30 BRITISH BIRDS. 
LOXIA CURVIROSTRA ann LOXIA PITYOPSITTACUS. 
COMMON CROSSBILL and PARROT CROSSBILL. 
(Puate 13.) 
English ornithologists, having voluntarily cramped their ideas by putting 
on the straight jacket of a binomial nomenclature, have for the most part 
treated the Common and Parrot Crossbills as distinct species. The facts 
of nature do not warrant such a conclusion in the least. A large series of 
examples from Europe, Siberia, China, Canada, and Mexico show some 
differences in size, especially in the bill, which varies almost as much as 
that of the Lesser Redpole or the Reed-Bunting. Crossbills from the 
pine-forests of Europe have the largest bills ; those from Mexico have 
nearly as large bills, but the upper mandible is slightly weaker. Ex- 
amples from the larch- and spruce-forests of Europe and Asia have both 
mandibles weaker; whilst those from Canada have still smaller bills, and 
approach very near to the Himalayan Crossbill in this respect. The 
length of wing varies much less, being as under :— 
Length of wing. Height of bill. 
L. pityopsittacus . . 4°3 to 4:0 inches. ‘6 to ‘5 mech. 
emecwcana . a 2 Al ew 5; (DD ay) mes 
L. curvirositra. . . 39 ,, 37  ,, ess ee lene 
L. americana. . . 35 ,,33 _,, SOG (8 yas 
L. himalayana . . 3'1,,30 ,, 500) By (Ors 
It is probable that in a sufficiently large series the measurements of 
each of these supposed species would be found to overlap that next to 
it, and that all these forms are conspecific and nothing but local races. 
It is not known that they differ in colour or in any other respect 
except in size, thickness of bill, and choice of food. The two last- 
named peculiarities are probably cause and effect. In ‘ Naumannia’ for 
1853, p. 78, is a plate of twenty bills of Crossbills to illustrate a paper 
by Brehm, who attempts to discriminate between six species of Parrot 
Crossbill and eight or more species of Common Crossbill. Scotch 
examples are intermediate between the Parrot and Common Crossbills 
of the continent; they probably feed on both kinds of cones. The fact 
that the tropical form of the Old World is a small weak-billed race, whilst 
that of the New World is larger and stronger-billed than its northern 
representative, is probably also merely a question of food. The synonymy 
of the two forms which are found in our islands is as follows :— 
