Avoidance options:
Avoid flying at first and last light as that is when birds move from nesting to feeding grounds and the likelyhood of a birdstrike increases.
Keep a landing light on.
Birds do tend to dive in many cases but remain unpredictable. The Australian military advocate maintaining track or if a late spot flying towards them, after all, they have more flying hours then you and will try and avoid you rather then dying.
Check out the MAFF (Ministry of Agriculture, fisheries & food) website, for it used to give good info about bird migration although I cannot verify that it still does so.
Avoid flying along coastlines or directly above rivers/lakes/rubbish tips/ farmers ploughing. All of these include a greater risk of birdstrike.