Spring overshoots

Spring migration is in full swing by April, bringing with it the possibility of scarce overshoots such as Woodchat Shrike, Redrumped Swallow, Alpine Swift and Hoopoe. Matt Eade provides all the information you need to target, find and identify such specie

Overshoots are vagrants to the UK that should otherwise be on the Continent and, each spring, we are graced with small numbers of these much-anticipated species. The arrival of April fills birders with excitement: the longer daylight hours facilitate the opportunity for pre- and postwork birding, during a time when migrants are firmly on the mind. Whether you’re a coastal patchworker, an inland city-dweller or somewhere in between, it’s important to know that migrating birds can ‘spring up’ almost anywhere on passage. While searching among the throngs of common migrants – which also provide great joy – deep down each of us is pondering thoughts of digging out that scarce spring overshoot.

With each passing day during peak spring migration, when there’s constant turnover of migrants, close attention is paid to weather maps, wind directions and the goings on from the near-Continent and even further southwards to North Africa. In most cases, many of these annual spring overshoots will have migrated north from Africa where they have overwintered, rather than in southern Europe. Therefore, conditions this distance away will have an enormous effect on what could realistically arrive on our shores.

This feature will focus on the perfect weather for spring overshoots and falls, the habitats and the likely overshoots you can expect during April, along with identification advice for each species.

Rules of migration

Migration, admittedly, can be painstakingly slow and often the weather is to blame. “Was it a clear night last night?”, “Is there murk in the Channel?” or even “Is there a cold snap currently in the Alps?” are all questions raised when the going is tough and summer visitors, yet alone spring overshoots, still seem weeks away.

But, when the conditions and timings are right, it really is all systems go. Patience and repetitive visits are key to hitting the jackpot, but playing close attention to the weather can also have its advantages.

To coincide with a large fall along the south coast it is paramount that the anticyclonic conditions – which initiate such movements – don’t spiral too far north into the UK. Overcast conditions along any coastal stretches can prove particularly fruitful for finding myriad common migrants, but only if the conditions on the opposite side of the water have been favourable for a mass move – it can be that critical. In addition, light offshore winds (which can tire the birds during their journey) often ensure they rest up before heading northwards to their

breeding grounds. Optimum mornings for a maximum yield of migrants are usually when there are clear conditions overnight on the near-Continent, transforming to misty or drizzly weather along our coastline in the very early hours, grounding the migrants and creating a substantial fall. It’s important that a combination of factors at the height of migration are put into play, although predicting such events can be challenging.

Clear and calm conditions are favourable for migration. However, newly arrived migrants can be gone in a flash on making landfall, so strong is their drive to continue their tortuous journey northwards. On some mornings at the peak of spring migration very few migrants can be found at all along the coast at prime locations, emphasising the point that inland sites can be just as productive. It’s also interesting to note that, during clear and calm conditions, seawatching sites have witnessed numerous passerines (Whinchat, Common Redstart and Willow Warbler to name a few) flying in and heading high inland without taking a moment’s rest. Therefore, playing strict attention to the weather, especially if making a one-off visit to the coast to witness migration, is very much a sensible option, as on that one day where you find copious numbers of common migrants there is every possibility that a scarce spring overshoot could be lurking not too far away.

Should prolonged southerly or southwesterly airflows originating from the Sahara (intertwined with anti-cyclonic conditions spanning western Europe) be forecast, there can be fewer more idyllic conditions for highly anticipated spring overshoots. A rare event such as this, though, can prove to be a long wait, but as shown in the spring lockdown of 2020, it can be worth it. For example, when temperatures were close to breaking records and alarms of drought were radiating through the various news channels, in Sussex alone no fewer than 20 Hoopoes were recorded in April – a result of classic overshoot weather. The same could be said for the April 2014 influx of Bluethroats along the south coast – an event yet to be repeated. A south-easterly airflow also provides mirrored excitement as any east coast location can reap the rewards of abundant spring overshoots, especially those heading north to Scandinavia – (Red-spotted) Bluethroat and Wryneck, for example.

Differing airflows have their own advantages, but on the assumption that a steady south-easterly, southerly or south-westerly airflow will be dominating proceedings, it is highly likely that a different suite of scarcities is only days away from making landfall here.

