The birds are getting busy, responding to increasing day-length and getting ready for the coming territorial disputes (starting already I think), foraging and breeding. I have a theory that they are so busy and absorbed by the stress of the approaching spring that they forget the road that goes through their territory and are unaware of the car rapidly approaching as they chase and hurtle.
I have noticed that when I slow down to less than 45mph there are fewer, actually no, casualties. I haven't been able to find any speed check data for small birds, but it somehow makes sense that driving above 50mph brings us into conflict with the top speed of the natural world: exceeding it.
So, sometimes we should try to remember that songbirds will become more active over the next few weeks and that this will carry on well into summer. Birds will have thoughts elsewhere, so I shall try to think of them and go a bit slower, take more time to get there. Now I slow down for horses, deer and birds too.