Fact-checked by Grok 2 weeks ago

Wader

Waders, also known as shorebirds, are a diverse group of birds belonging to the order Charadriiformes, characterized by their long legs and bills adapted for wading in shallow water to forage for small invertebrates such as worms, mollusks, and crustaceans along shorelines, mudflats, estuaries, and wetlands.^[1] These birds typically have compact bodies, long wings suited for flight, and bills varying in length and shape—from short and stout in plovers for surface pecking to long and curved in curlews for probing deep into mud—enabling them to exploit different food sources in their aquatic habitats.^[1]^[2] With approximately 220 species worldwide, waders are found on every continent except Antarctica, though they are most abundant in temperate and Arctic regions.^[1]^[3] Taxonomically, waders encompass several families within Charadriiformes, excluding more marine groups like gulls and auks; key families include Charadriidae (plovers and lapwings), Scolopacidae (sandpipers, snipes, and godwits), Recurvirostridae (stilts and avocets), and Haematopodidae (oystercatchers).^[1]^[4] Their habitats range from coastal beaches and tidal flats to inland marshes and freshwater ponds, with many species exhibiting remarkable adaptability to both saline and freshwater environments.^[1] Behaviorally, waders are often gregarious, forming large flocks during migration or non-breeding seasons for protection and efficient foraging, and they employ specialized feeding techniques, such as the rapid "sewing machine" pecking of snipes or the scything action of avocets in water.^[2] Reproduction occurs primarily in the breeding season, with most species laying 2–4 eggs in simple ground scrapes or nests camouflaged in vegetation, and both parents often sharing incubation and chick-rearing duties.^[1] A hallmark of many wader species is their long-distance migration, with some traveling thousands of kilometers annually between Arctic breeding grounds and southern wintering sites in Africa, South America, or Australasia, relying on stopover sites for refueling.^[2] Notable examples include the bar-tailed godwit, which completes one of the longest non-stop flights in the animal kingdom, and the red knot, known for its dramatic plumage changes and flocking behavior.^[2] As of 2024, waders face significant conservation challenges, including habitat loss from development and agriculture, climate change impacts on migration routes, and disturbance from human activities, leading to population declines in species like the Eurasian curlew and northern lapwing; the IUCN Red List update reclassified 16 shorebird species to higher threat categories, with global populations plummeting.^[5]^[6] Efforts by organizations such as the Wildfowl & Wetlands Trust focus on wetland restoration and monitoring to support these ecologically vital birds, which play key roles in controlling invertebrate populations and indicating wetland health.^[7]

Taxonomy and systematics

Definition and scope

Waders, also known as shorebirds in North American English, represent an informal grouping of long-legged birds primarily from the suborders Charadrii and Scolopaci within the order Charadriiformes, excluding gulls, skuas, and their allies.^[8] This assemblage encompasses species adapted to wading in shallow waters, such as coastal mudflats, estuaries, and wetlands, where they forage for invertebrates and small aquatic prey. The term "waders" highlights their characteristic behavior of standing or walking in water to access food sources, distinguishing them from other Charadriiformes like auks or gulls that exhibit different ecological niches.^[2] Key families within this grouping include Charadriidae (plovers and lapwings), which feature compact bodies and short bills for surface pecking; Scolopacidae (sandpipers, snipes, and phalaropes), known for varied bill shapes suited to probing sediments; Haematopodidae (oystercatchers), with robust, wedge-shaped bills for prying open shellfish; and Recurvirostridae (stilts and avocets), characterized by exceptionally long legs and upcurved bills in some species. Glareolidae (pratincoles and coursers) is sometimes included with caveats, as these birds blend wader-like terrestrial foraging with aerial insect-catching, placing them taxonomically in the Lari suborder but ecologically aligned with shorebird lifestyles in certain contexts.^[9] Unlike formal taxonomic ranks such as orders or families, waders do not constitute a monophyletic clade; instead, they are united by convergent ecological similarities, including habitat preferences and foraging strategies, rather than strict phylogenetic descent.^[10] The usage of "wader" originated in British English ornithology to describe these birds' wading habits, a convention still prevalent among ornithologists in Britain and much of the British Commonwealth (except Canada), where "shorebird" is reserved for North American contexts.^[11] This informal designation has persisted in field guides and conservation efforts, facilitating discussions of species that share vulnerability to habitat loss despite their polyphyletic origins.

