The Supposed Occurrence of the Blue Goose in California
The Supposed Occurrence of the Blue Goose in California
The recurring statement that the Blue Goose (Chen caerulescens) is of casual or occasional occurrence in California, an assertion which, on rather weak evidence, has had wide acceptance, renders it particularly desirable that the capture of every bird supposed to belong to this species be investigated, and the identity of the specimen be thoroughly established. This, however, is not always possible, as the birds on which hunters’ statements are based are seldom saved long enough to afford an opportunity for examination.
The present remarks are incited by a recent instance, in which the capture of a Blue Goose appeared to be well authenticated, and which may serve as a demonstration of the extreme care to be used in accepting records whereby closely similar species may be confused.
A letter was received from F. J. Smith, of Eureka, Humboldt County, California, stating that he had in his possession a specimen of the Blue Goose, taken in that vicinity, on October 22, 1908, and requesting permission to send it to the Museum of Vertebrate Zoology in order that his identification be confirmed. The bird arrived soon after, and was carefully examined. Although the Museum collection contains no specimens of Chen caerulescens, it does contain a fairly large series of Chen hyperboreus hyperboreus, and on comparison the supposed Blue Goose proved to be a bird of this form, in the grayish, immature, plumage.
A search through descriptive literature failed to bring to light any statement clearly defining differences between the immature plumage of caerulescens and hyperboreus, and the question naturally arises as to whether previous supposed instances of the occurrence of caerulescens in California have not also been founded upon young birds of hyperboreus, the two forms being so very similar in this stage.
The Blue Goose was first included in the list of California birds upon the strength of the statement by Belding (Zoe, III, 1892, p. 97) regarding the capture of two specimens near Stockton, February 1, 1892. Fragments of one of them, head, neck, wings and legs, were submitted to Mr. Ridgway, and by him pronounced to be juvenile caerulescens. While the authority in support of this record is thus of the highest degree, still, considering the apparently close similarity of the two species hyperboreus and caerulescens in the immature plumage, and the absence of corroborative evidence since the time of Belding's record, we are surely justified in demanding stronger proof of the occurrence of the Blue Goose in California.
The specimen suggesting these remarks is an example of the ease with which mistakes in identification can be made. From written descriptions alone there was nothing to disprove its being caerulescens, either that species in immature plumage having no distinctive peculiarities serving to distinguish it from the same stage of hyperboreus, or else such differences having never been clearly set forth; but comparison with examples of hyperboreus unmistakably demonstrated the fact of its belonging to this species.
