The attacking bird needs to raise apogee to GEO anyway - after that the plane change is relatively cheap. They might not even raise perigee.
Raising the apogee, then changing the inclination there is relatively cheap - and you can adjust the plane change and apogee to time a collision. Remember - there is no need to recircularize. Just collide. If the goal was to recircularize then I don't know if raising the apogee would be worth it, maybe for extreme cases. But not for a collision.