VARIATION IN CAROTENOID-BASED COLOR IN NORTHERN FLICKERS IN A HYBRID ZONE

Abstract

We studied variation in the carotenoid color of flight feathers of hybrid Northern Flickers (Colaptes auratus) and its correlation with reproductive performance and survival. Color scores provided by a digital camera revealed in 218 individuals a continuous spectrum from yellow to red. Males tended to be slightly redder than females. Within individuals, an analysis of color change with age revealed that males, but not females, became redder with age. Except for yearling females, body condition did not improve with age, sug- gesting that color is not linked to body condition measured during incubation. We did not detect any correlations between feather color and measures of reproductive performance, such as clutch size, hatching success, or fledging success, or return rate to the study area. In a hybrid population where intraspecific variation in color is controlled partly by genes, hue or brightness may not be a useful signal of individual quality, contrary to other studies of birds. About 25% of flickers had one or more tail feathers that differed from the rest of the plumage. In each case, the ''odd'' feathers were paler or yellower in color and may have been caused by diet or stress when the feathers were lost and regrown during winter. Such odd colors support the hypothesis that red carot- enoid pigments are costly to maintain under stressful conditions. Received 25 January 2002, accepted 5 August 2002.