In search of Steppe Whimbrel

It’s unsurprising if you have not heard of a Steppe Whimbrel; the subspecies was declared extinct in 1994. In this context, a new paper in Wader Study, based on detailed studies of two birds that were found in Mozambique in 2016, adds immensely to our knowledge.

Bleak times for the Numeniini

The curlew family is facing huge pressures across the globe. Eskimo Curlew and Slender-billed Curlew are either extinct or close to extinction, with no confirmed sightings for 56 and 18 years, respectively. We are definitely losing species but are we losing diversity within individual species too – as suggested by the rarity of the Steppe Whimbrel and the fragmenting distribution of the Hudsonian Godwit? There is a lot of information about the current status of different populations and subspecies of the Numeniini  family in Why are we losing our large waders? a WaderTales blog about curlews, godwits and the Upland Sandpiper based on a review paper by James Pierce-Higgins and colleagues.

As a species, the Whimbrel is categorised as ‘of least concern’ but the ‘once extinct’ Steppe Whimbrel would be considered as ‘critically endangered’ if it were to be a species, rather than a subspecies.

Whimbrel are circumpolar in distribution and it is generally accepted that there are four subspecies:

• phaeopus breed from Iceland through Scandinavia and into western Siberia; they spend the non-breeding season largely in western and southern Africa.
• variegatus breed across the rest of north-eastern Russia and migrate to southeast Asia and Australia.
• hudsonicus breed across northern Canada and Alaska and migrate to Latin America.
• alboaxillaris are thought only to breed in the steppes of Russia and Kazakhstan, at the centre of the European land-mass, and to winter only in southeast Africa.

First find (and identify) a Steppe Whimbrel

The fact that Steppe Whimbrel was considered to be extinct just 25 years ago gives a clue as to how hard it is to find one. Details about recent records are summarised in a new paper in Wader Study by Gary Allport and colleagues, that forms the basis of this WaderTales blog. Three breeding sites have been identified, holding a maximum of 19 breeding pairs, in total, and a maximum autumn count of 11 birds has been recorded on passage, on the shores of the Caspian Sea in 2010. The two birds that Gary found in Maputo, Mozambique in February 2016 are the first wintering records in Africa (or anywhere else) since 1965.

The photographs above show that the two birds found at Maputo by Gary Allport of BirdLife International are different in several respects to the phaeopus with which they associated:

• Steppe Whimbrel are bigger
• There are cleaner/paler in overall appearance
• The rump is paler
• They have white axillaries

For more information see Allport, G. & C. Cohen. 2016. Finding Steppe Whimbrel: discovery and identification in southern Africa. AfricanBirdlife 4: 48–54. If you come across what you think is a Steppe Whimbrel, possibly in eastern Africa during the non-breeding season, check for white under-wings and take as many pictures as possible!

At the time of the discovery of the two Steppe Whimbrels, BirdLife had already got a strategy in place to deal with the unexpected appearance of a Slender-billed Curlew – ever hopeful that this species is not extinct. If seen in the non-breeding season, a bird was to be caught and satellite-tagged, in order to try to find its breeding area. The same procedures seemed appropriate for the Maputo Steppe Whimbrels and one bird was duly caught and tagged. That’s probably another story – anticipation – tension – concern for the bird’s safety – relief when it accepted its tag and behaved normally – and elation when data started coming in.

Local movements

The Maputo area, in which the two Steppe Whimbrel were found, comprises about 6 km of tidal muddy sand banks and flats. The area is heavily used by people, with zoned sections for various uses including traditional worship and tourism. The two Steppe Whimbrel were found by chance in February 2016, at the high tide roost on the upper beach. One was bigger than the other, suggesting a female and male. No other alboaxillaris were found in a larger population of 650 Whimbrel photo-identified in Maputo Bay. This paper talks about the discovery: Allport, G. 2017. Steppe Whimbrels Numenius phaeopus alboaxillaris at Maputo, Mozambique, in February–March 2016, with a review of the status of the taxon. Bulletin African Bird Club 24: 27–37.

The local movements of the two Steppe Whimbrel in Maputo Bay, Mozambique, were studied opportunistically from February to March 2016. Both birds were found to be part of a local sub-population of ca. 30 Whimbrel which held individual feeding territories on sandy shorelines. There are important details about behaviour and habitat-use in the Wader Study paper. The male was seen more frequently and predictably.  Knowledge of his movements made it possible to catch him, by dazzle-netting at night, on 6 March. Metal and colour-rings were added, together with a PTT satellite tag. A DNA sample proved that he was indeed a male.

