[undersuit]

Birds have already been observed to use cigarette butts for nest building, and no resultant population crash has happened for them.

https://www.newscientist.com/article/2138655-birds-use-cigar...

Maybe the food being given to the crows is more beneficial than any of the downsides of the exposure to the butts.

[jackgolding]

If you read through to a linked article you'll find there is indeed long term health effects to the birds https://www.newscientist.com/article/mg22730341-600-birds-lo...

[undersuit]

I never said there weren't. I specifically worded my comment to suggest that the benefits might outweigh the harm.

[anotherevan]

For instance, if the crows are picking up enough, then there will be less birds using them for nesting material, which is a more prolonged exposure.

[rhombocombus]

It seems to offer some sort of advantage in pest resistance, and I would assume over the (sometimes) shorter lifespan of the birds that do this that advantage outweighs the toxicity of the butts.