Introducing Common Migrant Moths (part 1) - the Big Seven

It has been a slow start to the year for moth recording, but everything changed last night (22 May 2026) with the arrival of warm air from the south (likely from North Africa). Such conditions are ideal for finding migrant moths down here on the Dorset coast, and I approached the trap this morning with some anticipation. As well as bleary eyes: I was up at 4.20am, arriving only just before our local Robins and House Sparrows.

The final trap tally was almost 200 moths from 69 species. Seven of these species were migrants. Moth migration is a particular interest, and this morning's arrival gives me the perfect opportunity to look at the subject in a bit more detail. In this (and the next) post I'm reviewing the common migrant species that we get in the UK, several of which turned up here this morning. 

There's much to say about moth migration, but I'll keep it short for the present post. In summary, we are talking about those moth species that arrive, but do not generally overwinter, in the UK. While early arrivals may breed successfully, their offspring are unlikely to survive the winter months. As such, they are unable to establish permanent breeding populations. For the time-being. 

This caveat is important. Over the last 20-30 years, the British Isles have seen the arrival and establishment of several moth species (such as Jersey Tiger) who's status has changed from migrant to resident breeder. Indeed, British populations of many longer established species (like Large Yellow Underwing and Angle Shades) are regularly augmented by arrivals from continental Europe or further afield. In such cases it is impossible to tell for certain whether the moth in your trap has experienced a cross-Channel journey or just flown in from a local population, although weather conditions along with the presence of known immigrant species alongside them can provide useful hints.

So - which species are the known migrants? For a newcomer this is a bit baffling, but there is help at hand. The status of British moths is explained in the better field guides (see my blog post reviewing identification resources), and migrant species are considered in some depth by the Atropos journal and website. Atropos runs a 'flight arrivals' page where recorders can post details of new sightings, although I don't post on this as often as I probably should. For users of Facebook, Steve Nash runs the Migrant Lepidoptera (GB & Ireland) group, which carries news and images of migrant arrivals. There is a similar account on BlueSky.

OK - let's have a look at the common migrant species. These are spread across several moth families, suggesting that the tendency to migrate is either an innate Lepidopteran characteristic or has evolved separately many times. Now is not the time to speculate! Certainly, some families seem to be disproportionately represented in the migrant lists - notably the Crambid micro-moths as we will see. This and the next blog do not take a taxonomic approach. Instead, they focus on abundance, describing the migrant species that you are most likely to encounter. 

This blog post starts with what I'm calling the 'big seven' - the species that are so common that absolute numbers simply cannot be obtained. Some arrive in massive influxes: for example around 3 million Silver Y moths were recorded per hour on Shetland in 1996 (quoted in Randle et al., 2019). But please note that these are only 'big' in the sense of numbers. As we'll see, one species is very small indeed.

So let's begin with the Silver Y moth (pictured below and at the start of this post). This is found across continental Europe. Flying during the day as well as night, it is a fairly conspicuous species. Look for it nectaring on flowers during a sunny afternoon - as well as in the moth trap.

Silver Y Autographa gamma - Dorset 17.5.25

It's clear how Silver Y got its name. The combined shape and colour of the obvious Y-shaped mark are usually diagnostic, but bear in mind that there are a number of moths with a similar form and resting position that could cause confusion. Several are very rare migrant species (not covered in this post), but there are two common residents that need to be ruled out - Plain Golden Y and Beautiful Golden Y (below). In both cases the Y mark is usually split and lacks the silver sheen.

Non-migrant confusion species 1 - Plain Golden Y Autographa jota - Dorset 23.6.20

Non-migrant confusion Species 2 - Beautiful Golden Y Autographa pulchrina - Dorset 15.6.18 

Silver Y is a true migrant, in that the offspring of moths that have bred in Britain have been recorded undertaking a return migration to the continent in search of warmer winters (Chapman et al., 2002). While numbers in Britain have declined, its range has increased (a curious pattern found in some other moth species). Like several other moth migrants, Silver Y is arriving here earlier in the year as climate patterns change.

The second common migrant moth is even more conspicuous - the Hummingbird Hawk-moth (below). This is largely day-flying, although a few do turn up in moth traps. It is a real crowd-pleaser, buzzing around flowering plants and bushes in a distinctly hummingbird-like manner. Getting a photo can be a real challenge: they never seem to keep still.

