'eastern' lesser whitethroats in norfolk
Richard Porter and Andy Stoddart
Introduction
Lesser Whitethroats of eastern forms have been reported in Norfolk on a number of occasions but no detailed notes have been published in the Bird Report. In the wake of three further examples in Autumn 2009, this note provides a description of each bird, discusses the taxonomy and identification of the Lesser Whitethroat complex and reviews the status of eastern forms in Norfolk and Britain. Finally, proposals are made to assess future claims through the County Records Committee.
‘Eastern Lesser Whitethroats’ in 2009
On 8th October 2009 Chris Mills found a pale, sandy-looking Lesser Whitethroat at Gun Hill, Burnham Overy Dunes. The bird was a concolorous sandy-brown across the mantle, wings and tail, paler and browner than curruca. This colouration extended up on to the nape and hindcrown, with pure grey tones restricted to the ear coverts. The darkest area was around the eye, giving a ‘masked’ appearance. The tertials were prominently fringed sandy and the closed wing showed an obvious ‘panel’. The underparts were white with a buff hue along the flanks. The extent of white in the outer tail feathers was not seen and the bird was not heard to call.
On 13th October 2009 Richard Porter found and photographed an ‘Eastern Lesser Whitethroat’ in the Plantation on Blakeney Point. The bird was present until 18th October, mainly in the ‘Lupins’, during which period it was also watched, photographed and videoed by James McCallum and Andy Stoddart. Its image appears amongst the Plates. First seeing it in flight, RFP was immediately struck by the conspicuous white outer tail feathers; then when it perched by the small bill and rather ‘dinky’ appearance. It also appeared quite short-winged with a short primary projection considerably shorter than the exposed tertials. Its plumage was similar to a nominate Lesser Whitethroat but was warmer, paler and browner on the mantle, scapulars and wing feather fringes, entirely lacking any grey hues and slightly sandy in tone. A dark alula stood out prominently. The brown upperparts extended strongly across the whole nape and hind-crown to create a noticeable pale ‘hood’ or ‘shawl’ effect which contrasted with the grey head. The forehead, fore-crown, lores and ear coverts were pale grey, the ear coverts slightly darker, forming a subtle ‘mask’. Paler grey feathering above the eye created the impression of a diffuse supercilium. The underparts were extensively suffused with a warm sandy buff colour which contrasted with the white throat. The outer tail feathers were extensively white. In one photograph the underside of the left outer tail feather can be seen to be extensively clean white on both webs. On several occasions it was heard to give the typical Lesser Whitethroat ‘tak’ call. Photographs of this bird appear in the Plates. Note that in the first of these, taken into sunlight, the bird appears greyer than in life. The sandy buff hues in the underparts and the warm, brown hues in the upperparts appear reduced, rendering the bird more curruca-like. In the second photograph, taken in bright but cloudy conditions, the true hues are more apparent.
On 10th November 2009 JRMcC found and sketched another ‘Eastern Lesser Whitethroat’ at Wells. In size and structure it also resembled a small nominate Lesser Whitethroat and its primary projection also appeared short. Its mantle, scapulars and wing feather fringes were a medium brown with sandy hues, paler than the Blakeney Point bird, and this brown tone also extended up onto the nape and hind-crown as a ‘shawl’. Its head markings were indistinct as the rear ear-coverts were also brown, increasingly flecked with grey towards the eye. The forehead, fore-crown, lores and the forward part of the ear coverts were pale grey, darkest before and below the eye. The breast-sides and flanks were extensively suffused with a sandy colour. The outer webs of the outer tail feathers appeared all white, with the adjacent feathers having neat whitish tips.
Taxonomy
All three birds were identified as ‘Eastern Lesser Whitethroats’, subtly but clearly distinct from nominate Lesser Whitethroat, but assigning them to a specific form was no easy matter. The taxonomy of the Lesser Whitethroat group is famously complex, with up to a dozen forms proposed. Shirihai et al. (2001) rationalise these into five forms:-
• Curruca (‘Northern Lesser Whitethroat’) of northern Europe and northern Asia. The form blythi found east of the Yenisei (‘Siberian Lesser Whitethroat’) is not recognised as a valid taxon.
