Migration blogs on WaderTales

Here’s a selection of over forty WaderTales blogs that celebrate the wonder of shorebird migration. The focus is mainly on the East Atlantic Flyway, because that’s where I learnt about waders, but there’s a blog about the shocking drop in the numbers of waders that use the Yellow Sea migration route, an amazing story about a shorebird that links Egypt with the far east of Arctic Russia, some thoughts about teenage waders, focused on Hudsonian Godwits in Chile, and much more. 

Multi-species blogs

• Which wader, when and why? summarises the annual migration patterns of over 40 species of wader that visit Britain and Ireland.
• Sixty years of Wash waders celebrates the longest-running wader-ringing project in the UK  (and the world?), by summarising six decades of migration research.
• Are there costs to wearing a geolocator? considers the use of geolocators in studies of migration and the costs for small birds like Semipalmated Sandpipers.
• Wader declines in the shrinking Yellow Sea discusses the link between the amount of reliance on the Yellow Sea and population declines, across migrant wader species.
• Tagus estuary: for birds or planes? Although the focus is on Black-tailed Godwits, this blog is relevant to anyone who cares about estuaries that provide fuel for waders on migration.
• How many shorebirds use the East Asian-Australasian Flyway? summarises a stock-take of waders that link Russia & Alaska with Australia & New Zealand.

Oystercatcher

• Migratory decisions for Icelandic Oystercatchers explains how a new project is examining the costs and benefits of being a migrant.
• Which Icelandic Oystercatchers cross the Atlantic? Big ones – small ones – which gender – depends where you live? Do resident birds pair up?
• Oystercatcher migration: the Dad Effect is a fascinating story. It shows that the migratory behaviour of Iceland’s Oystercatcher chicks is aligned with the behaviour of their fathers, not their mothers.
• When mates behave differently examines how migratory behaviour affects the timing of nesting and potential breeding success.

Sociable Lapwing

• Following Sociable Lapwing describes how geolocators have revealed two distinct migration routes and identified key stopover sites. This is vital information for conservationists, keen to learn more about unsustainable hunting practices that are threatening the viability of this endangered species.

Ringed Plover

• Well-travelled Ringed Plovers from Chukotka in north-east Russia spend the winter in Somalia, Egypt, the Red Sea & the Persian Gulf. In Chukotka these Ringed Plovers breed alongside Buff-breasted Sandpipers heading for South America, Knot that will migrate to Australia and Spoon-billed Sandpipers that may migrate to Bangladesh. It’s a small world!

Grey Plover

• Plovers from the north is a blog about the global migration patterns of Grey Plovers (Black-bellied Plovers), with an Australian focus.

Dotterel

• Scotland’s Dotterel: still hanging on. The fate of Dotterel that breed on the plateaux in Scotland’s highest mountains may be more closely linked to changes taking place in North Africa than to warming conditions in their nesting areas.

Curlew

• The flock now departing reveals fascinating details about Curlew migration with descriptions of four occasions when two tagged birds ended up in the same migratory flock.
• A Norfolk Curlew’s summer does not appear to be a migration blog but it is! Join ‘Bowie’ as he flies to Portugal, avoiding forest fires.

Whimbrel

• Whimbrels on the move summarises a paper about the movements of Icelandic, ringed Whimbrel, using ringing and colour-ringing data.
• Iceland to Africa, non-stop discusses the speed of migration of Icelandic Whimbrel in spring and autumn.
• Whimbrel: time to leave summarises a paper about the consistencies and variability of annual migration patterns of individual Whimbrel.
• A Rhapsody of Whimbrel asks whether Whimbrel use time and weather cues in their travel ‘planning’ and might their plans change during the course of their lives?
• Winter conditions for Whimbrel looks for links between the conditions that individual Whimbrel experience in Africa and the subsequent breeding success in the Iceland.
• A Whimbrel’s year ties together all of the work in Camilo Carneiro’s PhD. Can Icelandic Whimbrel ‘catch up’ if there is a delay within the annual cycle?
• Whimbrels arrive in Iceland starts with observations of flocks of tired Whimbrel arriving on the south coast of Iceland, after five days in the air.
• In search of Steppe Whimbrel summarises a migration paper about two very special individual Whimbrel. Will this knowledge help to rescue a subspecies?

