A dummies guide to Vis-mig

Birds on visible migration (vis-mig) can provide some of the most spectacular of ornithological experiences, so much so that there is a band of birders who dedicate their time to seeking out such events. I count myself as one of them albeit on a lower plane than the most obsessive of aficionados. It is a sub-sect of the birding family that will spend hours scouring weather maps for tell-tell signs of a possible upcoming vis-mig happening and will then ensure that they are at their chosen vantage point by, or shortly after, dawn. There are websites devoted to the observations gathered by such birders (for example Trektellen) and also WhatsApp groups where data can be instantly shared. It is an inclusive world in which the celebration of bird migration is a central pillar. People that you have never met become virtual friends and places that you have never visited become as familiar as your own back garden. Those that get their vis-mig kicks from sea watching will hopefully excuse my lack of reference to that noble art in this post. It is something that I have done (sometimes in frenzied bouts) but will be sticking to watching birds that move over dry land, my own chosen vis-mig arena. There are of course times where these two 'worlds' overlap as will be seen.

But what is 'vis-mig'? It's a tricky question to answer. To put it simply, any bird that flies through an area on active migration is deemed to be on visible migration. So an overnight fall of Robins, thrushes or warblers  - even though they are migrating - would not qualify. To complicate matters, these birds may then disperse during the morning, making their way by moving through vegetation at ground level - they too are migrating but will not be thought of as on 'vis-mig'. I have watched, over the course of an hour, 40+ Chiffchaffs moving eastwards, following a tree line along the spine of the South Downs, each bird hopping from tree top to tree top. Vis-mig? Definitions get a bit blurred, don't they. I'm sure that we all have our own definitions of what does and does not count. For this post I am dealing with birds that have passed overhead without stopping.

Where do you go to partake in such excitement? The answer to that is anywhere that you can scan the sky. I have picked up on movement in the most unlikely of places such as over city centres, while watching football matches, looking out of moving cars and glancing out of office windows when meant to be working. However, to give yourself some hope of witnessing movements regularly and with a chance of spectacle it is best to find a half decent vantage point that normally (but not always) requires some sort of geological quirk such as high ground or a river valley. The coast will normally guarantee some top notch watching as birds concentrate in higher numbers here, and will normally fly parallel with the seashore as they migrate (this is where a cross over with sea watching is inevitable.) But beware when on the coast! Streams of moving birds might be a little way inland, or further out over the sea. And if you are watching inland a bird stream will not necessarily take an obvious route but might, for instance, follow the base of a hill, the top of high ground, along a line of trees, the course of a river or even a major road or railway line. All bets are off in reality but some places are more reliable than others. This is a facet that gets the seasoned vis-migger to don a detective's hat to try and discover the best areas from which to watch. But again, beware! A site might only be good if precise weather conditions prevail and also occur at the right time of year. A bad first session is about as useful a guideline to the suitability of a site as would be a good first session - a site needs to be checked out many times, at varying times of year and in varying weather conditions before you can get a firm grip on its promise and suitability.

My early tastes of 'vis-mig' success came at Dungeness in Kent. 14 April 1977 found me mesmerised by a stream of Linnets arriving in off the sea and heading north  - my final total of 1,000 was an underestimate and opened my eyes to this style of birding. Within five years I had started to find suitable viewing points on the Kent shingle and spend more time watching the skies while others sea watched or searched the bushes. October seemed best, with finches the main components of any movement, including two memorable mornings with 10,000 Chaffinches (22 October 1982 - more on this watch later) and 820 Tree Sparrows (17 October 1983). We had also learnt that a light NW wind produced the best results. Even within the confines of this area we identified spots away from the seashore that could bring different results. By standing between the main pits on the RSPB reserve you commanded a 360 degree view where no large bird could escape your optics. This shift in site was vindicated on 21 May 1995 with a Honey Buzzard and a Serin. In later years this same spot would provide me with Black Kite, further Honey Buzzards, Iceland Gull, Bee-eater and Hawfinch. However, the lure of the beach was still strong and found me spending several recent autumns panning the skies for avian gold which were highly successful - but could I have similar experiences closer to home? Locally did such viewpoints exist and could they deliver?

In 2014 I had more time on my hands to investigate those very questions. I wanted to find places close to home if possible. Using the uberpatch as a search area I identified a number of sites that were worth a look. Over the subsequent years they have all largely proved their worth. Site A - Epsom Downs Open views in all directions although some folds in the downland can hide flight lines. Particularly good for pigeons, larks, pipits and hirundines in the autumn but yet to convince me that it is a good site for thrushes and finches. Spring suitability unknown. Site B - Banstead In effect my back garden. Views compromised to the north and west but saved by good sightlines to the south and east. Punches well above its weight and can be spectacular for thrushes in the autumn (see later) and raptors in the early spring. Has a decent list of surprises such as Little Egret, Honey Buzzard, Short-eared Owl, Woodlark and Hawfinch. Early spring Chaffinch movements good. Site C - Canons Farm Superb sightlines in all directions but has so far not delivered, bar a couple of hirundine days. Movement can be messy and confusing. Has potential though.

Site D - Denbies The new kid on the block which I only started watching from with any regularity last autumn. Apart from one truly spectacular morning of hirundines (see later) it has proved to be good place for picking up Meadow Pipits on the move. Early days but they have been promising. Site E  - Box Hill Looking down onto the Mole Valley and the accompanying river, this would seem to be the pick of the viewpoints but the heavily wooded northern view is detrimental. A number of wooded valleys north of here are also used as flightiness so dilute what you pick up from the open south-facing slopes. Still, decent thrush movements have been recorded in the autumn but little else. Site C  - Colley Hill A bit of a poor man's Box Hill on the map but I actually prefer it here and the sightlines are cleaner. Good for thrushes and better than Box Hill for pipits and finches. Have recorded Great White Egret, several Woodlarks and plenty of Hawfinches. Only a mile inland from here the open farmland and meadows around Mogador can be very good and I have witnessed several big thrush days.

Still to be convinced about the wonders of vis-mig? I've gathered together the narrative from a few of the most spectacular days that I have had the pleasure to witness. Please take a look and hopefully be converted. The more people that look the more we find out about this fascinating ornithological side line.

After the thrushes came the Chaffinches

Dungeness, Kent 22 October 1982

90,000 House Martins

Dungeness, Kent  24 September 1989

Charmed by Goldfinches

Dungeness, Kent 19 October 2017

Redwingmageddon

Banstead, Surrey 13 October 2021

The dam bursts

Dungeness, Kent 22 September 2024

(picture at top of post from this very day)

There is another big day that I want to share, one that occurred on 26 September last autumn - I was vis-migging at Denbies from dawn and was surprised to find that hirundines were already on the move. As this was the first autumn that I'd been watching from this site I was intrigued by the fact that they were all coming from the south and heading straight up the Mole Gap, following the river northwards. For maybe 90 minutes I observed this until the stream quietened down. Luckily I then scanned out far to the south-east where (another?) stream of hirundines were on the move - all moving on a more to be expected easterly bearing. This necessitated a change of viewpoint. Within 10 minutes I was standing directly under them, birds following the base of the North Downs scarp slope. The numbers were incredible - this was most unlike Surrey! By 10.45hrs the movement had fizzled out, a few still moving but starting to hang around, confusing any meaningful count. The final total of 31,300 House Martins was a county record, ably backed up by 7,200 Swallows. And all local.