• Halimodendri (‘Central Asian Lesser Whitethroat’ or ‘Steppe Lesser Whitethroat’) of the steppes of Central Asia
• Minula (‘Desert Lesser Whitethroat’) of the Central Asian deserts
• Margelanica (‘Margelanic Lesser Whitethroat’) of western China
• Althaea (‘Mountain Lesser Whitethroat’) of the Central Asian mountains
Shirihai et al. group these five forms into four allospecies (an acknowledgement of the clinal nature of their characters), with halimodendri included within curruca. There remains much debate, however, over the taxonomy of the complex, with no unanimity over the forms recognised or their grouping into species. Cramp (ed.) (1992), for example, recognises blythi, whilst Baker (1988) and Svensson (1992) also recognise the form and include within it halimodendri. All these authors (as well as Svensson et al. 2010) treat the Lesser Whitethroat as a single polytypic species.
King (1998), however, identifies three species groupings based on the existence of three separate song types. These are ‘Northern Lesser Whitethroat’ (incorporating curruca, blythi and halimodendri), ‘Desert Lesser Whitethroat’ (incorporating minula and margelanica) and ‘Hume’s Lesser Whitethroat’ (althaea). Porter & Aspinall (2010) also adopt a three-way ‘split’ but include halimodendri within ‘Desert Lesser Whitethroat’, considering it ‘closest to minula (genetically, vocally and morphologically)’.
Identification
The characters of the forms discussed above can be summarised as follows:-
• Curruca shows a long wing-point, distinct grey hues in the upperparts and (in juveniles) dusky washes on the outermost tail feather and a dark patch along the shaft.
• Blythi shows a very slightly shorter wing-point, whiter underparts, browner or more gingery hues in the upperparts and (in juveniles) a tendency to more white in the outermost tail feather.
• Halimodendri shows a shorter wing-point, medium-brown or sandy upperpart hues, sandy hues to the breast-sides and flanks, a paler crown and (in juveniles) more extensive pure white in the outermost tail feather with no dark patch along the shaft.
• Minula is small with a short bill, a very short wing-point, a long-tailed apparance, pale yellowish-sand upperpart hues, yellowish-buff hues to the breast sides and flanks, a pale crown with a bland indistinct face pattern and (in juveniles) very extensive pure white in the outermost tail feather with no dark patch along the shaft.
• Margelanica resembles minula but is larger.
• Althaea is large with a rather large head and stout bill, dark grey crown and ear-coverts and a grey-brown back.
A grating or buzzing, tit-like call ‘che-che-che-che-che’ is typical of some eastern forms, especially minula, but all Lesser Whitethroats also give the familiar ‘tak’ call.
‘Eastern Lesser Whitethroats’ in Britain
There is a long history of ‘Eastern Lesser Whitethroats’ reaching Britain in mid to late autumn and sometimes wintering. For example, Witherby et al. (1940) list thirteen records of blythi, all from Scotland, and Williamson (1968) describes blythi as a ‘regular autumn drift-migrant’. BOURC categorises blythi as a scarce migrant but no other forms are currently on the British List though there is an acceptance that birds of one or more other forms are occurring (Kehoe 2006). In addition to curruca and blythi, birds showing the characters of at least halimodendri and minula appear to be reaching us.
‘Eastern Lesser Whitethroats’ in Britain have traditionally been referred to blythi but are increasingly being labelled halimodendri, either because of greater awareness of the characters of this form or because of Shirihai et al.’s ‘demotion’ of blythi. Halimodendri may indeed be a regular vagrant or even a scarce migrant. In addition, one or two birds resembling minula have also reached Britain, notably a bird on Teesside in November 2000 (Money 2000). Eliminating halimodendri will, however, always be problematic. DNA analysis of another minula-like bird in Aberdeenshire in 2004 (Baxter & Broadbent 2004) showed it to be closer to halimodendri.