Hummingbird Hawk-moth Macroglossum stellatarum in action - Dorset 12.6.15

Identification is straightforward: Hummingbird Hawk-moths are unlike any of our common hawk-moths and the combination of white, black, grey and orange colours - plus the distinctive flight pattern - is diagnostic. The distribution of this species within Britain has increased markedly over the last 45 years and there is recent evidence of adults being able to successfully overwinter here. This year, one was seen as early as February here in Dorset. Globally, the range of the species stretches from continental Europe right across to East Asia.

The next two common migrant species are both members of the same family as the Silver Y (the Noctuids), but lack its particular profile and markings: they stand out less from the many other species in that large family. Nevertheless, both have distinctive characters that enable easy identification.

Unlike many migrant moths, Dark Sword-grass (below) has shown a major decrease in numbers since the 1970s. Nevertheless, it is still recorded across much of Britain, although it remains unclear whether the species has successfully overwintered here. Last year it was the first migrant moth to turn up in my Dorset trap - on 21 February 2025, which seems unusually early for a cross-Channel arrival. But you never know. Globally. the species is widespread, occurring in South America, southern Africa and Australia as well as Europe, Asia and North America where it is most commonly found.

Dark Sword-grass Agrotis ipsilon - Dorset 16.3.23

Superficially, Dark Sword-grass looks like many other large noctuid species, but it has a particular diagnostic feature enabling easy recognition - a narrow black triangle ('dart') protrudes from the kidney mark (facing down in the above photo), with two more black darts pointing towards it from the end of the wing. See the enlarged image below:

Dark Sword-grass - detail of wing marking

The last noctuid in this list - the Delicate (below)- has a distinctly southern and eastern distribution in Britain. It is rare in Scotland and North Wales.

Delicate Mythimna vitellina - Dorset 7.6.17

The light (delicate?) tracery of wavy brown cross-lines on a lighter background is pretty much unique to this species, although the background colour can vary. Paler adults, such as the one pictured above, have been shown to result from more rapid development at higher temperatures - so have probably arrived from somewhere hot and dry like southern Spain. Globally, the species is restricted mainly to Europe although it has also been recorded in the Canary Islands.

The remainder of the 'big seven' are all 'micro-moths' - see another post for more about the differences between 'micro' and 'macro' moths. The first two lie within the Crambid family, which contains some of my favourite moth species.

At first sight, the Rusty-dot Pearl (below - from this morning) appears relatively undistinguished. However, once you have got your eye in, its characteristic warm orange-brown colour with (usually) darker oval and kidney markings coupled with a strongly triangular shape clearly point to this species. Globally, the species has a large range that extends from Europe to South Africa and Japan.

Rusty-dot Pearl Udea ferrugalis - Dorset 22.5.26

The second common Crambid migrant, Rush Veneer (below, also from this morning), is more variable in colour and pattern than Rusty-dot Pearl. Fortunately, its long and narrow shape cannot be confused with any other common British moth (although there is a similar American species). The one pictured below is quite light in colour: others can be darker. The species has a similarly wide global range to Rusty-dot Pearl.

Rush Veneer Nomophila noctuella - Dorset 22.5.26

The final 'big seven' migrant is anything but big! The Diamond-back Moth (below) is absolutely tiny, about 6-8mm in length. You can easily miss them in a moth trap. Yet this minute insect is one of the world's great travellers, turning up in every continent except Antarctica (although I bet that a few have turned up there as well that no-one has yet discovered). They fly both during the day and night.

Diamond-back Moth Plutella xylostella - Dorset 24.5.18

Identification is fairly straightforward (if you can spot them in the first place); in their characteristic form, the wavy-edged light patch on the back provides a clear contrast with the dark sides of the moth. Given their small size, some form of magnification is helpful to make this out.

Diamond-back Moths can arrive in huge influxes, and in some years are probably the most abundant of all of the 'big seven' migrants to Britain described above. For example, hundreds of thousands arrived in May 2000, probably from Southern or South-eastern Europe (Chapman et al., 2002). There were only five in my trap this morning, but to witness a mass arrival is an impressive sight that I have only experienced once - on the island of Inner Farne off the coast of Northumberland several years ago, where every bit of vegetation seemed to be dotted with tiny moths.

