News

The 2025 IWSG annual conference will be taking place from 26-29 September in Groningen, netherlands. Registration and abstract submissions will open on 1 May. Deadline to submit an abstract & registration is 1 July. There is a limit to the number of participants so don't miss to register asap! Visit the website to find out more about the upcoming conference: [embed]https://www.waderstudygroup.org/conferences/2025-groningen-netherlands/[/embed]   Featured image: Colour-ringed Black-tailed Godwit, The Netherlands (© Simon Gillings).

On behalf of the 2025 IWSG conference organizing team.

We are now accepting workshop proposals for the upcoming conference ! If you have an idea for a workshop, we would love to hear from you. Workshops can focus on anything related to waders; methodologic tools, management discussions, societal engagement or any other relevant topic. The workshops will take place Friday 26th of September. If you are interested in hosting a workshop, please submit a short abstract or description of your proposed workshop by April 1st to iwsg.conference.2025@gmail.com. This should include the workshop’s topic, the expected duration, objectives, and any relevant details. Also mention any additional budget that might be needed to cover workshop costs.

  Featured image: Redshank, Tringa totanus ©Antoine Dusard.

The IWSG Annual Conference will be held from 26-29 September 2025 in Groningen, the Netherlands. Applications are now open for IWSG conference grants to support delegates from low-income countries. Eligible applicants can receive up to €800 to help cover conference registration, travel, and accommodation costs. A total of 12 grants will be awarded — 6 for West African applicants and 6 for other low-income country applicants.   All information to apply and application form are available on the conference webpage: [embed]https://www.waderstudygroup.org/conferences/2025-groningen-netherlands/#7[/embed]  

26 September — 29 September 2025

Dear IWSG Members, We hope this message finds you well. We are reaching out to seek your support in an important research initiative focusing on the migration strategies and wintering behaviours of waders in the Western Indian Ocean region. The islands of the Western Indian Ocean are at the southern limit of the West Asia – East Africa Flyway. These islands host diverse assemblages of palearctic waders, yet, compared to other flyways, they remain among the least studied and least understood. To fill this knowledge gap, the research team at UMR ENTROPIE (Université de La Réunion) has launched a project funded by the French Office for Biodiversity (OFB) dedicated to tracking waders in this region. As part of this initiative, we have deployed six Ornitela 3G GPS devices to track whimbrels across La Réunion and Mayotte, with plans to expand our study to Madagascar, which hosts an even greater number of waders. However, our ability to continue this research is challenged by the fact that Ornitela has ceased the production of 3G GPS devices due to the global transition to 4G and 5G networks. Unfortunately, most countries along our study flyway still rely on 3G, making these devices crucial for our work. How can you help? If you or any colleagues have unused Ornitela 3G GPS units that are no longer usable in your study areas due to the discontinuation of 3G networks, we would be deeply grateful if you could consider donating or selling them to us at a friendly price. Acquiring additional GPS devices would significantly enhance our capacity to track more birds and improve our understanding of wader migration in this understudied region. If you are interested in contributing, please feel free to contact me via email: florinah.razafimandimby@univ-reunion.fr. Alternatively, you can send devices directly to the following address: Razafimandimby Harivavikoa Florinah UMR ENTROPIE: "Unité Mixte de Recherche – Écologie Tropicale des Océans Pacifiques et Indien" Université de La Réunion 15 Avenue René Cassin, CS 92003 97744 Saint Denis Cedex 9 Île de La Réunion, France Phone: +262692707229 We also encourage you to share this request with any colleagues who might be able to assist. Your support would be invaluable in helping us advance this research and contribute to a better understanding of wader migration in the Western Indian Ocean region. Thank you in advance for your generosity and support! Best regards, Florinah Razafimandimby PhD Student, Université de La Réunion On behalf of my co-supervisors Matthieu Le Corre and Audrey Jaeger

