15/02/2011
Share 

Ticks in waiting

32778ef1-9f63-4af3-8a6f-ab4bf024ba7f
Madeiran Firecrest, photographed on Madeira in April 2009. Photo by Andrew Moon.
Madeiran Firecrest, photographed on Madeira in April 2009. Photo by Andrew Moon.

In the April issue, I outlined the most likely Nearctic bird forms that might reach general acceptance as new ‘tickable’ species, and which had vagrancy potential to Britain (or see Birdwatch 214: 32-35). More potential splits emanate from elsewhere, however, including the North Atlantic and Mediterranean, and some of these are likely to provide new vagrants to Britain or new species for your Western Palearctic list.

A number of splits from this region were unveiled in the second edition of the Collins Bird Guide, for example Seeböhm’s and Maghreb Wheatears and Striolated Bunting, and others were hinted at (‘Basalt Wheatear’). Others still were not split at all (Marmora’s and Balearic Warblers), yet there is no doubt that the momentum lies firmly with the trend for recognising highly distinctive taxa as full species, often as a result of genetic studies.

Balearic Woodchat Shrike
Balearic Woodchat Shrike is tangibly, but subtly, different in appearance to the nominate form – note the lack of a white basal primary patch in particular. Photo by Oliver Smart (www.smartimages.co.uk).

The same geological and climatic phases that provided reproductive isolation for North American bird forms during the last 20 million years or so have also produced dramatic effects closer to home. This has caused avian divergence on the North Atlantic islands of Madeira, the Canaries, the Azores and Cape Verde, and in Mediterranean Europe and North Africa.

North Atlantic islands

The Cape Verde Islands have had many endemic forms named over the years. Most of these, however, are clearly related to European counterparts, resulting in a history of re-lumping and re-splitting. Therefore, these forms are unlikely to provide a surprise list addition on current knowledge, and any ‘countable’ birds will merely involve the resurrection of a former status. However, other insular endemic centres may yet provide a new species or two.

Great Spotted Woodpecker has a distinct DNA lineage on Tenerife, in the Canaries. It is certainly isolated and possesses diagnostic plumage features, though it does resemble another insular subspecies in Corsica and Sardinia.

Madeiran Firecrest is now generally split, but Tenerife Goldcrest is also distinct, with its buff-toned underparts, black forecrown and pale lores. Birds on the Canaries are differentiated enough to have formed two subspecies, the most recently named being ellenthalerae on El Hierro and La Palma. The Azorean forms of Goldcrest appear to be very close to their mainland counterparts, however.

Another notably distinctive Macaronesian passerine is Tenerife Robin. It has a deeper orange-red breast colour, a white eyering, grey forehead and neck sides and a white belly. The form has two distinct lineages on the Canaries, representing two colonisation events. There has been no official split as yet, but when it comes it could divide Robin into three species.

The familiar Blue Tit is widely known to involve more than one evolutionary lineage, and the blue tits in North Africa and the Canaries have recently been separated as African Blue Tit. A new subspecies of African Blue Tit has been described from Gran Canaria, split from the Tenerife/La Gomera subspecies. The Fuerteventura, Lanzarote and Moroccan forms have most recently been included in the North African subspecies ultramarinus. Vocalisations are different in all forms, though, and the ‘blue tit’ complex could be composed of up to six species.

Long-billed Crested Lark
North-west Africa is a hot-spot of endemic forms, and thus potential splits. Long-billed Crested Lark already features on many tour itineraries, and represents an entirely different lineage to Crested Lark. Photo by Arnoud B van den Berg (www.soundapproach.co.uk).

Canary Island Chaffinch has been shown to be genetically removed from the africana and coelebs subspecies, indicating that it may be as worthy of visiting birders’ attention as the endemic Blue Chaffinch. Further genetic sampling of ‘Common’ Chaffinch is needed, but Canary Island Chaffinch again appears to demonstrate two possibly incipient species lineages in the islands. Speculative work on the Azores Chaffinch might also produce a surprise.