The male was noticeably plump when caught, suggesting that he was already preparing for northward migration. Data gathered from the tag during the period before departure added valuable extra information about key feeding areas north of the main study area, where mangroves make it hard to observe birds.

Time to fly north

The female Steppe Whimbrel was last seen in the Maputo area on 28 February 2016, and it is suggested that she may have left the areas on or shortly after this date. The last sighting of the male was on 24 March 2016 and, using information from his PTT satellite tag, the Mozambique team know that he started to migrate the next day. Although nearly a month after the possible departure of the female, this is still one month earlier than the onset of migration for the phaeopus subspecies. This is not unexpected; phaeopus birds are heading for higher latitudes than alboaxillaris, which breed in the heart of the Eurasian continent, in the steppes of Asia.

Upon leaving Mozambique, the tagged male headed over Tanzania before the scheduled transmission phase ended. At the start of the next recording period, the bird had travelled to the northern end of the Great Rift Valley in Ethiopia. He then turned in a more easterly route to the Somali coast. During the tag’s next ‘off phase’ he crossed the Gulf of Aden where he was picked up moving up and down the coast before settling on some salt-pans in the area of Little Aden.

The tagged bird made a 4,659-km journey in six days to Aden, Yemen and his migration route was consistent with the direction of travel for the known breeding areas of alboaxillaris. The track data are the first firm evidence of a long-suspected African transcontinental migration route for southeastern Afro-Palaearctic coastal waders.

The tag was attached to the back of the Steppe Whimbrel. Feathers have been parted to show the  tag. After two months, the tag dropped off.

The tagged Steppe Whimbrel stayed in the Little Aden coastal area of Yemen until 10 May, when the pattern of fixes changed to a stationary location in the northwest side of the bay. This suggested that the tag had fallen off the bird, possibly floated across the bay on the prevailing southeast wind and then settled on the shoreline. Confirmation of the loss of the tag came on 14 August, when Gary Allport came across the same Steppe Whimbrel, wearing colour rings, back in Maputo. That must have been a great moment.

Key take-home messages

If you are on the African shores of the Indian Ocean, in Africa’s Great Rift Valley or perhaps the coasts of western India or the Middle East, please check out any Whimbrel you see. Steppe Whimbrels live up to their names – look out for the white (albo) underwing (axillaris). Perhaps you will find the next Steppe Whimbrel and it will be in a location where capture is again possible. Maybe your bird will carry the next PTT transmitter for long enough to tell conservationists where to look for what must be a tiny population of breeding Steppe Whimbrel. Peter Ryan of the Percy Fitzpatrick Institute of African Ornithology (University of Cape Town), has recently secured funding from the Mohamed Bin Zayed Fund to tag Steppe Whimbrel. He and Gary are on the look-out for any birds that might be suitable for further study. 

One of the great things about this tracking study is that it acts as a trial-run, should anyone find a Slender-billed Curlew or (even more unlikely) an Eskimo Curlew. We know that BirdLife scientists and their colleagues have the skills needed safely  to catch a rare, large wader and to maximise the amount of information that can be gathered about its migratory movements. Fingers crossed that it’s not too late to find out what is happening to other Steppe Whimbrel, or possibly even Slender-billed Curlew. Sadly, I think that we have to admit that the Eskimo Curlew is now almost certainly extinct.

Paper

Click on the paper details below to link to the Wader Study website. Full text is only available to members of the International Wader Study Group.

Allport, G.A., P.W. Atkinson, M. Carvalho, N.A. Clark & R.E. Green. Local site use and first northbound migration track of non-breeding Steppe Whimbrel Numenius phaeopus alboaxillaris (Lowe 1921). Wader Study 125(3). doi:10.18194/ws.00126

 

 

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Graham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.

 

 

 

Winter territories of Green Sandpipers

Winter is a very different prospect for a Green Sandpiper that spends the non-breeding season in the UK, rather than Spain, Portugal or countries in northern Africa. Are British winterers living life ‘on the edge’ and how do they cope? One way is to defend resources within clearly-defined territories.

