Brown on Immaturity vs. Individual Variation. 
47 
i88 3 .j 
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 perfectly transparent , the 
texture of the brain and its blood vessels 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 immediately 
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 
Loxia leucoptera passed under the knife of Mr. J. Amory 
Jeffries, of Boston. First stating that from this incomplete ma- 
terial no positive deduction can be made, Mr. Jeffries 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 birds 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. 
