I have this memory that goes back about forty years, when my marvelous father took me for the first time to observe waders at the Saline di Siracusa, SE Sicily, Italy (my homeland); there was this salt-pan now in disuse, right at the southern gates of my city and the ponds for collecting sea-salt, that day, had a water level of a few centimeters, it was the end of August (I had just turned nine), and when we got to almost two hundred meters you could already hear dozens and dozens of wader calls: the restless and chattering redshanks, which echoed everywhere, the frantic dunlins that continuously flew in circles, hundreds of them, little stints that swarmed like grasshoppers along the muddy banks, pecking, chirping, the spotted redshanks with their bisyllabic call, tu-iì’t, could be heard all around. As you looked out from the embankment, the ponds were literally covered with 10-15 species of waders, with thousands of individuals. I remember, it was an incredible emotion, a feast for the eyes, to be there, with my first Leica telescope (the silver one), the result of almost a month’s salary from my fantastic dad who had given it to me for my birthday, with enormous sacrifices but knowing that it would be a traveling companion for me for many years to come, and would keep me firm on my healthy passion for birdwatching. Well, we were there, enraptured by all that diversity: each species with its characteristic bill depending on the type of prey and where it was sought, so short and stubby beaks (the “ringed-plovers”, the golden and the grey plovers along the canals and muddy banks, the hundreds of Kentish plovers on the beach), long and straight bills (the godwits, the redshanks and the spotted-redshanks, the greenshanks), long and curved downwards (the curlews) or upwards (the delicate and very elegant avocets). The length and shape of the bill, together with the length of the legs, already quickly directed you towards the genus and towards a very specific group of species, the plumage characteristics then, made you identify the exact species. It was exciting for me to be able to distinguish maybe 15 different species or more, within a radius of 500 square meters. And then listen to their vocal emissions, watch them fly back and forth, unstoppable and tireless. Virtually all of them came from thousands and thousands of kilometers away, from the distant Arctic.
That day we estimated about 25,000 waders in total. And so, for two decades, every June-September (post-breeding/post-juvenile migration), and February-May (pre-breeding migration), I was around all the former salt marshes, ponds, swamps and other wetlands of Sicily, counting 10,000/20,000 waders on peak passage days, looking for the rarest species among them (and therefore finding some Terek Sandpipers, the Red-necked Phalarope, discovering the first Lesser Yellowlegs for Sicily and the first Pectoral Sandpipers etc etc.).
But these remain only memories now, because those numbers are only tied to the past and to those magnificent days of happy childhood and serene adolescence, when everything was easy and wonderful, when the days were crystal clear and sunny, yes, but a cool breeze blew even in August and I thought that the world was infinite and its wonders eternal. Then I saw the wetlands reduce, in number and extension, I saw them remain completely dry earlier and earlier, I saw them privatized for commercial and agricultural purposes, I saw some covered in cement for tourism or buried to obtain land to cultivate (in Sicily as in Tunisia or Morocco and elsewhere), and I heard those thousands of calls echoing less and less, and I saw fewer variegated plumages to study, and fewer individuals to “picker” one by one in search of the rarest species. Today, some of the rare species are observed with increasing frequency (also most likely due to climate change), outside their usual migratory routes, but all the once common species are increasingly scarce, with ever-decreasing populations.
Waders are called “the sentinels of global warming”, that because they can be considered the indicators of climate change par excellence. Of the 245 wader species in the world, the demographic trend is known for at least 192 species. We know that of these, 57% are in moderate to very severe decline, 12% are increasing, while the other species have stable populations. For species that migrate to and from the Arctic, the trend is even more pronounced and clear: a very high percentage is in strong decline. In North America, for example, 26 of the 28 wader species followed in a targeted scientific study showed, between 1980 and 2019, a strong decrease and a constant decline trend especially in recent years (Smith et al. 2023). Of all the bird species in the world, waders and birds of agricultural and semi-steppe areas are those that show a more evident generalized decline. In a large study in 2014, also from North America, it was seen how the risk categories of several species of migratory waders have increased from minimal risk to vulnerable or even highly threatened (Galbraith et al. 2014).
Shorebirds that migrate to the Arctic during the spring to breed and raise their chicks, taking advantage of the abundance of prey (various invertebrates) during the short Arctic summer, have declined in the last twenty years due to habitat loss and poaching in wintering areas and along migration routes. Just to give a few examples: one of the most important wintering and stop-over site areas in the entire Mediterranean basin and North Africa, the Gulf of Gabés and the Island of Djerba, in southern Tunisia, has lost over 70% of its low-tide muddy coasts over the last twenty years due to the continuous tourist development that has led to the increasingly invasive construction of tourist accommodation and recreational facilities (which has come to a halt, or at least slowed down, after the terrorist attacks of 2015, 2020, 2023).
This has led to a considerable loss of habitat suitable for feeding and resting for wintering waders and migratory ones passing through, with a very strong impact on the survival, for example, of young ones during their first migration to the south. Changing geographical areas and continents completely, a terrifying percentage of the key wintering and migration stopover areas of the so-called East Asian-Australasian Flyway (EAAF), mainly in China (e.g. along the Yellow Sea), have been destroyed in the last twenty years. Furthermore, very heavy poaching is recorded throughout China, against all wildlife, and consistently against waders. Finally, the systematic and widespread collection of molluscs and other marine invertebrates, for food, “magic” pharmacopoeia and more, has led to a dramatic decrease in food sources in the surviving areas. This is just to give two macroscopic examples, but even a partial list would require a tome of hundreds of pages.
