Why is it that birds can't produce toxins whereas other animals (including mammals) can?

Question

"there are many more species of venomous/poisonous reptiles (e.g. snakes), amphibians (e.g. poison dart frogs), and fish (e.g. stonefish). There are no species of venomous bird; however some birds are poisonous to eat or touch, such as the pitohui, the ifrita, and the rufous shrike-thrush. "

http://en.wikipedia.org/wiki/Venomous_mammals

Answer 1

Your question isn't phrased quite right - those birds listed in the wikipedia article do produce toxins. However, they are contained in their feathers and are a passive defense, as opposed to toxins manufactured and stored as venom (an active system). The poison dart frogs also mentioned in the article possess the same type of passive defense, as their toxins are stored in their skin. There is essentially no difference between the frogs and the birds mentioned.

Birds evolved from reptilian ancestors and it is not outside the realm of possibility that there are birds out there with oral toxins like those produced by snakes or other reptiles. No one is looking for them, however. And frankly, a bill is probably not a great delivery system for an oral toxin.

A completely different topic is whether or not toxins are actually manufactured by an organism (as is the case with snake venom) or is ingested and stored for reuse by an organism (like the poison arrow frogs, which store alkaloids contained in insect prey).

Answer 2

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Answer 3

Interesting question.

Evolution tends to dispense with features that are not needed for survival. Birds have an enormous advantage in being able to fly away from predators, so a venom would not be particularly useful.

Answer 4

Perhaps it is a combination of venomous birds obtaining no advantage by being so (hence it is 'ignored' by natural selection), and venom being costly to produce, energetically-speaking, and birds are already high-metabolism creatures.

Answer 5

It's not that they can't, they just don't. Birds just have not evolved the adaptation of venom producing glands.

Answer 6

Flight is both an offensive and defensive technique.

Answer 7

because they can fly to escape predators