Evolutionary history

The order Charadriiformes, encompassing waders and their relatives, traces its origins to the Late Cretaceous period, with molecular clock analyses estimating the most recent common ancestor of the group at approximately 93 million years ago (95% confidence interval: 84–102 Mya). This estimate is derived from multigene sequence data calibrated with multiple fossil constraints, indicating that at least 14 major lineages within the order predate the Cretaceous-Paleogene (K-Pg) boundary at 66 Mya, allowing several clades to survive the mass extinction event. The fossil record, however, does not preserve pre-Eocene charadriiforms, with the earliest unequivocal remains appearing in the early Eocene, around 53–56 Mya; notable examples include Charadriisimilis essexensis, a modern-type charadriiform represented by a partial skeleton from the London Clay Formation in Essex, UK, which exhibits traits aligning it closely with crown-group Charadrii.^[12]^[13]^[13] Phylogenetic analyses resolve Charadriiformes into three monophyletic suborders: Charadrii (plovers, oystercatchers, stilts, and allies, including waders proper), Scolopaci (sandpipers, jacanas, and seedsnipes), and Lari (gulls, auks, skuas, and buttonquails). The divergence among these suborders occurred in the late Cretaceous, between 79 and 102 Mya, with Charadrii forming the sister group to a clade comprising Scolopaci and Lari; this basal split for Charadrii is estimated near the crown-group most recent common ancestor at 93 Mya. Diversification within these suborders accelerated in the Paleogene, particularly during the Eocene thermal maximum, as evidenced by the post-K-Pg radiation of genera, which correlates with the expansion of coastal and wetland habitats.^[12]^[12]^[12] Key evolutionary adaptations in waders, particularly within Charadrii, include the elongation of legs and bills, which facilitated probing and foraging in soft substrates like mudflats and shallow waters. These traits likely evolved under selective pressures in post-Cretaceous coastal environments, where increased availability of intertidal zones post-K-Pg supported specialized feeding strategies; for instance, longer bills enabled deeper penetration into sediments for invertebrate prey, while extended legs minimized body contact with water to preserve insulation. Within Charadrii, plovers (family Charadriidae) occupy a basal position cladistically, characterized by shorter, more generalized bills and legs suited to surface pecking, whereas more derived families like Haematopodidae (oystercatchers) show further specialization. In contrast, Scolopacidae represents a derived lineage within the sister suborder Scolopaci, featuring highly specialized long, flexible bills for deep probing, underscoring the parallel evolution of wading adaptations across suborders.^[14]^[12]^[12]

