Among all the various investigation as contributors, the issue of bird control should receive top billing.
In my view this is not comparable to the Sully-Hudson incident regarding the bird hazard itself.
Assuming that the initial ident are gulls (in video), and first flight of the day. It is typical for gulls to rest on flat open ground where bird-lookouts have a good field of view of predators. Most airport bird management recognizes this and sends out a vehicle to clear the runway if it has not been active for a length of time. Too many lessons learned in the data about this in the early jet years.