The Red Crossbill Irruption of 1951
Unquestionably the most spectacular ornithological phenomenon of the summer of 1951 was the prodigious numbers of red crossbills, Loxia curvirostra Linnaeus.
These spectacular nomadic finches were reported continuously and in substantial numbers from all parts of the park. They were the repeated subject of questions and comments by large numbers of visitors most of whom have only the most casual interests in birds. At the Rim Village they could be observed repeatedly at distances of a very few feet as they pecked systematically, possibly for minerals, at the andesite blocks of the retaining wall. The same behavior was observed less frequently at fireplaces and at broken places on the pavement of the highways.
Crossbills were relatively abundant during the summer of 1950, but the numbers observed then were greatly eclipsed by the numbers recorded this season. My field notes yield a reasonably useful comparison in terms of the numbers of crossbills seen per hour in the field during several summers in the park.
| Year
|
Hours in the field
|
Number of Crossbills Seen per Hour |
| 1940 | 50 | 0.1 |
| 1941 | 50 | 0.1 |
| 1942-1945 | no records | |
| 1946 | 65 | 0.9 |
| 1947 | no records | |
| 1948 | 74 | 0.5 |
| 1949 | 42 | 1.0 |
| 1950 | 111 | 1.7 |
| 1951 | 110 | 5.5 |
Although no nests were found I am quite certain that breeding has occurred in the park during 1951. Pairs were seen repeatedly, singing was common, courtship display was observed several times, copulation was observed once, a juvenile bird was observed being fed, and the specimens obtained for the park collection were in breeding condition.
With respect to periods of abundance in the past it is interesting to note that Miller and Miller (ms. 1926) observed only a few in 1926. Superintendent E. C. Solinsky reported them as abundant in October 1930. Campbell (1934) saw none during the summer of 1934. According to Aldrich (1938, 1940) red crossbills were abundant during the summer of 1938 when there were good crops of cones on the white-bark pines and mountain hemlocks; they were less abundant again in 1939 and quite uncommon during 1940. During 1938 Aldrich (1940) observed a juvenile being fed by an adult.
The “mineral pecking” behavior which was observed so frequently this summer was also observed repeatedly during the summer of 1938 (Aldrich, 1939) and less commonly during 1939 and 1940.
The specimens obtained during 1950 and 1951 indicate that the race involved in this irruption is bendirei Ridgway.
References Cited
Aldrich, Elmer C.
1938. Notes on the Sierra Crossbill. Crater Lake National Nature Notes,11(3): 27-29
1939. Notes on the salt-feeding habits of the Red Crossbill. Condor, 41(4): 172-173.
1940. Notes on the birds of Crater Lake National Park, Oregon. Condor, 42(2): 89-90.
Campbell, Berry
1934. Annotated list of the vertebrates of Crater Lake National Park. Mimeographed, National Park Service, Crater National Park, 22pp.
Miller, Loye, and Alden H. Miller
1926. Birds observed in Crater Lake National Park during the season July 1 – August 15, 1926. Manuscript in the files of the Museum of Vertebrate Zoology, University of California, Berkeley.
