Genetic analyses have documented restricted gene flow between two subspecies of Orange-crowned Warbler (Oreothlypis celata), and it is thought that south-central Alaska may be a zone of secondary contact between O. c. celata and O. c. lutescens. We evaluated six morphological variables in museum specimens and netted individuals of O. c. celata from central and southwestern Alaska, of O. c. lutescens from central inner-coastal California, and of putative hybrid or introgressed Orange-crowned Warblers from the Kenai Peninsula of south-central Alaska. Additionally, we evaluated data for two variables only of netted O. c. lutescens from the panhandle of southeastern Alaska. Our analyses of wing chord length, mass, tail length, and color of backs and undersides indicated that samples obtained from the Kenai Peninsula had means that lie between, and for the most part were significantly different from, the means of samples of presumably pure O. c. celata from farther north and west in Alaska, and O. c. lutescens from farther south and east in Alaska and/or farther south in central inner-coastal California. However, we found no significant differences among the means of tarsal lengths for three taxa/localities. Additionally, we found that the back and underside colors of putative intergrades tended to be closer to O. c. lutescens than to O. c. celata. The distribution of data points around the means for Kenai Peninsula samples did not appear to be bimodal for wing chord length nor for color of backs or undersides. This suggested that Kenai Peninsula samples were mainly composed of intergrades between populations of pure O. c. celata and O. c. lutescens, and were not samples composed mainly of a mixture of the two pure subspecies. These results also suggested, for wing chords, masses, tail length, and color of backs and undersides, that a blending inheritance pertained in putative intergrades between O. c. celata and O. c. lutescens.

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