lO Birds of Massachusetts 



of the " islands " of the Canadian zone to be mentioned, later. The 

 Transition zone is a region of nicely adjusted balance. Southern 

 species endeavoring to extend their range to the north, here meet 

 northern species pushing down towards the south. Since. this re- 

 gion, then, is one in which a large number of species are able to 

 live, there is bound to be a more or less keen cornpetition for living- 

 room among its inhabitants. If one species for any reason loses 

 ground, another will sooner or later take its place. Interesting 

 cases of this sort are recorded "^ in which Wood Thrushes have 

 invaded the former ranges of the Hermit Thrush after the great 

 mortality among the latter in 1895. A number of other instances 

 of a species losing ground on the borders of its range may be ex- 

 plicable by the fact that individuals habitually frequenting such 

 outlying localities are cut off in numbers by some severe and unex- 

 pected disturbance, so that their former habitat is left vacant for 

 occupancy by others. Many other causes doubtless enter into 

 the complexity of the problem. Cutting off of timber changes 

 both the future plant life and climate of the spot and consequently 

 the fauna. Thus cutting away a spruce forest, with its coolness 

 and dense shelter, gives rise to a growth of deciduous trees, whose 

 open branches allow the sun to dry up the moisture formerly held 

 by the denser trees, and thus a new fauna comes in. 



Following is a list of forty-five birds of the Austral zones 

 which range north into the Transition zone of Massachusetts and 

 here breed : 



Tympanuchiis cupido, Bonasa umbellus umbellus, Colinus virginianus, 

 Zenaidura macrura, Sterna dougalli, Sterna antillarutn, Larus atricilla, 

 j^gialitis vocifera, ^gialiiis meloda, Bariramia longicauda, Butorides 

 virescens, Ardetta exilfs, Megascops asi'o, Antrosfomus vociferus, Coccygus 

 americanus^ Sayornis phoebe^ Myiarchus crinittis, Tyranmis tyraunus^ 

 Vireo Jlavifrons, Lanius ludovicianus migrans, Sitta carolinensis, Trog- 

 lodytes aedon, Cistothorus stellaris, Cistothorus ■pahistris, Galeoscoptes 

 carolinensis, Harporrhynchus rufus, Sialia sialis, Hylocichla mustelina, 

 Dendroeca discolor, Dendrceca vigorsii, Deiidrveca cestiva, Helmintho- 

 fhila chrysoftera, Piranga erytliromelas, Icterus galbnla, Sturuella 

 magna, Agelceus phceniceus, Molothrus ater, Passerina cyanea, Pipilo 

 erythrophthalmus, Spizella socialis, Spizella pusilla, Ammodravius cau- 

 ■dacutus, Ammodramus hensloivii, Ammodramus savannarum passerimis, 

 Pooecetes gramineus. 



1 Faxon, W., and R. Hoffmann; The Birds of Berkshire County, Massachu- 

 setts, pp. 9, '10. Allen, F. H.; St. Johnsbury Caledonian, Sept. 11, 1896. 



