VI 



INTRODUCTION. 



cdo-e of the eggs of more than one tenth of the species of birds ascertamed to exist. 

 Those of whole genera, and even families, are comparatively unknown. Yet it is 

 not difficult to see that Oology promises to become an important auxiliary both 

 in aidino- to determine natural divisions, and to enable us to decide in regard to 

 varieties the specific identity of which is in doubt. Let us take an instance. The 

 Brown Thrush of North America [Mimus rufus) is usually classed in the same generic 

 group with the Cat-Bird [Mimus felivox). The eggs of these birds are very unlike, 

 and apparently demonstrate that they do not belong together. Without looking 

 at all to the external structure of these birds, Oology would seem to indicate that 

 the Cat-Bird, though closely allied to the true Mocking-Bird, is at least one step, 

 and that the Brown Thrush is even farther, removed. If we ask where the former 

 belongs, its eggs point out the Wood Thrush, the Hermit Thrush, and Wilson's 

 Thrush as its nearer kith and kin, with whom it is not usually classed. With the 

 Brown Thrush the case would be even plainer. It would require but a glance at 

 the eggs of the birds of North America, supposing them spread out before us, to 

 satisfy us that, if we accept this test, the Brown Thrush should be counted as a 

 Toxostoma, and classed with the T. curvirostris, T. longirostris, &c., from whose 

 eggs its own could hardly be distinguished. 



In regard to the value of Oology in determining disputed points of identity of 

 species, the case of Biiteo montanus may be cited as a striking illustration. Much 

 more might be said upon both these points, but, until more has been learned in 

 regard to the eggs of the birds of all the other parts of the world, it is at least 

 premature to consider how far Oology may be taken as a safe guide in classifi- 

 cation. As to its value in determining questions of identity or diversity, this 

 cannot well be disputed. 



In presenting to the consideration of all interested in the natural sciences the 

 results of his own investigations, largely aided by the co-operation of others, the 

 hope is indulged that it will not be forgotten that the field has been one hitherto 

 unexplored, that all has been new and untried, and that there has been but little 

 in the writings of those who have gone before to lessen the need of his own investi- 

 gations. Whatever deficiencies may be found in the present pages, and that there 

 must be many is necessary and inevitable, may be remedied in future numbers, if 

 they who may become aware of them will but point them out and supply the 

 means of rectifying them. The co-operation of all interested in the science, through- 

 out the Union, is invited. To those who may add anything to our common stock 

 of knowledge, due credit will be promptly and gratefully rendered. 



Boston, April, 1857. 



