Does it necessarily follow that an eagle must be able to carry its
prey? Can't it just kill it and begin eating it on the spot?
Exactly what I was going to ask. After all, modern martial eagles kill
small antelope, but do not carry them off. They simply eat them on the
ground. Golden eagles feed on young pronghorns, and eat them on the
ground as well. The bird need not be able to lift the prey item in
question.
Also, golden eagles are good test case, but other (larger) species
should also be considered. In the NW portion of North America, for
example, sea eagles would be a good candidate. I suspect that a sea
eagle could grab and carry an infant (and kill and consume a young
child on the ground). Similarly, martial eagles in Africa kill large
prey items more often than golden eagles, if I remember correctly.
That still doesn't mean that such attacks actually occurred, or were
likely if they did, but I would not rule it out based on carrying
capacity alone. Also, wingforms may make a difference. Species with
large mass, but low wing loading are more likely to get aloft with
large prey. There is a paper listing the wing parameters for African
Raptors already published, I'll pull out the reference.