Kaneh, I love you (in a completely Platonic sort of way).
And yes, I think they're just long pruning shears, as the sort you'd use to trim tree branches are long and heavy as hell and therefore wouldn't be very maneuverable in a narrow nest space. You'd be more likely to mash the yukkuri parent to pieces than get the branch off without waking it.
^As much as I approve of senseless violence towards reimus and marisas, I doubt that this anon killed the mother with pruning shears. Stupid anko-brain was probably asleep and didn't even notice that anon stole her babies. Until it was too late, of course.
If the place is big enough for a yukkuri to fit through, its big enough for a pair of pruning shears to go through. As much as I'd like to think the mother got a pair of shears through the eyes, he probably just cut it off. It causes the mother more anguish that way to see the kids missing in the morning.