Bar-tailed Godwit

• Bar-tailed Godwits: migration & survival compares the efficacy of using rings and lettered flags to answer migration and conservation questions.
• New Bar-tailed Godwit Subspecies explains why taymyrensis should be considered as two separate populations, with important message for Bar-tailed Godwit conservation.

Black-tailed Godwit

The individual movements and breeding season behaviour of Icelandic Black-tailed Godwits have been studied for twenty years. They have been supported by thousands of birdwatchers who report colour-ringed birds.

• Why is spring migration getting earlier? discusses the pioneering role of new recruits to the Black-tailed Godwit population.
• Overtaking on Migration explains how Portuguese birds manage to overtake Black-tailed Godwits that winter further north, as they race to get back to Iceland early.
• Waiting for the wind – spring flocks of Black-tailed Godwit in Scotland reveals how dependent migrating godwit flocks are on weather patterns.
• Should Black-tailed Godwits cross the Sahara? investigates the trade-offs for limosa Black-tailed Godwits that winter in Iberia, instead of crossing the Sahara.
• Generational Change uses colour-ring sightings to explore how Black-tailed Godwit populations have changed in distribution and migratory timing.
• Black-tailed Godwits are on their way home reveals importance of Tagus Estuary (Portugal) to England’s breeding limosa Black-tailed Godwits.

Hudsonian Godwit

• Teenage waders is ostensibly about Hudsonian Godwits but raises general questions about the conservation of young shorebirds.
• Navigating a vast ocean follows Hudsonian Godwits, as they fly north across the Pacific Ocean and the Gulf of Mexico. How do they compensate for wind-drift?

Knot

• Red Knot pay the price for being fussy eaters compares the fortunes of Knot and Turnstone that stop off in Delaware Bay. As they fatten up to travel to the Arctic, the inflexibility of Red Knot make them more prone to unpredictable food supplies (and climate change).
• Subspecies, connectivity and conservation in shorebirds focuses on Red Knot that spend the non-breeding series in Chile, asking whether the concept of a subspecies may distract from local conservation priorities.

Sanderling

• Travel advice for Sanderling summarises research to understand the pros & cons of spending the non-breeding season in widely different locations.

Dunlin

• Dunlin: tales from the Baltic focuses upon declines of a disappearing population of schinzii Dunlin but set in a global context.

Semipalmated Sandpiper

• Gap years for sandpipers discusses the pros and cons of breeding every year. It is a long way from Peru to Alaskan and Canadian breeding grounds. There appears to be a trade off between migrating north in spring, to try to rear youngsters, and taking a gap-year. Staying in Peru increases the probability of survival, thereby securing more breeding attempts in future years.

Spoon-billed Sandpiper

• Spoon-billed Sandpipers: Track & Trace is another detective story. Spoon-billed Sandpipers are in big trouble, with an estimated population of just 660 birds, including youngsters. By satellite-tracking a small number of birds, an international research team has been able to identify new stop-over and wintering sites. This information will help to target efforts to protect habitats within key estuaries and to reduce hunting pressure.

Great Snipe

• Flying high with Great Snipe discusses the differing altitudes of daytime and nocturnal flights, set within broader research into migrations between Sweden and the Congo Basin.

Snipe & Jack Snipe

• Snipe & Jack Snipe in the UK and Ireland compares the migratory strategies of the two species and laments the decline of Common Snipe, as a breeding species.

Common & Spotted Sandpiper

• Not-so-Common Sandpipers mixes information about migration with a review of Common & Spotted Sandpipers by Phil Holland.

Green Sandpiper

• Green Sandpipers and Geolocators summarises a Ringing & Migration paper about changing behaviour patterns in Green Sandpipers that wore geolocators to study their migratory journeys. See map alongside.

