This is just me, and may actually be an awful idea, but, I am the type that if a horse acts scared of water, you'de better guess where he's going in the next 5 minutes... also, I take kittens outside and throw them in their first snow... I'm not big on letting animals skitter around something forever thinking that it's dangerous... so, I would be taking a bird, not even all of them, and manually plopping her in the middle of that tire and dumping a handful of dirt on her back... Likely, that will make her shake it off, and maybe figure it out, if one figures it out, they all will.