  Featured image: Numenius phaeopus. ©Gertjan van Noord

by Deborah Buehler originally published in Wader Study 131(2) Imagine a place where the wind feels like a hair dryer – hot and dry. A place where faces are covered to protect against sand and sun. Now imagine a coastline, the sea brilliant blue and separated from salt flats and desert by a low line of dunes. And at the interface of land and sea, shallows and intertidal flats covered with birds. This is Banc d’Arguin, Mauritania. Banc d’Arguin is one link in a chain of important habitats that migratory shorebirds depend on for their survival. It is part of the East Atlantic Flyway, one of eight major migratory routes used by birds to move between breeding and wintering grounds. In human terms, a flyway is like a string of connecting flights. A problem early in the itinerary (say an outage that shuts down check-in) could cause a series of delays and the potential of missing the purpose of the travel (say a wedding or a funeral). It is similar for the birds, but with much higher stakes. Migratory birds from the north use Banc d’Arguin as a crucial non-breeding site while resident waterbirds and migrants from the south use the area for breeding. In 1973, during a British expedition, recoveries of ringed shorebirds and terns began to establish the significance of the area and its connectivity with coastal wetlands in Europe and with tundra breeding grounds beyond. Banc d’Arguin is now recognized as a site of international importance and the entire area was designated as a National Park by the Mauritanian government in 1976. The monitoring of waterbird populations in Parc National du Banc d’Arguin (PNBA) is also decades old with the first shorebird counts conducted in January/February 1980 and six further winter counts conducted in 1997, 2000, 2001, 2006, 2014 and 2017¹. Additionally, teams from the Royal Netherlands Institute for Sea Research (NIOZ) have conducted winter counts within the Iwik region of PNBA every year since December 2003. In this issue of Wader Study, El-Hacen and colleagues report on these two decades of annual monitoring complementing and updating larger-scale studies on long-term waterbird population trends². From December 2003 onward, the researchers conducted counts, after high spring tide in the last week of November, or in December or January. Counts were performed on a single day 1–2 hours before the predicted high tide and usually on a day when high tide fell in the early afternoon to standardize tide height and time of day as much as possible. The study area around the village of Iwik was subdivided into six counting units that covered all the roost sites (see Fig. 1 in the paper) and teams of one to two people covered each of the six units in the study area. [caption id="attachment_18558" align="aligncenter" width="699"] Shorebirds and waterbirds on intertidal flats with the village of Iwik in the background (photo: Jan van de Kam).[/caption] The Iwik region supports different waterbird groups: shellfish-eating shorebirds that breed to the north and spend the non-breeding season in PNBA, fish-eating waterbirds that breed in PNBA and are either resident or spend the non-breeding season to the south, and finally gulls and terns. The researchers analysed overall trends for these three waterbird groups and also selected the most common species within each group to assess individual trends over time (eight shorebird species, six species of large-bodied waterbirds, and six gull and tern species). In the analyses, they combined species that were difficult to distinguish in the field (e.g., small herons). To statistically analyze waterbird numbers over time, El Hacen and colleagues used generalized additive models (GAMs), which can estimate non-linear trends, identify periods and magnitudes of change, and account for the fact that the numbers one year are affected by what they were the year before (lack of independence among consecutive counts). Over two decades of study, the researchers found that waterbird numbers decreased from 120,000 to 80,000 birds in the Iwik study area. The models indicated that the decreases were non-linear and not the same across waterbird types. Shorebirds, which made up 90% of total waterbirds, declined in the first half of the study period from 2003 to 2012 and then stabilized from 2013 to 2023. Large-bodied waterbird numbers (cormorants, herons, spoonbills, flamingos and pelicans) were stable until 2012, increased to 2019 and then decreased from 2020–2023. Gull and tern numbers remained stable across both decades with no statistically significant variation. Looking at trends in the eight most common shorebirds, Red Knot Calidris canutus numbers followed the general trend, first decreasing, then stabilising after just over a decade. The decline of Red Knots in the Iwik area from 2003 to 2010 has been explained by decreases in the density