Cory's Shearwater Calonectris diomedea
- IdentificationVisual tips about this species
- BehaviourHabitat, behaviour, and food
- PopulationSubspecies and numbers
- ReproductionNesting and eggs
Identification
It is paler and greyer than other European shearwaters with an obvious pale straw-coloured bill. Even at a distance though it can be picked out by its larger size and much slower, steadier, less frenzied flight action.
Ageing
Juveniles and adults alike.
Voice
At night they produce a cacophony of sound in which individual birds sound somewhat like crying babies.
Sexing
Sexes similar.
Length
50cm
Behaviour
They return to their breeding colonies at night, when the area becomes alive with their calls.
Migration
The species is strongly migratory. Birds are present in their breeding areas from late February to October-November. Non-breeding birds summer in the North Atlantic from the Bay of Biscay to the New England coast. All of these birds move south to winter off South Africa.
Habitat
Oceanic.
Food
Delights in oily food, particularly oily fish, offal and fish eggs.
Population trends
Numbers have apparently remained stable in the Mediterranean but is still vulnerable to invasion by rats, egg-collecting and increased disturbance due to the spread of tourism.
Subspecies
The nominate race C.d.diomedea breeds in the Mediterranean. C.d.borealis breeds on the Azores, Madeira, Berlenga and Canary Islands.
Where in Britain and Ireland
Occurs in variable numbers each year off the south coast during late summer and early autumn. Never easy to see, the best site is probably Porthgwarra in Cornwall during early August. The average annual total in Britain between 1990-1999 was 1,519 and 5,116 were seen in Britain in 1998.
Population in Europe
The European population stands at somewhere between 120,000 and 175,000 pairs.
Where in Europe
Readily seen from most Mediterranean headlands or by taking a boat journey around the Balearics or the Greek Islands.
Best UK Site
Gwennap Head, Porthgwarra - Cornwall This southwest-facing headland is situated at the SW tip of west Cornwall and is accessed from Polgigga. Leave Penzance west on the A30 and at Catchall, turn left onto the B3283 to St Buryan. After St Buryan, join the B3315 and continue towards Land's End for two miles. At the sharp right hand corner in Polgigga, turn left to Porthgwarra. Follow this long, winding and very narrow road to the end and park in the pay-and-display car park just beyond the tea-room and telephone box. Gwennap Head is then reached by taking the coastal footpath from near the tea-room westwards for about 300 yards. An obvious promontory of rocks allows for cover from rain and an excellent vantage point in which to view passing seabirds. Most Cory's pass in a line just beyond the Runnel Stone and can be seen in large numbers. A light to moderate south-westerly wind is essential. [Taken from the book 'Finding Birds in Britain' by Lee Evans, which includes details of more sites for this species]
Nests
End of May and June. Nests in colonies, amongst boulders in rocky ravines, nest constructed from twigs and seaweed.
Eggs
1, white, laid in late May to end July. Incubation takes 52-55 days. Fledging period is not known. 1 brood per year.
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