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Tuesday, July 19, 2011

FOREST BIRD SURVEY: BIRD POPULATIONS IN CONNECTICUT AND RHODE ISLAND

The Brown-headed Cowbird above was a fairly common invader of forest environments throughout the region.
Southern New England conservation groups have identified the development of a high level, quantitative database on wildlife resources as key to developing substantive regional open space acquisition strategies.  To meet this need, Bird Conservation Research, Inc. is developing such a database for the forest birds of southern New England- by far the most diverse wildlife group of the region. 

The first two stages in our investigation were to survey quantitatively the forest birds of eastern Connecticut and Rhode Island.  These studies are now complete, and have produced the land-planning atlas, Forest Birds of the Last Green Valley, as well as scholarly papers.  This atlas was distributed at no cost to every town conservation commission in the research area, and its distribution has been followed up with explanatory presentations (with the assistance of the Connecticut Cooperative Extension System) to town conservation commissions, regional watershed councils and conservation groups.  To date, the major findings of our work have been discovery of: 1) broad patterns of winter and summer bird diversity across the region, 2) major winter-summer shifts in densities of permanent resident species, 3) environmental heterogeneity across the region exerting a major influence on species density distributions, 4) even the most common species having non-uniform distributions, 5) no one tract being sufficient for preserving regional forest bird diversity.  Such findings demonstrate, for example, that coastal forests are the principal reservoir for wintering species and have among the highest priorities for regional protection.  

The next phases of the investigation was to survey of forest birds of central, northwestern and southwestern Connecticut in both summer and winter.  State of the art field, analytical, and Geographic Information Systems mapping procedures are being used to make the database accessible to conservationists. 

The analysis of forest bird survey data continues, with much larger samples from eight years of study leading to more accurate and precise measurements of regional populations Measurement of populations relies on construction of detectability curves– graphical representations of how easily a species is detected at increasingly greater distances from a point. More data lead to increasingly realistic detectability curves.  Although computations for the over 100 species detected during surveys will be continuing for some time, some population estimates completed to date follow:

Black-throated Blue Warbler:
Northeast CT: 5091
Southeast CT: 0
Central CT: 925
Northwest CT: 34,798
Southwest CT: 898
Rhode Island: 1333



Red-shouldered Hawk:
Summer:
Northeast CT: 171
Southeast CT: 261
Central CT: 33
Northwest CT: 98
Southwest CT: 174
Rhode Island: 219
Winter:
Northeast CT: 47
Southeast CT: 31
Central CT: 16
Northwest CT: 33
Southwest CT: 63
Rhode Island: 31
Northeast CT: 17,447
Wood Thrush:
Southeast CT: 23,401
Central CT: 37,816
Northwest CT: 21,374
Southwest CT: 20,076
Rhode Island: 11,474



Pileated Woodpecker:
Summer:
Northeast CT: 321
Southeast CT: 369
Central CT: 363
Northwest CT: 980
Southwest CT: 379
Rhode Island: 80

Winter:Northeast CT: 424
Southeast CT: 367
Central CT: 194
Northwest CT: 195
Southwest CT: 699
Rhode Island: 27

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