My buddy is a nefop observer. I know when he gets an incidental take on a comercial boat he documents the hell out of it, takes samples, then tags it, and boots it over. The zip ties might be a code laguage to other observers.
Could be part of a carcass drift study. A set number of dead birds are marked & released at sea, then surveys check adjacent shorelines for the number that show up over time.
Gives us an idea of how many dead birds from a spill make it to shore, provided basis for statistical analysis.
I think those are birds that were marked by SEANET observers looking for dead beached birds. The zip ties probably prevent double counting. Lots of ducks and gulls washing up with these harsh conditions. Might be worth contacting SEANET with your observation.