I consulted 2 of our Department's top avian ecologists. Without the birds in hand, it is impossible to be sure of species ID, but the top guess is scrub jay. They advise doing some observations of those trees and see if you can sight focused activity - like around a nest - and then note which species are most frequently going to that area. As to what happened to the nestlings, high winds could have just upset the nests enough for nestlings to get ejected. Alternatively, or in addition to the cold, windy front, is that when cold(er) temperatures and poor foraging leads to nestlings starting to starve, parents will sometimes fling them out - and essentially bet-hedge that a new nesting attempt would go better. Nature can be fairly tough at times.