Volume 2, number 1 of Western Birds, published 1971
Separation of the Northern Waterthrush (Seiurus noveboracensis) from the Louisiana Waterthrush (S. motacilla), both in the field and in the hand, presents difficulties that are not adequately treated in either the popular or technical ornithological literature. The purpose of this article is to analyze the published identifying characters in light of my own field and museum experience.
In the course of investigating the relationships and plumage characters of the large gulls of western North America (Devillers, in prep.) a number of specimens had to be examined, and distributional data checked. Also, field studies, particularly in the San Diego region, northern Baja California, and the Salton Sea, have resulted in a better understanding of the distribution of some species. In this paper we summarize available data on winter distribution, timing of migration, abundance, age ratios, and habitat selection of the Glaucous Gull Larus hyperboreus, Thayer’s Gull Larus thayeri, Yellow-legged Western Gull Larus occidentalis livens, Western Gull Larus occidentalis occidentalis and L. o. wymani, Glaucous-winged Gull Larus glaucescens, and Mew Gull Larus canus brachyrhynchus.
The northward spread of the Herring Gull (Larus argentatus) into Iceland in the last several decades has resulted in extensive hybridization with the Glaucous Gull (L. hyperboreus; Ingolfsson, 1970). Hybridization between these species in North America is almost unknown, although two apparent hybrids have been collected in New Jersey in recent years (Jehl and Frohling, 1965). In the eastern Canadian arctic, where the species are widely sympatric, interbreeding is unrecorded. In the western Canadian arctic and in Alaska occasional hybridization has been inferred (Dwight, 1925; Ingolfsson, 1970). Because hybrids may provide evidence about the relationships and evolutionary history of species, they are of particular interest to biologists.
The Whip-poor-will (Caprimulgus vociferus arizonae) has been extending its range northward and westward in recent years as evidenced by records from the Sheep Mountains in southeastern Nevada (Johnson, Condor 67:93-124) and the Hualapai Mountains in western Arizona. Phillips, et al. (The Birds of Arizona, 1964) give the range in Arizona as "common summer resident of Transition and Upper Sonoran zones of southeastern and (in recent years) central Arizona; ranges west to Pajaritos Mountains and northwest less commonly (no specimen) to the Hualapai Mountains."
Early in the morning of 14 November 1970 I discovered a male Whip-poor-will Caprimulgus vociferus in one of the mist nets in my yard on Pt. Loma, San Diego, California. At this time the bird was examined in detail by Virginia P. Coughran, Pierre Devillers, G. Shumway Suffel, and myself; it was measured, described, and photographed (color slide deposited in the San Diego Natural History Museum). We felt the bird might be of the eastern race, C.v. vociferus. To confirm this, the bird was compared directly with material in the San Diego Natural History Museum (SDNHM) by Joseph R. Jehl, Jr. It was then banded and released.