Bird distributions are ever-shifting. Countless factors are at play, moulding species' ranges and populations on an annual basis. Some of these we have a good understanding of – habitat loss, weather conditions or climate change, as examples – yet others we will likely never fathom.
This dynamism adds many layers of intrigue to birding, and leads us to pose questions that are constantly pondered and debated. What will be the next first for Britain? Will this year produce another influx of [insert species]? And, perhaps the most pertinent of all: what will be the next to become a British breeder and go on to colonise on these shores?
It's a question that has long fascinated birders, stimulating our imaginations and generating thoughts of exotic species seen on foreign travels that could become increasingly familiar on home soil – a snapshot into what now seems an alternate reality, yet might one day become the norm.
In my lifetime, some have already accomplished this. Little Egret was a very scarce post-breeding visitor when I was born in 1990, yet is now so commonplace that it is a near-daily sight across my native Lincolnshire Fens – as it is in many areas of England and Wales. Two decades on and Great Egret and Western Cattle Egrets are now well advanced along the same path to becoming established features of our avifauna.
It is widely acknowledged that increasingly mild winters have played a significant role in the northward march of these three waterbirds, and indeed the warming climate has traditionally underpinned the 'what next?' discussion.
Northbound
Birders have historically looked to southern European species as the most likely to spread north. Purple Heron, European Bee-eater, European Serin and Zitting Cisticola are among those species long cited as the next to establish themselves here.
Some of these have now bred here on multiple occasions. Yet they have ultimately failed – so far, at least – to form a toehold that would classify them as successful colonists. The reasons for this are often unclear, although presumably population dynamics, habitat limitations and an unpredictable climate all play their part.
While many of these traditionally predicted species continue to flirt with our shores, tantalising on an annual basis, others are surging from obscurity to be in with real contention of becoming Britain's next breeding bird. Some of these would have seemed far fetched even a decade ago. You only have to look at the aforementioned egrets to see how quickly things can change.
In fact, it is another waterbird that is arguably in pole position to claim the title of our next colonist. Following in the footsteps of the egrets as its population explodes across south-west Europe, the addition of Glossy Ibis to Britain's breeding avifauna looks inevitable – and could well happen in 2022.
The rise of Glossy Ibis in Britain over the past decade now renders it the most likely species to next breed in Britain – and it could well be 2022 in which it tries to nest (Hans Glader / BIA).
The upturn in British records since the mid-2000s reflects a rise further south, especially in Spain's Doñana National Park – something that ringing recoveries have confirmed. In France, the species is prospering from the boom of invasive Louisiana Crayfish and now breeds in the north-west of the country. For example, the breeding population at Lac de Grand-Lieu went from none in 2014 to 113 pairs in 2021.
Most British records occur during autumn or winter influxes, generally involving young birds, but the past couple of years have shown a noticeable shift to resident groups for which the next step is surely to reproduce. Ausden et al (2019) suggested "there are probably very few wetlands in Britain large enough to support breeding colonies", but wetland creation and expansion has undoubtedly helped the species – both the Cambridgeshire Fens and Somerset Levels are odds on to host the first successful nesting attempt.
Gull takeover
Following close behind is another rapidly expanding waterbird. The westward spread of Caspian Gull has been well documented, with records on the up across much of western Europe as the species increases both its breeding and non-breeding ranges. Having colonised Poland in the early 1980s, then first appearing in European Herring Gull colonies in eastern Germany about a decade later, Caspian Gull's population has ballooned across both countries; it is now estimated that there are 1,800 breeding pairs in Germany alone.
The first pure pair of Caspian Gulls bred in The Netherlands in 2014, yet as many as 90 pairs were noted in 2021. This rapid westward expansion shows no signs of slowing (Arie Ouwerkerk / www.agami.nl).
There is plenty of evidence to show the larger Caspian Gull's dominance over European Herring: it has infiltrated and quickly taken over many large gull colonies in these two countries as its north-westerly spread continues, in line with a northward retreat of European Herring. As if to exemplify this, take a look at the rapid colonisation of The Netherlands by cachinnans: after first pure pair bred there in 2014, the embryonic population had rapidly risen to around 90 pairs (including hybrids) across two main colonies by 2021.
