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‘Central Asian Lesser Whitethroat’ Curruca curruca halimodendri 

Alan Harris

Abstract DNA-based birding is the new ‘New Approach’ to bird identification. Here, we review some of the contributions that genetic analysis has made to our understanding of bird migration and identification, predominantly focusing on work undertaken at the University of Aberdeen Wildlife Forensics laboratory, in collaboration with birders and ringers across Europe. Since 2012, genetic analysis of 170 migrant Lesser Whitethroats Curruca curruca has shown that ‘Siberian Lesser Whitethroat’ C. c. blythi is a rather common migrant in western Europe in mid to late October, occasionally overwintering, and that the ‘Central Asian Lesser Whitethroat’ C. c. halimodendri, while showing a similar temporal pattern of occurrence, is much rarer. No genetically confirmed ‘Desert Lesser Whitethroats’ C. c. minula have occurred in Europe, but the confirmation by Peter de Knijff’s lab of a ‘Hume’s Whitethroat’ C. althaea in the Netherlands offers hope that there are still new discoveries to be made. We also report on the genetic analysis of an apparent Italian Sparrow Passer italiae seen in Devon in 2017–18 and suggest that it is not a genuine Italian Sparrow but may have arisen from the hybridising Spanish/House Sparrow populations in North Africa. DNA-based birding is discussed in the context of the history and future of bird recording, and in terms of birders’ experiences of their hobby.


It is sometimes difficult to look at the future of birding in a positive light. Bad news arrives daily, with the climate crisis driving catastrophic social upheaval and pressure on habitats and the wildlife they support. In the absence of any appetite for lifestyle change at a corporate, governmental or individual level in the industrialised countries that are causing the problem, one has to hope that some technological solutions to climate change will be sufficiently effective to ameliorate the worst of the damage; because, of course, technology does keep moving on. Many of these new technologies have found their way, one way or another, into birding. And, as with most new technologies, the early years of adoption can both move us forward and contribute new complications to what should, on the face of it, be a simple and enjoyable hobby.

Change, whether new technologies, new identification criteria, new taxonomies,or new assessments, is a part of birding, yet can be threatening or counterproductive if the pace outstrips the ability of birders to buy into and be carried along by that change. The use of molecular biology in everyday birding is an example. I previously wrote (Collinson 2017) about the impact of genetic DNA analyses for our understanding of bird identification, bird migration and the evolutionary relationships between birds. That paper highlighted some of the gains in knowledge that we have achieved by performing genetic analyses on migrant birds, and argued that such technology adds value to, and complements – rather than supersedes – ‘normal’ birding. 

This article, a summary of the Bernard Tucker Memorial Lecture from 2020, aims to update and expand on some of the issues raised in Collinson (2017), and to ask where birding is going next. That it should be dedicated to Bernard Tucker seems appropriate, given that the man himself was such an enthusiastic pioneer of evidence-based advances in birding, and yet at the same time was so careful to carry people along with his ‘revolution’. 

‘Always ready for hard, tough pioneering, and open to new ideas and experiences,’ his obituary read, ‘he possessed the judgement, the caution and the practical sense to avoid rash leaps and to consolidate thoroughly and methodically as he went along. He was the least dramatic of men, but he did much to bring about a revolution in ornithology and to guard it against the reaction which awaits a revolution if it goes too far and too fast’ (Brit. Birds 44: 46).

The news that most bird species (and many subspecies) can be identified fairly routinely by analysis of a short fragment of their mitochondrial DNA is not news to most birders, nor will it come as a surprise that DNA can be isolated from the tiniest of feathers, mouth swabs, faeces or drops of blood or other tissue. In fact, with modern sequencing techniques, we don’t even need this much contact with the bird: we can sieve the air that they breathe or the water they have bathed in (or worse!) and establish, with a bit of work, which species were there. Although not yet common in the field of ornithology, ‘environmental sampling’ is impacting heavily in other fields of science and conservation. Want to survey a pond for Great Crested Newts Triturus cristatus? No longer do you have to go through the tedious twentieth-century process of wandering around at night with a torch actually looking in the pond for newts. A cup of pond water can be taken to the lab and, for a price, all of the DNA in the water can be sequenced. If Great Crested Newts were there, science will find them. If a Baikal Teal Sibirionetta formosa was there, science will find that too. 


