Introduction

The Orange-crowned Warbler breeds widely over much of western and northern North America, and east across Canada. Four subspecies of this warbler are recognized and differ to varying extents in their plumage, molt patterns, and size. This species prefers habitats with shrubs and low vegetation, often in aspen forest or in riparian or chaparral areas, which provide cover for its nest, placed on or near the ground. Like other warblers of its genus, the Orange-crowned gleans insects from leaves, blossoms, and the tips of boughs, but it also eats some berries and fruit and is attracted to suet feeders in winter. Where sapsuckers (Sphyrapicus sp.) drill holes in tree trunks, this warbler is often the most common species seen feeding on the sap.

Often numerous in suitable habitat, this may be the most abundant breeding paruline in some areas. Its song is highly variable and individuals can often be separated by their distinctive song patterns. Some populations, particularly those at northern latitudes, are strongly migratory, while those breeding along the California and adjacent coastline may move only short distances in fall and winter.

The Orange-crowned Warbler has been the subject of extensive studies of its molt, pterylography, and ecto-parasitism (Foster 1967a, b; 1969). Much past information on the species’ ecology, behavior, and breeding, however, has been anecdotal. Only recently have more comprehensive studies been made, especially of V. c. lutescens in Contra Costa Co., central California (Gilbert 1986, 1994), V. c. orestera in Arizona (Zyskowski 1993), and of V. c. sordida on the Channel Is. off s. California (MKS and CvR). This account is based largely on these studies. Information on other subspecies and populations would be desirable, and could form the basis for ecological comparisons among races, between insular and mainland populations, and among populations at different latitudes.