BB October 2014
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Report on rare birds in Great Britain in 2013 Nigel Hudson and the Rarities Committee Chairman’s introduction monorhis on Fair Isle (one of them just about This is the 56th annual report of the British twitchable), a long-staying but wide-ranging Birds Rarities Committee. Regular readers Bridled Tern Onychoprion anaethetus on the will immediately notice a small but signifi- northeast coast, a tragically short-lived cant addition to the data presented for each White-throated Needletail Hirundapus cau- species. Following the familiar trio of statis- dacutus, and a Pacific Swift Apus pacificus tics – showing the number of accepted that eventually settled to feed over a coastal records (i) prior to 1950, (ii) for the period marsh in Suffolk for two days. The aston- from 1950 onwards but excluding those (iii) ishing repeat occurrence of an Ascension for the report year – a status summary Frigatebird Fregata aquila and an early describes relative rarity and any apparent autumn Red-billed Tropicbird Phaethon trends in occurrence. Inspired by the authors aethereus were two headline events where the of our sister report on Scarce Migrants, Nigel bird concerned managed to avoid the gaze of Hudson has developed a system which is most observers, ensuring that these two more appropriate for vagrants. It is based on species maintained their position just beyond the statistics for the last 30 years (it will be the reach of British twitchers. September saw a record arrival of five Brown Shrikes Lanius updated for each report) and describes each cristatus, a tally which outstripped that of the taxon’s frequency of occurrence (its status) closely related Isabelline Shrike L. isabellinus then, for more regular vagrants, whether (of which there were four individuals, during their occurrence in Britain is increasing, October). Other autumn arrivals included decreasing or stable (the trend). Any influxes the second-best showing of Booted Warbler or breeding records are also noted, while the Iduna caligata, the 11 in 2013 exceeded only term ‘not yet determined’ is used where we by 13 in 1993; the joint-best year for Arctic know our data are incomplete. Ultimately, we Warbler Phylloscopus borealis (equalling the hope that this change will help readers derive 16 recorded way back in 1981); and 11 even more from our report, highlighting Western Bonelli’s Warblers P. bonelli, the best- more clearly the status of vagrants to Britain ever haul for this species. The highlights of and how each species has fared in recent the winter for many observers came from the years. More details are given under item 5 in far north, first with an unprecedented arrival our ‘principles and procedures’ list on p. 582. of Ivory Gulls Pagophila eburnea, and then The new status summary makes it even with the appearance of not one but two live easier to determine the highlights of 2013. Brünnich’s Guillemots Uria lomvia off the Among these, a spring Dusky Thrush Turdus English coast, the second of these remaining eunomus was a welcome precursor to an for a few days in a south-coast harbour. For exceptional summer of rarities, during which the latter species these are the first accepted many younger observers gratefully accepted records in England since 1977. The one their first opportunity to connect with birds disappointment was that the same weather that had either been absent or at least not conditions failed to bring a significant arrival lingered in recent years. These included two of Ross’s Gulls Rhodostethia rosea. Other male Swinhoe’s Storm-petrels Oceanodroma highlights in 2013 featured a good showing © British Birds 107 • October 2014 • 579–653 579 Hudson et al. 16 Britain. A good example is provided 14 by comparing the records of Citrine 12 Wagtail with those of Siberian Stone - 10 chat Saxicola maurus (fig. 1). The stone - 8 chat was definitely 6 a candidate for removal during a 4 run of good years in the 1990s, but 2 has subsequently returned to being 0 50 52 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 02 04 06 08 10 12 a genuinely rare bird. The westward Fig. 1. The pattern of occurrence of Siberian Stonechat Saxicola maurus spread of the wagtail (red) and Citrine Wagtail Motacilla citreola (blue) in Britain, 1959–2013. In these graphs, the trend is the key thing to focus on. The data are suggests that its derived from the ten-year running total, divided by ten (thus, for 1959, current increase will the figure is the cumulative total for 1950–59, divided by ten), which be sustained, but we provides a smoothed graph of typical counts. The burning question for are keeping a watch - BBRC is whether Citrine Wagtail numbers will remain at their current ing brief for now to high level or whether they might replicate the pattern shown by Siberian determine whether Stonechat. that will be the case. of a suite of passerines from northeast It was a very poor year for Nearctic gulls, Europe and beyond, with record totals of notwithstanding the fact that the total of Collared Flycatchers Ficedula albicollis and Bonaparte’s Gulls Chroicocephalus philadel- Two-barred Crossbills Loxia leucoptera and phia was a new record high for a single year. the second-best showing of Blyth’s Reed War- Spring and summer saw the biggest arrival of blers Acrocephalus dumetorum and Thrush Black Storks Ciconia nigra in recent years, the Nightingales Luscinia luscinia. 