To learn more about waders, it has always been necessary to correctly identify them. Most species identification traits had already been established when the (International) Wader Study Group was created in 1970, but knowledge on the biometrics, moult and plumage characteristics useful to determine the subspecies, age and sex of individuals was still lacking. The creation of the Wader Study Group Bulletin (WSGB) allowed shorebird enthusiasts to share their findings among the community and continuously improve their identification, ageing and sexing skills. Such articles first appeared in the second volume of the WSGB in 1971, where Tony Prater shared advice on ageing Common Snipe Gallinago gallinago (Prater 1971), and continue being published to this day (Ruthrauff et al. 2020).
Before the end of 1971, Tony Tree published a possible method for ageing Ruff Calidris pugnax (Tree 1971) and the need for ageing more shorebird species was clear. After a draft had been prepared in June 1971, an ageing guide was produced at the BTO Ringing and Migration Conference in January 1972. More papers on ageing and sexing were published in the 1970s, such as on Common Ringed Plover Charadrius hiaticula (Taylor 1974) and Lapwing Vanellus vanellus (Fletcher 1976), and preparations for a thorough guide on the ageing, sexing, biometrics and moult of all frequent western Palearctic species started. By the end of the decade, The BTO Guide nº 17 – Identification and Ageing of Holarctic Waders (Prater et al. 1977) had been written! This would become a reference book that would accompany shorebird researchers to catching sessions, but as the authors state in the preface, much remained “to be learned about wader populations, their moult strategies and the methods of ageing, sexing and identification”. Hence, the sheer volume of work published on these topics in the WSGB and Wader Study in the following decades was not surprising.
Information on the primary moult of Common Sandpiper Actitis hypoleucos (Nicoll & Kemp 1983) and problems with ageing Dunlin Calidris alpina (Gromadzka & Przystupa 1984) were shared in the first half of the 1980s. Later in that decade, a comprehensive description of the axillary feathers of Bar-tailed Godwit Limosa lapponica provided a method to determine their breeding origin (Nieboer et al. 1985) and a discriminant and graphical analyses of Norwegian Knot biometrics Calidris canutus (Wood 1988) was published.
Information on the unusual primary moult of breeding Dunlin in the central Taymyr was published in 1990 (Kania 1990) and, after only a few years, another paper on ageing was published in the WSGB: a tip to age the (then) elusive (and now extinct?) Slender-billed Curlew Numenius tenuirostris (Zenatello & Serra 2002).
In 2007, an ageing and sexing series was created, in order to summarise the existing knowledge of ageing and sexing shorebirds, but also to highlight key gaps in our understanding. It started with the curonicus subspecies of the Little Ringed Plover Charadrius dubius (Meissner 2007). This series has been growing ever since and all the parts can be found here.
Forty years after the paper on ageing Common Snipe, Włodarczyk et al. (2011) published a method to sex this species using biometric data. Knowledge on the plumage dichromatism, wing–mass relationships and field techniques to sex breeding Semipalmated Plovers Charadrius semipalmatus was published in 2013 (Nol et al. 2013). In 2017, Devort et al. shared a method to age Jack Snipe Lymnocryptes minimus during autumn and, three years later, Ruthrauff et al. (2020) described how to sex Bristle-thighed Curlew N. tahitiensis using measures of bill depth.
There is still much to learn about the identification of the subspecies, age and sex of waders, and so more papers are expected to be published on the subject in the future. This short compilation gives a taste of the sort of information gathered and how that has changed in the last 50 years.
Ageing of Snipe Tony Prater Volume 2. 1971 An ageing character of the Ruff Tony Tree Volume 4. 1971 A method for adult sexing Ringed Plovers Charadrius hiaticula l., in summer plumage Robert C. Taylor Volume 11. 1974 Ageing and sexing of Lapwings (Vanellus vanellus) Mark Fletcher Volume 18. 1976 Partial primary moult in first-spring/summer Common Sandpipers Actitis hypoleucos M. Nicoll & P. Kemp Volume 37. 1983 Problems with the ageing of Dunlins in autumn Jadwiga Gromadzka & Bogdan Przystupa Volume 41. 1984 Axillary feathers colour patterns as indicators of the breeding origin of Bar-tailed Godwits E. Nieboer, J. Cronau, R. de Goede, J. Letschert & T. van der Have Volume 45. 1985 Discriminant and graphical analyses of Norwegian Knot biometrics: the sex and race problem revisited A. G. Wood Volume 52. 1988 The primary moult of breeding Dunlins Calidris alpina in the Central Taymyr in 1989 Wojciech Kania Volume 60. 1990 Ageing Slender-billed Curlews Numenius tenuirostris: a useful tip Marco Zenatello & Lorenzo Serra Volume 97. 2002 Part 1: Ageing and sexing the curonicus subspecies of the Little Ringed Plover Charadrius dubius Wlodzimierz Meissner Volume 113. 2007 Sexing Common Snipe Gallinago gallinago in the field using biometric criteria Radosław Włodarczyk, Piotr Minias, Patrycja Gogga, Krzysztof Kaczmarek, Magdalena Remisiewicz & Tomasz Janiszewski Volume 118-1, 2011 Using biometrics to sex adult Eurasian Curlews Numenius a. arquata Ron W. Summers, Snæbjörn Pálsson, Brian Etheridge, Simon Foster & Bob Swann Volume 120-1. 2013 Plumage dichromatism, wing–mass relationships and assessing the accuracy of field sexing techniques in breeding Semipalmated Plovers Erica Nol, Simone Williams, Katherine Wainio & Andrea Storm-Suke Volume 120-2. 2013 Age determination of Jack Snipe by plumage characteristics Michel Devort, Gilles Leray & Yves Ferrand Volume 124-1. 2017 Through thick and thin: Sexing Bristle-thighed Curlews Numenius tahitiensis using measures of bill depth Daniel R. Ruthrauff, Colleen M. Handel, T. Lee Tibbitts & Robert E. Gill, Jr. Volume 127-1. 2020