The freak of nature

There is a tiny islet in the foggy Saragossa Sea
it has no name since no self-respecting explores
would put his name on it.
However, it had a Vulcan that erupted and when
the lava stream cooled seagulls found it a good
a place to nest.
Something strange happened some of the eggs
grew huge and when hatched had a wingspan
of 3metres and they were not of a friendly
disposition.
Glutinous they attacked goats and bigger prey  
and lone fishermen in their rowing boats it was
So you could not go to sea getting supper with
Carrying a shotgun.
It so happened the birds were infertile a freak
of nature but as birds they are long-lived if you
see them on a clear day you better keep your eyes
to the sky.