Habitats

Habitat plays a vital role in locating migrants of any kind, whether common or scarce. Although coastal locations, such as Portland Bill in Dorset, can produce greater quantity or quality, inland sites can be productive, too. High hilltops scattered throughout southern England can at times be dripping in migrants, when at the same time, the coast can be eerily desolate – local conditions play a vital role again here. It’s worthwhile when on the search for migrants to avoid an area where there is a vast amount of dense cover – the birds may be there but finding them could prove problematic. When inland, scattered bushes, trees and hedgerows at distinct high points will suffice. Geological features such as river valleys can also be good searching points. However, on the coast one can be spoilt for choice. Headlands, as well as protruding outwards due to their geology, are obvious land features themselves and attract greater numbers, while the habitat is generally sparser than low-lying coastal positions.

Species

We will begin with the birds which tend to overshoot when the airflow is chiefly southerly or south-westerly.

Starting with the obvious, Hoopoe is the classic contender for a spring overshoot find. It’s an exciting discovery

regardless of its status in the UK.

It’s immediately obvious if the views are favourable; however, it can be exceptionally shy and obtaining good views can be frustrating, so getting to grips with its distinctive undulating flight pattern, barred upperwing and broadly rounded wings will mean an unco-operative bird will still make the grade.

A classic spring overshoot and a likely contender for a fly-over record is European Serin. Annually, birds tend to filter in during late March and throughout April. Most reports usually state ‘flying along the coast’, which increases the chances of finding one when birding a coastal location. Although finding a fly-by serin may appear a difficult task, the birds have a helpful way of announcing their presence. A relatively short, but highpitched descending trill is the most helpful identifiable feature of a flying individual, although if the views are good, a short, forked tail and a lemoncoloured rump may be seen. If viewing a perched bird, its suffused yellow breast, dark streaking on the flanks and chubby bill are again helpful pointers. Spring birds can also be heard giving their ‘jangling keys’ song; learning the call will ensure any birder is primed for what will probably turn out to be a brief encounter.

Woodchat Shrike is another popular spring overshoot. Having a knack of turning up inland and being an expected visitor to the UK, its presence can be pleasingly obvious. Perched atop a bush with its stunning rufous cap, black mask, dark upperparts and clean white underparts on show, this at times approachable species can make for a satisfactory straightforward identification. Even in flight, a solid white rump and primary coverts contrasting with the dark upperparts triggers the immediate attention of the onlooker. Records of Black Kite are occurring with increasing regularity. Flocks arrive en-mass across the Straits of Gibraltar throughout February and March, so realistically, an April Black Kite is very much on the cards. Unlike the passerines which are more reliable in overcast conditions, to maximise your chances of finding this scarce bird of prey a southerly airflow during spells of anticyclonic conditions is key. Any coastal location or inland site with significant elevation could produce a sighting of this majestic raptor, but the ID isn’t as straightforward as one would hope. Close examination of the wings should reveal six primary fingers, an inner pale ‘window’ towards the wing-tip, an indistinct fork or notch in the tail (if the fork is apparent, a first-summer Red Kite could be having the last laugh), while its flight comprises deep wingbeats and prolonged gliding. Often the number one rule is, if you think it could be a Red Kite, it probably is!

Alpine Swift can be on birders’ radars as early as mid-March, with most records coming in April and early May. This large swift, with its obvious white

throat patch and belly, can patrol our skies pretty much anywhere it fancies, although it is typically found along cliff-tops or above towns, lingering mostly at the latter. These locations are chosen to ensure a safe roosting site, as well as providing suitable feeding spots. The fast and powerful flight, with its Eurasian Hobby-like appearance, is ample for a ‘swift’ identification, and helpfully, in March to mid-April, Alpine Swift is just as likely as our own Common Swift.

Purple Heron is rarely seen actively migrating in the UK. However, individuals can be located at their favoured habitats, namely marshes, reedbeds and lakes. New arrivals which have made landfall at their first accessible site can often be inadvertently flushed. Although secretive, separating this Ardea from its commoner congener is straightforward. Even when discretely on show within reed-fringed pools, its longer bill, darker plumage with distinct rufous-coloured neck and purple-tinged carpel, means there is little room for confusion. Even in flight, the lack of white ‘landing lights’ (a feature in Grey Heron) in the forewing will ring alarm bells. In flight, a distinct ‘kinked’ neck and trailing, tangled legs are further helpful indications. In April, juvenile Grey Herons will be far from leaving their nests, so any dark heron lurking is sure to be this attractive species. Another heron which is likely to turn up during April is Black-crowned Night Heron. Its habitat requirements differ substantially, though, with it preferring slow-flowing rivers, canals or small lakes. Plentiful trees ensure a safe roosting site, but as the name suggests, the ideal time to locate this elusive species is during the early or late hours of the day. A small heron, but in its adult plumage, unmistakable, with a silvery grey front, black crown and mantle. In flight, the pale grey wings contrasting with the dark mantle, combined with the short legs are helpful pointers if you come across a mobile bird.