486. The future of birding! Thom Shannon isolates DNA from feathers of an unidentified bird, while his colleagues look on anxiously. A silly and painfully staged scenario, attempting to illustrate the potential disconnect between normal and forensic genetic birding; University of Aberdeen, North-east Scotland.

Marielle Piber

Is this part of our dystopian birding future – the disconnect between the technology and the practical and financial limitations of the majority of birders who just want to watch birds? Thirty years ago, the editors of Not BB saw it coming, writing a spoof article about Scottish Crossbill Loxia scotica. They suggested that this species could be carrying an extra fragment of DNA that Common Crossbills L. curvirostra do not, and ended with the expectation that this new character would allow birdwatchers to confidently and easily identify birds in Scotland (fig. 1). It was funny because it was (it seemed) so ridiculous. Surely birding could never get this stupid? And yet, at the time of writing, the forlorn hope that such a fragment of DNA will some day be found is our only remaining option for ever being able to identify Scottish Crossbill (Lewis and McInerny 2022).


Fig. 1. Identification of Scottish Crossbill Loxia scottca according to the comedic geniuses at Not BB. ‘Genomic DNA is cut up and run out on a gel revealing an imaginary extra DNA fragment in Scottish Crossbill.’

Such has been the impact of DNA analysis in birding, driven by analyses in our labs at the University of Aberdeen and by similarly birding-oriented labs abroad, that we are no longer surprised to see scenes like that in plate 487, where birders are sent out to scoop up droppings or shed feathers from an interesting migrant bird in the hope that its identification can be confirmed in the lab.


487. ‘What’s shit is history’? The comedic and increasingly frequent spectacle of birders being sent out to scrape faecal samples onto leaves, tissues or the page of a notebook. Here, a faecal sample from a Siberian Stonechat Saxicola maurus is being collected; Northwich, Cheshire & Wirral, January 2020.

Mal Curtin

Why do we put up with such silliness? The most obvious answer is that we learn important things, at little or no cost or inconvenience to the birds themselves. For instance, even within our own lab, which is one of several doing similar work around the world in collaboration with birders and ringers, we have been able to achieve or confirm identification of several national and Western Palearctic firsts. These have included the Western Palearctic’s first Pale-legged Leaf Warbler Phylloscopus tenellipes (Headon et al. 2018), Eastern Yellow Wagtail Motacilla tschutschensis (Collinson et al. 2013), Audubon’s Shearwater Puffinus lherminieri (Flood et al. 2020) and Short-tailed Shearwater Ardenna tenuirostris (Archer et al. 2021). The list also includes the first British records of ‘Rough-legged Hawk’ Buteo lagopus sanctijohannis (Bosisto et al. 2021), ‘Eastern Grasshopper Warbler’ Locustella naevia straminea (Miles et al. 2015), Eastern Subalpine Warbler Curruca cantillans and Western Subalpine Warbler C. iberiae (Collinson et al. 2014), Stejneger’s Stonechat Saxicola stejnegeri (Cade & Collinson 2015) and Siberian Stonechat S. maurus (Collinson & McGowan 2012). We have also been able to identify multiple other national firsts for countries around Europe and Asia (e.g. Sweden’s (at the time) first confirmed Eastern Subalpine Warbler (Menzie et al. 2015) and Poland’s first ‘Siberian Lesser Whitethroat’ C. curruca blythi (Polkowski et al. 2022)). 

