27 April and 1 May Ile de Ngor
On 27 April we tried the first, brief offshore sortie of the spring, just a couple of kilometres off Ngor Island. Compared to 48 hours earlier, the sea was mysteriously dead, with no rafts of shearwaters and few terns or skuas, although we did see a few Cory’s and Cape Verde shearwaters in flight, leaping bottle-nosed dolphins and one adult long-tailed skua gave superb, if brief views as it chased a common tern then we chased it with the pirogue at full speed.
A brief visit to Technopole afterwards provided distant views of this sub-adult skua.
I am not an expert on immature skuas and remain unsure whether this, Technopole’s first skua whatever the species, is long-tailed or arctic. The brief circulation of the image to others gave a 50:50 split on four votes, people pointing to the small size and rather elongated shape (long-tailed), but brown, not grey general tones and long bill (arctic).
May 1 is a national holiday here and I took the morning off to visit Ile de Ngor and spend a couple of hours sea watching on the northern cliffs. The wind, from the north-west, was a bit stronger than in recent days. Shearwaters were again rafting offshore and flying around with no evident pattern – a mix of Cory’s and Cape Verde plus ten or so Sooty and a Manx, the latter two my first of the year. There were also huge numbers of terns foraging; thousands of mostly sub-adult common terns and Sandwich terns, at least two roseate terns and only one black tern.
I played a bit with trying to track more distant, flying birds with my relatively inexpensive camera and found that, subsequently enlarged, the images were adequate to identify the Cory’s as borealis.
This image is not a great example, but shows that the black tips to the primaries form a solid triangle, without fingers of white. This is Calonectris borealis, the nearer of the two breeding sub-species, nesting on Atlantic islands of which the Canaries are the nearest archipelago. It is now recognised by good authorities as a full species and is the type of Corys most often encountered by visiting birders to Senegal in October and early November, from which period most seabird observations have been made here. The “other Cory’s”, now called Scopoli’s shearwater Calonectris diomedea if you follow the British Ornithologist’s Union taxonomy, is a winter visitor here from its Mediterranean breeding islands. Jacob Gonzalis-Solis’ work at the University of Barcelona tagging Cory’s and Scopoli’s shearwaters (see publication 56) suggests that, if the birds we are seeing now are still on their way back to colonies, rather than non-breeders, they are en route to the Canaries from wintering grounds off South Africa and Brazil. Azores breeders take a western Atlantic route to benefit from prevailing winds.
Here is clip of today’s Cape Verde shearwaters – a difficult bird to reliably see away from its breeding grounds other than off Dakar during April-early June and October-early November.