of their preferred bivalve prey, which led the birds to consume a somewhat toxic alternative³. Bar-tailed Godwit numbers dropped continuously across the study period from 2003 to 2016, mirroring declines elsewhere in the flyway suggesting that factors beyond the Banc d’Arguin region, including climate change related shifts in food peaks in the Arctic during the breeding season, contributed to the decline. On the other hand, Whimbrels showed a steady and significant local increase indicating that conditions are favourable for Whimbrels in PNBA, at least in comparison to the rest of the flyway. The remaining five most common shorebird species showed year-to-year variations, but no statistically significant trends (Common Ringed Plover Charadrius hiaticula, Grey Plover Pluvialis squatarola, Dunlin Calidris alpina, Sanderling Calidris alba and Eurasian Curlew Numenius arquata). Amongst the six most common locally breeding waterbirds, three groups showed significant trends. Reed Cormorants Microcarbo africanus and small herons increased over the entire study period. Grey Heron Ardea cinerea monicae numbers increased strongly between 2003 and 2019, but then declined until the end of the study period. Other large waterbird species such as White-breasted Cormorant Phalacrocorax lucidus, Eurasian Spoonbill Platalea leucorodia, and Greater Flamingo Phoenicopterus roseus did not show statistically significant treads over the two decades, nor did the six most common species of gulls and terns. However apparent declines over the last 2–3 years may be ecologically, if not statistically, significant. For example, recent declines of the endemic subspecies of Grey Heron, Caspian Tern Hydroprogne caspia and West African Crested Tern Thalasseus albididorsalis coincide with the incidence of Avian Influenza in breeding colonies in West Africa.⁴ El Hacen and colleagues demonstrated the utility of annual and standardized monitoring of waterbirds near Iwik. They recommend that this annual monitoring be maintained, and that similar monitoring be established in the south of the PNBA. Such continued monitoring will increase knowledge about one link in a chain of critical sites along the East Atlantic Flyway. The other day, I felt a breeze as hot as the Mauritanian wind on my face. It reminded me of my own experiences working with shorebirds near Iwik in December 2006. I benefitted from a long-term collaboration between NIOZ and PNBA that has supported far more than winter counts. My study looked at the effect of age and environment on immune function in Red Knots and found that young birds at the lower quality Baie d’Aouatif roost site had higher white blood cell counts than adults or young birds at the higher quality Ebelk Aiznay site⁵. During my recent encounter with hair dryer hot wind, I was not in Mauritania, but rather far to the north, and the air was humid as well as hot. The heat and humidity created storms that unleashed a torrent of rain causing flooding in the subway. Due to delays, I nearly missed my regional train, a delay which would have caused me to miss the last regional bus at the next interchange, leaving me stranded. On long travels, success at each interchange depends on the last and each link is of paramount importance. In a world where climate change is making the weather unpredictable and violent, I feel solidarity with the birds, never quite sure what the next stop will bring, or if they’ll make it on time, on their tenuous journey from link to link.   ¹ Oudman, T., H. Schekkerman, A. Kidé, M. van Roomen, M. Camara, C. Smit, J. ten Horn, T. Piersma & E.-H.M. El-Hacen. 2020. Changes in the waterbird community of the Parc National du Banc d’Arguin, Mauritania, 1980–2017. Bird Conservation International 30: 618–633. ² El-Hacen. E.-H.M., J. ten Horn, A. Dekinga, B. Loos & T. Piersma. 2024. Two decades of change in nonbreeding population sizes of shorebirds and other waterbirds in the Iwik area of Parc National du Banc d’Arguin, Mauritania. Wader Study 131(2): 112–121. ³ van Gils, J.A., M. van der Geest, J. Leyrer, T. Oudman, T. Lok, J. Onrust, J. de Fouw, T. van der Heide, P.J. van den Hout, B. Spaans, A. Dekinga, M. Brugge & T. Piersma. 2013. Toxin constraint explains diet choice, survival and population dynamics in a molluscivore shorebird. Proceedings of the Royal Society B 280: S 20130861. ⁴ Davis, J. (2023). Bird flu outbreak spreads across West African migratory route. Natural History Museum. Accessed 31 Oct 2023. https://www.nhm.ac.uk/discover/news/2023/april/bird-flu-outbreak-spreads-across-west-african-migratory-route.html ⁵ Buehler, D.M., B.I. Tieleman & T. Piersma. 2009 Age and environment affect constitutive immune function in red knots (Calidris canutus). Journal of Ornithology 150: 815–825.   PDF of this article   Featured image: A large flock of shorebirds and six flamingos in Banc d’Arguin, Mauritania (photo: Jan van de Kam).