Aside from bumping up national and personal lists, we have learnt new things about the migration and identification of birds, and have been able to resolve long-standing problems and controversies. For example, when a number of apparent Elegant Terns Thalasseus elegans – a species restricted almost exclusively to the Pacific coast of the Americas – started not only turning up in Europe from the 1990s onwards, but also breeding in some Sandwich Tern T. sandvicensis colonies on the coasts of France and Spain, there was considerable debate around what these birds where. Were they really Elegant Terns, or hybrids with or between other ‘crested’ terns? Analyses of 13 different genes from tiny blood samples or feathers from some of the breeding birds and their offspring, conducted in two labs in Europe, were able to confirm that, amazingly, they were all genuine Elegant Terns (Dufour et al. 2017). Without genetic analyses, resolution of the identity of these birds as Elegant Terns would have had to wait until a ringed or radio-tracked bird from the Pacific reached Europe. We could have been waiting a long time.


488. Male Elegant Tern Thalasseus elegans attempting to mate with female Sandwich Tern T. sandvicensis. Although hybrid young have been produced from such couplings, the good news is that, as determined from genetic analyses, if a bird looks like Elegant Tern, you can be confident that it is one; France, June 2005.

Matthieu Vaslin

Lesser Whitethroats
In Collinson (2017), the possibility that genetic analyses could resolve the status of Lesser Whitethroat C. curruca subspecies in Britain and elsewhere in northwest Europe was discussed. Which subspecies of Lesser Whitethroats may be occurring here has been a conundrum for birders for some time. Nominate curruca is the breeding form, but migrant birds in late autumn or winter could be from anywhere, and may include the various Asian-breeding subspecies. Luckily, all subspecies can be differentiated on the basis of mitochondrial DNA (Olsson et al.2013). Since 2017, the trickle of Lesser Whitethroat feather and faeces samples sent to Aberdeen for analysis has become, if not a flood, then at least a shower, with (at the time of writing) DNA from 170 birds successfully sequenced. This has given us a pretty good idea of what is going on with migrant birds in Britain and northwest Europe (fig. 6). From birds analysed in our lab, we can say that nominate curruca arrives in Britain in April and May, with autumn migration from August onwards, peaking in September and tailing off through October and November. This is entirely as expected and is consistent with observations of Lesser Whitethroat migration across Europe. There are, of course, many Lesser Whitethroats around in June and July, but there are generally no worries regarding the subspecific identification of birds on the breeding grounds, and we received extremely few samples through the summer months.

By far the commonest of the extralimital subspecies of Lesser Whitethroat is Siberian Lesser Whitethroat, which has a breeding range that spans much of northern Asia, overlapping with that of many other autumn scarcities such as Yellow-browed Warbler Phylloscopus inornatus, Red-flanked Bluetail Tarsiger cyanurus and Olive-backed Pipit Anthus hodgsoni, and would perhaps therefore be expected to reach Britain with some regularity, though is it perhaps a surprise as to how many are occurring in Britain each year. Birds genetically identified by us as blythi are moving through Britain and neighbouring countries in good numbers during September, alongside nominate birds, followed by a massive peak in numbers in October (fig. 2), when they are the commonest Lesser Whitethroat subspecies identified in our lab. There is a sharp drop-off in November and December, though some birds are found overwintering in January–March, often appearing at bird tables in suburban gardens. One record from May suggests spring vagrancy, or a return migration.

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Fig. 2. Numbers of genetically confirmed Lesser Whitethroat Curruca curruca subspecies in northwest Europe by month, 2012–22.