However, changes in Arctic breeding areas also certainly play a role in the decline of waders. The timing of arrival in the Arctic has evolved over millennia to correspond to the peak “spawning” and “emerging” of invertebrates, so as to have maximum trophic availability for the reproductive cycle. Long-distance migratory waders generally begin their migrations northward, based on the “lengthening” of daylight in their wintering areas and adjust their migration peaks based on environmental conditions along their migration routes away from the Arctic. In contrast, Arctic invertebrates are non-migratory, and are influenced by local conditions such as air temperature and snowmelt to emerge, emerge and reproduce.
The Earth is warming, but not uniformly; climate change is accelerating in the polar regions, resulting in potential discrepancies between the arrival of migratory waders and the availability of their prey. Average annual temperatures in these regions have increased by 2–3 degrees C since the mid-20th century, with the greatest warming during winter. Data from numerous scientific papers suggest that invertebrates are emerging on average 1–2.5 days earlier per decade. Some shorebirds have responded by arriving earlier in Arctic breeding grounds, but this varies by species. Species that arrive late in a warming Arctic may adapt by starting to lay eggs earlier once they arrive, but the capacity to adapt in this way is limited. Therefore, discrepancies between shorebird arrival, nesting, and invertebrate availability may be at least partially offset by warming-induced prolongation of invertebrate availability and the lower energy requirements of chicks to maintain body temperature. If current climate trends continue, however, some shorebird species are expected to be unable to meet the energy needs for optimal breeding success, and chick survival will decline.
In addition to this issue, according to further targeted scientific studies, currently, in the Arctic, almost 70% of all wader nests are predated, which represents a fundamental change and a significant problem for these birds. Since about the 2000s of the 20th-21st century, changes in the number of lemmings have occurred in the Arctic. These rodents are the basis of the predator-prey food web in Arctic areas. Due to more frequent temperature fluctuations, melting and refreezing of the snow cover, lemmings have been unable to find food under the snow, leading to a breakdown of the cycle and the decline of lemming populations in several areas. For Arctic predators, wader eggs or chicks represent an alternative prey; the predation rate has therefore increased with the decrease in lemming numbers. Before 2000, when lemmings were most numerous, waders had a hatching rate of up to 100% and virtually no predation or only occasional random predation. Relatively low predation was one of the advantages of the long migration of waders to the Arctic, and ensured that enough young fledged each year to maintain an optimal level of global populations. However, the results of some studies show that, on the contrary, the Arctic today represents a vast ecological trap for migratory waders in terms of nest predation. Such predation, moreover, has become all the easier, the more the nests remain easily accessible due to melting ice and snow cover, and evaporation of wetlands that leave the nests dry (and therefore easily reachable on foot by mammalian predators).
As if all the problems connected to global warming in breeding sites were not enough, in all the rest areas located along the very long migration routes, the increasingly frequent, incisive and dramatic drought is causing almost all the mandatory rest sites (stop-over sites) to be completely dry upon the arrival of the migratory contingents, which therefore find no suitable sites for resting, but above all they find no prey and places to feed, with a consequent net increase in mortality during migratory movements. This is clearly evident for example in North Africa and southern Italy.
Just to give an example relating to my homeland, Sicily, in the last ten years, I have witnessed an inexorable evaporation and increasingly premature drying up of lakes, estuaries, and coastal wetlands. In 2024, practically ALL the wetlands used as a rest area by migratory waders were already completely dry at the end of May-beginning of June, just when the migration to the south begins for many species.
But even the species that nest in Europe, including those that nest here, have had very serious consequences due to the drought. In the 2024 breeding season, out of over 100 pairs of Avocet that I followed in SE Sicily, only 4 chicks fledged (fledging rate 0.04% compared to 1.2-2.5% in normal years), out of over 150 Black-winged Stilts, only 22 fledged (0.18% compared to 2-2.80%), out of over 50 Kentish Plovers, only 20 fledged (0.4% compared to 0.8-1.2% in good years), not to mention the flamingos, all the anatidae, the little terns and so on.
In short, a real ecological catastrophe, which involves all the aquatic birds, but first and foremost and most consistently and evidently the migratory waders.
And it is evidently no coincidence that the only species of the Western Palearctic that will soon be declared extinct, after the Great Auk (Pinguinus impennis) in the mid-19th century, is precisely a wader: the Slender-billed Curlew (Numenius tenuirostris) (Corso et al. 2014; Kirwan et al. 2015).
Some suggested further reading
Shaftel, R., D. J. Rinella, E. Kwon, S. C. Brown, H. R. Gates, S. Kendall, D. B. Lank, J. R. Liebezeit, D. C. Payer, J. Rausch, S. T. Saalfeld, B. K. Sandercock, P. A. Smith, D. H. Ward, and R. B. Lanctot. 2021. Predictors of invertebrate biomass and rate of advancement of invertebrate phenology across eight sites in the North American Arctic. Polar Biology 44: 237-257.
https://www.science.org/doi/10.1126/science.aaw8529
DOI: 10.4018/978-1-6684-9034-1.ch007
Galbraith H, DesRochers DW, Brown S, Reed JM (2014) Predicting Vulnerabilities of North American Shorebirds to Climate Change. PLoSONE 9(9): e108899. doi:10.1371/journal.pone.0108899
Paul A. Smith, Adam C. Smith, Brad Andres, Charles M. Francis, Brian Harrington, Christian Friis, R. I. Guy Morrison, Julie Paquet, Brad Winn & Stephen Brown, 2023. Accelerating declines of North America’s shorebirds signal the need for urgent conservation action. Ornithological Applications, 2023, 125, 1–14 https:// doi.org/10.1093/ornithapp/duad003