It is already clear is that there is no ‘standard image’ for these birds. They can vary considerably in their appearance, suggesting that we are seeing birds from a variety of source areas.
‘Eastern Lesser Whitethroats’ in Norfolk
To a great extent, this national picture has been mirrored in Norfolk. Taylor et al. (1999) note the occurrence of ‘about sixteen’ ‘Eastern Lesser Whitethroats’ to the end of 1998, referring them all to blythi, though the basis for these identifications is not known. To the end of 2008, a further seven reports have appeared in the Norfolk Bird Report though, again, no details or photographs have been published. Unfortunately, neither the British Birds Rarities Committee (BBRC) nor the Norfolk Records Committee has historically sought submissions of ‘Eastern Lesser Whitethroats’ so not all of the records have been formally assessed. The published reports are:-
Eccles 12th/13th November 1999, described as showing ‘a number of features of the race minula’.
California 21st October 2003, described as ‘showing characteristics of halimodendri’.
Paston 24th/25th October 2003, described as ‘showing characteristics of halimodendri’.
Holme 20th-28th October 2003, described as ‘probably one of the eastern races’.
Winterton 11th/12th October 2006, described as ‘showing characteristics of one of the eastern races’
Winterton 30th September 2007, described as ‘showing characteristics of an eastern steppe-type bird’, though tentatively assigned to halimodendri in Dye et al. (2009). This bird has been submitted to BBRC and is currently (March 2010) listed as ‘Held’. Sheringham 3rd October 2007, described as ‘showing characteristics of an eastern steppe-type bird’. This bird has been submitted to BBRC and is currently (March 2010) listed as ‘Held’.
A late record for 2008 is also published in this Report:-
Wells East Hills 2nd-5th November 2008, thought to be closest to minula (pers. comm.). Photographs of this bird are at www.freewebs.com/punkbirder/desertlesserthroat.htm.
Documenting Future Claims
‘Eastern Lesser Whitethroats’ are clearly occurring in Norfolk with some regularity but are probably also overlooked due to a lack of observer interest and awareness. They are very subtle birds and a number of late autumn Lesser Whitethroats may well have been of one of these eastern forms.
However, identifying individual birds to a specific form will always be a challenge and will often not be possible. Although they are separable from curruca in the field, firm identification to form is likely to remain elusive given the clinal nature of their characters and a still-unresolved taxonomy.
BBRC has now requested high-quality submissions of ‘Eastern Lesser Whitethroats’ of forms other than blythi but in the absence of a stable, agreed taxonomic framework and reliable field identification criteria, publication of any records of ‘new’ forms seems unlikely in the short term (Kehoe 2006).
Despite this vacuum, it nevertheless seems appropriate for Norfolk to attempt to record the appearance and document the status of these birds more fully than has been the case in the past. The County Records Committee has therefore decided to request with immediate effect claims from Norfolk of birds considered to be of a form other than curruca. The Committee is fully aware of the difficulties in assigning individual birds on the blythi/halimodendri/ minula cline but would like to retain on file records of well-documented birds which do not match the characters of curruca. Accepted birds will be published as ‘Eastern Lesser Whitethroats’ and records will be held for future reference in the hope that ongoing work on genetics, vocalisations and morphology may provide a more definitive taxonomy and shed further light on the provenance and identity of these birds.
As with, for example, ‘Siberian Chiffchaff’, the precise documentation of plumage hues is vital to identification. A claim of an ‘Eastern Lesser Whitethroat’ should therefore demonstrate that the bird was observed well over a considerable period of time in a variety of lighting conditions so that an accurate assessment of plumage hues could be made. All efforts should be made to describe these hues as precisely as possible. Above all, every attempt should be made to photograph the bird and, ideally, take sound recordings. Trapped birds should be extensively photographed and have full biometric details taken. The removal of a feather for DNA and/or stable isotope analysis would also be invaluable.
Acknowledgements
Many thanks are due to James McCallum and Chris Mills for their contributions to this note.
