Did dinosaurs really scratch?

I love one aspect of the predatory dinosaur that I have not seen mentioned in the literature: before the fight, you see him scratching (or her? Females might have been larger and more fit to fight Kong). This scratching is a genial idea from the animators and forced me to ask if dinosaurs could scratch. Impossible to know? Actually not, and here I got my answer from famous ethologist and Nobel Prize winner Konrad Lorenz: scratching with a limb is a useful stereotyped behavior that appeared in our evolutionary time long before dinosaurs, with the first amphibians (Lorenz & Leyhausen, 1971). Why was it scratching? Perhaps because of the mosquitoes that I mentioned earlier?

Konrad Lorenz (1903-1989). Source: http://www.dabase.org/lorenz.htm

Birds in the Sumatra region are nearly three times as diverse as reptiles, so there probably were many species on Skull Island, but even though we listen to them we only get to see a few types:  some flying around when they reach the island, one that flies scared from a nest when Kong is about to place Ann on it (I could not identify this bird) and the vultures that fly above and feed on the Tyrannosaurus carcass.

Vultures flying above. Source: http://kingkong.wikia.com

I have a question for next week: why the dinosaurs did not suffer the size reduction typical of originally large animals when they colonize small islands?