January 27, 2008
BBRC seeking submissions of all Siberian Chiffchaff records in 2008
Establishing the status in Britain of ‘Siberian Chiffchaff’ Phylloscopus (collybita) tristis has long been problematic.
Key to this problem is the correct identification of the form – the difficulties of separating true Siberian tristis (largely from east of the Yenisey) and ‘fulvescens’ (on the West Siberian Plain) from abietinus (from Scandinavia and western Russia west of the Urals) continue to plague both observers and records committees. In particular, it has become obvious that different observers (and indeed different records committees) hold different perceptions of what constitutes true tristis and therefore apply different threshold criteria for acceptance into the local record. The recording of this form across Britain can therefore best be described as uneven and has never been attempted nationally. As a consequence, our knowledge of the true British status of tristis is incomplete and we do not yet know definitively whether tristis can best be described as ‘scarce but regular’ or ‘rare but regular’.
Putative Siberian Chiffchaff, Bedfordshire, January 2004 © Nigel Blake,
from the surfbirds galleries
Context
Fortunately, three factors have now combined to help us move forward. Firstly, the work of Dean and Svensson has provided welcome clarifications over the identification of this form (British Birds 98: 396-410). Secondly, the rise of digital photography has greatly increased the availability of good quality images of birds in the field. Similar improvements in sound recording technology have also made recording birds increasingly feasible. Thirdly, BBRC has now moved to free up its resources to focus on the recording of subtle or rare bird forms not previously assessed. With these three developments now in place, we have the opportunity to make progress with the Siberian Chiffchaff issue.
Identification
Observers and records committees may find it useful to have a brief summary of the conclusions of Dean and Svensson. The traditional view that any Chiffchaff lacking green in the crown and mantle and lacking yellow in the face and underparts can be labelled tristis has now been refined. Dean and Svensson have confirmed that true tristis is defined additionally by the presence of pale brown or grey-brown hues above and the presence of warm buff in the supercilium, ear-coverts, breast-sides and flanks. ‘Fulvescens’ is similar in appearance though may be a little paler overall and may show very limited yellow and olive hues. This clarification has in turn highlighted the problem of ‘grey and white’ Chiffchaffs. Such birds are not all consistent in appearance nor attributable to a single ‘type’ but some individuals, at least, match aspects of the traditional image of tristis. However, when they also lack the pale grey-brown and buff hues now firmly linked with the form, they cannot be assigned to it. The origins of such individuals remain unclear but may include eastern abietinus and intergrades between abietinus and tristis. In summary, the identification of tristis rests on the following criteria:-
Absence of olive in the crown and mantle
Absence of yellow away from the underwing
Presence of a grey-brown or pale brown hue in the upperparts
Presence of warm buff in the supercilium and ear-coverts
Presence of buff at the breast-sides/flanks
Very black-looking bill and legs
A thin, piping near-monosyllabic Bullfinch-like or Dunnock-like call
A song markedly different from western Chiffchaff’s
For further guidance and useful biometric characters see British Birds 98: 401-402.
Putative Siberian Chiffchaff, Dorset, January 2004 © Garry Taylor,
from the surfbirds galleries
The Way Forward
2008 has been designated as a ‘trial year’ in order to try and gain a deeper understanding of the British status of tristis. BBRC is therefore seeking submissions of of all Chiffchaffs in 2008 considered to be tristis according to the criteria outlined above. Submissions may take any of the following forms but observers and recorders should try to ensure that as many categories of evidence as possible are secured. It is worth emphasising that any records committee assessing claims of tristis will be reliant on descriptions and photographs which accurately capture critical plumage hues. The precise analysis and description of such hues is therefore vital.
Field Descriptions
Field descriptions will be an important source of information but (particularly if unaccompanied by images or recordings) must be very detailed and focus specifically on a full and precise evaluation of plumage hues. Notes should demonstrate that views were good enough and over a long enough period to assess the bird’s true appearance and that full account has been taken of the effect of light conditions on perceived hues. Any transcriptions of calls or songs should be as detailed as possible.
Photographs
Observers are encouraged if at all possible to take photographs of any putative tristis. Furthermore, every effort should be made to obtain photographs which accurately represent the bird’s plumage hues. These may best be taken in dull, flat light rather than in bright sunshine. An accompanying note setting out to what extent the photographs accurately portray the bird’s appearance would be particularly useful.
Sound Recordings
Sound recordings of calling and/or singing birds should be obtained wherever possible. Modern mobile phones/mp3 players/ipods can often capture adequate recordings.
It should be emphasised that this exercise is not intended to formally ‘accept’ or ‘reject’ claims. This is very much an exploratory, learning process. The priority is to secure as much evidence as possible of the number of true tristis which might be reaching Britain.
Process
In 2008 we would like counties to assess all claims of tristis against the above criteria and then submit all those which meet, or come close to meeting them, to Nigel Hudson, BBRC Secretary. We would also like counties to provide summary details of any claims which are assessed locally as falling clearly outside the criteria. These summary details should include location, date and reason for non-acceptance (for example plumage not meeting criteria, call or song not meeting criteria or absence of sufficient critical detail).
Both full claims and summary data for local non-acceptances will then be examined outside the ‘mainstream’ flow of BBRC business by a small team made up of Colin Bradshaw, Alan Dean, John Martin, Andy Stoddart and Grahame Walbridge. Chris Kehoe will contribute to the process on behalf of BOURC. Following the review, conclusions will be presented to BBRC in 2009 with recommendations on how the occurrence of this form might best be documented now and in future.
