O. M. G.....LOLLLLLL!
Only mammals have mammary glands that produce real milk. Birds produce what is called “crop milk,” food that is partly digested in the crop and then coughed back up and fed to fledglings.
I suppose a male flamingo can do that, although I haven’t found a source to confirm it. I think there are bird species where the mother and father share the duty of feeding their young.
All that said, it doesn’t have much bearing on whether this shows that homosexual behavior is “natural.” They are really desperate to prove that, but from either a religious or a Darwinian point of view, homosexuality is unnatural, because it involves sex without procreation and does not help preserve the species.