Dimorphism: Specifically in Birds

   Hello! I wanted to talk about dimorphism today because I've seen it happening more and more as I improve my photo taking abilities when it comes to birds.   

   Sexual dimorphism is when the different sexes have different morphological characteristics which don't have a direct effect in reproduction. There are many different ways that this can happen including size, weight, color, markings, or behavioral or cognitive traits. I've observed this more times than I can photograph but my goal is to have as many photos of both males and females logged. My next goal is to get the female version of red-winged blackbirds but have thus far only been able to photograph the males.

This is the male red-winged blackbird (Agelaius phoeniceus) which has the brightly colored bands on his wings. I saw few females but they blended better with their surroundings and moved more quickly, making it hard to photograph them.

   I learned that the sexy son hypothesis explains that males with more elaborate coloration are chosen more often than dull males, even when accounting for differentiation in vision for different species. In birds, most of the time the males are the more brightly colored of the two. It is thought that this occurs because females have more to lose in terms of reproduction. 

The male mallard (Anas platyrhynchos) here is much more brightly colored than the female. 

This is a male common grackle (Quiscalus quiscula) which has greenish blue coloratuon and yellow on his wings. 

While this is a female common grackle (Quiscalus quiscula) which still shows some of the blue in her head but is a more dull brown and lacks the yellow coloration of the males.

   In some species, the males just leave after copulation but in others the males remain to help. Sometimes the males even become the primary caregivers to the young. The differences in their plumage have shown to follow this trend and suggest to female the fitness of the males along with other factors like body condition and survival.

   These traits aren't always wholly beneficial for the males either as their brighter colors may put them at a disadvantage with predators. But, even if the males die more often from predation as long as they keep reproducing successfully the trait will continue on because they are still successful enough to have offspring.

   Larger males are also favored for a multitude of reasons including better chances during migration and are better prepared for reproduction upon arrival. I haven't noticed this in my personal experience yet as the species I've documented are about the same size.

   Sexual dimorphism is very common and occurs in many other animal species including frogs, insects, and fish just to name a few! I chose to look at birds because I have the best photos of them as opposed to other animals so far. As always I hope you learned something because I sure did!

Yours, 

Jade