References
Baker, K. (1988). Identification of Siberian and other forms of Lesser Whitethroat. British Birds 81: 382-390.
Baxter, P. & Broadbent, I. (2004). The apparent Desert Lesser Whitethroat in Aberdeen.
Birding World 17(12): 502-504.
Cramp, S. (ed.) (1992). The Birds of the Western Palearctic, vol VI. Oxford University Press, Oxford.
Dunmore, G.E. (ed.) Norfolk Bird & Mammal Report 1999 – 2007.
Dye et al. (2009). Birds New to Norfolk. Wren Publishing, Sheringham, Norfolk.
Kehoe, C. (2006). Racial identification and assessment in Britain: a report from the RIACT subcommittee. British Birds 99: 619-645.
King, J. (1998). Three lesser whitethroats. Birding World 11(4): 122.
Money, D. (2000). The Desert Lesser Whitethroat on Teesside. Birding World 13(11): 451-453.
Petttersson, M. (2001). A Central Asian Lesser Whitethroat in Sweden. Birding World 14(1): 12-15.
Porter, R.F. & Aspinall, S. (2010). A Field Guide to the Birds of the Middle East (second edition). T. & A.D. Poyser, London.
Punkbirder www.freewebs.com/punkbirder/desertlesserthroat.htm.
Shirihai H. et al. (2001). Sylvia Warblers - Identification, Taxonomy and Phylogeny of
the Genus Sylvia. Christopher Helm, London.
Svensson, L. (1992). Identification Guide to European Passerines. Stockholm.
Svensson, L. et al. (2010). Collins Bird Guide. HarperCollins Publishers Ltd., London. Taylor, M. et al. (1999). The Birds of Norfolk. Pica Press, Robertsbridge, East Sussex. Williamson, K. (1968). Identification for Ringers. 3. The Genus Sylvia. British Trust for Ornithology, Tring, Hertfordshire.
Witherby, H.F. et al. (1940). The Handbook of British Birds. H.F. & G. Witherby Ltd., London.
Introduction
Lesser Whitethroats of eastern forms have been reported in Norfolk on a number of occasions but no detailed notes have been published in the Bird Report. In the wake of three further examples in Autumn 2009, this note provides a description of each bird, discusses the taxonomy and identification of the Lesser Whitethroat complex and reviews the status of eastern forms in Norfolk and Britain. Finally, proposals are made to assess future claims through the County Records Committee.
‘Eastern Lesser Whitethroats’ in 2009
On 8th October 2009 Chris Mills found a pale, sandy-looking Lesser Whitethroat at Gun Hill, Burnham Overy Dunes. The bird was a concolorous sandy-brown across the mantle, wings and tail, paler and browner than curruca. This colouration extended up on to the nape and hindcrown, with pure grey tones restricted to the ear coverts. The darkest area was around the eye, giving a ‘masked’ appearance. The tertials were prominently fringed sandy and the closed wing showed an obvious ‘panel’. The underparts were white with a buff hue along the flanks. The extent of white in the outer tail feathers was not seen and the bird was not heard to call.
On 13th October 2009 Richard Porter found and photographed an ‘Eastern Lesser Whitethroat’ in the Plantation on Blakeney Point. The bird was present until 18th October, mainly in the ‘Lupins’, during which period it was also watched, photographed and videoed by James McCallum and Andy Stoddart. Its image appears amongst the Plates. First seeing it in flight, RFP was immediately struck by the conspicuous white outer tail feathers; then when it perched by the small bill and rather ‘dinky’ appearance. It also appeared quite short-winged with a short primary projection considerably shorter than the exposed tertials. Its plumage was similar to a nominate Lesser Whitethroat but was warmer, paler and browner on the mantle, scapulars and wing feather fringes, entirely lacking any grey hues and slightly sandy in tone. A dark alula stood out prominently. The brown upperparts extended strongly across the whole nape and hind-crown to create a noticeable pale ‘hood’ or ‘shawl’ effect which contrasted with the grey head. The forehead, fore-crown, lores and ear coverts were pale grey, the ear coverts slightly darker, forming a subtle ‘mask’. Paler grey feathering above the eye created the impression of a diffuse supercilium. The underparts were extensively suffused with a warm sandy buff colour which contrasted with the white throat. The outer tail feathers were extensively white. In one photograph the underside of the left outer tail feather can be seen to be extensively clean white on both webs. On several occasions it was heard to give the typical Lesser Whitethroat ‘tak’ call. Photographs of this bird appear in the Plates. Note that in the first of these, taken into sunlight, the bird appears greyer than in life. The sandy buff hues in the underparts and the warm, brown hues in the upperparts appear reduced, rendering the bird more curruca-like. In the second photograph, taken in bright but cloudy conditions, the true hues are more apparent.
