Bill morphology and diet of a filter‐feeding seabird: the broad‐billed prion Pachyptila vittata at South Atlantic Gough Island

One hundred and fifty diet samples collected from broad‐billed prions Pachyptila vittata at South Atlantic Gough Island and Tristan da Cunha over four years during the breeding season showed that they fed almost exclusively on copepods (0.7–4.1 mm in size), consistent with a bill morphology adapted for filter‐feeding. Food is sieved from the surface of the ocean by means of palatal lamellae, of which there are 112–136 on either side, 0.16 mm apart. The filtration area of both rows of lamellae together amounted to 785 mm 2 and the bill held 4.1 ml of water with a maximally extended mandibular pouch. Both sexes of broad‐billed prions look outwardly alike but morphometric measurements proved that males are slightly larger.