BTO migration blog

Spring and autumn are exciting times for anyone who watches birds. Here on this blog we will make predictions about when to expect migrant arrivals and departures, so that you know when and where to see these well-travelled birds.

Thursday 5 September 2019

5th -11th September

It’s been 3 weeks since the last migration blog and a lot can happen during that time,
especially when birds are departing for the coming winter months. During the next couple
of weeks we will be updating the blog on a weekly basis to bring you the most up to date
news of what is on the move, what to expect in the coming week (based on the weather
forecast and the time of year) and a few predictions of what rare and scarce species
may turn up, so a little of something for everyone.
Last month we started the blog with a follow up on the Two-barred Crossbill influx that
occurred mainly on the Shetland isles. The number of birds being reported fell away
towards the end of the month and, for now, seems to have come to an end with only the
odd single bird being reported.
We also highlighted  Aquatic Warbler in the last blog and since it was published single
Aquatic Warblers have been seen in Dorset, Somerset, Hampshire, Powys and Cornwall,
making it a good autumn so far for this species, let’s see what the next few weeks bring.
The past week has been particularly good for Pied Flycatchers with birds reported across
the country with a particular bias to the south and east coasts, which is to be expected for
a species that will be heading towards France and Spain on their southward migration.

BirdTrack reporting rate graph for Pied Flycatcher showing the spike in
reports in late August compared with the historical average

So what should we be looking out for in the coming week? The weather patterns at
the moment show a northeasterly airflow over the weekend which could result in
good numbers of Wrynecks, Barred Warblers, Whinchats and Red-backed Shrikes. East
coast locations will give you the best chance of seeing one of these species and with
the Spurn migration festival taking place this weekend why not go along and join one of
the guided walks? ( Scarce species seen at this time of
year include Citrine Wagtail, Booted, Arctic and Bonelli’s Warbler, Lesser Grey Shrike and
Tawny Pipit, all of which have a peak reporting rate in early September.
Whilst the numbers of some waders like Wood, Green and Common Sandpiper fall
away for Bar-tailed Godwit the early part of September is when numbers in the
UK peak.  Having bred in the Arctic Circle from Lapland east to Taymyr in Russia
birds head to the UK to either winter here or use it as a stopover before heading
onwards to West Africa. Bar-tailed Godwits tend to prefer estuaries and saltwater
habitats more than their freshwater loving Black-tailed cousins but that doesn’t mean
they don’t turn up away from the coast. Reservoirs can host small flocks of Bar-tailed
Godwits and they can often appear alongside Whimbrels as they also pass through the UK.

Bar-tailed Godwit - some will still be in breeding plumage at this time of year. Photo Nick Clayton.

So far it has been a quiet year for seabirds such as Cory’s and Great Shearwater, but as
we progress into September there is still time to find these amongst the southbound
Manx Shearwaters. Balearic Shearwater is a species marked as critically
endangered on the IUCN European Red List of species but September is the best
month of the year to see them, with hotspots including Portland Bill, Portgwarra and
Berry Head. Some birds reach the North Sea and places like Flamborough Head, Spurn
and Sheringham are all worth a look from given the right conditions. Leach’s Petrel is
another seabird to have a peak in their reporting rate during September with the west
coasts being particularly productive following westerlies brought on by low-pressure
weather systems rattling across the Atlantic. You can find a video on how to separate
Leach’s Petrel from the commoner Storm-petrel here.
Two seabirds to look out for this week, particularly with westerly winds forecast, are Fulmar and Sooty Shearwater. Right now both are on the move but for very different reasons, and with very different destinations. The Fulmars on the move will be birds dispersing away from their breeding sites. It is thought that most of them will not go very far, staying in the North Atlantic, periodically visiting nesting cliffs or prospecting possible nest sites for the future. However, the Sooty Shearwaters are on their spring migration, moving through the North Atlantic on their way to their natal islands further south for the forthcoming breeding season, which takes place during our winter. For some, this will involve a flight of over 10,000km (6,500 miles).

Sooty Shearwater - Photo by Joe Pender

Species focus

Ortolan Bunting is a scarce visitor to the UK with the majority of sightings occurring in
September, but like many species, the number of records has steadily been falling each
year. During the period 1968-1969, a total of 87 birds were noted but in the period
2010-2016 only 33 birds were seen. In recent years however there has been an upturn in
records, with 74 reported in 2016, and this has in no short way been the result of
increased sound-recording of nocturnal migrants, or nocmig which accounted for 30 of
the 74 records. More research needs to be done to see how widespread and regular this
nocturnal movement of Ortolan Buntings is but it at least shows they are using the UK
during their migration and possibly in greater numbers than the reports of birds seen
during the day may indicate. 
Sonogram of Ortolan Bunting call - Nick Moran

Weather for the week ahead.

The weekend's weather looks to be set for north westerlies along the North Sea coasts and a mixture of north westerlies and westerlies for the rest of Britain and Ireland. Seawatching during this period from any west or east coast location could produce Leach's Petrel, Skuas, Manx and Sooty Shearwaters, and Guillemot and Razorbills. The rest of the week is dominated by westerly airflows with the remnants of hurricane Dorian due to hit the top of Scotland and the Northern Isles from mid-week. This westerly bias to the wind direction could result in Nearctic waders arriving with species like Buff-breasted, Bairds, Semipalmated and Pectoral Sandpipers the most likely species to occur.

Scott Mayson and Paul Stancliffe

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