On 10th November 2009 JRMcC found and sketched another ‘Eastern Lesser Whitethroat’ at Wells. In size and structure it also resembled a small nominate Lesser Whitethroat and its primary projection also appeared short. Its mantle, scapulars and wing feather fringes were a medium brown with sandy hues, paler than the Blakeney Point bird, and this brown tone also extended up onto the nape and hind-crown as a ‘shawl’. Its head markings were indistinct as the rear ear-coverts were also brown, increasingly flecked with grey towards the eye. The forehead, fore-crown, lores and the forward part of the ear coverts were pale grey, darkest before and below the eye. The breast-sides and flanks were extensively suffused with a sandy colour. The outer webs of the outer tail feathers appeared all white, with the adjacent feathers having neat whitish tips.
Taxonomy
All three birds were identified as ‘Eastern Lesser Whitethroats’, subtly but clearly distinct from nominate Lesser Whitethroat, but assigning them to a specific form was no easy matter. The taxonomy of the Lesser Whitethroat group is famously complex, with up to a dozen forms proposed. Shirihai et al. (2001) rationalise these into five forms:-
• Curruca (‘Northern Lesser Whitethroat’) of northern Europe and northern Asia. The form blythi found east of the Yenisei (‘Siberian Lesser Whitethroat’) is not recognised as a valid taxon.
• Halimodendri (‘Central Asian Lesser Whitethroat’ or ‘Steppe Lesser Whitethroat’) of the steppes of Central Asia
• Minula (‘Desert Lesser Whitethroat’) of the Central Asian deserts
• Margelanica (‘Margelanic Lesser Whitethroat’) of western China
• Althaea (‘Mountain Lesser Whitethroat’) of the Central Asian mountains
Shirihai et al. group these five forms into four allospecies (an acknowledgement of the clinal nature of their characters), with halimodendri included within curruca. There remains much debate, however, over the taxonomy of the complex, with no unanimity over the forms recognised or their grouping into species. Cramp (ed.) (1992), for example, recognises blythi, whilst Baker (1988) and Svensson (1992) also recognise the form and include within it halimodendri. All these authors (as well as Svensson et al. 2010) treat the Lesser Whitethroat as a single polytypic species.
King (1998), however, identifies three species groupings based on the existence of three separate song types. These are ‘Northern Lesser Whitethroat’ (incorporating curruca, blythi and halimodendri), ‘Desert Lesser Whitethroat’ (incorporating minula and margelanica) and ‘Hume’s Lesser Whitethroat’ (althaea). Porter & Aspinall (2010) also adopt a three-way ‘split’ but include halimodendri within ‘Desert Lesser Whitethroat’, considering it ‘closest to minula (genetically, vocally and morphologically)’.
Identification
The characters of the forms discussed above can be summarised as follows:-
• Curruca shows a long wing-point, distinct grey hues in the upperparts and (in juveniles) dusky washes on the outermost tail feather and a dark patch along the shaft.
• Blythi shows a very slightly shorter wing-point, whiter underparts, browner or more gingery hues in the upperparts and (in juveniles) a tendency to more white in the outermost tail feather.