The numbers present some questions, not least whether the massive October peak in samples of blythi means that most Lesser Whitethroats occurring in Britain and northwest Europe at this time are in fact ‘Siberian’. We urge caution because the sampling is, of course, non-random – there is a tendency for samples to get sent to us for analysis because ringers and birders suspected that the bird looked odd and/or was suspected of being ‘eastern’. This is a tricky call to make – remember, Shirihai et al. (2001) proposed synonymising nominate curruca and blythi because they considered there were no consistent plumage details to separate them. Tentative identifications of ‘potential eastern’ are, in our experience, made on the basis of birds having the brown of the mantle creeping up the nape and even onto the crown, and/or a larger than normal amount of white in the outer tail feathers, or alternatively of upperparts being generally ‘sandy’, ‘sandy grey’, ‘pale’, or any combination of these three. Birds where the grey ear-covert patches are indistinct, that look small or that have particularly small-looking bills may also be called out as ‘eastern’. The plain fact that a bird is occurring late in the autumn is often also enough of a trigger for feathers or faecal samples to be sent to the lab for subspecific identification. So, there is a potential bias for samples from unusual birds to be sent to the lab, and maybe the peak of October blythi is an artefact of that. However, random sampling of birds at ringing sites on the east coast of England, and in northern Scotland, where a sample from just about every Lesser Whitethroat that drops a feather or a poop in October will make its way to the lab, also provides a high proportion of autumn blythi. We would need more systematic sampling to determine exactly what proportion.

The other consequence of genetic sampling of Lesser Whitethroats has been the addition of ‘Central Asian Lesser Whitethroat’ C. c. halimodendri to the British List (BOU 2020). This subspecies remains rare but, to date, we are aware of 15 that have been genetically identified in northwest Europe (11 in Britain). The monthly distribution pattern appears similar to that of blythi, with one September record (from Spurn, Yorkshire) followed by a modest peak in October (eight records), which tails off through November (three records). There are also three records in winter. This subspecies breeds in southeast Russia through Kazakhstan, Uzbekistan and Turkmenistan to northwest Mongolia.

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489a–d. A genetically confirmed ‘Siberian Lesser Whitethroat’ C. c. blythi (a & b), Nanjizal, Cornwall, October 2018; and a genetically confirmed ‘Central Asian Lesser Whitethroat’ C. c. halimodendri (c & d), Spurn, Yorkshire, October 2018.

Kester Wilson

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Tim Jones/Spurn Bird Observatory

With so many birds having been genetically identified, does knowledge of which subspecies these birds were shed light on key identification criteria for the taxa? At this point, there does not appear to be any smoking gun, with side-by-side comparisons of halimodendri and blythi suggesting that the differences from nominate birds are subtle and variable. Photographs of genetically identified birds caught for ringing show that blythi have brown feathering on the nape, which extends onto the rear-crown, giving them an overall browner ‘feel’ than nominate birds, for which there is usually a relatively sharper distinction between the brown mantle feathering and the grey nape (plates 001–004). There is a tendency for the upperparts to be paler and any bird for which the description includes the word ‘sandy’ usually turns out to be blythi. This is striking on the first British record – from Fair Isle on 3rd October 1921. The specimen (NMSZ 1921.119.1) (plate 490) is now at NMS Royal Scottish Museum, and we were able to confirm its identity genetically – representing an exceptional bit of spotting by Eagle Clarke and colleagues over a century ago. 


490. The first British Siberian Lesser Whitethroat, Fair Isle, 3rd October 1921. Although time may have caused some fading, this individual’s ‘sandy’ appearance certainly conforms to that of many, but not all, genetically confirmed blythi.

National Museums Scotland

Birds genetically identified as halimodendri are a mixed bag when it comes to appearance, but tend to look small with a short bill and rather short primary projection. There is usually some brown feathering extending from the nape onto the crown, but generally not to the same extent as in blythi. The upperparts can appear pale but, in our experience, are generally a colder, earthier tone rather than the warmer or sandier tones shown by nominate birds and blythi respectively. The amount of white on the inner edge of the outer tail feather is variable and cannot be used to distinguish this taxon. Lighting conditions can affect the apparent coloration of all taxa. 

