Monday, 7 April 2014

Quest for the Wild Canary 7: Seabirds

Cory's Shearwater
Oceanic islands are often famous for their seabird colonies, at least until introduced predators wipe them out, and before the arrival of humans the Canaries were surely no exception. Today almost all of the remaining breeding birds nest on offshore islands or inaccessible cliffs, but in the past they would certainly bred extensively on the mainland, especially as the islands had basically nothing that would prey on seabird chicks, not even the land crabs that are widespread in the tropics.  The only real limit would have been availability of food within reach of the nesting colonies.

As we visited the Canaries in February, only wintering birds were around, but we had five species for the week. The most spectacular views were of over 100 Cory’s Shearwater Calonectris diomedea, seen from the ferry between Tenerife and La Gomera. Cory’s Shearwater breeds on all the main islands, as do several other tubenoses, of which the most important are probably Madeiran Storm Petrel and Macaronesian (Little) Shearwater Puffinus baroli. Sadly, at least two, possibly three species will no longer be seen at any time of year.
Former breeding territory of P.holeae
The Lava Shearwater P.olsoni and Dune Shearwater P.holeae are known only from subfossil remains from the eastern islands, and were probably wiped out as a result of human impact. Both were closely related to the living Manx Shearwater P. puffinus, which still breeds on some of the islands in burrows in laurasilva forest. Dune shearwaters seem to have made their nesting burrows in open sandy areas, and were probably wiped out by human predation on their nests within a few centuries of the human arrival, but Lava Shearwaters nested in lava tunnels and survived until as recently as the 12th century. Given the nocturnal habits of nesting shearwaters there is a remote possibility that it might still survive. So if you see a slightly odd looking Manx Shearwater anywhere near the Canaries, please get a photo!

Northern Gannet
Looking out to sea from various sites around the islands yielded a few observations of wintering Northern Gannet Morus bassanus , and on the last day we finally found a group of feeding Sandwich terns Sterna sandvicensis, which were probably on their way back north to their breeding grounds.
Sandwich Tern
Lesser Black-Backed Gull
Around the harbours we picked up a few Lesser Black-Backed Gull Larus fuscus, but the majority of the gulls were Yellow-Legged Gull L.michahellis. There is some debate about these – some regard the gulls of the Macaronesian islands as a separate species/subspecies called Atlantic Gull L. (m) atlantis, but other reckon that the only true atlantis are found on the Azores. In behaviour they were the same as any of the large gulls though – spending most of their time hanging round the harbours looking for food items discarded by tourists.
Yellow-Legged Gull
Next time, I will look at the waders we found on the islands, and also one of the most spectacular of the land birds we encountered – the famous Houbara Bustard

(images from Wikipedia)

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