IO 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 competition 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 x 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 : 



Tympanuchus cupido, Bonasa nmbellus umbellus, Colinus virginianus, 

 Zenaidura macrura, Sterna dougalli, Sterna antillarum, Larus atricilla, 

 ^Egtalitis vocifera, sEgialitis meloda, Bartramia longicauda, Butorides 

 virescens, Ardetta exilis, Megascops asio, Antrostomus voctferus, Coccygus 

 amertcanus, Sayornis phcebe, Myiarchus crinitus, Tyrannus tyrannus, 

 Vireoflavifrons, Lanius ludovicianus migrans, Sitta carolinensis, \Trog* 

 * lodytfs* aedon, Cistothorus stellaris, Cistothorus palustris, Galeoscoptcs 

 carolinensis, Harporrhynchus rufus, Sialia sialis, Hylocichla mustelina, 

 Dendroeca discolor, Dendroeca vigorsii, Dendrceca cesfiva, Helmintho- 

 pkila chrysoptera, Piranga erythromelas, Icterus galbula, Sturnella 

 magnet, Agelceus pkceniccus, Molothriis ater, Passerina cyanea, Pipilo 

 erythrophthalmus, Spizella socialis, Spizella pusilla, Ammodramus cau- 

 dacutus, Ammodramus hensloivii, Ammodramus savannarum passerinns, 

 Pocecetes graminetis. 



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

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



