Some birds, such as my pet Pionus chalcopterus, are not sexually dimorphic. People can't tell them apart, and even trained avian vets are not 100% certain with an inspection probing the vent.

I understand that when not "in season" there is no physical difference as internal sex organs are atrophied to save weight.

But how do they tell the difference?

Do they have dimorphic markings that bird eyes (but not humans eyes) can see?

  • 2
    $\begingroup$ Since we're not birds there's no way of knowing for sure, but I would imagine calls/songs and possibly pheromones have something to do with it. There may also be anatomical differences as well that humans haven't discovered yet. $\endgroup$
    – MattDMo
    Aug 27, 2015 at 17:42
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    $\begingroup$ Behavioral differences are likely a part of it, at least for some species. $\endgroup$ Aug 29, 2015 at 21:14

1 Answer 1


As very well explained also in Wikipedia https://en.wikipedia.org/wiki/Sexual_selection_in_birds , visual signaling is only one of the way birds uses to pick a partner, olfactory and acoustic signals also play a major role.

  • $\begingroup$ Thanks for the link. I would still like to know about Pionus specifically though. $\endgroup$
    – JDługosz
    Oct 4, 2016 at 16:37
  • $\begingroup$ I can't find anything about Pionus specifically, but I don't see why it should be different. $\endgroup$
    – alec_djinn
    Oct 4, 2016 at 20:24

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