I've had this happen to me once before too!
Like you have been saying, they were little doves.
But I'm not sure what it means.
I think it means one of two things.
Either that Spring has sprung. (Or come...)
Or...
That it's a sign that your town is increasing in populartiy.
(Not that people love it but that the enviroment is getting greener.)
Safe bet it is the first thing but it's just that nothing happens at the start of other seasons which would make it sound like the second one is correct or on the right path.