Gulls: osteology

Skull

Identification of gull skulls can be very tricky, because in  many species they are very much alike. Especially those of the similar sized  and closely related species. Individual variation in size and the difference between the sexes may be considerable. Males tend to be larger and more robust than females. And to make things even more complicated: a large individual  of a smaller species may be larger than a small individual of a larger species. Many gulls travel over long distances from their summer grounds to their wintering area. Sometimes they even cross oceans by following ships or during strong winds and storms. Therefore individuals of most species and subspecies can be found far from their normal distribution.  In many cases it is not possible to identify a dead gull with certainty only by its  skull. Other characteristics such as plumage colors and patterns and bill colors are important for correct identification.