1SS3.J Browx on Immaturity vs. hidividiial Variatiott. A*! 



On November 9, 1882, 1 found both species of Crossbills un- 

 usually numerous in Scarborough, Maine. Wishing to obtain a 

 good autumnal series, I used my gun freely among them and 

 procured specimens illustrating almost every known phase of 

 plumage except that of nestlings. Of males there are highly- 

 colored red birds, yellowish birds, greenish birds, and birds in a 

 garb of mixed colors. In the case of some of them traces of the 

 first plumage unmistakably indicate immaturity,* and these birds 

 agree exactly with all of the others in an osteological condition 

 which stamps the entire lot as young of the year. The vertex 

 of the skull is incompletely ossified ; it is easily indented by the 

 edge of my thumb nail ; and it is ferfectly tratzsparent^ the 

 textiu'e of the brain and its bloodvessels being plainly discernible 

 underneath. According to my experience, resulting from dissec- 

 tion of nearly four thousand specimens of North American birds, 

 this is a condition which cannot exist in any Passerine species 

 after maturity. 



But for a severe attack of illness which, almost imrriediately 

 after the capture of the birds above mentioned, put a stop to my 

 investigations for the season, I should have had more elaborate 

 evidence to offer as the result of systematic dissection. As it is, 

 however, the decapitated bodies of my two rosiest examples of 

 Loxid leticoptera passed under the knife of Mr. J. Amory 

 Jeftries, of Boston. First stating that, from this incomplete ma- 

 terial no positive deduction can be made, Mr. Jeftries gives his 

 opinion of the comparative maturity of the specimens as follows : 



"The fasciae joining the borders of the iliac bones to the 

 vertebrae seem to be less dense and broad than in most adult Fin- 

 ches. The syrinx appears to be rather small for a Sparrow 

 (though not knowing the species I cannot be positive), which 

 points to youth. Certain divisions and relations of the muscles 

 point to the same conclusion. The same is true of the flexible 

 tendons of the extensor muscles of the back. The condition of 

 the testes and vasa deferentia — both specimens being males — 

 points to a young bird. On the other hand, I can find nothing 

 indicative of extreme age or that is diagnostic of adult life. 

 Finally, the bii'ds would seem to me to have been hatched in the 

 spring and shot in the fall." 



* There are such specimens of L. leucoptera in the reddish phase. 