It is an increasingly familiar bird on British shores outside the breeding season, as identification awareness improves alongside a genuine expansion in numbers. Gone are the days of this being a scarce visitor – it is now an impending colonist that will surely soon try to breed in the east or south-east of England, perhaps at an inland site such as a gravel pit. The first attempt could well prove to be a mixed pairing with European Herring Gull, but the Dutch situation surely highlights that a full-on colonisation could quickly follow.
Curiously, another likely colonist isn't yet on the British list – although this is set to change imminently. Black-winged Kite has been experiencing a staggering rise across much of the Western Palearctic (WP) over the past couple of decades, spreading across Europe from populations in Iberia and the Middle East.
Could seeing Black-winged Kites on roadside wires become the norm in Britain in the future? Its rapid expansion across France certainly suggests so (Kit Day).
In France, the species first bred in 1990 and has climbed to as many as 1,400 pairs, breeding in almost every department as far north as Pas-de-Calais. Described by some as 'the Collared Dove of the 21st century', Black-winged Kite reproduces quickly and can breed almost all year round in France, often in degraded agricultural habitats that are otherwise poor for fauna. It isn't fussy in terms of nest sites and individual pairs have been known to breed successfully up to six times in a calendar year.
The species doesn't mind cold weather and sea crossings are not an obstacle, as recent reports from the Channel Islands and French Breton islands show. Records are rapidly increasing in the Low Countries to the point it is now an expected vagrant, with Belgium hosting a breeding attempt in 2020. Most extralimital birds are seen in France in April and May, so perhaps spring 2022 will produce the first British record.
Another raptor is arguably already ahead in the race to breed on British shores: Pallid Harrier must rate as among the most likely to be next as it continues its westward expansion. It has bred in numerous western European countries in recent years. After a pair successfully raised four chicks in The Netherlands in 2017 (and again in 2019), successful nesting occurred in north-west Spain in 2019 (the female being from the 2017 Dutch nest) and then in northern France, close to Calais, in 2020. As Montagu's Harrier has sadly ebbed away to the point of near-extirpation in Britain, any small harrier over a British cereal field is almost as likely to be a Pallid.
This male Pallid Harrier held territory in Lancashire in spring 2017. It could well prove the forerunner of regular breeding attempts here (Mike Roberts).
Regular hybridisation with Hen Harrier in Scandinavia shows that the British uplands – the domain of our imperilled Hen Harrier population – should not be ignored as potential Pallid territory. Evidence so far hints that it might even be the most likely spot for a first nesting attempt, even if that ends up being a mixed pairing with Hen Harrier. In April-May 2017, a male Pallid displayed over a Lancashire moorland for three weeks, and then a male took up residence in Co Limerick, Ireland, in May-June 2021, attempting (but failing) to pair up with local female Hen Harriers.
Welcome warbler
While there is little doubt that the upturn in records is in part due to improved identification awareness, Blyth's Reed Warbler is clearly a species on the up in northern Europe and it will surely soon breed in Britain. Wintering across the Indian subcontinent and breeding in a broad range across much of Siberia and west into Scandinavia, it has increased considerably in southern Norway and bred in The Netherlands for the first time in 2021, when a pair raised at least two youngsters on Texel.
Less than a decade ago, Blyth's Reed was virtually unknown as a spring visitor to Britain – at least away from the Northern Isles – yet in recent years a number of territorial males have been found in song, with several of these well inland or in suitable breeding habitat, and lingering for significant lengths of time in the early summer period.
Singing Blyth's Reed Warblers, such as this one in Lincolnshire in June 2020, are increasingly frequent in Britain (Pete Garrity).
This reached a peak in 2020, when in excess of 30 birds were found across Britain in May and June. Although fewer appeared in 2021, a handful nonetheless held territory and this appears now to be the norm as opposed to the exception it was just five years ago. It is perhaps not all that fanciful to speculate that Blyth's looks set to become more established on these shores than the closely related Marsh Warbler, a species that has long ebbed and flowed as a nester here but has always remained rare.
