Given the reported time elapsed after takeoff and altitude when passengers
noticed problems, it makes a birdstrike far less likely because at this time of
year geese (it would need to be that size to create the kind of problems) are v
unlikely to be moving about at the height and in the formation needed to damage
both engines. It is just possible, but if so it's really a very freak
event.
not to mention a complete lack of "evidence" in the photos published thus far, as ground crew I have seen a number of aircraft return after bird strikes and there is generally a lot of bird(s) remains spread all over the fuselage and/or wings