We will now look at the potential overshoots that occur when the winds are chiefly easterly and south-easterly winds.

Another shy and secretive potential overshoot is Wryneck. While typically encountered in August and September, April is the ideal month to find this cryptic bird on spring migration. Although far from annual in some coastal counties during spring, like Hoopoe, its secretive nature means that it often isn’t until the bird is flushed that its presence is revealed. A sharp eye will note the obvious single black line running down the mantle and the disproportionate longer tail and rather erratic, short flight, finishing off with the typical ‘dive’ deep into adjacent scrub. Patience is key to see the bird again, so standing still away from the immediate area may produce another sighting, although with Wrynecks nothing is guaranteed!

Bluethroat is a charming passerine, yet highly secretive. Often seen hopping on the ground either along coastal patches with limited vegetation or, most likely, on marshes, its nervous and erect stance, together with its cocked tail are clear clues. When face to face with a White-spotted Bluethroat, the name says it all, but despite the close proximity of its breeding locations in northern France, the species is still a sought-after find in southern England.

The east coast and northern isles are most favourable for finding its Redspotted congener.

Although many of the aforementioned species have involved coastal influences, there is one stand-out spring overshoot which inland patchworkers can look forward to: Red-rumped Swallow. Undesirable weather is by far the ideal scenario in which to go and find this bird. Any inland waterbody, especially large lakes or reservoirs where other hirundines are known to congregate, can prove productive for a find. There can be one slight issue, and that is the abundance of other hirundines around at the same time. Thankfully, Red-rumped Swallow is larger and adopts a unique flying style; it has a distinctive drawn-out glide, interrupted by several short wingbeats, before re-enacting the glide. Other useful features are its jet black undertail coverts (contrasting heavily with the pale vent), pale underwing coverts and long tail streamers, are all helpful clues. When an individual (or less commonly, a pair) is hawking low for insects, the distinct two-tone rump, unbroken orange/ rufous nape and lack of any markings on the chin and breast are immediate evidence as to the presence of this smart hirundine.

Among the annual spring overshoot scarcities, there is always the hope of a rarity in the mix. Great Spotted Cuckoo is a species which is easily identifiable, making itself a much-hoped-for find for the regular patchworker – as a noc-mig record in Gloucestershire in 2021 proves, you don’t necessarily have to be based at the coast! Subalpine Warbler, Western Bonelli’s Warbler and European Bee-eater are other likely candidates during the latter two weeks of April and could be the final flourish to this exciting month.

So, there is no better time than now to brush up on the identification of spring overshoots, check the forecast and get in the field. ■

Perhaps the most iconic of all spring overshoots, Hoopoe should present few identification challenges. It is a scarcity that can be found just about anywhere, from southern headlands to inland paddocks and even gardens.

Is there a better-looking spring overshoot than male White-spotted Bluethroat? In south-easterly or easterly winds in early April, scour coastal scrub in the hope of a flash of sapphire blue and fiery orange from this delightful chat.

Woodchat Shrike is a potential target following southerly winds from late March until June.

European Serin is often encountered as a fly-over at south coast headlands, so knowing its flight call is important. If you see the bird, look for the small size, short, stubby bill and, if views are good, a yellowish-green basal colour (inset).

Black Kite can be tricky to identify at distance or in poor light, but the six clear primary ‘fingers’ are a good way to separate it from the more widespread Red Kite.

Two aerial visitors which see numbers peak in April and May are Red-rumped Swallow (above) and Alpine Swift (right). Both are distinctive birds, but getting to know their key features and flight styles is important, particularly when faced with a big flock of commoner congeners. Each is readily found both on the coast and inland, making either an attainable target for any birder in spring.

Black-crowned Night Heron is one of April’s most anticipated southern visitors. It’s not particularly rare and is prone to sizeable influxes in some years, but is generally rather elusive and hard to see. Finding one would make any birder’s spring.

Purple Heron has long been touted as a likely British colonist, yet for now it remains a scarce migrant. When compared to Grey Heron, look for a smaller bird with less overall bulk. Breeding adults, such as this, show an intricate plumage of orange, brown and purple, with these elusive birds tending to favour reedbeds and other vegetated wetlands.

Calm and clear mornings on the coast may seem ideal for bird activity, but can be frustrating as many migrants will pass straight through overhead.