A question about sexual dimorphism (1 Viewer)

[Leiothrix]

I wanna known what's the proportion of sexual dimorphism in birds.
Is there anyone known this?
I tried to search this on internet, but failed to find useful information.

 

[Leiothrix]

Sexual dimorphism and homomorphism in birds, which one account for larger proportion?
I think this question is easier to answer than the former one.

 

[halftwo]

Hi Leiothrix,

That's a big question. It depends on how you define dimorphism really.

If you count all species with slight, but visible (to humans) differences - eg . slight size differences, tail lengths, bill colour etc (I'm thinking eg. Barn swallow, Common kingfisher, many cisticolas in Africa, etc.) then there there are a lot more species than those with completely different plumages/size & shape.

And there are many with differences only in size (length/weight) but whose plumage features are virtually identical (many birds of prey eg.).

So your question is complex! Where would you draw the line when it comes to choosing whether one species is sexually dimorphic (which would you choose for Silver-eared mesia for instance)?!

H

 

[Reuven_M]

Plus birds where the males tend to be brighter, but there is a lot of overlap

 

[Leiothrix]

Thank you.
Let me make my question concrete.
Only considering plumage color, what about the proportion of sexual dimorphism in birds by human eyes. Which part are larger? Dimorphism or homomorphism?
Sexual dimorphism here means easy to identified by human eyes in wild.

 

[StarainBoy]

Check the third paragraph of Three Things I Never Knew About Raptors for a brief treatment of dimorphism in birds of prey.

 

[Acrocephalus]

Hi,

This may be of certain help. The article contains a lot of interesting facts about sexual dimorphism (both size and plumage) and the role it plays this dimorphism. Many examples too (73 bird species comprising of 83 populations).

Owens I.P.F. & Hartley I.R. 1998. Sexual dimorphism in birds: why are there so many different forms of dimorphism? Proc. R. Soc. Lond. B 265 : 397-407.

 

[jaco]

Thank you.
Let me make my question concrete.
Only considering plumage color, what about the proportion of sexual dimorphism in birds by human eyes. Which part are larger? Dimorphism or homomorphism?
Sexual dimorphism here means easy to identified by human eyes in wild.

I don't think that makes it any easier to answer. There is no magic line that defines a species as sexually dimorphic or not... many of the differences are slight, but nonetheless observable. For many species, it is only the extremes of either sex that can be accurately sexed by humans. The degree of overlap between sexes varies species to species, but exists very much on a gradient.

The short answer is you're not going to get a short answer, no matter how you rephrase the question.