Do seagulls eat baby ducklings

Yes!

I wouldn't have believed it possible myself, but I witnessed this very thing happening on holiday in Holland a number of years back. The ducklings weren't even lost - they would swim behind their mother in a line and seagulls were swooped down and just picking them up. They'd then land and swallow the ducklings whole - not pleasant to watch.

When we arrived there were at least nine ducklings present... a week later as we left, there were only two. Not a great fan of seagulls anymore...