Readers may be aware that there are two genetic subtypes (clades) of halimodendri, referenced as ‘2a’ and ‘2b’. Type 2a has been found breeding in Kazakhstan but type 2b is known only from migrating birds in Kazakhstan and Xinjiang, with an unusual – possibly extralimital – record from eastern China. Most records in northwest Europe have been of type 2b, with the only type 2a that we are aware of having been a bird in Aberdeen, North-east Scotland, in December 2004. This bird – the only one for which any of the authors have seen more than just a couple of feathers! – looked particularly cold and pale in the field, even compared to typical type 2b birds. Prior to genetic analysis, there were several claims of small, greyish birds as putative Desert Whitethroat C. minula, which has a breeding distribution thought to be restricted to China. Given that, to our knowledge, no Desert Whitethroats have been identified genetically anywhere outside China, it seems likely that previous claims of birds ‘showing characteristics of minula’, were in fact more likely halimodendri

Bearing in mind that each of these genetic identifications costs money and takes time, what have these 170 analysed birds taught us? We have a pretty good idea of which subspecies are occurring in northwest Europe, and when. We have a better idea of what birders and ringers should be looking for, and we know that blythi is a rather common autumn passage migrant. Although it is not inconceivable that the occasional nominate bird does overwinter, no samples from overwintering nominate birds have ever been sent to us for analysis. Any overwintering bird is much more likely to be one of the two eastern subspecies proven to occur in Britain. This is by no means the end, though: a Hume’s Whitethroat C. althea was recently sequenced at Peter de Knijff’s lab at the Leiden University Medical Centre, the Netherlands ( The bird was the first Dutch record of this relatively distinctive species, and we at Aberdeen hope to see Britain’s first record one day, too! 

Italian Sparrow
Spanish Sparrow Passer hispaniolensis is a long-standing resident in Europe, with a patchy distribution centred around the Mediterranean Sea, extending into western and central Asia. The House Sparrow P. domesticus is a more recent colonist, arriving in Europe from the Middle East with the spread of grain farming, starting about 6,000 years ago. Hybridisation between different bird species is common but does not by itself lead to blurring of species boundaries, as the hybrids themselves often prove to be less fit than their parent taxa. In the central Mediterranean region, however, something unusual happened: hybridisation between House and Spanish Sparrows produced an intermediate species that breeds true, with a DNA makeup that is a mixture of the two parent species but which is stable and maintained in spite of ongoing levels of hybridisation with both Spanish and House Sparrows in their contact zones in the south and north respectively. This is an uncommon (in birds, at least) case of speciation by hybridisation, and has led to most of Italy (spilling across the border into neighbouring countries), Malta, Corsica and Crete being populated mostly by what we know as Italian Sparrow Passer italiae. So far so good; but it is also known that modern-day hybrids between Spanish and House Sparrows in places away from the central Mediterranean can look like Italian Sparrow, too. Furthermore, levels of current hybridisation between Spanish and House Sparrows in parts of North Africa, and the crossing of hybrids with each other and back to the parent species, continue to give a high level of variety in the sparrows there (Elgvin et al. 2011; Hermansen et al. 2011; Trier et al. 2014).

When an apparent Italian Sparrow turned up in gardens in East Budleigh, Devon, in November 2017 (plate 491), it created a problem. Not only was it an extremely unlikely (natural) vagrant, but there were also valid doubts over whether a ‘genuine’ Italian Sparrow could be identified in an extralimital context on plumage alone. Alternative explanations included the possibility that it was a hybrid between a House Sparrow and a vagrant Spanish Sparrow, or ‘just’ a weird House Sparrow. Could a genetic analysis help? Steve Waite, under licence and with the householders’ permission, was able to trap the bird and take two small contour feathers from its underparts for DNA analysis in the spring of 2018 (see


491. Male sparrow Passer sp., resembling Italian Sparrow P. italiae (right) with a male House Sparrow P. domesticus, East Budleigh, Devon, December 2017.