Life in Hertfordshire

Ken Smith, Mike Reed and Barry Trevis have been studying a colour-ringed population of Green Sandpipers in Hertfordshire (an English county just north of London) since 1983. The focal point of their activities is Lemsford Spring, a Hertfordshire & Middlesex Wildlife Trust nature reserve. The site is  a set of disused watercress beds that provide plenty of freshwater shrimp (Gammarus pulex) in shallow lagoons fed by freshwater springs. Over the years they have been able to use their colour-ringed birds to study return rates from year to year, behaviour and local habitat use. Using radio-tags they have looked at nocturnal activity patterns and more recently they have been using GPS geolocators to find where their birds go to breed.

The highest numbers of Green Sandpipers in southern England occur in late summer, when many passage birds pass through the country, but a few birds stay for the whole winter. The Lemsford studies show that colour-ringed birds have a high return rate from one winter to the next. These birds are actually in the general area of Lemsford for most of the year, only leaving to breed for two or three months. Upon return, in late summer, they use other local sites such as gravel pits, only switching to the watercress beds in the autumn.

Individuals birds visit a suite of sites; by tracking birds wearing radio tags, the team were able to establish that even birds that fed at Lemsford Springs (below) during the daytime would roost communally at the local gravel pits overnight.

Effects of cold weather

The research team found that the patterns of behaviour of the Hertfordshire Green Sandpipers varied with local weather conditions. During extremely cold weather in January and February the birds switched to roosting overnight at the watercress beds, where they could also feed. In these conditions, with the water frozen at gravel pits, roost sites were accessible to predators. Automated monitoring of tag locations showed that birds were active for around 80% of each daytime period at all times of year. Nocturnal activity varied from around 16% in autumn to over 40% in cold conditions in midwinter. This suggests that a low level of night time activity is normal in Green Sandpipers and that higher levels, found during extremely cold winter conditions, are the result of birds attempting to increase their daily food intake.

Annual survival

The return-rate of colour-ringed birds can be used as a surrogate for survival rates, bearing in mind that any bird that changes its wintering area will reduce the apparent survival rate, although still alive. (See WaderTales blog on measuring survival rates based on review paper in IBIS)

Once established in the Hertfordshire area, individual Green Sandpipers were likely to turn up in subsequent  winters, with little difference in return-rates between young birds, ringed in their first winter, and adults. There was considerable variation from year to year, with the return rates varying from 68.7 to 100%; the lowest being between 1986/87 and 1987/88, when another local winter site (Cole Green) became unsuitable. Birds using that site presumably went elsewhere or died. The average apparent annual survival rate was 83.5% (or 84.7% if account is taken of the disappearance of Cole Green). In the only other similar study, in northern Germany, the mean return rate was only 56%, with few birds returning in the year after a severe winter. In the Hertfordshire study, there is a correlation between the overall return rate of colour ringed birds from one winter to the next and the number of nights with air frost in the first winter (r = -0.86, n = 7, P < 0.05). These results suggest that birds suffer increased mortality in severe winters.

Territoriality

One of the interesting things that became apparent, once individuals could be identified using colour-rings, was that some of the Hertfordshire Green Sandpiper were highly territorial, with similar patterns of behaviour each year.

When Green Sandpipers appear in late summer they are usually found in small flocks, which include the colour-ringed full-grown adults and young birds of the year. At some point in the autumn, possibly triggered by low temperature or shortening day-length, the behaviour suddenly changes, with some of the birds establishing defended territories on the lagoons, from which they chase all interlopers. This initial burst of territoriality has been captured in the excellent images above and below this paragraph. Once the territories are established they are maintained by subtle calling displays, with only occasional full-on disputes.

During periods of very cold weather, additional birds arrived from other local sites and, for a short period in January 1984, the number of birds present on the reserve more than doubled (to a total of 16). The newly-arrived birds attempted to establish their own territories and devoted up to half of their time to boundary disputes, far in excess of that of the residents. When the weather conditions improved the additional birds left the reserve.

Territorial disputes

During the autumn and early winter of 1985, the research team attempted to investigate territoriality through activity watches of birds present on the lagoon at Lemsford. Every minute, each bird was scored as feeding, resting or disputing. Most watches were over at least one hour and all were completed during the period October to December. On the graph, the solid line and points are the counts of the numbers of birds, and the open symbols are the percentage of time that birds spent in dispute.