by Deborah Buehler originally published in Wader Study 131(3) You can learn a lot from poo. [caption id="attachment_18743" align="aligncenter" width="699"] Zackenberg Fjord in July 2022. How do researchers find out what birds are eating in a place like this? (© Mikhail Zhemchuzhnikov 2022)[/caption] For example, how can one determine what birds eat across the vast stretches of the Arctic tundra? The Arctic is a place where it is hard enough to find birds, and much harder to see what goes into their beaks. However, understanding the diet of birds that breed in the Arctic is paramount for understanding their habitat needs in a rapidly changing climate. Of particular interest is the possibility of mismatch between the peaks of breeding and food sources. Such mismatches could be caused by shifts in the timing and intensity of the seasons in the Arctic region, where climatic changes are most pronounced. To test for such mismatches, researchers need to understand both the peak abundance of various prey species (usually arthropods) and what growing chicks of various species actually eat after hatching. In this issue of Wader Study, Mikhail Zhemchuzhnikov and colleagues present the first use of DNA metabarcoding to identify multiple prey species in faecal samples from chicks of several shorebird species, breeding in Greenland¹. The researchers collected the data between 6 and 25 July 2022 in the high Arctic tundra at Zackenberg in northeast Greenland (74°28’N, 20°34’W). They captured shorebird chicks from six species that breed regularly in the area: Dunlin Calidris alpina, Red Knot Calidris canutus, Red-necked Phalarope Phalaropus lobatus, Red Phalarope Phalaropus fulicarius, Ringed Plover Charadrius hiaticula and Ruddy Turnstone Arenaria interpres. The researchers captured the chicks by hand during the pre-fledging period (before the chicks were old enough to fly). To collect the faecal samples, they put the chicks in a disinfected and sectioned plexiglass box. Each section contained one chick and was lined with two layers of fresh tissue paper. To minimize any negative impacts, chicks were released after 10 minutes if no defecation occurred. If a chick did leave a sample, it was scraped from the tissue using a clean disposable plastic spoon and stored in 96% ethanol at -20°C until laboratory analysis. How exactly can DNA barcoding a poo sample determine what a shorebird chick has eaten? DNA barcoding can identify taxonomic groups (e.g., species, family, or class) using short, standardized segments of DNA²; the DNA of what a bird has eaten remains at least somewhat intact within its droppings. The segment of DNA commonly used for Metazoans is usually a section of the gene known as “Cytochrome c oxidase subunit I”, located in the mitochondria of cells. This gene has a mutation rate roughly three times that of other forms of DNA². That means it is more likely to harbour genetic differences, even between closely related organisms. Primers specific to the gene are used in a polymerase chain reaction (PCR) to make many copies of this piece of DNA. These copies are then sequenced to determine their exact code. Every species has a unique sequence (“barcode”), just as every person has a unique fingerprint or each item for sale in a store or shop has a barcode. These DNA barcodes are then compared with a reference library to identify taxonomic groups. In DNA metabarcoding, a sample contains sequences of many potential organisms. For example, different arthropod groups have been found in a sample of shorebird poo. The proportion of copies for one particular sequence variation divided by the total number of copies (reads) is called Relative Read Abundance (RRA). [caption id="attachment_18745" align="aligncenter" width="699"] Red Knot Calidris canutus chicks before being released after their faeces were sampled. (© Roeland Bom)[/caption] How could