It's worth adding that Diamond-back Moths can be a serious agricultural pest. The Natural History Museum has published a short article about the species here.

Right - those are Britain's top seven most common migrant species. The next blog will look at those that are a bit rarer, but still turn up in sizeable numbers. Watch this space.

References

Chapman, J.W., Reynolds, D.R., Smith, A.D., Riley, J.R., Pedgley, D.E. and Woiwod, I.P. (2002). 'High‐altitude migration of the diamondback moth Plutella xylostella to the UK: a study using radar, aerial netting, and ground trapping.' Ecological Entomology, 27(6), pp.641-650. (link)

Chapman, J.W., Lim, K.S. and Reynolds, D.R. (2013). 'The significance of midsummer movements of Autographa gamma: Implications for a mechanistic understanding of orientation behavior in a migrant moth.' Current Zoology, 59(3), pp.360-370. (link)

Parsons, M. and Clancy, S. (2023) A Guide to the Pyralid and Crambid Moths of Britain and Ireland. Atropos Publishing.

Randle, Z. et al. (2019) Atlas of Britain and Ireland's Larger Moths. Pisces Publications.

See also the field guides and websites listed in a separate blog post.

Global range data is from GBIF.

Dartmoor Highlights - and a question of ethics

The Common Redstart (above) may be Britain's most attractive summer visitor, but it's getting increasingly difficult to track one down. In Dorset, where I'm based, they are very scarce breeders, more usually seen passing through the county on migration. Which makes the perfect excuse for a birding excursion over the border into Devon. 

A spring visit to Dartmoor is an annual event in my birding calendar - see this post from a couple of years ago. Two locations take centre stage. My first stop this morning was Yarner Wood, which has the honour of being England's first National Nature Reserve (NNR), established in 1952. Now expanded into the East Dartmoor NNR, the site is managed by Natural England. A leaflet about the reserve can be downloaded here (1.9MB).

The oak woods at Yarner are positively festooned with bird and bat boxes. The first nestboxes that I came across were all occupied by Blue Tits, and the busy comings and goings of the parents showed that nestlings were in residence. But further up the track a dart of black and white revealed the presence of a male Pied Flycatcher (below). He perched conveniently close to the path:

Pied Flycatcher (male) - Yarner Wood, Devon, UK

Nationally, Pied Flycatcher number have decreased massively - a 53% drop between 1995 and 2023 (see the data from the British Trust for Ornithology here), although losses appear to have levelled off - possibly as a result of nestbox provision in places like Yarner Wood. My non-scientific impression this morning was that numbers seem similar to my previous visits.

Unfortunately, the same can't be said for Wood Warblers, which the official NNR leaflet says that Yarner is 'famous' for. Not now, I'm afraid. It's many years since I last saw or heard a Wood Warbler there - and none were apparent this morning.

My second destination of the morning was Emsworthy Mire, a Devon Wildlife Trust reserve at the head a valley just below Haytor. The sun was out, but a sharp wind was blowing.

  

View over Emsworthy Mire, Dartmoor. Haytor in the distance.

I could hear a singing Common Redstart as I entered the reserve, following the path that winds between a network of dry stone walls that mark out the site of this former farm. Some of the fields contained a stunning display of Bluebells - the best that I've seen there.

Bluebells at Emsworthy Mire

On previous visits I have watched Redstarts in the vicinity of the old barn that sits roughly in the centre of the reserve. It is surrounded by mature trees (mostly Sycamore) which contrast markedly with the more windblown Hawthorn and Ash dotted around the fields. As I approached the barn, I saw that a couple of other guys with cameras had beaten me to it. A female Common Redstart hopped onto a stone wall, but speedily disappeared. A male then flew up into a nearby tree ...

... and then descended to perch on an old stone wall right in front of me:

Common Redstart (male) - Emsworthy Mire, Devon

This was fantastic, although I couldn't help but wonder why he had come so close to the path. The answer was soon apparent:

Common Redstart with mealworms (not placed there by me)

Mealworms do not naturally inhabit the top of stone walls, and one of the photographers must have placed them there. My initial feeling was one of disappointment, as I was not observing the bird's natural behaviour. But then again, I was pleased to get such good views and I'm very happy with the resulting images. It's a bit of an ethical dilemma.

