How do they know?

[predding]

We live in a remote area and have very few seagulls visit. Just the other day we were driving by a newly plowed field and noticed several hundred seagulls feeding. How do they know where to feed and how are they attracted so fast to something like this?

[Kilala]

I'd say it was the scent of the soil, as it is very strong to a well tuned animal like the seagull when freshly ploughed.

[gastwo]

As added info to back-up Kilalas' answer, we work 25 miles off-shore, and when there is an off-shore wind blowing, we can smell agricultural activities like slurry spreading and grass cutting/hay making - and thats just with human nostrils (or is it olefactory sense?)