Sexual Dimorphism in Birds

What is this bird hiding in the reeds?


This bird is one of the most widespread species in North America, but many people have trouble identifying it. Why?


The difficult in identifying this bird is due to sexual dimorphism. Don’t worry this is still a “G” rated post. Sexual dimorphism is when the male and female of the same species look different.


The main reason males birds have brighter coloring is to attract female birds. The ultimate goal fused into the DNA all living organisms (even humans) is to survive and pass on their genes to the next generation to perpetuate the species. Among vertebrates, males birds have some of the most vibrant colors and patterns. If you want to see some of the most spectacular bird plumages and very unique mating behavior check out the Birds of Paradise.


But what about the female birds, why are their feathers much less colorful? Most female birds needed to blend in with their surrounds as they spend more time sitting on the nest incubating the their eggs and providing shelter to their chicks. If the females were brightly colored, like their male counterparts, they and their nestlings would be easier seen by potential predators.


By now you are probably thinking this image is of a female bird and you are correct. It is a female Red-winged Blackbird. Check out the second image to see what the well named adult male Red-winged Blackbird looks like.

Male Red-winged Blackbird

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