I enjoy blogging because I am learning new things about birds as I write. I always knew that White-throated Sparrows come in bright and dusky morphs (the photo above is of a bright bird, the one below is a dusky one). You might be tempted to say that the bright birds are males and the dusky ones are females, but the only way to tell the sexes apart is by wing length or, in the breeding season, by cloacal condition.
Researchers have found that each morph usually breeds with its opposite type (dull males mate with bright females and visa versa). The two morphs have different chromosome arrangements. Compared with dull males, bright males are more aggressive, more territorial, and more "apt to seek matings outside the pair bond." Dusky females, on the other hand, provide more parental care than bright females. No other bird, even those with distinct morphs, share such complicated genetic, plumage, and behavioral differences.Zonotrichia albicollis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu.bnaproxy.birds.cornell.edu/bna/species/128