Autumn and Winter at Slimbridge

I visit WWT Slimbridge fairly regularly and have been lucky enough to have some great sightings from the hides, including some rarities. My favourite time of year to visit is during Autumn and Winter migration periods...

AUTUMN

In Autumn, lots of passage migrants pass through Slimbridge. This Spotted Redshank will have probably spent the breeding season in Scandinavia and after feeding and resting on the reserve for around a month will continue its journey down to central Europe or equatorial Africa to over winter.

Like some other passage migrants found in the UK, Ruff breed in Scandinavia and are passing through Slimbridge on their way to their non-breeding grounds in sub-Saharan Africa. However, not all birds make their journey to Africa - some over winter in Britain; a few at Slimbridge. 

Unless a bird is ringed or has a satellite tag, we'll never know for sure where it is from. For example, this female Wheatear could have bred in Alaska, Greenland, Siberia, Scandinavia, Iceland or anywhere in continental Europe!

By early Autumn the young birds which had fledged the nest months ago, like these Swallows, are almost adult birds. They may still lack a little of the adult bright plumage but they can now find food for themselves.

The Summer Walkway path at Slimbridge follows the seawall down to the edge of the Severn Estuary. During Autumn you can see good numbers of wading birds, such as Dunlin, Grey Plover, Little Stint, Black-tailed Godwit, Sanderling, Curlew Sandpiper and Bar-tailed Godwit all feeding out on the estuary.

In this photo of a flock there are two Little Stint (another passage migrant) mixed in with the larger, and more common, Dunlin. 

Another passage bird which is a regular during Autumn at Slimbridge is the Curlew Sandpiper, a small brown wader, usually found with other wading birds. They breed in the high-Arctic tundra and migrate to Africa to over winter, some stopping off at Slimbridge along the way. 

They were quite distant and this was the best shot I could get! 

I was really pleased to see this Black Tern, which stayed at Slimbridge for a few weeks. It was really tricky to photograph as it was so quick, but I managed to get a few sharp photos.

The Black Tern was lost from the British Breeding Birds list in the 19th century due to extensive land drainage. It is now an annual (though uncommon) passage migrant - this bird probably fledged in Eastern Europe and was making its journey to Winter in Africa when it stopped off at Slimbridge. 

By Autumn most of the Avocet pairs which bred at Slimbridge during the Spring and Summer have headed off to winter in West Africa. 

The Common Crane used to breed in Britain up until the 1600's, until they were hunted to extinction. However, in 2015 the WWT teamed up with conservationists in Germany, where there is a large Crane population, and established the Great Crane Project. 

As a result, the WWT released 100 juvenile Cranes on the Somerset Levels, some eventually found their way to Slimbridge, stayed and bred. This is one of them, a female named Kia, who nested on a pool in the reserve last year.

There is a great page which explains the Great Crane Project in more detail here: https://www.rspb.org.uk/our-work/conservation/projects/great-crane-project/

Most of the Common Cranes at Slimbridge are resident, though a few do pass through on passage each Autumn. 

Slimbridge is no stranger to having the odd rarity drop in - I was lucky enough to see this Collared Pratincole which stayed in the South Lake area for a few weeks in October 2022.

The Collared Pratincole breeds in Southern Europe and North Africa and over winters in sub-Sarharan Africa - this one was a long way off course!

Unlike most other wading birds they hunt their insect prey on the wing, like a Swallow. To see a Collard Pratincole in the UK is quite rare; when they are seen they are usually sighted on the coast. 

Its time to wrap up warm, we're heading into...

WINTER

Winter is a really good time to visit Slimbridge as massive flocks of wildfowl and waders spend the winter there, like these Lapwing.

Some of these birds are resident and have bred nearby, whilst others have bred in Central Europe and have migrated to the UK to over winter.

I managed to capture the iridescence on this Lapwing's plumage.

Their 'pee-wit' call really brings the wetland to life and is one of my favourite sounds.

Like the Lapwing, some Teal are resident, while others have bred in Siberia and Northern Europe, and have migrated to the UK to over winter. 

The Eurasian Wigeon follows a similar breeding cycle and migratory route as the Teal. This photo is of a female.

There is a resident Water Rail who feeds on the seed dropped the the bird feeders hanging overhead at the Willow Hide!

During in the winter large numbers of Black-tailed Godwit from Scandinavia and Iceland can been seen on the reserve, feeding on the large lakes, scrapes and pools. 

The Greater White-fronted Geese start arriving in October, leaving around March, and can reach up to 250 individuals on the reserve. 

There are two different sub-species of Greater White-fronted Geese, both of which can be found at Slimbridge in winter; these two above are the Greenland race, which have orange bills and are dark brown. 

These have pink bills and are slightly paler in colour, meaning that they are of the albifrons sub-species and will have bred in Siberia rather than Greenland.

It is really helpful when a bird has an identifying character like this, it means you can work out where it has probably migrated from without ringing or satellite tagging them.

During winter last year a Glossy Ibis was at Slimbridge for over a month, feeding in the surrounding fields. The WWT think that extremely dry conditions in its native habitat of Iberia forced it north to escape drought. 

In recent years Glossy Ibis have been seen more frequently in Britain and the BTO suggest that there is a strong possibility that within the next 20 or so years they will be nesting, quite probably on the Somerset Levels.

Hopefully this video has worked...!

Large flocks of over 300 Barnacle Geese come to Slimbridge every winter from their breeding sites in Greenland and Svalbard.

When this drake Greater Scaup first came to the reserve in November 2022 it was still a 1st Winter bird and was moulting into its adult plumage. Now, it is a fully grown drake, sporting a beautiful grey vermiculated back, glossy green head and white flanks which may be difficult to see on this record shot.

The Greater Scaup is an uncommon winter migrant to the UK - the population that visit the UK are mostly from Scandinavia and Northern Europe where they have bred. 

One of the most famous winter bird species at Slimbridge is the Bewick's Swan. These lovely swans are smaller than the familiar Mute Swan and migrate from their breeding grounds in Siberia every year to over winter in Britain.  

They face threats along their migratory route - wildfowlers in Northern Europe continue to shoot them for meat and they are heavily affected by lead poisoning. As they have no teeth, they have to collect stones to grind down their food in their gizzard; they find bits of lead shot in fields where they have been feeding, mistake them for stones and ingest the lead. Only 4-5 pieces of lead is enough to kill them.

The EU has now banned lead shot, which means the problem in Europe will be slightly reduced in the future. However, the UK has not banned lead shot.

The founder of Slimbridge, Sir Peter Scott, first started observing Bewick's Swans in the 1950's and he noticed that every adult bird has unique black markings on its bill, like a fingerprint.

He started to recognise individual birds every year, showing that many return  year after year; some birds have returned for over 20 years.

The WWT have now recorded over 100 different individual Bewick's Swan bill patterning.

To finish off is a bird I saw only a few days ago at Slimbridge - a White-rumped Sandpiper, a vagrant to the UK all the way from the high Arctic. It was quite distant but I got good 'scope views of it feeding in the muddy margins of the South Lake.

Like most vagrants, no one knows for sure how it got to the UK.

I hope you've enjoyed this blog and have seen why bird migration fascinates me so much.