Chris Townend

Most bird species, and many subspecies, are fairly easy to identify genetically because they evolved at least a few tens of thousands of years ago and have diverged genetically from their nearest relatives to a degree that their DNA is easily distinguishable from that of any other bird. Not so for the Italian Sparrow, which arose a relatively very short time ago from the coalescence of the DNA genomes of its two ‘parent’ species and hasn’t had time to genetically diverge from the parental DNA. Genetic analyses have shown that every version of a gene (allele) in Italian Sparrows is either the same as that of House Sparrow or Spanish Sparrow or a combination of the two (remember, sparrows, along with the rest of us, carry two copies of most genes, one from each parent). Nevertheless, there are a few genetic clues that help us to unravel the mystery. Genomic analyses have shown that Italian Sparrows from Italy nearly always carry an unusual variant of House Sparrow mitochondrial DNA ND2 genes nicknamed ‘dom2’ (Ait Belkacem et al. 2016). Furthermore, some of the reasons why Italian Sparrow does not merge freely with House and Spanish Sparrows appear to be due to selection of sex-linked genes on the Z chromosome, and it has been shown that Italian Sparrows nearly always carry two copies of the ‘Spanish’ allele of a gene called CHD1Z (Elgvin et al.2011).

In our initial screen of genes from the East Budleigh sparrow, its credentials soon took a knock. Its ND2 mitochondrial DNA was the ‘standard’ House Sparrow allele (‘dom1’), and it was carrying two copies of the ‘House’ allele of CHD1Z, rather than the Spanish alleles we were hoping for had the bird been a ‘real’ Italian Sparrow. It had failed its first two key tests. However, the situation, it turns out, is more complicated than just that. To start with, Italian Sparrows from Malta nearly always carry the ‘dom1’ ND2 allele (Ait Belkacem et al. 2016; fig. 3). Furthermore, Runemark et al.(2018) showed that not all Italian Sparrow populations are genetically comparable. The East Budleigh bird was, according to our research, unlikely to be an Italian Sparrow from Italy, but could it be from one of the Mediterranean Islands?


Fig. 3. ND2 alleles of European and North African sparrows. From Ait Belkacem et al. (2016). Alleles are colour-coded for ‘Spanish’ Passer hispaniolensis (red and orange) and ‘House’ P. domesticus (blue, yellow and green), with green representing the ‘dom2’ version usually present in Italian Sparrows P. italiae, at least those from Italy.

Runemark et al. (2018) performed a full genomic analysis of Italian Sparrows from Sicily, Corsica, Malta and Crete, and revealed an unexpected twist. When we think about how speciation by hybridisation happens, we think of widespread hybridisation by the two parent species giving intermediate offspring that breed together to form a hybrid swarm of generations with variable plumage, all being different mixtures of the two parental sets of DNA, which over time, perhaps due to selection for particular gene and plumage combinations, eventually all share the same, mixed gene and chromosome combinations and all look the same. At this point, when the hybrid population all has the same DNA combination and has coalesced on a stable plumage pattern – and is breeding true without merging back into the parent species – we can infer that speciation by hybridisation is complete. What the Runemark paper showed was that this process of coalescence had most likely happened independently on four occasions – on Sicily, Malta, Corsica and Crete – and that, although the Italian Sparrows on these different islands look the same, they in fact had four different functional, stable hybrid combinations of House and Spanish Sparrow gene alleles. So, the gene combinations we might expect on Italian Sparrows from Italy would not necessarily hold for Italian Sparrows from the Mediterranean islands. In fact, the only smoking gun for Italian Sparrow identification appears to be that, across the 20,000+ genes that sparrows have, one of them, a gene called WNT4, is always represented by two ‘Spanish’ alleles in all populations of Italian Sparrow. And WNT4 in the East Budleigh individual? Two House Sparrow alleles! The bird in Devon appeared, genetically at least, to be no sort of Italian Sparrow at all. When we combined genetic data across all of the genes we sequenced and drew a phylogenetic tree, the East Budleigh bird fell squarely within genetic House Sparrows (table 1; fig. 4) – unsurprising, really, since all the genes we tested turned out to be the House Sparrow allele. 