the researchers be sure that what turned up after barcoding the samples truly reflected everything the birds had eaten? Additionally, how could they be sure that digestion did not degrade the DNA of some species more than others? These important questions were addressed in an earlier study on cavity-nesting birds that allowed the filming of parents feeding chicks³. Data from the camera footage validated that DNA metabarcoding of faeces accurately represented the ingested arthropod groups. This also validated that digestion did not bias the results for any particular group. Perhaps most exciting was that the study reported a high correlation between the relative read abundance of different variations and the consumed biomass of arthropod groups seen on the camera footage. If this is generally the case, then it means that read numbers retrieved from DNA metabarcoding can also be used to quantify the relative biomass of arthropod groups in bird diets. Following the DNA metabarcoding method used by Verkuil and colleagues³, Zhemchuzhnikov and colleagues showed that two-winged flies (Diptera) are a core component of Arctic shorebird chick diets: they were present as a majority in all droppings, except one Ringed Plover sample. Within Diptera, the dominant groups were Culicidae (mosquitoes), Chironomidae (non-biting midges), Muscidae (house flies), and Empididae (dagger or dance flies). Interestingly, the Ringed Plover sample showed a different arthropod composition. There were many reads from Lepidoptera (mainly geometer moths) and Hymenoptera (mainly parasitic wasps) and fewer from Diptera. The researchers speculated the parasitic wasps might represent secondary prey species (prey of the prey eaten by the chick). Blattellidae (cockroaches) were also found in this sample (and four others) but probably represent contamination during sample handling. The authors acknowledge that they sampled only a short time of the year and had only a small number of faecal samples per shorebird species. The next steps might include a longer sampling period to capture diet shifts within species during the breeding season. Additionally, the practice of using read numbers to approximate the relative contributions of prey taxa is quite new and has only been validated for an insectivorous songbird³. Despite the study’s limitations, Zhemchuzhnikov and colleagues have expanded the use of DNA metabarcoding to a new location in Northeast Greenland. They have provided new insights into the needs of Arctic breeding birds at a time when this region is warming and changing rapidly. This study is part of a rapidly increasing pool of knowledge generated by DNA barcoding, showing how this method can be used to better understand ecological diversity in various environments and how these environments support the harboured biodiversity. To quote Ben Panko in Smithsonian Magazine⁴ “The key to protecting life on earth may be barcoding it”.   ¹ Zhemchuzhnikov, M.K., T.S L. Versluijs, R.A. Bom, R. Blok, J.D.L. van Bleijswijk, J. Reneerkens & J.A.van Gils. 2024. A DNA-based dietary study of shorebird chicks in Greenland. Wader Study 131: 178–179.  ² International Barcode of Life. 2024. What is DNA barcoding? International Barcode of Life. Accessed 29 Nov 2024 at https://ibol.org/about/dna-barcoding/ ³ Verkuil, Y.I., M. Nicolaus, R. Ubels, M.W. Dietz, J.M. Samplonius, A. Galema, K. Kiekebos, P. de Knijff & C. Both. 2022. DNA metabarcoding quantifies the relative biomass of arthropod taxa in songbird diets: Validation with camera‐recorded diets. Ecology & Evolution 12: e8881. ⁴ Pando, B. 2017. The key to protecting life on Earth may be barcoding it. Smithsonian.com. Accessed 29 Nov 2024 at https://www.smithsonianmag.com/science-nature/how-dna-barcoding-opens-new-doors-conservation-180963431/   PDF of this article   Featured image: Incubating sanderling. Zackenberg, Greenland.  