From early October, which corresponds to the end of the autumn moult, between 6 and 11 birds were present at Lemsford, feeding together as a group with little or no interaction. Around mid-October, the number of disputes started to increase. It varied in intensity from day to day but, over a few weeks, the numbers of birds present fell to four or five. These birds took ownership of exclusive territories that were largely maintained for the whole of the winter. Ken Smith was able to find all of the missing Green Sandpipers within 15 km of Lemsford. Some of these individuals would occasionally pop back to Lemsford, get involved in a fight and leave again. In extreme weather interlopers can spend the whole day trying to feed on the lagoons and being chased off.

From observations at Lemsford, it appears that, once territories have been established, local birds are well aware of their boundaries and neighbours. Should a bird stray into a neighbouring bird’s patch, a low-key call is sufficient warning to avoid a disagreement. Ken reports that the big disputes, with chasing and out-and-out aggression, only occur when the territories are being established or when a new bird tries to feed in an established territory. During extremely cold weather, in the 1980s, there would be lots of extra birds attempting to feed in the spring-fed watercress beds, by trying to squeeze into perceived gaps between territories. Such cold conditions are very rare nowadays.

A changing climate

Over the three decades of the project, there has been a tendency for cold winter temperatures to become less frequent across Britain & Ireland. During this time, the distribution of Green Sandpipers has expanded northwards, as you can see in the figure below.

The left-hand and central maps show the winter distributions of Green Sandpiper in the periods of the two winter atlases of 1981-84 and 2007-11, respectively. The surveys underpinning these maps were organised by the British Trust for Ornithology with BirdWatch Ireland and the Scottish Ornithologists’ Club. The expansion of the range represents a 56% increase in occupied 10-km squares, with an obvious extension into Scotland and across northern England, where winter temperatures are colder. Data collected for Bird Atlas 2007-11 included measures of effort, enabling relative abundance to be quantified. In the right-hand map, darker squares represent areas with higher numbers of Green Sandpipers. The Lemsford site is marked with a star.

As, mentioned earlier, there is an indication that annual return rates to Lemsford (and in the German study) relate to the conditions birds experience in the winter period prior to departure for their breeding grounds. In Scotland and Northern England, where freezing conditions occur more frequently, it might be expected that survival rates will be lower than in southern England. For winter populations to establish themselves in new (colder) sites, young birds will need to spend their first winters in these areas and then return in subsequent years. Local population can potentially grow unless or until knocked back by a cold winter.

Where to in spring?

In recent years, the research team have deployed harness-mounted geolocators to ascertain the movements of a small number of individuals during the course of a full annual cycle. Another WaderTales blog discusses migration and the effects of harnesses on the behaviour of individuals. See Green Sandpipers & Geolocators.

Summary and papers

This thirty-year study is an excellent example of what can be discovered through long-term observations of a small population of waders. You can read more about the Hertfordshire Green Sandpiper research in these papers (links in bold):

• K W Smith, J M Reed & B E Trevis (1984) Studies of green sandpipers wintering in southern England. Wader Study Group Bull, 42.
• K W Smith (1986) Green Sandpiper. In The Atlas of Wintering Birds in Britain and Ireland, pp 222-223, Poyser, Carlton.
• K W Smith, J M Reed & B E Trevis (1992) Habitat use and site fidelity of green sandpipers Tringa ochropus wintering in southern England. Bird Study, 39, 155-164.
• Smith, K W, Reed, J M & Trevis, B E (1999) Nocturnal and diurnal activity patterns and roosting sites of Green Sandpipers Tringa ochropus wintering in southern England. Ringing & Migration, 19, 315-322.
• Smith K W (2002) Green sandpiper in The Migration Atlas: movements of the birds of Britain and Ireland. Wernham C V, Toms M P, Marchant J H, Clark J A, Siriwardena G M & Baillie S R. (eds). T & A D Poyser, London.
• Smith, K.W., Trevis, B.E. & Reed, M. (2018). The effects of leg-loop harnesses and geolocators on the diurnal activity patterns of Green Sandpipers Tringa ochropus in winter. Ringing & Migration 32: 104-109.

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Graham (@grahamfappleton) has studied waders for over 40 years and is currently involved in wader research in the UK and in Iceland.  He was Director of Communications at The British Trust for Ornithology until 2013 and is now a freelance writer and broadcaster.