The KOS Subspecies Review

Introduction

Over the years, the treatment of rarer subspecies in the Kent Bird Report has been rather inconsistent. There are a number of records of some extremely rare subspecies that have been published without any supporting documentation, despite the fact that they are rarer and often more difficult to identify than many species for which descriptions are a pre-requisite for publication. During 1999 the KOS embarked upon a review of all reports of rare and scarce subspecies recorded in Kent. This short paper outlines the way in which the review was conducted and details the results. A more detailed paper is in preparation for the 2000 Kent Bird Report.

Review Process

The first stage of the review was to ensure that we knew which rarer forms of each species had been reported in the county. Having done that, we undertook a review of each form's status in the county so that we could establish whether it was sufficiently rare for us to require a description. This gave us a list of candidate subspecies, which might require supporting details prior to publication in the Kent Bird Report.

The KOS Rarity Panel with assistance from other members of the KOS Editorial and Records Committee then investigated the identification of each subspecies in order to establish whether it was identifiable and under what circumstances. Although some subspecies are relatively straightforward to identify, others can only be identified in the hand, whilst a few might only be identifiable when compared with a series of skins in a museum. Each committee member involved in the review was responsible for a subspecies or group of subspecies. Each member compiled a list of important references and summarised the key identification features for each subspecies. Each member also made recommendations as to whether the subspecies was identifiable and whether the Rarity Panel could assess it.

At a meeting of committee members involved in the review, we made a number of decisions as to which subspecies would require descriptions in the county. It should be noted that during the course of the review the British Ornithologists Union elevated some of the subspecies to full species status (Green-winged Teal, Mealy Redpoll). These species are included here. The fact that these subspecies have been elevated to full species status demonstrates the need to treat the publication of rarer subspecies more critically than has often been the case in the past.

Results

From the 1st January 2002 the KOS will require descriptions to support any claims of the following (sub)species.

Greenland White-fronted Goose Anser albifrons flavirostris - This subspecies has been recorded in the county on at least two occasions. Detailed descriptions of this form must document all the subtle differences between this form and the nominate race.

Taiga Bean Goose Anser (fabalis) fabalis - Tundra Bean Goose Anser (fabalis) rossicus is the most commonly occurring form in Kent, whilst Taiga Bean Goose is thought to be very rare. These two forms are often difficult to separate in the field and thus detailed descriptions will be a pre-requisite for acceptance of Taiga Bean Geese claims.

Pale-bellied Brent Goose Branta bernicla hrota - A very scarce but apparently fairly regular visitor to the county. This form may well attain full species status within the next few years. Readers should note that the Black Brant Branta bernicla nigricans is assessed by the BBRC.

Green-winged Teal Anas carolinensis - This form has recently been elevated to full species status. The identification of females remains virtually impossible and the KOS will continue to assess claims of males only.

Kumlien's Gull Larus glaucoides kumlieni - This form has recently been dropped from the BBRC list, partly due to identification difficulties, however the KOS will continue to assess and publish acceptable claims of classic individuals, whilst less obvious individuals will be published as 'showing characteristics of'.

Grey-headed Wagtail Motacilla flava thunbergi - A rare spring migrant through the county. This form is already on the county description list.

Ashy-headed Wagtail Motacilla flava cinereocapilla - A very rare visitor to Kent.

Black-headed Wagtail Motacilla flava feldegg - This form has not yet been recorded in Kent, but members are reminded that any claims are assessed by BBRC. Readers will be interested to know that the Yellow Wagtail complex is likely to undergo some revision and some subspecies are likely to be elevated to full species status in the next few years.

Lesser Whitethroat Sylvia curruca minula - There is one claim of this form from the county. Shirihai et al suggests that this form may be sufficiently distinct to be regarded as a full species. BBRC will assess claims of this form and thus all claims of this form should be supported by a description.

Siberian Chiffchaff Phylloscopus collybita tristis - Tristis Chiffchaffs are recorded almost every autumn in Kent and this subspecies is already on the county description list. The KOS Rarity Panel feels that some reports may be erroneous and as a result we will be looking for detailed descriptions that convince us that all relevant plumage and vocal characteristics are noted and that the circumstances of the observation allow such detail to be recorded.

Great Tit Parus major - The race occurring in the UK is newtoni . In the hand claims of the nominate form major will be considered by the KOS.

