yellow-bellied sapsucker, hermit thrush, ruby-crowned kinglet, and eastern 

 phoebe, that winter in the southeastern U.S., have also been demonstrated 

 using results from the Breeding Bird Survey. 



The osprey is a breeding resident which is relatively abundant in coastal 

 Maine. It nests on coastal islands and on the mainland along the shores of 

 marine and estuarine waters. Available information on the locations of nesting 

 ospreys is included in atlas map 4. No complete inventories of the breeding 

 osprey population in coastal Maine have been conducted, but a majority of the 

 island nests have been located. 



16-20 