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Fig. 4. Phylogenetic tree based on genetic analysis of the East Budleigh sparrow.

The problem is, of course, that the Devon bird looks exactly like an Italian Sparrow. If it isn’t one, then what is it? First-generation hybrids between Spanish Sparrow and House Sparrow can look extremely Italian Sparrow-like, and there have been some Spanish Sparrows recorded in Britain that were seen romancing the local House Sparrows. There is a possibility, therefore, that the East Budleigh bird was the offspring of one such couple – but the genetics did not bear that out. Such a first-generation hybrid would be expected to have one Spanish and one House Sparrow allele of every nuclear gene, whereas the East Budleigh Sparrow demonstrated only House Sparrow alleles. Another possibility is that it was a bird from North Africa, where there is a fluid and complex situation with ongoing hybridisation between Spanish and House Sparrows, yielding a complex of Italian Sparrow-like birds, particularly in Algeria and Tunisia. Ait Belkacem et al. (2016) were able to show that these recent hybrids were genetically diverse but predominantly carry the House Sparrow ‘dom1’ ND2 allele. There seems to be no reason why a bird from the mess of North African hybrids could not carry entirely House Sparrow alleles for the genes that we have sequenced.

To determine exactly what the identity of the East Budleigh sparrow was will require a full genomic analysis. Its identification as a bona fide Italian Sparrow is, however, dead in the water. On the basis of current evidence, we suggest that it was a (presumably ship-assisted) bird from the North African Spanish/House Sparrow hybridising populations.

The weird origin and genetic status of the Italian Sparrow continues to create problems for taxonomists and records committees. If there have been (at least) four separate independent stabilisations of hybrid genomes on Corsica, Sicily, Malta and Crete, then we really should regard Italian Sparrow not as one species but as at least four species – morphologically identical but genetically distinguishable. At that point, for the purposes of birding, we may as well pretend that Italian Sparrow doesn’t exist at all!

The importance of gathering all the evidence
In the example of the East Budleigh Sparrow above, we can show how DNA analysis can inform but not always solve identification conundrums. Irrespective of how inconvenient or inconclusive the evidence may be, Bernard Tucker would have understood the importance of gathering all the evidence. Tim Melling described Tucker’s tenacity in his review, on behalf of BOURC, of the British records of Moustached Warbler Acrocephalus melanopogon (Melling 2006). Commenting on the (now rejected) record of a breeding pair in Cambridgeshire in 1946, Tucker opined: ‘In the nature of the case, the nest cannot be very far from where the young were seen, and since we know it is there it ought to be findable. I therefore feel strongly that as soon as the vegetation has died down a little, no pains should be spared to find the nest. Every bit of the reeds and other aquatic vegetation within a reasonable distance should be combed out, even if it means some deep wading, and a similar determined effort should be made to find what nests exist in the brambles, etc.’ One has to admire his willingness: first, in the best tradition of BB editors, to send other birders out up to their knees in sludge to satisfy his own intellectual curiosity; and secondly, and most importantly, because he was clearly troubled by some aspects of the descriptions and recognised that, unless the nest was found, the record would never be above doubt. Bernard Tucker would certainly have wanted DNA evidence, had the technology to obtain it been around at the time.

To paraphrase the Karate Kid, ‘too much of the good stuff is the bad stuff’. It would be naïve not to consider mission creep in DNA analysis and ask what the future holds. In the old days, specimen records were the norm for recording of scarce or rare birds, both in Britain and internationally. As concerns for animal welfare and conservation increased, and perhaps concomitant with rises in living standards and an increased level of empathy with the natural world, specimen collecting pretty much died out, to be replaced by artwork, sight records and descriptions in the post-Second World War period (fig. 5). The 1980s saw the rise of the New Approach to Identification (Grant & Mullarney 1989), with better optics facilitating the field scrutiny of feather tract details, and the SLR camera allowing a gradual rise in grainy–excellent photographs of many scarce and rare birds. With the invention of the digital camera, everyone became a photographer, and now most rarity reports are supported by digital images. One wonders what future generations will make of the ‘badlands of historical uncertainty’ from 1945–2000, where many important bird records exist supported only by subjective descriptions and lack any objective evidence in the form of a specimen or photograph. Add to this the inevitable march of progress and the use of DNA to support, or as the basis of, identifications. Most birders have the ability to put their phone’s camera up to the lens of their telescope and get a record shot of whatever they are looking at. Very few have the ability to perform a genetic analysis, and in an environment where genetic analyses of some birds may now be considered essential to their acceptance, this has the potential to take some of the fun out of birding.