Willow Tit Parus montanus borealis - Although there are no Kent records, there are published UK records of the form borealis . Claims of this form are considered by BBRC.

Long-tailed Tit Aegithalos caudatus - The form occurring in the UK is rosaceus . The KOS Rarity Panel will consider claims of the continental form caudatus. However observers are reminded that detailed notes are a pre-requisite for acceptance.

Hooded Crow Corvus corone cornix - This subspecies was formerly much more regular in the county, with flocks sometimes occurring during the winter months. Hooded Crow has undergone a decline in the county and during the period 1989-98 averaged just 4 records per year, with no more than 8 in any one year. This means that it is now rare enough to be considered a Kent rarity. Observers are reminded that descriptions should conclusively eliminate the possibility of hybrids. It should also be noted that Hooded Crow is likely to be elevated to full species status in the near future.

Mealy Repoll Carduelis flammea - Mealy Redpoll was accorded full species status by the BOU in 2000. The species is thought to be a scarce autumn and winter visitor to the county, but is tricky to identify and thus full descriptions will be required for all future claims.

Northern Bullfinch Pyrrhula pyrrhula - The form commonly occurring in the UK is pileata . The nominate form known as Northern Bullfinch has been reported in Kent in the past (e.g. 2 trapped at Sandwich Bay on 17th October 1994 ). The KOS will only consider claims of trapped birds since we regard field identification as being unsafe.

The following subspecies were considered by the review, but have not been added to the KOS description list.

Cormorant Phalacrocorax carbo - The continental form sinensis is thought to be occurring in the county in some numbers. However, the separation of sinensis from carbo is not straightforward and reliable identification characters are lacking. The KOS understands that work on the separation of these forms is ongoing and it is likely that an identification paper may be published in the future. When such a paper is published the KOS will review whether descriptions might be required.

Sykes Wagtail Motacilla flava beema - There have been a number of claims of this form in the county, all of which are considered unacceptable. It is the opinion of the KOS that the presence of aberrant birds and hybrids between flava and flavissima that closely resemble the form beema renders the field identification of beema unsafe. Such birds are present in breeding populations not only on the Isle of Sheppey and elsewhere in Kent, but also on the near continent in northern France.

White-headed Wagtail Motacilla flava leucocephala - As with Syke's Wagtail the field identification of this form is considered unsafe due to reports that offspring produced by hybrid pairings of flava and flavissima resembling this form.

Ring Ouzel Turdus torquatus - Birds from the breeding populations on the continent may occur on a regular basis in Kent. The committee feels that it is not possible to reliably separate the various forms of this species.

Lesser Whitethroat Sylvia curucca blythi - The recently published book on Sylvia warblers by Shirihai et al has concluded that this form should be included within S. [c.] curruca because of it's overall resemblance to the nominate form and because more than 25% are inseparable from curucca . The committee will therefore not assess claims of this form.

Willow Warbler Phylloscopus trochilus acredula - There is evidence to suggest that birds of the race acredula probably pass through Kent. However the identification of this form is very problematical due to the presence of ' acredula-type ' birds occurring in many different populations of Willow Warbler. The committee feels therefore that there is too much variation (much of it clinal) for claims of this form to be assessed.

Blue Tit Parus caeruleus - It is not possible to reliably separate the different subspecies of Blue Tit.

Coal Tit Parus ater ater - The subspecies occurring in Britain is britannicus . Continental Coal Tits are regular visitors to Kent, especially in autumn, when occasional large influxes take place. It is thought that this form is too common for entry onto the KOS description list.

Jackdaw Corvus monedula - The subspecies occurring in Britain is spermologus . There are a number of published claims of monedula and soemmeringii in Kent. Due to significant variation in all populations the committee feels that it is difficult to identify these forms with any certainty. Therefore we regard all previous claims as unproven and will not be assessing future claims.

If any KOS member wishes to raise any questions about this review, then the Rarity Panel would be pleased to hear from you. Please direct any such questions to Barry Wright in the first instance.

The following committee members past and present took part in this review; Pete Akers, Gordon Allison, Chris Bradshaw, Jon Braggs, Geoff Burton, Phil Chantler, Gary Howard, James Hunter, Ian Hodgson, Richard Jenkinson, Adam Rowlands, Don Taylor, Barry Wright.

References:

Shirihai et al……