Content continues after advertisements

Mediterranean islands

The Mediterranean has its own set of islands known for their high prehistoric endemicity, and some of the islands retain their insular speciation potential to this day.

Sicilian Rock Partridge has been estimated as being separate for at least 200,000 years, and is almost as distinctive as other Alectoris partridges, though smaller. Recently defined fieldmarks include an almost concolorous tail, rump and mantle, a narrow broken collar, dark undertail coverts and vermiculated uppertail coverts, though all are subtle and relative.

Recently, attention has also been drawn to Balearic Woodchat Shrike. Breeding from Ibiza through to Corsica and Sardinia, it has already occurred in Britain on a few occasions. There are no confirmed records of intergrades, and the form has no visible white patch at the base of the primaries. It also has a narrower black forehead, a paler chestnut rear crown and a deep-based, square-looking bill.

In the eastern Mediterranean, Cyprus could yet hold surprises in addition to its long-split eponymous wheatear, but hopes that one of them might prove to be Cyprus Scops Owl – an endemic resident – have yet to be confirmed by clear evidence.

Iberian peninsula

This area of Europe was one of a few key refugia (havens for isolated relict populations of once widespread animals) during the Ice Age glaciations. It is home to several novel forms, of which two in particular stand out.

Iberian Woodpecker has long been noted as halfway between Levaillant’s in North Africa and the pan-European Green Woodpecker, and may occupy a directly intermediate speciation stage. Likewise, Iberian Pied Flycatcher, though currently viewed as a subspecies of Pied, shows features intermediate between that species and the newly split Atlas Flycatcher. However, it seems to be genetically closer to Pied, and perhaps not a good species. Iberian Pied (and indeed Atlas) Flycatcher could conceivably overshoot on migration to reach Britain, so any well-marked ‘Pied’ should be studied carefully. Iberiae has larger white forehead and primary patches than Semi-collared and Pied, but Atlas is even more strongly marked; females and immatures of both are less well known.

North Africa

A continental area of significant endemism is the Atlas Mountains of Morocco, Algeria and Tunisia, a region now attracting more attention from birders and ornithologists as the full extent of its avian novelties becomes more widely known. However, the number of named species and subspecies shows much inconsistency at present. One can expect more on these forms soon, but in the meantime, some divergent forms may deserve species status.

The two subspecies of Long-legged Buzzard sometimes seem rather arbitrarily attributed to one species. They are geographically isolated, and the North African cirtensis is smaller and more like Common Buzzard in size, while the south-east European and Asian rufinus is more distinctive and twice as heavy. Cirtensis is also more migratory. However, the more superficially eagle-like rufinus has been known to hybridise with Common Buzzard, thus muddying the waters.

The African form of Black Kite, known as Yellow-billed Kite and occurring north to Egypt, has already been split in some quarters. As well as a yellow bill, adults have more rufous underparts and biometric differences.     

North Africa’s Great Spotted Woodpecker may be separable, perhaps more so than the Canary Islands form. Atlas Mountains birds have extensive red on their vents and bellies, a pale orange chest and flanks and a red chest patch with some black spotting. However, this appearance may betray a rare genetic throwback in the region, as some continental ‘Great Spots’ occasionally show North African features.

Moroccan Magpie
The mauretanica subspecies of Magpie (right) is clearly different with its blue skin patch behind and under the eye. Photo by Arnoud B van den Berg (www.soundapproach.co.uk).

Little Green Bee-eater is represented by two plumage-differentiated clades in the region, but the two subspecies in the Nile basin and Sinai are still close genetically. Intraspecific molecular analyses haven’t been thoroughly undertaken yet, while the existence of a third clade in India may also confuse the issue.