Andy Stoddart, on behalf of BBRC
Posted by Surfbirds at 9:10 PM | Comments (0)
January 9, 2008
BBRC and BOURC seek records of vagrant "Canada" Goose
Following the recent split of Canada Goose (Branta canadensis) into two species (B.canadensis or Greater Canada Goose and B.hutchinsii or Lesser Canada Goose) neither species is currently on category A of the British list. Both species appear to occur in Britain as vagrants, but their status requires further clarification.
The "conventional" 10 or 11 taxa are now divided between the two species, but there is major variation within some of the recognised taxa. The confusion amongst birders is understandable. BBRC and BOURC need to work closely together to establish three things:
Lesser Canada Goose with Barnacle Geese, Dumfries & Galloway, October 2006
© Colin Bushell, from the Surfbirds galleries
On the basis of which records can either species be added to category A of the British list? Can we identify potential vagrants to specific and sub-specific form? What is the status of each of the various taxa?
We need the help of observers who have seen either species in Britain in a potentially wild (vagrant) state. Even if you do not know what form you saw and even if you feel the origin was doubtful the record will be of value. There is no date limit so any record from any year is welcome, but records need to be well documented. Photographs would be ideal (as many images as possible are helpful - not just the good ones) but field notes will also be acceptable alone provided they were contemporaneous. An assessment of size, bill structure and plumage tones are all important along with date (month/year at least) and location. All accepted records will be acknowledged in the usual way in the report. It is probably best not to assume that someone else will be sending in a complete record, all data can make a contribution.
Descriptions and photographs should be emailed to or sent by post to the BBRC secretary, Nigel Hudson, by March 31st 2008. We will scan and return any non-digital images by return. Photocopies or scans should suffice where there are only field notes.
Email records to: secretary@bbrc.org.uk
OR send records to:
Nigel Hudson
Post Office Flat,
Hugh Street,
St Mary’s,
Isles of Scilly,
TR21 0LL
For further details contact jimmy.steele@ncl.ac.uk
The BOU decision on the taxonomy of Canada Goose can be found at:
http://www.bou.org.uk/recnews05.html
The AOU decision can be found at:
http://www.aou.org/checklist/suppl/AOU_checklist_suppl_45.pdf
There are many useful websites on Canada Goose forms many of which carry extensive further references and images. The labelling of images is rarely verified by biometrics or ringing data and there are probably many assumptions in assigning vagrant individuals to form.
The conventional taxonomy has been challenged in the seminal work by the late Harold Hanson, the first part of which has recently been published. His taxonomic approach, which proposes over 100 taxa in 6 species, is highly controversial but his documentation of skins is exceptional. From a British perspective his museum records demonstrate that there are some populations of interest to UK birders which are not particularly well represented by the conventional taxonomy. There are still no clear answers.
Posted by Surfbirds at 1:45 PM | Comments (0)
August 19, 2004
Records of non-native birds in the UK
A joint appeal from the British Ornithologist's Union and the Rare Birds Breeding Panel
The Rare Breeding Birds Panel (RBBP) has, since 1996, monitored the establishment and spread of many non-native species breeding within the UK and produces an annual report (published in British Birds) detailing, county by county, the numbers and breeding status of these species. The British Ornithologists’ Union Records Committee (BOURC) is responsible for the maintenance of the British List and the categorisation of species on the List. The two bodies work together in relation to introduced species.
In the current context, the two relevant British List categories are defined as follows:
Category C - Species that although introduced now derive from the resulting self-sustaining populations.
Category E - Species that have been recorded as introductions, human assisted transportees or escapees from captivity and whose breeding populations, if any, are thought not to be self-sustaining.
Species on Category C form part of the official British List, those on Category E do not (unless they are species on Categories A, B or C of the List).
The BOURC uses the information gathered by RBBP to decide whether a species may be eligible for elevation from Category E to Category C and makes recommendations to the Joint Nature Conservation Committee (JNCC) accordingly. In this way, changes to our national avifauna can be tracked, status changes recorded, official lists updated and information gathered that helps us better understand the effects of humans on bird populations.
It has become apparent that the data submitted on non-native species, on which the RBBP bases its annual report, are far from comprehensive and that the overall picture of the status of many species is thus incomplete. There are several reasons for this. Some observers may be unaware of the need to record introduced species. Others may show a marked disinterest in submitting such records to their county recorders and that, in turn, makes it impossible for the recorders to provide RBBP with the information required.
BOURC, RBBP and JNCC believe that it is very important to maintain an up-to-date and comprehensive view of the status of introduced non-natives species. Also, one of the key recommendations of Defra’s recent Non-native Species Working Group’s review of policy (www.defra.gov.uk/wildlife-countryside/resprog/findings/non-native/report.pdf) was to “Establish adequate monitoring and surveillance for non-native species in Great Britain.â€
We therefore appeal to all observers to submit records of non-native species seen in the wild to their county recorders.. In this context, we would ask for records of all species on Category C (except Red-legged Partridge and Common Pheasant) and Category E, but not those with the joint categorisation AC (see BOU Website for full British List).
For any non-natives falling into those categories, it would be very helpful to submit full details, including (where known) locality, date, numbers, age/sex and especially breeding activity/status. Only in this way will we be able to monitor the status of these species to the ultimate benefit of our native avifauna.
Posted by Surfbirds at 7:15 PM | Comments (0)