Red Crossbills Feeding on Juniper Galls
Red Crossbills Feeding on Juniper Galls
At noon on May 26, 1938, two Red Crossbills (Loxia curvirostra), apparently male and female, were watched for over fifteen minutes as they systematically foraged in the Utah junipers adjacent to our dwelling on the south rim of the Grand Canyon, Arizona. The birds were working on the small pear-shaped galls (about 1 cm. long), that were fairly common on these trees. These galls were made by one of the gall midges or flies, Rhopalomyiu sabinae, of the family Cecidomyiidae. Examination of the galls disclosed that the untouched ones either bad the egg or larva of this insect in their hollow centers, whereas all the galls that the crossbills had worked on were cut open and the insect egg or larva removed. The birds, intent on feeding, could be approached very closely and their method of attack determined. The gall was pierced on opposite sides near the base by the tips of the bird’s bill; continued closing of the bill cut the gall completely through, except for the base. Finally, though this could not be perfectly seen, the tongue was deftly protruded into the opened gall to obtain the exposed egg or larva. The whole process of feeding on one gall took less than a couple of seconds, and obviously the bill played no part in extracting the enclosed egg or larva.
No other crossbills were observed feeding on the galls, although they were seen in yellow pines nearby. It is interesting to speculate as to whether this pair of birds alone had made the discovery of this available source of food.
Frank Richardson
Grand Canyon, Arizona, June 3, 1938