Major families and species

The family Charadriidae, encompassing plovers and lapwings, includes approximately 66-69 species distributed across 9-12 genera, representing a basal lineage within the shorebird radiation.^[15] Notable genera include Charadrius (ringed plovers and allies), Vanellus (lapwings), and Pluvialis (golden plovers), with the ringed plover subgroup featuring species adapted to coastal and inland habitats. A representative species is the Northern Lapwing (Vanellus vanellus), characterized by its distinctive crest and widespread distribution in Eurasia. Scolopacidae stands as the largest family of waders, comprising around 95-97 species organized into several subfamilies, such as Tringinae (shanks and phalaropes) and Calidrinae (godwits, curlews, and sandpipers); as of 2025, recent taxonomic splits, such as the division of the Whimbrel into Eurasian Whimbrel and Hudsonian Whimbrel, have slightly adjusted these counts.^[15]^[16] Key genera include Tringa (shanks), Calidris (sandpipers), and Numenius (curlews), reflecting diverse foraging adaptations from probing mudflats to picking invertebrates. The Common Redshank (Tringa totanus) exemplifies the family, known for its alert demeanor and red legs in wetland environments across Europe and Asia. Phylogenetic analyses based on DNA sequences have resolved Scolopacidae as monophyletic, overturning earlier classifications that deemed it polyphyletic by grouping disparate taxa like turnstones and dowitchers.^[17] Other significant families include Haematopodidae, with 12 species of oystercatchers in the genus Haematopus, specialized for prying open bivalves along coasts worldwide. Recurvirostridae encompasses 9-10 species of stilts and avocets across genera like Himantopus and Recurvirostra, noted for their long legs and upturned bills suited to shallow waters. The inclusion of Thinocoridae, featuring 4-6 species of seedsnipes in genera Attagis and Thinocorus, remains debated due to their seed-based diet and terrestrial habits in Andean regions, though molecular evidence supports their shorebird affinity. Globally, waders number approximately 217 species, with phylogenetic trees derived from DNA data illustrating close inter-family relationships within Charadriiformes, such as the sister grouping of Charadriidae and Scolopacidae.^[18]

Physical characteristics

Morphology and adaptations

Waders, also known as shorebirds, exhibit a wide range of body sizes, from the diminutive Little Stint (Calidris minuta), weighing approximately 20–40 grams, to the substantial Eurasian Curlew (Numenius arquata), which can reach up to 1.36 kilograms.^[19]^[20] This variation in size supports diverse ecological roles, with smaller species adapted for agile movements in dense vegetation and larger ones for probing deeper substrates. Many waders display cryptic camouflage through streaked or mottled plumage patterns on their upperparts, which blend with sandy or muddy backgrounds to evade predators during foraging or nesting.^[14] A defining morphological feature of waders is their long, thin legs, which enable them to wade efficiently in shallow water or mudflats while keeping their bodies elevated and dry.^[21] These legs are typically unwebbed, providing stability on soft terrain, though some species, such as phalaropes (Phalaropus spp.), possess partial webbing or lobed toes at the base, facilitating swimming in open water or during oceanic stages of migration.^[22] In many scolopacid waders, females exhibit slight sexual dimorphism in leg length, with larger females having proportionally longer legs than males.^[14] Wader bills show remarkable diversity in shape and function, reflecting adaptations to specific prey and substrates. Sandpipers (Calidris spp.) typically have straight, probe-like bills for inserting into sediment to extract invertebrates, while curlews like the Eurasian Curlew (Numenius arquata) feature long, decurved bills suited for probing curved burrows in mud or soil.^[14] Oystercatchers (Haematopus spp.) possess stout, wedge-shaped bills reinforced for prying open bivalve shells.^[14] This bill morphology often correlates with hindlimb structure, optimizing overall foraging efficiency across habitats.^[14] Sensory adaptations enhance waders' ability to forage in challenging environments. Many species have relatively large eyes, which allow for improved visual acuity in low-light conditions, such as dawn, dusk, or overcast days on tidal flats.^[23] Probe-foraging waders, including sandpipers and curlews, feature specialized tactile pits at the bill tip containing Herbst corpuscles—mechanoreceptors that detect vibrations from buried prey, enabling remote sensing without visual cues.^[24] These pits are densest in longer-billed species, supporting precise localization in opaque sediments.^[14]

