488 J- A. ALLEN ON BIRDS 



XIII. Notes on Birds observed in Western Iowa, in the months of July, August and September ; also 



on Birds observed in Northern Illinois, in May and June, and at Richmond, Wayne Co., 



Indiana, between June third and tenth. Bu J. A. Allen. 



Read June 3d, 1868. 



A. CAEEFUL examination of our present data concerning the distribution of American 

 Birds, will soon fully convince one that the range in the breeding season must form the basis 

 for defining the limits in latitude of the different avi-provinces and faunae ; at other seasons 

 the migratory species are rarely localized for any considerable period, and hence, though 

 forming an important element in the faunal features of the regions they visit, they cannot 

 properly be considered as inhabitants of any of them. This becomes the more evident 

 when we consider that though a given species may be represented for weeks at certain 

 points in its migratory range, it is only by a succession of individuals and not by a single 

 set. 1 Those birds which seek high northern latitudes in the breeding season, and sub- 

 temperate or tropical in winter, pass nearly two thirds of the year in long journeys, rarely 

 pausing for any long interval, beginning slowly to retrace their steps almost as soon as they 

 reach their southern limit. Their breeding country, then, however short their residence 

 there, is their only true home ; and here it is that their influence is most positive. This is 

 no less the case with those species whose migrations are less extended, and which are, to a 

 greater or less degree, winter residents in stations not far remote from their summer homes. 

 In studying the distribution of the birds in any country, the investigator is almost at once 

 checked by the lack of proper data. Even in countries where ornithology has been long 

 cultivated, as in Europe and the older portions of our own country, is the deficiency hardly 

 less than in regions more slightly known. The cause of this is, of course, the slight lapse 

 of time since the geographical distribution of animals has come to be critically studied, and 

 the present want of interest in the subject among many who could otherwise greatly aid 

 its advance. At present we do not know with sufficient exactness the avi-fauna of any 

 considerable region, even when we know pretty definitely all the species occurring there. 



1 As might be naturally supposed, in migratory species rang- earlier in Massachusetts than they do about Hudson's Bay, or 

 in" far to the north in the breeding season of any locality in the valley of the Mackenzie River. Again in autumn we 

 where they breed abundantly, those that arrive first in spring find that in general the individuals last seen are larger than 

 are not those that remain and breed at that point. The differ- summer specimens, and in most cases that winter specimens, in 

 ence in size so well known to characterize birds of the same many so-called resident species, are larger than those found at 

 species, breeding in different latitudes, affords the means of the same place in summer; also that unusual visitors from the 

 demonstrating this ; we have found that in several species those north are generally rather smaller than the average of the 

 that first arrive in Massachusetts are, in general, very appre- species, as in Pimcola enucleator (P. canadensis Cab.) JEgi- 

 ciably larger than those that arrive later, or than those that olhus linaria, and others. The migration seems to be by a 

 remain through the summer. This has been especially noted general swaying southward in winter, and northward in sum- 

 in Turdus migratorius, T. Swainsoni, T. Pallasi, Dendrceca mer, of all the representatives of the species, those found 

 mstiva, Spizella socialis, and in other sparrows and warblers, farthest north or south in winter being also those living respec- 

 and in some of the Tringece. It is also fair to infer that in tively farthest north or south in summer; though there is, 

 general birds do not arrive at their breeding stations long be- doubtless, a greater tendency in the more mature and vigorous 

 fore they set about the duties of incubation, since those species birds to seek higher latitudes, especially in the breeding season, 

 that pass but a little to the north of Massachusetts are noticed than the younger and weaker. All experienced collectors of 

 to pair and commence building their nests within a few days birds, moreover, are well aware that those that first arrive in 

 after the species is first noticed there, while D. aslioa, and the spring are of brighter tints than those coming later, and are in 

 few other species which range to the Arctic Circle, are seen for every respect apparently the most perfect representatives of 

 nearlv a month before they begin nesting, and do not breed their kind. 