Another new-age option, but rather more fanciful, is Rosy Starling. Like those species already covered, this is a bird that few would have considered as a remote possibility for breeding in Britain even a decade ago. It is a warmth-loving and highly nomadic passerine whose range and breeding success fluctuates significantly in response to weather conditions and food availability.
Yet while its nomination here might seem more towards the 'wildcard' end of the spectrum there is little doubt that westward influxes are on the increase, in terms of both frequency and volume. Spectacular arrivals in three of the past four summers dating back to 2018 culminated in the first successful breeding in France in 2020, when up to 15 nests produced young in the south-east of the country, as well as record arrivals in Britain in 2020 and again in 2021.
It is likely that, at this time, Britain fails to support the climatic niche required by this species, and it is still an optimistic nomination as a UK breeder – but as warming continues, these shores will presumably become increasingly suitable.
Rosy Starling is an optimistic shout for a future British breeder, although the successful nesting of up to 15 pairs in southern France in 2020 hints that it may not be too fantastical to imagine such an event occurring in Britain one day (Aurelien Audevard).
American invaders
The potential colonisation of Nearctic species on this side of the Atlantic is something that truly fascinates birders. Two or three decades ago, the obvious nomination would have been Ring-billed Gull. And although a number of mixed pairs with Common Gulls have been observed (and the appearance of several hybrids confirmed that breeding was successful in some instances), a pure pair was never seen.
The recent demise of Ring-billed in Europe is well documented to the point that it is verging on becoming a true rarity once more, rather than the next colonist. The species ultimately failed to achieve what Lesser Black-backed Gull has managed in the other direction in becoming an established part of North American avifauna, although it certainly came close.
So, as a more extravagant suggestion, what about Ring-necked Duck? This diving duck is on the rise in Europe – especially Britain and Ireland, where numbers have rocketed in recent winters – reflecting a gradual population increase across its native North America. A number of hybrids with Tufted Duck evidently point towards mixed pairings in Europe, so is it all that far-fetched to think that a pure couple could soon breed on a remote Scottish loch? As if to demonstrate the point, a pair was observed in suitable habitat on a Highland waterbody for at least a week in mid-June 2013, although no breeding behaviour was noted. All it needs is for another pair to go a step further …
Is it really that fanciful to think that Ring-necked Duck might breed here in the future? Records have increased considerably in recent winters in line with a rising population in its native North America, with flocks such as these in South Wales in February 2022 becoming more familiar (Paul Roberts).
Based on current trends, these are among the most anticipated species to breed next in Britain – varying from the 'near-certain' (Glossy Ibis, Caspian Gull) to the 'unlikely' (Rosy Starling). Of course, nothing is guaranteed in nature and history has taught us that predictions for the next colonist often turn out to be wrong. At various points, the establishment of Common Rosefinch, European Serin and numerous others in Britain has seemed inevitable, only to fade away again.
Two further species to consider – albeit a little further down the line – are Western Swamphen (increasing rapidly and spreading north in France) and Elegant Tern (a pure pair bred in France for first time in 2021), and there will be no doubt others that come into contention during the next decade or two. The key, as always, is to keep an open mind and remember that predictions are never an exact science!
Acknowledgements
Thanks to Hugo Touzé, Joachim Pintens, Mars Muusse and Ronald Klein for sharing their expertise.
References
Ausden, M, White, G, and Santoro, S. 2019. The Changing Status of the Glossy Ibis Plegadis falcinellus in Britain. International Glossy Ibis Network.
Ławicki, L, and Perlman, Y. 2017. Black-winged Kite in the WP: increase in breeding population, vagrancy and range. Dutch Birding 39: 1-12.
North American Breeding Bird Survey trends. Accessed via www.mbr-pwrc.usgs.gov/
van Busekom, R, Kok, D, and Steijn, L. 2021. Struikrietzangers broedend op Texel: nieuwe broedvogel voor Nederland. Dutch Birding website.
- This article was first published in the April 2022 edition of Birdwatch.