18 in 2013 surpassed only by the 23 in 1991. Citrine Wagtail Motacilla citreola had its The challenge of distinguishing wandering joint best-ever year and this species continues birds and new arrivals remains a tough one to hover desperately close to relegation from and, in reality, as in previous influxes, the the BBRC list. As alluded to in last year’s true total of different individuals may have introduction, we discussed the thresholds for been somewhat lower. Ultimately we may removing species from the list at our AGM, well overestimate the number of individuals in the wake of the recent Scarce Migrant involved in such cases but, unless there is reports in BB, which highlighted several strong evidence to link occurrences, we tend species that are close to national rarity status to err on the side of caution. We always according to our present criteria. We resolved welcome offers from those interested in using that, although these criteria are valuable, we the Committee’s data to investigate such will begin to take a more considered judge- issues further. ment and ultimately a threshold of about ten The rarest birds featured in this report are records a year, in combination with an as follows: analysis of trends in occurrence and some 1st ‘Eastern Grasshopper Warbler’ insight into changes in distribution or popu- Locustella naevia straminea/mongolica, lation increases to guide our decisions in ‘Stejneger’s Stonechat’ Saxicola maurus future. The real challenge is determining at stejnegeri what stage we relegate or readmit a species 1st & 2nd Alder Flycatcher Empidonax that may be going through a periodic alnorum increase or decline in its occurrence in 1st–4th ‘Eastern Black Redstart’ 580 British Birds 107 • October 2014 • 579–653 Report on rare birds in Great Britain in 2013 Phoenicurus ochruros phoenicuroides/ BBRC made progress with some long- rufiventris/xerophilus standing reviews in 2013, most notably with 2nd Ascension Frigatebird Fregata aquila, the Druridge Bay curlew, the results of which Indigo Bunting Passerina cyanea, Cape were published in BB earlier this year May Warbler Setophaga tigrina (Collinson et al. 2014). We have also made 2nd & 3rd ‘Moltoni’s Subalpine Warbler’ progress with the Royal Tern Sterna maxima Sylvia cantillans moltonii, ‘Eastern Yellow and ‘Eastern Subalpine Warbler’ Sylvia cantil- Wagtail’ Motacilla flava simillima/plexa/ lans albistriata reviews, although there is still tschutschensis/taivana/macronyx some work to be done before we can publish 3rd Western Orphean Warbler Sylvia our conclusions. The Subalpine Warbler hortensis, Cedar Waxwing Bombycilla complex poses a variety of issues and the cedrorum Committee’s position was set out by Andy 4th Canada Goose Branta canadensis Stoddart (Stoddart 2014). As Andy’s paper interior/parvipes, Red-billed Tropicbird emphasised, we encourage the submission of Phaethon aethereus, Semipalmated Plover all records of Subalpine Warblers from 2015 Charadrius semipalmatus, Short-billed onwards, a decision that will remain in place Dowitcher Limnodromus griseus, even if the proposed split is not adopted by Mourning Dove Zenaida macroura BOURC. We have also been able to publish 4th–6th ‘Northern Harrier’ Circus cyaneus the second and third records of ‘Moltoni’s hudsonius Subalpine Warbler’ S. c. moltonii and ‘Eastern 5th Thick-billed Warbler Iduna aedon Yellow Wagtail’ Motacilla flava simillima/ 5th & 6th Baikal Teal Anas formosa plexa/tschutschensis/taivana/macronyx, both 6th Pacific Diver Gavia pacifica, Lesser of which are already on the British List on Sand Plover Charadrius mongolus, the basis of historical (i.e. pre-BBRC) Ovenbird Seiurus aurocapilla records. These records do not require a cate- 6th & 7th Swinhoe’s Storm-petrel gorisation review as BOURC considers cate- Oceanodroma monorhis gorisation only at the level of species, not of 7th Pacific Swift Apus pacificus subspecies. We also completed the voting on 8th Hudsonian Whimbrel Numenius a series of Cackling Goose Branta hutchinsii hudsonicus, White-throated Needletail records, which have been passed to BOURC Hirundapus caudacutus for consideration. BOURC is continuing to 9th Hermit Thrush Catharus guttatus consider records of ‘Thayer’s Gull’ Larus 10th ‘Balearic Woodchat Shrike’ Lanius (glaucoides) thayeri, ‘Daurian Shrike’ Lanius i. senator badius, Siberian Rubythroat isabellinus and Pale-legged Leaf Warbler Calliope calliope Phylloscopus tenellipes. This year we have not published the statis- Sadly, no progress has been made with the tics of records processed, which have been reviews of Macaronesian Shearwater Puffinus included in this introduction since 2007.