After the RAF lost an aircraft which attempted to "duck under" a flock on the approach, the mantra promulgated at the time was "birds always break down", so don't do it!
Birds do what ever Their flight profile permits to avoid the closing hazard.
Of course their are a myriad of bird hazard strikes by all types of birds but my comments are aimed at the statistical hazard to safe flight (multiple medium-large) birds in a regime where little margin exists for multiple damaging sites to the aircraft.
In spite of the Sullenberger incident the largest threat to flight has been lounging water fowl on or near the runway. When startled these birds go up just high enough to maneuver sideways to clear the threat. Unfortunately the plane also wants to go up after reaching Vr.
Once airborne this type of bird again uses its flight ability to peel off horizontally away from the threat. Considering the closing speed between them there is darn little the pilot can do to avoid the birds. The best course is to leave it up to the birds since their programing in this regard is natural.
If we get into the lesser statistical threats like the Sullenberger incident or the Italian B737 other less common factors are involved.