The booklet for the 2024 edition of the IWSG Annual Conference is now finalized: note that this version does not include the list of participants (delegates, a full version has been sent to you by email)

The program for the 2024 edition of the IWSG Annual Conference is now finalized: The French Biodiversity Agency (OFB) and the LPO-BirdLife France look forward to welcoming you to Montpellier from September 20 to 24, 2024. On behalf of the IWSG 2024 Conference Team.  

by Deborah Buehler originally published in Wader Study 131(1)

Flying takes energy—a lot of it.

The airlines are certainly making this argument, as evidenced by the price of plane tickets these days. Humans can’t fly without substantial technical assistance, yet birds fly all the time. Shorebirds, for example, fly when migrating to and from breeding grounds, when moving between feeding areas, and when displaying to attract mates during the breeding season. Given that flight is costly, it makes sense that birds might try to optimize aspects of their flights to minimize energy consumption and to maximize reward. In this issue of Wader Study, Anders Hedenström reports on his investigation into how Common Redshanks Tringa totanus adjust their flight speed to optimize energy budgets in different ecological contexts.¹ How birds modify aspects of their behaviour in the context of optimization theory has fascinated shorebird researchers for decades. Flapping flight is energetically costly and studying it has led to theoretical models, that predict optimal speeds in different circumstances.² Hedenström’s study investigates whether wild Redshanks adjust their flight speeds in accordance with model predictions. [caption id="attachment_18101" align="aligncenter" width="700"] Anders Hedenström with equipment to track flight speed at the field site on the island of Öland in the southwestern Baltic Sea. (photo: Lotta Berg)[/caption] What makes flight costly? The mechanical power required to fly comes from the work done by muscles to overcome the pull of gravity and drag. To generate this power, muscles consume energy from stores of fat, protein, and carbohydrates originally ingested as food. Researchers have found that the relationship between the cost of flight and the speed of flight is U-shaped. In other words, flying takes the most energy during take-off and at very slow speeds, energy consumption decreases at moderate ‘cruising’ speeds, and then rises again at very fast speeds. Researchers use this ‘power curve’ to derive theoretical ‘optimal’ flight speeds in different circumstances including migration, foraging and displaying to attract mates. During migration, cruising speed is predicted to either optimize flight speed to minimize the time spent migrating or to minimize the total energy costs of the journey. For example, if early arrival at the breeding grounds means beating competitors to the best territories, then the first strategy of time minimization might be favoured. On the other hand, if food resources are limited, a strategy that favours energy economy might be best. A way to understand this in human terms is buying a plane ticket. If you need to arrive urgently, perhaps to visit someone who is ill, you might buy a more expensive flight to get to your destination faster. However, if money is very tight and you have time to spare, the optimum strategy might be to take a cheaper flight with several stopovers. This will allow you to make the journey with the funds you have available, but you’ll arrive three or four hours later. Birds also fly when searching for food. These foraging flights are short trips taken between local food patches. When foraging, birds usually fly faster than cruising speeds during migration, especially if the habitat provides plentiful food. How fast will depend on the rate at which the birds can lay down fat and energy reserves (fuel deposition rate). Theoretically, birds will either optimize flight speed to minimize the time spent foraging or minimize the energy expended to gather food. Perhaps there are predators in the area and the birds must forage as fast as possible before retreating to a safer place to rest. However, if food is scarce, birds might fly more slowly so that they can maximize their net energy gain by minimizing energy spent feeding. In our human analogy, foraging flight is like working to save money for the plane ticket. If you have a good job and can get long shifts, you’ll save quickly even if you need to spend a bit of money to get to work. On the other hand, if work hours are few and you have a long commute, you might skip a short shift because the pay is not worth the expense of getting there. Money saved is money earned after all. Finally, during the mating season, some birds spend a lot of energy on intricate display flights to attract mates. Because flight is costly, these displays are considered honest signals of fitness including health, good genes, and ability to provide resources. In some species, a long and drawn-out display might be preferred. In this case, the optimal flight speed would minimize the energy expenditure per unit of time. One the other hand, if acrobatics are preferred over display length, then the expected flight speed would be faster. In our human analogy, perhaps this is money spent trying to woo someone to come with you. You might spend more to convince someone who might pay for your ticket next week than on someone who might just share the costs of the hotel and rental car. In birds these predictions are fascinating, and though they have been validated in some species in wind tunnels,³ they are mainly theoretical for birds flying in the wild. Hedenström studied flight speed in several species but chose Redshanks for this investigation because they display a range of flight behaviours including long haul migrations in spring and autumn, ‘commutes’ between local feeding areas, and aerial displays to attract mates. He was able to observe all these behaviours in wild Redshanks on the island of Öland in the southwestern Baltic Sea. [caption id="attachment_18102" align="aligncenter" width="700"] Researcher