The Galerida lark forms of North Africa are highly confusing, but Long-billed Crested Lark has a discrete history of evolutionary separation, being strongly divergent from Crested and forming a separate clade from Thekla. It is found on the high plateaux of the Atlas Mountains from Morocco to Algeria, and has a longer, more slender bill.

The Tunisian subspecies of Dupont’s Lark has also recently come under consideration by ornithologists. It has a relatively long bill and feet, and rufous-toned plumage. It appears to be the more basal lineage, though all three populations have a separate recent history and are rather isolated. Splitting the species would make the European form highly endangered.

The complete relationships of the grey shrike complex are still unresolved, particularly among the Southern Grey Shrike taxa. Genetic work has revealed that there may be several species, and Iberian Grey Shrike should perhaps include the two North African forms. In taxonomic terms, nominate Great Grey Shrike ‘nests’ firmly within the Southern Grey Shrikes, suggesting further reclassification.  

Egyptian Swallow, from the River Nile valley and delta, might be another good call. It is non-migratory, strikingly red underneath and shows some genetic divergence from European birds.  

The Moroccan forms of Tawny Owl, Dipper, Shore Lark (see Birdwatch 212: 36-39), Blackbird, Reed Warbler, Short-toed Treecreeper, Raven, Desert Sparrow, Rock Sparrow, Crimson-winged Finch and Common Crossbill (or see Birdwatch 211: 30-35) are all of taxonomic interest, but particularly distinctive is Moroccan Magpie, with its blue eye patch and higher calls, and the two North African forms of Chaffinch, which differ from the European subspecies in calls, song and plumage; the Tunisian subspecies spodiogenys is also genetically isolated from all other chaffinch forms.

Continental Europe

Lilford’s Woodpecker is the subspecies of White-backed Woodpecker in the Mediterranean, Turkey and the Caucasus. It is barred on the back and flanks, more buff coloured on the underparts and has a brighter red vent. It also represents a different lineage to the northern European and Japanese subspecies. American and Eurasian Three-toed Woodpeckers were widely split during the last decade, but the darker alpinus subspecies may also need another look. It has less white on its mantle and narrower head stripes than nominate tridactylus, and the back is boldly barred.

Lilford's Woodpecker
Lilford’s Woodpecker, the form of White-backed Woodpecker found in the Mediterranean, Turkey and the Caucasus, has an obviously barred back, often with barring on the flanks, too. Photo by Dominic Mitchell.

The 13 or so subspecies of the Yellow Wagtail complex fall into at least two distinct clades over the Northern Hemisphere, depending on your taxonomic viewpoint (see Birdwatch 215: 35-37). The dark-capped birds of the Mediterranean have a distinct call type, as well as a variable but cohesive plumage pattern. Black-headed Wagtail, the most distinct, has long been favoured by birders as a potential split, but the true relationships of the group are certainly more complex than that. Stricter adherents to the phylogenetic species concept may wish to try to see all the Yellow Wagtail subspecies that appear in Britain.

Moltoni’s Warbler
is already split in The Netherlands and Italy from Subalpine Warbler, and is a separate lineage from the other three subspecies. Vagrants in Belgium and The Netherlands have been accepted, and at least three birds are under consideration in Britain. It is best identified by vocalisations, and as a spring male – any other plumage may not be identifiable in the field on current knowledge. Western and Eastern Subalpine Warblers are less divergent from each other than either is from Moltoni’s, but are also possibly separate species.

Reed Bunting falls into two main subspecies groups, with the familiar northern group having a thin conical bill and the southern group a shorter, blunter, thicker bill. The two breed within 30 miles of each other in Italy, but no hybrids or mixed pairs have been recorded. There are minor differences in body size and colour, as well as winter diet and feeding habitat. Sound recordings have shown that, on average, the songs differ in their complexity and frequency range.

Depending on how rigorously one applies the idea of a discrete diagnosable biological unit, there may yet be more species defined from the region.

References

For a full list of references, please click here.