well, ray ,the risk of encountering birds decreases with higher altitude,even though big birds were seen at FL 270 . In the case of the 767 I was pointing the risk of hitting birds at high speeds,no matter what FL you're at.
We do accelerate/decelerate at FL100,no problem in doing that.And you do not remember well,the econ descent is dependent of cost index,and for a CI of 50,the econ will be 320 kts,a bit fast,one may say.
If I have a choice,and I usually have,I reduce at FL100 at 250kts. Why? Main reason birds,and also,in my area of operation,especially in summer,moderate to heavy turbulance bellow FL80 (hot,windy..) So,a lot more comfy flying at 250 kts. A bit of waste ,you say..a bit of waste of what?
As I see,you're pretty young.I can assure you,after getting one pigeon right between front windshields (loud bang,FO jumping out of chair,myself ducking under the dashbord,hopefully speed around 210 kts,only bloodstains..
) you'll change your enthusiam for high speeds close to the ground.
If you still think you're safe and fast ,check this photos :
http://aviation-safety.net/database/...0402-1&lang=en
( I hope I'm allowed to put that link here,the pictures are very impressive and must be seen by any pilot,speedy or not)