[jna_sh]

For an animal to evolve to fill this niche, the niche would have to convey some advantage that favours their survival and reproduction (i.e. natural selection). Aside from the fact that this isn’t actually a terribly efficient process and is subject to lots of random effects, the niche in its current form as influenced by human activity is clearly not conveying a survival benefit, or the vultures wouldn’t have declined. A member of another bird species deciding to take to scavenging trash heaps whilst happening to have a mutation that protects it from diclofenac (which is toxic to lesser degrees in other non-vulture birds) is not impossible, but unlikely, and could very well be a process that occurs at a timescale that is incompatible with the rate of continued change by humans.

[account42]

Other (especially non-avian) scavengers could have better reactions to the cattle drug that the article blames for poisioning the vultures and thus thrive when their competition is gone.