72 BULLETIN 621, U. S. DEPARTMENT OF AGRICULTURE. 
The attacking and driving away of crows by smaller species is a 
matter of common knowledge. This is especially true of the king- 
bird, which appears to maintain a sworn vengeance against its much 
larger relative. Its antipathy is most marked during the nesting 
season, when a pair or two of kingbirds are frequently an effective 
means of protecting poultry and crops in the immediate vicinity of 
their nests. In this connection, Maj. Allan Brooks, of Okanogan 
Landing, B. C, remarks, in a letter to the Biological Survey, that 
" the crows are generally kept away from the immediate neighbor- 
hood of houses and poultry yards by the number of kingbirds (two 
species) present." Though other small birds vigorously attack crows 
when the young or eggs are in jeopardy, none appears to possess to 
the same marked degree the unceasing animosity of the kingbird. 
Probably the most important natural agency in the reduction of 
the number of crows is a disease popularly referred to as " roup." 
Though no exhaustive study of this malady has been made, a few 
points regarding its nature have been established. Technically it 
may be termed an ulcerative keratitis, in which there also appears an 
inflammation of the mucous membranes, accompanied by exuda- 
tions from the eyes and nostrils. In severe cases the secretion about 
the eyes covers the cornea and blindness follows. Experiment has 
proved that the disease is contagious among crows, and also that it 
is specifically different from the roup of poultry. 1 
Heavy inroads have at times been made by this malady on the 
numbers of crows at their winter roosts. Becoming partially or 
totally blind in the advanced stages of the disease, the disabled birds 
suffer from lack of food and soon succumb under the combined at- 
tacks of disease, hunger, and cold, or fall easy prey to the preda- 
tory mammals and birds which take advantage of their helplessness. 
In one instance the writer witnessed a barred owl, closely pursued 
by a large flock of frenzied crows, making away with a sick indi- 
vidual too weak to resist. 
Prof. E. H. Eaton, describing an outbreak of this kind, states : 2 
About the middle of December, 1901, a malady broke out among the crows 
(Corvus americanus) of Ontario County, N. Y., which, ere spring, had deci- 
mated the ranks of the local "roost." As soon as winter had fairly begun 
reports commenced to come in of crows which had been " blinded by freezing 
of their eyes," as the farmers expressed it. * * *. 
All the sick birds were suffering from an acute inflammation of the pharynx 
and the anterior portion of the head, including the nostrils and eyes. Often 
there was a mucous discharge from the nostrils. The eyes were usually blinded 
by a membrane forming over the exterior of the cornea. Sometimes only one 
eye was seriously affected, and this was usually the left one, as far as I 
noticed. If this membrane was rubbed off the eye looked quite clear again 
1 Information supplied by the Bureau of Animal Industry. 
2 The Auk, XX, pp. 57-58, 1903. 
