In regards to pigeon diets; I've seen vets and wildlife rehabilitators mention that pigeons can eat a variety of vegetables,(appears corn and peas are recommend for young ones if they're abandoned and need to be cared for, in particular) berries, and insects as well, and according to ornithologist, rock pigeons regularly have a varied diet similar to that in a nature setting. I'm wondering where the idea that pigeons can't digest foods besides seeds and grain comes from?
So I have to ask you:
Do you know what anatomical part of the plant corn kernels and peas are?
Given that you called them vegetables, I have to assume not.
They are seeds.
Seeds have a VERY different structure from the rest of a plant’s anatomy.
They are embryonic tissue wrapped in a protective shell. Almost pure protein, and in terms of digestion, closer to processing meat than any other part of a plant’s anatomy.
Leaf, stem, root, tuber and vegitable flesh are largely comprised of Cellulose, the stuff that makes wood rigid.
Animals cannot process cellulose on their own.
They need bacteria for that, which is stored in a specialized organ called the Cecum, which branches off from the intestine in many species, and it just an extra length of it in others (such as humans and ruminants.)
In most birds, the cecum branches off of the intestines and food does not directly pass through it. Bacteria are excreted from it to digest the vegetation that the body cannot break down unaided.
Animals that eat a lot of leafy or fleshy vegetation have very large caeca to store the volume of bacteria required to break it down enough to get any nutrition out of it.
Here, for example, is the Cecum of a horse.
@why-animals-do-the-thing talked about the cecum in their post about why feeding a cat a vegetarian or vegan diet would kill it, and they found this helpful comparative image set.
Animals with a low cellulose diet tend to have either a very small cecum or none at all.
So, the idea that a pigeon cannot process cellulose stems from the fact that pigeons have less of a cecum than a DOG does.
Let’s have a look at the anatomy of a genuinely omnivorous bird that eats everything from flesh to bugs, to grass and does a LOT of grazing on vegetable matter:
A chicken has, not one cecum, but TWO very long Caeca.
Chickens eat a LOT of vegitation, so they need a LOT of storage space for their bacterial partners.
Now, let’s look at a pigeon.
See that teeny little blip of a cecum?
That’s all they need because the only cellulose in a seed diet is the shell of the seed, which pigeons swallow whole.
Unlike parrots, finches, and other seed eating birds, Columbids to not remove the shell from the seed.
The shell is an absolutely necessary source of dietary fiber that finches and psitticines get no use out of.
Animals that can process sugars need to be able to detect them.
Pigeons have 40 taste buds. None of which can detect sweetness.
Their enjoyment and selection of favorite food items is based more on texture than taste.
Pigeons who have never seen other birds eat a berry, when offered a berry, will generally fail to recognize it as a food, so the conclusion I have reached is that feral pigeons who do eat them have observed song birds do it, and with food being scarce and most of the,m being hungry, they don;t have the option to be picky.
That’s why you see ferals eating discarded hot dogs when they are not even remotely built to be flesh eaters.
Insects are actually very nutritionally similar to the embryonic tissue that seeds are, and there tend to be insects on or in seeds that birds pick up and swallow.
But now let me ask you:
Have you spent any time observing feral pigeon flocks?
Have you ever seen them employ hunting behavior?
Honing in on something that moves, stalking it and pecking it up like a chicken or corvid (both of which are omnivorous) would?
Because watching pigeon flocks is a big part of my research, and I have yet to see them react in a predatory manner to live insects.
Peeps are interested in the movement, but consumption largely seems to be incidental rather than intentional.