Been away for a while and just come upon this thread. Had a similar problem back in the 70s taking off at dawn in a Mk1 Victor tanker. Bird clearance done 10 mins prior but warm runway surface too attractive and they returned unseen. At about 100kts a large flock of gulls had time to get clear but at rotate a second flock had insufficient time at we went through it. Sounded like machine gun fire. Twas copilot's T/o so I was watching engines - they all became very unsteady! Luckily they were primitive straight through Saffires so they survived although all were rejected as beyond economic repair. I decided not to raise the gear as I considered it could have been damaged and it might not come down again. Immediate ILS and o'weight landing. Breaking action reduced by slippery seagull carcases. It was later said that over 200 birds had bought it. We didn't thanks to engines operating well away from the surge line. The copilot is now a very senior and highly regarded Monarch captain. Hi Dave.