Fig. 5. From ‘what’s hit is history’ to the future of bird recording. The figure traces the history of bird recording, from science to citizen science to ‘fun’ science, and projects to a future where, amongst other things, routine DNA sampling and a growing suspicion of sight records unsupported by objective evidence take the fun out of birding. The lines in the future show possible scenarios – will DNA recording plateau, limited by the number of labs with the interest and inclination to do it? Or will it become more prevalent to the extent that it impacts on sight recording and the ability of birders to engage with their hobby?

Martin Collinson

But let’s not, for the moment, invent or anticipate problems that don’t yet exist. Genetics may have taken the fun out of seeing ‘Eastern Stonechats’, but it is adding immeasurably to our understanding of bird migration, systematics, ecology and conservation. It is not the intention that birders should await the white smoke rising from the chimneys of the University of Aberdeen in order to find out what they have seen. Luckily, most birds are pretty easy to identify the old-fashioned way. DNA analyses add an extra level of ‘gathering all the evidence’ that itself can add to the enjoyment of the hobby and advance our scientific understanding of what birds are out there and what they are doing. Every DNA identification costs about £30, and excessive numbers of samples could bankrupt the most open-handed of labs. DNA labs rely on the skill, experience and discrimination of birders and ringers to realise where the identification grey areas are, and which birds are a priority for genetic work. It is a collaboration, and we should be excited about the discoveries that have been made to date, and those that will undoubtedly be made in the future.

None of this would be possible without the heroic efforts of the birders, ringers, ornithologists and general public who go out of their way to collaborate with our genetic laboratory and other labs. We are grateful to The Sound Approach for their continuing support, and to the undergraduate students who come to us for training and leave with a previously unsuspected fondness for Chiffchaffs.

We are also grateful to the many people who have contributed to our fundraiser ( All money is used to support genetic identifications, such as those laid out in this paper.

Please remember that the unlicensed removal of feathers from birds is illegal in the UK and our lab is not able to accept material that has been collected in breach of law or national ethical regulations, neither from within the UK nor internationally.

Ait Belkacem, A., et al. 2016. North African hybrid sparrows (Passer domesticusP. hispaniolensis) back from oblivion: ecological segregation and asymmetric mitochondrial introgression between parental species. Ecol. Evol. 6 (15): 5190–5206.

Archer, P., et al. 2021. Short-tailed Shearwater at Tramore, Ireland, in June 2020. Dutch Birding 43: 183–197.

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J. Martin Collinson Tereza Senfeld and Thomas J. Shannon, c/o School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen AB25 2ZD; e-mail [email protected], [email protected] and [email protected]

Steve Waite, Seaton, Devon; e-mail [email protected]


Martin Collinson is Professor in Genetics at the University of Aberdeen and runs the Wildlife Forensic Genetics laboratory at the Institute of Medical Sciences. Tereza Senfeld and Thom Shannon are PhD students working with The Sound Approach on bird genetics. Steve Waite is a birder, ringer and moth-er who patches the Axe Estuary, Devon.

Issue 12
Start Page: 
J. Martin Collinson, Tereza Senfeld, Thomas J. Shannon and Steve Waite
Display Image: 
Article Series: 
The Bernard Tucker Memorial Lecture
the New ‘New Approach’ to Identification

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