have a 1d4/3 and 40/507d bodies too - mostly use the 7d for bif but this year in iowa i used mostly the 1d4 it was a mixed bag on focus
granted i'd had the camera for about a month, the weather was bad most of the time i could shoot before the trip so i didn't get to "learn" the body as well as i should have so i set it up based on some info from luminous landscape i got maybe 60% keepers using 400do and sigma 150-500 vs the 1d3 rates
we have sandhill cranes in migration for the last month or so and after tinkering with settings my rate has increased
1d4 is a great body but you do have to play with it some before it performs as you would expect for bif
that said any other task is like falling off a log for this body and good glass