To be clear, I would never bait a site in order to obtain a photograph - but then photography has never been my prime motivation when watching birds (or indeed any other wildlife). Having said that, it's always very satisfying to have a nice picture that records the things that I have seen, and in some cases such a photo can also act as a useful identification tool. Before writing this blog post, I had a bit of an online dive into various birding websites and forums and I see that my dilemma is shared by many. A good example is this article by Pete Garrity, which rehearses these arguments (and more) in some detail; I certainly agree with his key take-home message that the welfare of the bird must come first. There is a similar conclusion in a thoughtful blog by Adam Juckes, who emphasises (correctly in my view) that much depends on the particular circumstances of each case.

As it happens, supplementary feeding is in the news at the moment, with the well-publicised change of stance by the RSPB - link here (in summary: feed seasonally, feed safely).  The spread of diseases like trichomonosis is part of the problem, but recent research also has highlighted the potential for ecological harm to arise from the provision of additional food in certain circumstances - for example by giving a competitive advantage to bird-feeder visitors (like Great Tits) over declining insect-feeders (like Pied Flycatchers) (Broughton et al., 2021). I've stopped putting out bird feeders in my garden for this reason. But we have to acknowledge that in the wider world, supplementary feeding is well established - many (if not most) eco-lodges in the Neotropics will have fruit and nectar feeding stations for toucans, tanagers, hummingbirds and the like - and I have spent many happy hours watching (and indeed photographing) the birds that visit them. 

There are no easy answers, and in many cases it will simply be a case of fact and degree. The occasional baiting of a site like Emsworthy is unlikely to cause material harm and may indeed provide some benefit to the bird(s) concerned. The Common Redstart seemed happy enough to accept an easy meal. In an ideal world, photographers using this method should perhaps 'come clean' as to how they obtained their image, but that might be asking too much!

But as soon as a rare and infrequent practice becomes widespread then alarm bells should start to ring. At that point, much more serious thought needs to be given about the likely effect on the species concerned. This becomes particularly important when birds are the subject of conservation concern, a factor that is recognised in the UK by various laws (unnecessarily complicated in my view, but that's a separate discussion) that protect certain species - notably Schedule 1 of the Wildlife & Countryside Act 1981 (as amended) (explained here) in respect of breeding birds. As it happens, Common Redstart is not (at time of writing) a Schedule 1 bird, but its range has declined in recent years along with a slight population decrease (information from the BTO on this is here). To me, this suggests that we should think very hard when carrying out actions like supplementary feeding that could affect its natural breeding behaviour. But perhaps I'm being over-cautious. And clearly there are many more pressing problems affecting wild birds such as habitat loss, climate change, pesticide use, agricultural intensification, hunting ... the list goes on.

My visit to Emsworthy finished on a less controversial note. I didn't linger by the barn, heading off instead on the circular route that runs around Emsworthy Mire. I was near to the south-western corner of the reserve when I finally heard the call of a male Cuckoo nearby. He was easy to locate:

Cuckoo male - Emsworthy Mire

  And he wasn't alone. A female was nearby, resting on a fencepost:

Cuckoo female - Emsworthy Mire

Neither of these are great photos, but I was keeping my distance in a landscape that offered very little natural cover. Not that the Cuckoos appeared unduly bothered; they were more occupied with each other - the male calling loudly and flying after the female when she moved further along the fence line. At the same time, both Cuckoos were being repeatedly mobbed by other birds - mostly Meadow Pipits. You can understand why, of course, although what baffles me is that the same birds fail to recognise a giant Cuckoo chick in their own nest. There is much of interest in the life of the Cuckoo. 

My last view of was of both Cuckoos sitting almost side by side further along the fence (below). Note the Meadow Pipit on the middle post. Both birds then flew away across the moor.

Reference

Broughton, R. Shutt, J. and Lees, A. (2021) 'Rethinking bird feeding: are we putting extra pressure on some struggling woodland birds?' British Birds, 115 (1). pp. 2-6.

 

Enjoying Sand Lizards at Arne

 

Sand Lizards are one of Britain's most spectacular reptiles, and it is always a privilege to get good views of them. One of the advantages of being a reptile surveyor is the opportunity to attend training days to improve survey and identification skills. Today was one such session, held at the RSPB's Arne reserve next to Poole Harbour in Dorset, UK - a site that I know well as a local volunteer. Among its many wildlife attractions, which will be familiar to viewers of past series of BBC's 'Springwatch', the reserve hosts all six of Britain's native reptile species.

