Go Fly a Kite!

I was in Tagajo yesterday morning and alongside the river were dozens of トンビ (tonbi or kites/Milvus migrans) soaring overhead. I tried to snap a few pics but wasn't too successful.

There were also several ducks and a flock of seagulls picking up dead fish and then dropping them again. I saw a lot of dead fish so I wonder what killed them? I think it was the following...