I remember reading that some airports had problems with seagulls dropping shells on the runway to crack them open, then landing on the runway to eat their meal, making the birds and shells a hazard.
A network of stainless steel cables strung across open
spaces will prevent seagulls from diving on public areas
where they compete with humans for burgers and fries.
A real problem exists with gulls at seaside airports
where birds drop clams and other shellfish on the
runways to break the shells. In one instance the birds
stopped dropping their clams at one airport when a
clever PCO painted seagulls flying in a search pattern
(as seen from the top) on the runways. The flying birds
were afraid to drop their shellfish, lest the "other
seagulls" get to it before they do.
From page 3 (of 28) of this PDF file:
http://www.dscp.dla.mil/subs/proserv...te/pestjun.pdf