Well, the clues we really have about their behavior can probably mostly be gathered from their fossil remains, specifically skeletal fossils. Short arms, (relatively) large "hands" with three long claws, a funky second digit on their "feet", longish tail (relative to its body)... seemed about 30ish lbs.....
Arboreal locomotion in extant animals is adapted to in a bunch of different ways. Suction or some other form of adhesion (like in frogs or something)... long arms (think monkeys)... small size (chipmunks, birds, snakes.. don't wanna break the branches I assume)... being able to grip or grasp with a hand (monkeys) or claw thing (like birds gripping a branch) or maybe a prehensile tail... maybe there's other examples of adaptions for arboreal locomotion that I can't think of right now.
I feel like their funky claws and short arms were probably more for slashing at things, hunting, killing, all that stuff like maybe how Jurassic Park depicts it. But just because a feature doesn't seem specifically adapted to a certain function doesn't necessarily mean the animal is (well, was) completely incapable of said function, so perhaps it could still climb. After all, humans don't seem particularly well adapted for getting around in the water, but that doesn't stop Michael Phelps (now I'm imagining velociraptors competing in fanciful Olympic events like tree climbing... )
Maybe it had the bird-gripping-a-branch thing going for it, the whole modern bird thing you pointed out could mildly support that hypothesis. Perhaps its tail was flexible, prehensile-like (yet kinda doubtful).
I just finished a really interesting terrestrial vertebrate class where we talked about things like this. Adaptions conferring to functions, being able to tell something about an animal based on what it looks well adapted for. Pretty interesting. But honestly, I'm just a lowly undergrad. These are simply my musings, definitely not fact.