A hot summer is here again, in Southern Sicily and all around the Mediterranean Sea. It seems that even moving a leg or a hand would be hard and seat drips into my eyes and blur the view. But in Linosa, or any other European island, as well as along the coasts and in the open sea, the sea is constantly furrowed by tireless wave engravers, drafters of the green-blue palettes of the sea: the shearwaters!
On moonless summer nights, in heavens quilted with stars, their melancholy, sometimes spooky, singing echoes on the islands. And then, the unstoppable birder starts to study the shearwater and sea birds in general.
For several years, also thanks to my friend Robert Flood, I have been studying the variations of the underwing pattern in the Scopoli’s Shearwater (Calonectris dimodea). This is the species of Calonectris sp. breeding in the Mediterranean sea, with its Oceanic counterpart, the Cory’s Shearwater (Calonectris borealis), breeding in the Eastern Atlantic, from Galicia (NW Spain) and Berlengas Is (off WC Portugal), W to Azores and S to the Canary Islands. Until recently, they were considered conspecific with Cape Verde Shearwater (Calonectris edwardsii ), Cape Verde Shearwater (Calonectris edwardsii), but are now separated into three separate sister species.
The only Italian records of Cory’s so far were two adults found in the Scopoli’s breeding colony at Linosa Island on 16th May 1987 and on 11th August 2009, but none were ever recorded at sea or any other Italian site. Therefore I have been trying for years to find some specimens in the field, or in any case to understand more about identifying these taxa. Robert, author of numerous field guides and handbooks on seabirds (some of the most beautiful ornithological works published in the last twenty years), needed photos and data of Scopoli’s Shearwater and I helped him gathering information for his soon-to-be-published identification guide of shearwaters.
The main difference between Scopoli’s Shearwater and Cory’s Shearwater lies in the different pattern of the wing tip seen from below in flight. In Scopoli’s, there are white stripes (“tongues”) running along the inner webs of the outer primaries, almost to the tip; they’re wider at the feather’s base and narrowing towards the distal portion, while the tip is always grey-black.
In the Cory’s however, these white “tongues” are practically absent or not visible at all, and the underwing shows the whole “hand”, from base to the tip a dark, blackish colour. Usually, also the “wrist” area is more heavily and densely mottled dark, forming a duller carpal patch. This is the first and best key-character reported by all modern field guides on bird identification.
As a result of our studies and continuous observation however, it can be shown that especially in Scopoli’s, there is a certain variability: some individuals (mainly young) show very little white, only along the inner web of P9 (numbered descendant from outermost P10). This means that in the field, the typical pattern for identifying Scopoli’s Shearwater is sometimes really difficult to see. Sometimes, in fact, only a very little white can be noticed, with often a barely visible pale shade in the centre of the “hand”. So under normal conditions, identification can be extremely difficult.
If we add to this that in strong sunlight Cory’s may seem to show a rather pale underwing with a much paler tip, the task to find a vagrant bird in the Mediterranean becomes really complicate. This is the time when exceptional optical instruments really make the difference.
Therefore, I rely on the best birdwatching optics. And believe me, after decades of experience, I love nothing more than my Leica Noctivid 10×42 and my Leica APO Televid 82 spotting scope. I rely on them, because the smallest details matter. With an extra help: numerous times, when the wind is not favorable, and the shearwaters pass really far away, I add the Leica 1.8x extender to my Leica APO , so as to get up to 90 magnifications !! And no shearwater escapes anymore … (hopefully )
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