Dimorphism in birds

When I was a child I always wonder why their are 2 types of birds feeding the same chick but their appearance was very different ( Purple sunbird)
Why do male and females appear different in same species? What trick does evolution has played, what are its advantages and at last why do male appearance is somewhat shiny and beautiful .

Great question! I’m looking forward to reading the answers. Sexual dimorphism is pretty interesting to me, too. At a simple level, male ornamentation seems to be a strategy used by many bird species to help in finding a mate. Yet, if a female is sitting on a nest or caring for a brood, it may be an advantage to be inconspicuous to avoid predators.


I agree with your explanation but there are some contradictions and questions
first why does males had to be attractive in first place in order to find mate why not female find mate,
and second in some species males and females have equal sharing in caring of chick and yet males have striking colour


Google is a great reference for this sort of question, I’ve found.


True! And, true of so many things we discuss here instead.

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This Wikipedia article on ornamentation has a good overview on some of the theories about this. It’s worth noting that while female ornamentation isn’t as common as that in males, it does exist and presumably for the same ultimate reason as in males: there are situations where it will increase their evolutionary fitness.


Those are some great questions, and those questions have inspired a lot of biologists over the years. Whether an individual should be ornamented or not depends on the costs (attracting predators to a nest or to the individual bird, and sometimes making it harder to fly (like a peacock tail) or more visble to their prey) and the benefits (attracting more mates, or “fitter” mates, or making rivals less likely to challenge your territory). In some cases it is more straightforward to explain why male birds are often more ornamented than females, such as cases where males don’t help at the nest and might attract multiple mates, such as birds of paradise, manakins, and sage-grouse. In other cases like jacanas and phalaropes, the males are the choosier ones and do more caring for the young, and so the females are more ornamented.

In cases where the birds form monogamous social pairs and both parents care for the young, it is more complicated to explain, but probably often involves cases where the female still invests more in the young (and so is under pressure to be more choosy than the males since she has to grow the eggs with her own resources) or when the female mates with more males beyond her social mate (and so there is pressure for males to be more attractive in order to be picked by more females to father these “extra-pair” offspring).


The Wikipedia article on Sexual Selection is pretty informative.


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