After a while sitting on the decision I recently purchased a 400 5.6, to my 70d body.
Im trying to get some experience shooting birds. I went to a local fish pond, with great conditions, clear sky and low sun in early morning. while shooting birds in flight I used all the AF points, due to an even background. when I got home I saw that many of my photos are badly focused, even when the bird was not coming toward me. shooting with continuous AF...I have herd that the 70d's focusing system wasn't the best...can this be the issue? is it technique that I need to practice? would love any input.