Various migratory birds will fly much higher than 14000' so it's not impossible that something feathery went down an air intake. I believe a 727 had a (feathered) hawk through the radome somewhere up around 30000' in the '70s (the version I heard had its carcass entering the cockpit via the footwell and busting the first officer's leg!) and another airliner ingested a vulture even higher than that. Think both occurred over Africa/Middle East though.
Gulls are far too lazy to climb that high, particularly if there's any prospect of snaffling a pasty or a 99.