The session was led by Gary Powell and Nick Moulton of Amphibian and Reptile Conservation, and was carried out under licence as the Sand Lizard is a protected species. As always, the welfare of the animals comes first.

It is rarely easy to find wild reptiles, especially on very sunny days like today when their activity levels were already high by mid-morning. It is much better to search on cooler and cloudier days when lizards and snakes need longer to warm up before they can start moving around. More basking time means that they should be easier to spot. But you can't guarantee it! 

Even with the many eyes of our group, it took over an hour to locate the first Sand Lizard - the handsome individual pictured at the start of this blog. The green colour shows that he's a breeding male, and we are now well into that season on the Dorset heaths. Sand Lizards have been out of hibernation for a couple of months here (I saw my first of the year back in mid-March). Males emerge a week or so later than females, and their full breeding colour takes a short while to develop. 

A second male this morning, moving through a bundle of dead Gorse, was similarly colourful but less willing to pose for a picture (below).

Sand Lizard (male) - RSPB Arne, Dorset

But what about the females? Unlike Common Lizards, which give birth to live offspring, female Sand Lizards lay their eggs underground, usually one clutch of 4-12 eggs per season. Understandably, the females are quite choosy about where they do it and will dig several (sometimes many) 'test burrows' before deciding that one is suitable to accommodate their future young. 

The presence of these test burrows is a good indication that you have a breeding population of Sand Lizards on site. According to the literature their construction usually takes place in late May. However, we saw a good number on the heathland this morning. Climate change seems to be bringing this activity, and many other natural processes, forward in time.

Two Sand Lizard test burrow entrances - RSPB Arne, Dorset

What makes a successful egg burrow for a female Sand Lizard? Bare ground is favoured, but a balance is needed between soil that is too hard or compacted to excavate and sand that is so loose that the finished burrow will collapse. If rocks or large stones are encountered underground then digging will probably be abandoned. Sunny, south facing sites are preferred, within close proximity to cover such as  deep heather or a gorse bush.

This morning, we were extremely lucky to come across a female Sand Lizard in the process of excavating a burrow (photo below). Only her tail is visible.

Female Sand Lizard digging an egg burrow (tail only visible) - RSPB Arne

The lizard was too busy digging to bother about (or possibly even notice) our presence. We left her to it: will this burrow meet her exacting requirements, I wonder? But when she is finally satisfied, she will emerge from the favoured burrow before reversing back in to lay her eggs. The burrow will then be carefully filled in so that it cannot be detected. Any excavations remaining obviously visible will be discarded test burrows that didn't make the grade.

It will usually take two or three years for Sand Lizards to reach maturity and start breeding. Before that, juvenile lizards will roam the heathland in search of prey; these are markedly smaller than adults, with a similar colouration to adult females (brown or grey with 'ocellated' spots - i.e. black with white centres). We found one of these juveniles a bit further down the track: it was basking on a tree stump but then moved under the cover of some nearby vegetation (below).

Juvenile Sand Lizard in cover - RSPB Arne, Dorset

The presence of breeding Sand Lizards on heathland at Arne is encouraging news for Britain's rarest native lizard. Over the wider Purbeck Heaths National Nature Reserve, of which Arne is only a part, a programme of conservation actions aimed at benefitting the species, supported by co-ordinated monitoring by reptile surveyors, is seeking to turn around the fortunes of this endangered reptile. I am proud to play a very small part in these activities. And it's great to be able to observe these magnificent reptiles in such a beautiful natural setting.

For more information about how to identify Sand Lizards, and other lizards in Britain (both native and non-native), as well as a short list of references, see an earlier blog post - link here. This blog also contains a list of the experts upon who I have relied in gaining understanding of these species: needless to say, any errors in this blog are however my own responsibility.

For more information on conserving Sand Lizards and other reptiles contact Amphibian and Reptile Conservation.

While sightings can never be guaranteed, Sand Lizards are regularly seen from the trails at RSPB Arne. Guided walks can also be booked that will give a more detailed insight into these and other heathland species - contact RSPB Arne Events for more information.