i'm wondering if 15-25 generations (that's approximately how many generations of garden birds were there since the invention of the cigarettes with filters) are enough for evolution to actually show this trend here
Tangentially related - there was the russian experiment on fox domestication that had decent success in selecting for "tameability" with just 3 generations.
I think some birds are actually pretty smart and can learn by imitating other birds, so it's a cultural thing. All it takes is one bird to discover it.
Take a look at this video: "Crow uses a vending machine". It was an experiment where they trained crows to collect coins and put them into a vending machine for a few grains.
http://www.bbc.com/earth/story/20160912-a-soviet-scientist-c...