Corsica

Corsica island, the first week of April. Islands are 'speciation machines', where populations evolve in isolation from the mainland to become distinct species. We came in search of these unique species - and populations that may be on their way to becoming species.

Spring is still young. We drive into the central mountain range, where the snow has melted except on the high peaks. Here unique bird populations are isolated in the forests of Corsican Pine (Pinus nigra laricio), which provides seeds for food.

First stop Col de Sorba, a birding 'hot spot'. Here we find the only species endemic to Corsica: the Corsican Nuthatch (Sitta whiteheadi), named after the Victorian naturalist and explorer John Whitehead (who discovered it in 1883 - having just shot one). It is smaller and rounder than the common European species S. europaea. The males have a diagnostic stripe on the crown of the head - in common with its closer relatives Krüper's Nuthatch (S. krueperi) and Algerian Nuthatch (S. ledanti), which are found in Turkey and Algeria respectively.

Also at the Col: Corsican Finch, Carduelis corsicana, an island species restricted to Corsica and Sardinia. It used to be considered a sub-species of the Citril Finch (C. citrinella), which is found mainly in the Alps and Pyrenees, but differs from this by having a brighter yellow breast and a streaked brown back.

But when is a species a species rather than a sub-species? Well, to be a separate species an island population should not be able to successfully interbreed with a mainland population - but this is academic as they do not meet. So a judgement is made based on differences in the way they look or, with new technology, differences in their DNA. But maybe the song is more important - after all this is how birds court each other to mate. The Corsican Nuthatch and Corsican Finch certainly have unique songs.

Flitting around among the Corsican Nuthatches were other tree climbers, searching for insects. Great Spotted Woodpeckers are smaller, thinner billed and with darker underparts the further south in Europe they are. Corsican populations are regarded as a distinct sub-species: Dendrocopus major parroti. You can see that this one has reddish tints on the throat and breast.

The Eurasian Treecreeper on Corsica, Certhia familiaris corsa, is also regarded as a separate subspecies from the mainland C. f. macrodactyla - with more contrasted upperparts and buff-tinged underparts (which may be seen here between the legs and the tail - unless it's a shadow).

A bird with a bill specially evolved for seed eating, and a member of the Finch family, is the Red Crossbill (Loxia curvirostra). (Loxia comes from the Ancient Greek loxos, meaning 'crosswise', and curvirostra is Latin for 'curved bill'). The Crossbill on Corsica is also regarded as a separate sub-species, L. c. corsicana. The literature says that it has a stronger bill, with a 'less decurved upper mandible', which may be an adaptation to the thin-scaled cones of the Corsican Pine. Maybe more importantly, its call is distinct from other Mediterranean Crossbills.

After Col de Sorba we explored other highland areas. The Winter Wren Troglodytes troglodytes shows a lot of variation in plumage over its distribution, with around 27 sub-species - three in Scotland alone. T. t. koenigi is confined to Corsica and Sardinia. I searched for it in vain for a couple of days, until I followed a hunch to investigate a patch of shrub on the shaded side of a valley - and there I could hear them scuttling like mice in the undergrowth (Troglodytes comes from the ancient Greek 'trogle', hole, and 'dyein', to creep). Then up they popped for a photo.

The Coal Tit (Parus ater) varies in plumage colour over its range - changing from greys to browns to yellows - but always with a black head and bib (ater is Latin for dull-black). P. a. sardus is restricted to Corsica and Sardinia.

Other species of Tit vary in plumage over Europe. Long-tailed Tits (Aegithalos caudatus) vary from having all white heads in northern Europe, to black banded heads in the south (as the sub-species on Corsica, A. c. irbii, which also occurs in Spain for some reason).

Variation in plumage in the Great Tit is more subtle. The sub-species Parus major corsus is also found in Spain in addition to Corsica. Yet for some reason Sardinia has its own sub-species P. m. ecki...

...whereas the Blue Tit sub-species Cyanistes caeruleus ogliastrae is found in Corsica and Sardinia as well as Spain.

There are also two sub-species of finches on the Tyrrhenian Islands, though what their characteristics are eludes me. They are the Greenfinch chloris madaraszi...

...and the Goldfinch, Carduelis carduelis ischusii.

Some regard the Chaffinch on Corsica as a distinct sub-species, Fringulla coelebs tyrrhenica, but not the IOU (International Ornithologist's Union) - and I follow their word.

We saw many Jays of the Corsican sub-species, Garrulus glandarius corsicanus, but surprisingly did not get a shot of such a big bird as they were nervous and skulky in the trees. We also saw Tyrrhenian Island rapture sub-species of Sparrowhawk (Accipiter nisus wolterstorffi) and Buzzard (Buteo buteo pojana).

If you come from Central Europe, even the species of common birds on Corsica are not the common species. The Sparrow is the Italian Sparrow (Passer italiae), unsurprisingly confined to Italy and its islands, The brown head of the males easily distinguishes them from the House Sparrow.

And here the Crows are Hooded (Corvus cornix)...

...and the Starlings Spotless (Sturnus unicolor).

But spare a thought for the poor Cirl Bunting (Emberiza cirlus), for he has no sub-species at all. Maybe that's why he looks so pissed off.

Two species of lizard (both Small Lacertas) are restricted to the islands of Corsica and Sardinia. We saw only one, but in abundance: Tyrrhenian Wall Lizard (Podarcis tiliguerta), a male here sunbathing - on a wall. (Tyrrhenia is the name Greeks and Romans called Etruria, the land of the Etruscans on the mainland, which we now call Tuscany. Corsica lies in the Tyrrhenian Sea).

And to add colour to our days, Green-winged Orchids, Orchis morio (or near relative) in the sun...

...and Cyclamen repandum in the shade of the woods.

But now we must away to the coast, for there are warblers to be seen. Capu Rossu lies midway along the west coast, just west of Piana.

Dense coastal maquis. Perfect for warblers.

There are four resident Sylviid Warblers on Corsica. Blackcap and Sardinian Warbler are found throughout the Meditterranean, and we had no trouble seeing them on the island. But we never expected such amazing views and photographs as we had of the Dartford Warbler (Sylvia undata), a speciality of south-western Europe...

...and the cherry on the cake, Marmora's Warbler (Sylvia sarda) - confined to the Tyrrhenian islands

Soon the migrants will arrive: Spectacled Warbler, Western Orphean Warbler and Moltoni's Warbler. Something to come back for.

A great trip. Time to celebrate with the friendly locals!