September feeding frenzies in the Strait of Gibraltar

September is the month of the flying fish in the Strait of Gibraltar. If they turn up in good numbers they unleash a chain of spectacular events as all kinds of predators converge on this rich food resource. It is the dolphins that get things moving by chasing the fish near the surface where seabirds also get a chance to have a go at them. Yesterday morning was a calm easterly, ideal for a feeding frenzy. It was also the end of the Calpe Conference on the evolution of bird migration, so what better time than to go out on a boat and see what was happening.

Rafts of Cory's Shearwaters Calonectris diomedea at the entrance to the Bay of Gibraltar soon have a hint that the morning would be a good one...

Once round Europa Point and into the entrance to the Mediterranean, a wonderful spectacle unfolded which combined dolphins, breeding shearwaters and migratory seabirds. A migrating Loggerhead Turtle Caretta caretta was a promising sign...

Soon we found the pods of Common Dolphins Delphinus delphis that were frantically chasing the flying fish...

Cory's Shearwaters flew over the pods keeping an eye for shoals of fish

Several thousand Cory's Shearwaters were about, having flown down the Mediterranean coast some 400 kilometres to feed in these rich waters where the Atlantic meets the Mediterranean. These are daily feeding movements as they have hungry chicks in their nests.

As soon as the dolphins have got going, the shearwaters get busy catching the fish that try to escape by gliding...

...and competition is severe among the shearwaters

but the shearwaters do not have it all to themselves as gulls try and steal the tasty meals...

but gulls are insignificant compared to the big bullies that, passing by on migration, get attracted by the concentrations  - Arctic Stercorarius parasiticus and Great Catharacta skua (below) skuas are more formidable opponents...

other migrants also joined in the fun. Among these were juvenile Gannets Morus bassanus, just arrived ftom the North Atlantic.

Black Chlidonias nigra, Common Sterna hirundo and Sandwich Thalasseus sandvicensis terns moving towards the Atlantic wintering grounds also got drawn in...

as were other locally breeding shearwaters - the smaller and browner Balearic Shearwaters Puffinus mauretanicus

but the day belonged to the larger shearwaters, adding plunge-diving to their hunting techniques until the food was gone...

My thanks to Tony and Angie Watkins of Dive Charters for taking us out on their boat