tracking flight speeds. The infrared anemometer is measuring wind speed and direction in the background. (photo: Anders Hedenström)[/caption] Hedenström observed the birds at three study sites on a total of 81 days between April and October spread over the decade from 2012 and 2022. To measure flight speeds in the wild, he followed birds using an optical ranger finder, an ‘ornithodolite’, made from binoculars with built-in sensors for elevation angle and north, east, south or west bearing (azimuth). The ornithodolite is so named because it is used to study birds, ‘ornitho’, and because it works a little like a theodolite (an optical instrument, sometimes seen mounted on a tripod and used by surveyors to measure angles). ⁴ Distance from observer to bird was measured with an infrared laser. Concurrently, he measured wind speed and pressure either using an ultrasound anemometer near ground level, or the range finder to track helium filled balloons at higher altitudes. [caption id="attachment_18103" align="aligncenter" width="700"] Close up of the ornithodolite rangefinder. (photo: Anders Hedenström)[/caption] A series of time-stamped distance, elevation, and azimuth data for a bird constituted a run. Runs were classified as migratory flight, foraging flight or display flight based on flock size, time of year and flight behaviour. These were then combined with wind speed data so that airspeed could be deduced as the speed of the bird over the ground minus wind speed. These wind-corrected data yielded tracks which could be plotted on a map. Hedenström was able to analyse data from a total of 139 tracks distributed across migration (N = 84), local flights (N = 29), and display flights (N = 26). The data collected from Redshanks in the wild was compared to predictions generated by a theoretical model scripted in the R open-source programming language.⁵ The model produced a U-shaped relationship between aerodynamic power and flight speed for a bird of approximately Redshank size as determined by a sample of mass and wing measurements from Redshanks. The results indicated that airspeed differed depending on the ecological context (migration, foraging or display flight) and was influenced by flock size. During migratory flight, Redshanks flew faster than the predicted speed associated with the minimum cost of transport. This could indicate that the birds were minimizing the overall time required for migration. This is akin to opting for a faster flight which costs more rather than a slower but cheaper one. When foraging, Redshanks flew between patches of food (foraging areas) at faster airspeeds than birds during migration. This is consistent with the assumption that the birds need to save the most energy over the shortest period, just like when you work two jobs to pay for your plane ticket. Finally, when flying to perform aerial displays to attract mates, Redshanks flew at a speed predicted to use minimum power. This makes sense since the purpose of display flight is not to cover distance, but rather to spend as little energy as possible while still attracting a mate. Though Redshanks seemed to adjust their flight speeds in accordance with theoretical predictions regarding migratory, foraging and display flight, their airspeeds in relation to flock size and climbing speed were not as expected. The birds increased their airspeed with flock size rather than decreasing it as predicted, and they climbed towards cruising migration altitude at a much lower speed than the maximum possible. These results indicate that factors other than those considered by the model might be in play and more research will be required to solve these mysteries. Hedenström’s research shows that aerodynamic theory, and the models derived from it, are useful in predicting and understanding how birds optimize flight speeds in the wild. Though the data presented are limited to a single species and study area, they provide a tantalizing glimpse into how a seemingly simple behaviour, adjusting flight speed to balance energy budget, can be a rather complex exercise in optimization. Budgeting to buy a plane ticket provides an analogy for understanding the physiological optimization that goes into the lives of migratory birds. However, many people fortunate enough to afford recreational air travel do not have to think about how best to budget energy for survival. This study reminds us that organisms living in the wild are constantly balancing their energy budget. Anyone who has needed to fight for survival under conditions of restricted food, water or shelter knows this intimately. There is a link between energy and flight in humans too. The number of people on the brink of starvation rose from 80 million in 2017 to 350 million in 2023 in part due to the COVID-19 pandemic, climate shocks, and ongoing conflicts, yet there is $400 trillion worth of wealth on the planet.⁶ The coming decades could bring unprecedented human migration as people flee from unlivable circumstances. Perhaps we can learn something about the optimal distribution of resources from birds.   ¹ Hedenström, A. 2024. Adaptive flight speeds in the Common Redshank Tringa totanus. Wader Study 131(1): X–X. ² Hedenström, A. & T. Alerstam. 1995. Optimal flight speed of birds. Philosophical Transactions of the Royal Society B 348: 471–487. ³ Tobalske, B.W., T.L. Hedrick, K.P. Dial, & A.A. Biewener. 2003. Comparative power curves in bird flight. Nature 421: 363–366. ⁴ Pennycuick, C.J. 1982. The ornithodolite: An instrument for collecting large samples of bird speed measurements. Phil. Trans. Roy. Soc. B300: 61–73. ⁵ KleinHeerenbrink, M. & A. Hedenström. 2023. Tools for modelling of animal flight performance. R package version 1.1.0.3. Accessed at: https://github.com/MarcoKlH/afpt-r/ ⁶ Lederer, E.M. (2023). UN food chief: Billions needed to avert unrest, starvation. AP News. Associated Press. Accessed 13 Mar 2024. https://apnews.com/article/world-food-beasley-migration-starving-a88ae85e6fc5c2ecf7ddd6a9a6249aff   PDF of this article   Featured image: (c)Global Flyway Ecology