The Pinnacles of Sand Creek and Wheeler Creek have long been of interest to geologists because of their contribution to our knowledge of the pumice-scoria flows which descended the southern slope of Mount Mazama prior to its collapse. These Pinnacles are the results of the most intense fumarolic activity in the Park (Williams, 1942:8990). In this activity pumice and scoria were hardened in vertical columns by ascending gasses. The present form of the Pinnacles is the result of the modification of these original columns by wind and water erosion. Some of the Pinnacles are actually hollow and are sometimes referred to as "fossil gas vents."

Curiously little attention has been given to the fact that the pinnacles are of some ornithologic interest. Frequently they are used by birds as song perches in the same manner as dead trees are used. Of even greater interest, however, is the use of small cavities in some of the Pinnacles as nesting cavities. There are at present records of the use of such cavities by three species of birds. On June 26, 1952, I saw a pair of Mountain Chickadees, Parus gambeli Ridgway, carrying material into one of these cavities. Although I was unable to be certain, it appeared that the material was items of food indicating that the eggs had already been hatched. On the same day Park Naturalist Harry C. Parker and I observed a pair of Mountain Bluebirds, Sialia currucoides Bechstein, entering repeatedly an opening in one of the Pinnacles. At the time, we could not feel certain that nesting activity was in progress. However, on July 29 I saw a female enter the same opening and on August 4, saw both male and female carrying insects into the cavity. In the vicinity were two juvenile bluebirds apparently completely independent of the adults. They were catching insects on the wing. It would appear quite possible that these juvenile birds were from the first brood with which the observations of June 26 could be associated, whereas the food-carrying observed on August 4, was doubtless in conjunction with the rearing of the second brood.

On July 19, 1952, I discovered a pair of Violet-green Swallows, Tachycineta thalassina (Swainson), carrying food into a cavity in the Wheeler Creek Pinnacles. The young could be seen and heard plainly. Although Violet-green Swallows have been observed (Farner, 1952:74) rather frequently in Wheeler Creek Canyon and elsewhere in the Park, this is actually the first breeding record.

It should be noted that both the bluebirds and chickadees normally nest in cavities in tree trunks. The Pinnacles thereby constitute a curious, although understandable, substitute for tree trunks.

It is further of interest to note that Rough-winged Swallows, Stelgidopteryx ruficollis (Vieillot), have also been known to breed in Wheeler Creek Canyon (Farner, 1952:75). However, it appears that holes in the cliffs, rather than holes in the Pinnacles, are used.

References

Farner, Donald S. 1952. The Birds of Crater Lake National Park. University of Kansas Press. ix + 190 pp.

Williams, Howell 1942. The Geology of Crater Lake National Park, Oregon. Carnegie Institution of Washington Publication 540. vi + 162 pp.