333 
Great Invasion of Crossbills in 1909. 
In Italy articles and letters recording the extent and 
progress of the Crossbill invasion in that country have been 
published in the Journal 4 Avicula,’ in the c Bulletin’ of the 
Italian Zoological Society, and in some local newspapers, and 
further information, it is to be hoped, may still be forth¬ 
coming, not only from that country, but also perhaps from 
other parts of South Europe. 
Before giving the statistics which I have been able to 
obtain regarding the occurrence of Crossbills in various parts 
of the Continent, I wish to make a few remarks of a 
general character concerning the subject in question, and 
specially with reference to the following points connected 
with it, viz.: the cause which has determined or brought 
about this erratic migration or wandering of the species ; 
the country or countries from which the birds have chiefly 
come ; and, lastly, the influence or governing force, if there 
be any, which has regulated the course, expansion, and 
duration of the migration. 
Taking these points in the order above-mentioned, and 
commencing with that of the cause of this unusual movement 
on the part of a species not a true or regular migrant, the 
reason which naturally first presents itself to one’s mind is 
that of a scarcity of food in the bird’s habitual range ; and 
this, I venture to think, is probably the right one. 
The Crossbill, as is generally know n, is at times a veritable 
vagrant or gipsy among birds, as it has somewhat appro¬ 
priately been styled, its roving on such occasions being 
apparently influenced by alack of sufficient nutriment in the 
northern coniferous forests which are its chief home ; and 
this failure in its natural food-supply has probably been 
the cause of the species wandering in the present, as it has 
doubtless been in previous, instances. 
The exceptionally severe weather that prevailed throughout 
a considerable portion of the European Continent during the 
previous winter and spring months probably interfered with 
the development and ripening of the cones in the northern 
pine and fir woods, and brought about this failure in the 
bird’s principal food. 
