Autumn bird migration news: A week of two halves
Black terns have been moving en masse earlier this week © Andy Mason
It's very much been a week of two halves. The early part of the week saw large numbers of common migrants on the move and a huge movement of black terns through the country, with flocks in excess of 100 birds being counted on a couple of inland waterbodies. The latter part of the week was however much quieter.
Swallows and house martins dominated the visible migration during the first few days of the week, with smaller numbers of meadow and tree pipits, pied and yellow wagtails, and goldfinch, siskin, redpoll and chaffinch all moving.
The grey wagtail: bang on cue this year © Edmund Fellowes/BTO
A small number of grey wagtails were also counted, which is bang on cue for the first autumnal movements of this species.
As the wind turned south-easterly birds from the east were found, and included a few wrynecks, red-backed shrikes and icterine warblers, along with the fourth Blyth's reed warbler for Portland Bill in Dorset.
Eastern visitor: the wryneck © Jill Pakenham/BTO
It has been a much quieter week for rarities. However, a semipalmated plover, the find of the autumn so far, was discovered on Ventry Beach, Kerry. This is the fifth record of this North American species for Britain and Ireland and was probably another hurricane Katia blown waif. The east is also well represented with up to 12 pallid harriers. Only a decade ago this was a mega rarity.
What can we expect?
With high pressure settled over us for at least the next four to five days, visible migration counts will be at a premium. This doesn't mean that migration has come to a halt, migrants will still be on the move and probably in high numbers, it is just that they will be flying over at a much higher altitude making them near impossible to see. However, with the warm southerly airflow associated with the high pressure, coming from south-eastern Europe we could be in for a surprise from this direction. Please let it be a Tengmalm's owl in Norfolk!
Question of the week: What happens to a lost migrant?
The British Isles is well situated geographically to receive vagrant birds (birds that don't normally occur here). This has been illustrated perfectly this autumn with the arrival of several North American landbirds and the largest-ever arrival of pallid harriers from Eastern Europe and western Russia.
The North American birds arrived here in the wake of hurricane Katia, blown off course from their normal migratory route (which is often over 100km offshore over the western Atlantic) from North to South America. The predominantly westerly airflow across the Atlantic makes it very unlikely that these birds will ever get back to North America.
Having rested and fed these birds are likely to continue on their migratory trajectory, albeit on the wrong side of the Atlantic. Initially this might take them in a southerly direction but eventually they will turn south-west, the direction that would enable them to make landfall in South America. They will most likely perish in the Atlantic Ocean.
Having said that, it's suspected that individuals of some species, waders and waterfowl in particular, don't attempt to re-cross the Atlantic and simply continue their annual migrations on this side of the pond, often with flocks of similar species. Many such vagrants lead a relatively lonely existence, as they are unlikely to encounter members of their species ever again.
The prospects for birds arriving from the east seem to be rosier. Having rested, ringing evidence has shown that some of these birds are able to reorient and resume their migration trajectory. A rustic bunting ringed on Fair Isle in June 1963 was recovered on the Greek island of Chios four months later, suggesting that it had reoriented eastwards.
Have you noticed any birds leaving yet? Anything unsual or suprising? As always, we'd love to hear, so post a comment below.