Spotted Redshank

• Fewer Spotted Redshanks reviews migration patterns and changes in abundance of the species, in a British & Irish context.

Greenshank

• Migration of Scottish Greenshank may seem tame when compared to the massive journeys made by birds that winter in Australia. Blog based on neat small-scale study.

Here’s a link to the full list of WaderTales blogs. https://wadertales.wordpress.com/about/

The intention is to add one or two new blogs each month. You can sign up to receive an e-mail notification when a new one is published.

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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.

Travel advice for Sanderling?

Have you ever seen a colour-ringed Sanderling and perhaps wondered why it spends the non-breeding* season on a British or Irish beach rather than on one in Portugal, Ghana or even further south? Why fly from Greenland to Namibia, a distance of over 20,000 km, when spending the winter months in the UK or Ireland requires a flight of as little as 3,700 km? Perhaps the chance of survival is greater in other countries or perhaps birds that travel further have a larger lifetime breeding output? A paper by Jeroen Reneerkens and colleagues provides some of the answers.

*The term non-breeding season (rather than winter season) is used in this blog because Sanderling travelling as far as Namibia experience a southern summer at the same time as UK birds are experiencing a northern winter.

Pros and cons of travelling further?

At the end of the summer, juvenile Sanderling from Greenland start heading south. The first migration might take an individual to Scotland or Namibia, in southern Africa – or anywhere in-between. The circumstances that lead to these initial settlement patterns are unknown but an individual will repeat its first migratory journey every year, with some birds travelling just 7,400 km annually and others travelling over 44,000 km. It has been argued that, for a range of migration strategies to persist, different wintering sites will have balancing pros and cons. This suggests that costs of longer migrations might be matched by benefits gained at the non-breeding destinations. Is this really true?

Just six weeks after being ringed as a chick, this Sanderling was photographed in Mull (island off the west coast of mainland Scotland)

Using data provided by colour-ring sightings, Jeroen Reneerkens and colleagues assessed three factors that might affect the fitness of individual birds that spend the non-breeding period in different areas.

• Annual adult survival: If a bird from one non-breeding location is more likely to survive than a bird that spends the non-breeding season somewhere else, it should live longer and potentially have more breeding attempts within a lifetime.
• Age when a bird makes its first migration northwards: A young individual that flies north in its first spring will potentially have one more breeding opportunity than a bird that remains in the non-breeding area for its first summer.
• Timing of migration: There is a short breeding window in the High Arctic so a bird that migrates north earlier in the spring may have higher reproductive success, because it will have a higher chance to re-nest if a first clutch is lost. (There is more about this in Time to nest again?)

Studying marked birds

Sanderling were captured and ringed in breeding sites in northeast Greenland, at staging areas during migration (SW Iceland, N Scotland and the Dutch Wadden Sea) and in the non-breeding season (Scotland, England, Portugal, Mauritania, Ghana and Namibia). The different analyses in these studies used data from 5,863 Sanderling, of which 5,220 were individually colour-ringed.

Survival rates. By visiting key sites and collating additional reports of ringed birds from hundreds of birdwatchers, the research team were able to estimate the annual survival rates of Sanderling that spent the non-breeding season in England, France, Portugal, Mauritania, Ghana and Namibia. As can be seen in the table, the apparent survival rate in West Africa (Mauritania and Ghana) was much lower than that in Europe or Namibia. A bird with an annual survival rate of 0.75 is 67% more likely to die in any given year than a bird with a survival rate of 0.85. Confidence limits and methodological notes are provided in the paper. There is a WaderTales blog about the importance of measuring survival rates.

Age of first northward migration. The proportion of colour-ringed juveniles that migrated north in the first spring varied significantly, with virtually all Portuguese and English juveniles migrating north but only 35.8 % of those from Ghana and 9.6 % of those from Mauritania. (There were insufficient data to work out figures for Scotland, France and Namibia).