• Halimodendri shows a shorter wing-point, medium-brown or sandy upperpart hues, sandy hues to the breast-sides and flanks, a paler crown and (in juveniles) more extensive pure white in the outermost tail feather with no dark patch along the shaft.
• Minula is small with a short bill, a very short wing-point, a long-tailed apparance, pale yellowish-sand upperpart hues, yellowish-buff hues to the breast sides and flanks, a pale crown with a bland indistinct face pattern and (in juveniles) very extensive pure white in the outermost tail feather with no dark patch along the shaft.
• Margelanica resembles minula but is larger.
• Althaea is large with a rather large head and stout bill, dark grey crown and ear-coverts and a grey-brown back.
A grating or buzzing, tit-like call ‘che-che-che-che-che’ is typical of some eastern forms, especially minula, but all Lesser Whitethroats also give the familiar ‘tak’ call.
‘Eastern Lesser Whitethroats’ in Britain
There is a long history of ‘Eastern Lesser Whitethroats’ reaching Britain in mid to late autumn and sometimes wintering. For example, Witherby et al. (1940) list thirteen records of blythi, all from Scotland, and Williamson (1968) describes blythi as a ‘regular autumn drift-migrant’. BOURC categorises blythi as a scarce migrant but no other forms are currently on the British List though there is an acceptance that birds of one or more other forms are occurring (Kehoe 2006). In addition to curruca and blythi, birds showing the characters of at least halimodendri and minula appear to be reaching us.
‘Eastern Lesser Whitethroats’ in Britain have traditionally been referred to blythi but are increasingly being labelled halimodendri, either because of greater awareness of the characters of this form or because of Shirihai et al.’s ‘demotion’ of blythi. Halimodendri may indeed be a regular vagrant or even a scarce migrant. In addition, one or two birds resembling minula have also reached Britain, notably a bird on Teesside in November 2000 (Money 2000). Eliminating halimodendri will, however, always be problematic. DNA analysis of another minula-like bird in Aberdeenshire in 2004 (Baxter & Broadbent 2004) showed it to be closer to halimodendri.
It is already clear is that there is no ‘standard image’ for these birds. They can vary considerably in their appearance, suggesting that we are seeing birds from a variety of source areas.
‘Eastern Lesser Whitethroats’ in Norfolk
To a great extent, this national picture has been mirrored in Norfolk. Taylor et al. (1999) note the occurrence of ‘about sixteen’ ‘Eastern Lesser Whitethroats’ to the end of 1998, referring them all to blythi, though the basis for these identifications is not known. To the end of 2008, a further seven reports have appeared in the Norfolk Bird Report though, again, no details or photographs have been published. Unfortunately, neither the British Birds Rarities Committee (BBRC) nor the Norfolk Records Committee has historically sought submissions of ‘Eastern Lesser Whitethroats’ so not all of the records have been formally assessed. The published reports are:-
Eccles 12th/13th November 1999, described as showing ‘a number of features of the race minula’.
California 21st October 2003, described as ‘showing characteristics of halimodendri’.
Paston 24th/25th October 2003, described as ‘showing characteristics of halimodendri’.
Holme 20th-28th October 2003, described as ‘probably one of the eastern races’.
Winterton 11th/12th October 2006, described as ‘showing characteristics of one of the eastern races’
Winterton 30th September 2007, described as ‘showing characteristics of an eastern steppe-type bird’, though tentatively assigned to halimodendri in Dye et al. (2009). This bird has been submitted to BBRC and is currently (March 2010) listed as ‘Held’. Sheringham 3rd October 2007, described as ‘showing characteristics of an eastern steppe-type bird’. This bird has been submitted to BBRC and is currently (March 2010) listed as ‘Held’.
A late record for 2008 is also published in this Report:-
Wells East Hills 2nd-5th November 2008, thought to be closest to minula (pers. comm.). Photographs of this bird are at www.freewebs.com/punkbirder/desertlesserthroat.htm.