Timing of northward migration. Observations in Iceland provided information on the timing of migration of Sanderling from a range of non-breeding locations. This is the last possible stop-over site on northward migration, before birds migrate to their Arctic breeding sites in Greenland or Ellesmere Island in Canada. Birds from Ghana were observed in Iceland between 5 and 9 days later and those from Mauritania between 10 to 13 days later than the birds from Europe or Namibia. That is a considerable difference, given the short breeding period.

Flock of summer plumage Sanderling, on migration in Iceland

Summary

The authors asked the question “is there equal fitness throughout the non-breeding range?”, as inferred from the three measured discussed above. The answer seems to be “no”. Sanderling from non-breeding areas in West Africa had lower annual adult survival, delayed first northward migration and later passage through Iceland than birds wintering either further north or south.

Sanderling travelling north from Namibia do so by crossing the Sahara (generalised route – sample tracks are shown in paper)

Using geolocators**, the team was able to show that birds from Namibia bypassed potential staging sites in West Africa on the way north, flying north across the African continent to Europe, with some birds stopping briefly in the central part of the Mediterranean before spending a longer stop-over in NW Europe, thereby overtaking the Sanderling from West Africa. Namibian individuals used both Mauritania and Ghana as staging areas during southward migration.

** The use of geolocators is discussed in this blog.

The West African sites seem to be relatively poor places in which to spend the non-breeding months of the year. Food availability in spring is likely to be the chief problem. Theunis Piersma and colleagues have shown that the quality and biomass of prey available to shorebirds is lowest close to the equator, resulting in low fuelling rates and low body masses at departure for northward migration in Knot (Piersma et al. 2005).

Sanderling occupy a variety of different and widely-dispersed non-breeding sites between the northern tip of Scotland and the southern tip of the African continent. Here, they experience very different conditions which affect potential, life-time breeding outputs. Sites which appear to be poorer continue to be used, even though there are better options elsewhere, simply because individual birds have no knowledge of other potential areas where they could spend the non-breeding months.

A roll of the dice?

Once a juvenile Sanderling has settled upon a particular migration strategy and a spot in which to spend the non-breeding season, he or she will continue on the same annual cycle for the rest of his/her life. One of the big unknowns for waders/shorebirds – and for other groups of migrant birds for that matter – is just how these settlement patterns develop. (See Generational Change to read how young birds can create new patterns of migration).

Checking their data, Jeroen and his colleagues could see no pattern in the juvenile/adult proportions, sex ratios or sizes of the birds in different non-breeding areas that would help to explain differences in fitness. Birds from the same breeding areas of Greenland end up in non-breeding locations along the whole north-south range. It is almost as if the dice are rolled and a juvenile ends up where chance events take it.

At the level of the individual:

• A Sanderling that spends the non-breeding season in Ghana does not know that it would have a better annual survival rate and be likely to return earlier to Greenland each spring had it ended up wintering in England or travelled as far as Namibia.
• A bird in Namibia has no idea that it could have saved itself an accumulated migration distance of 37,000 km each year by stopping in England, without affecting its probability of survival.
• A first-year bird that spends its first potential breeding season feeding on the beaches of Mauritania, will be unaware that first-years from Portugal have all travelled north to Greenland.

It’s amazing what colour-ring readers have helped to discover but there is much still to learn about the migration strategies of individual waders.

Let’s hope that birdwatchers will continue to look out for colour-rings, as flocks of Sanderling chase the waves in and out on beaches throughout the world.

 

Paper in Journal of Animal Ecology

Low fitness at low latitudes: wintering in the tropics increases migratory delays and mortality rates in an arctic- breeding shorebird

Jeroen Reneerkens, Tom S. L. Versluijs, Theunis Piersma, José A. Alves, Mark Boorman, Colin Corse, Olivier Gilg, Gunnar Thor Hallgrimsson, Johannes Lang, Bob Loos, Yaa  Ntiamoa-Baidu, Alfred A. Nuoh, Peter M. Potts, Job ten Horn & Tamar Lok.

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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.