Documenting Future Claims
‘Eastern Lesser Whitethroats’ are clearly occurring in Norfolk with some regularity but are probably also overlooked due to a lack of observer interest and awareness. They are very subtle birds and a number of late autumn Lesser Whitethroats may well have been of one of these eastern forms.
However, identifying individual birds to a specific form will always be a challenge and will often not be possible. Although they are separable from curruca in the field, firm identification to form is likely to remain elusive given the clinal nature of their characters and a still-unresolved taxonomy.
BBRC has now requested high-quality submissions of ‘Eastern Lesser Whitethroats’ of forms other than blythi but in the absence of a stable, agreed taxonomic framework and reliable field identification criteria, publication of any records of ‘new’ forms seems unlikely in the short term (Kehoe 2006).
Despite this vacuum, it nevertheless seems appropriate for Norfolk to attempt to record the appearance and document the status of these birds more fully than has been the case in the past. The County Records Committee has therefore decided to request with immediate effect claims from Norfolk of birds considered to be of a form other than curruca. The Committee is fully aware of the difficulties in assigning individual birds on the blythi/halimodendri/ minula cline but would like to retain on file records of well-documented birds which do not match the characters of curruca. Accepted birds will be published as ‘Eastern Lesser Whitethroats’ and records will be held for future reference in the hope that ongoing work on genetics, vocalisations and morphology may provide a more definitive taxonomy and shed further light on the provenance and identity of these birds.
As with, for example, ‘Siberian Chiffchaff’, the precise documentation of plumage hues is vital to identification. A claim of an ‘Eastern Lesser Whitethroat’ should therefore demonstrate that the bird was observed well over a considerable period of time in a variety of lighting conditions so that an accurate assessment of plumage hues could be made. All efforts should be made to describe these hues as precisely as possible. Above all, every attempt should be made to photograph the bird and, ideally, take sound recordings. Trapped birds should be extensively photographed and have full biometric details taken. The removal of a feather for DNA and/or stable isotope analysis would also be invaluable.
Acknowledgements
Many thanks are due to James McCallum and Chris Mills for their contributions to this note.
References
Baker, K. (1988). Identification of Siberian and other forms of Lesser Whitethroat. British Birds 81: 382-390.
Baxter, P. & Broadbent, I. (2004). The apparent Desert Lesser Whitethroat in Aberdeen.
Birding World 17(12): 502-504.
Cramp, S. (ed.) (1992). The Birds of the Western Palearctic, vol VI. Oxford University Press, Oxford.
Dunmore, G.E. (ed.) Norfolk Bird & Mammal Report 1999 – 2007.
Dye et al. (2009). Birds New to Norfolk. Wren Publishing, Sheringham, Norfolk.
Kehoe, C. (2006). Racial identification and assessment in Britain: a report from the RIACT subcommittee. British Birds 99: 619-645.
King, J. (1998). Three lesser whitethroats. Birding World 11(4): 122.
Money, D. (2000). The Desert Lesser Whitethroat on Teesside. Birding World 13(11): 451-453.
Petttersson, M. (2001). A Central Asian Lesser Whitethroat in Sweden. Birding World 14(1): 12-15.
Porter, R.F. & Aspinall, S. (2010). A Field Guide to the Birds of the Middle East (second edition). T. & A.D. Poyser, London.
Punkbirder www.freewebs.com/punkbirder/desertlesserthroat.htm.
Shirihai H. et al. (2001). Sylvia Warblers - Identification, Taxonomy and Phylogeny of
the Genus Sylvia. Christopher Helm, London.
Svensson, L. (1992). Identification Guide to European Passerines. Stockholm.
Svensson, L. et al. (2010). Collins Bird Guide. HarperCollins Publishers Ltd., London. Taylor, M. et al. (1999). The Birds of Norfolk. Pica Press, Robertsbridge, East Sussex. Williamson, K. (1968). Identification for Ringers. 3. The Genus Sylvia. British Trust for Ornithology, Tring, Hertfordshire.
Witherby, H.F. et al. (1940). The Handbook of British Birds. H.F. & G. Witherby Ltd., London.