Plumage, coloration, and sexual dimorphism

Waders exhibit distinct seasonal variations in plumage, with non-breeding adults typically displaying muted tones of browns and grays that provide effective camouflage against mudflats and coastal habitats. For instance, the Dunlin (Calidris alpina) in winter plumage features grayish-brown upperparts, head, and breast with pale underparts, allowing it to blend seamlessly with the subdued colors of estuarine environments.^[25] These earthy hues and scaly patterns formed by pale feather edges on the back are common across many species, enhancing concealment from predators during foraging on exposed tidal flats.^[2] In contrast, breeding plumage often incorporates brighter and more contrasting colors to facilitate territorial and reproductive activities in Arctic or temperate nesting grounds. The Ruddy Turnstone (Arenaria interpres) in breeding season shows striking rufous upperparts streaked with black, paired with a bold black-and-white harlequin pattern on the head, neck, and breast against a white belly, marking a vivid departure from its drabber winter form.^[26] Similarly, the Killdeer (Charadrius vociferus) displays a bright orange-buff rump and rufous fringes on the upperparts during breeding, accentuating its otherwise brownish-tan body and black breast bands.^[27] These seasonal shifts result from biannual molts, where most waders replace body feathers twice yearly—once post-breeding into non-breeding plumage and again pre-breeding—often with substantial color changes to suit environmental demands.^[28] Sexual dimorphism in waders is generally subtle, with limited differences in plumage coloration between males and females outside of specific lineages. In most species, such as those in the family Scolopacidae, females are slightly larger than males, but plumage patterns remain largely similar across sexes, with any variations minimal and not strongly expressed except during peak breeding periods.^[29] A notable exception occurs in phalaropes (genus Phalaropus), where reversed sexual dimorphism prevails: females are both larger and more brightly plumaged than males in breeding season, featuring richer reds and grays to signal reproductive readiness.^[30] Juveniles, upon fledging, briefly retain elements of their downy chick plumage before undergoing a post-juvenile molt into a more patterned juvenile feathering, which they maintain through their first winter.^[31]

Behavior and ecology

Habitat preferences and distribution

Waders primarily occupy wetland ecosystems, including coastal mudflats, estuaries, saltmarshes, and inland freshwater marshes, ranging from tropical lowlands to arctic tundra. These habitats provide the soft substrates and shallow waters essential for their activities, with species favoring open, exposed areas during non-breeding periods and more vegetated or moist zones for breeding.^[32]^[33] Globally, waders exhibit a widespread distribution, with the highest species diversity concentrated in the temperate and arctic zones of the Northern Hemisphere. Approximately 50 shorebird species breed across Arctic tundra habitats, accounting for a substantial portion of global diversity, including about 35 species with primary ranges in the Arctic and 15 extending from subarctic regions. Australasia functions as a critical stopover area for migratory populations along the East Asian-Australasian Flyway, supporting diverse assemblages during transit.^[34]^[35] Microhabitat selections differ among families; for instance, plovers in the family Charadriidae typically select open shorelines, sandy beaches, and sparsely vegetated flats near water bodies, while scolopacids often exploit intertidal mudflats and wet tundra meadows. Certain species adapt to extreme elevations, such as the Tibetan sand plover (Anarhynchus atrifrons), which breeds in high-altitude wetlands on the Qinghai-Tibetan Plateau up to around 5,000 m.^[36] Most wader species demonstrate pronounced seasonal shifts, breeding in high-latitude northern wetlands during summer and wintering in tropical or subtropical coastal and inland sites, driven by food availability and climate. The vast majority are migratory, with only a small proportion—such as certain resident plover populations—remaining non-migratory year-round, resulting in low overall endemism.^[33]^[37]

Foraging and diet

Waders primarily consume invertebrates, including polychaete worms, crustaceans, bivalves, gastropods, and insects, which form the bulk of their diet in intertidal and wetland environments.^[38] For instance, smaller species such as the Curlew Sandpiper (Calidris ferruginea) rely heavily on polychaetes.^[38] Some species exhibit omnivory, incorporating plant material; dowitchers (Limnodromus spp.), for example, consume seeds from grasses, bulrushes, and pondweeds alongside marine worms and mollusks.^[39] Foraging techniques vary by family and are adapted to prey location and substrate type. Plovers (Charadriidae) employ visual hunting, using a pause-travel strategy to scan and peck at surface prey on mudflats.^[14] In contrast, sandpipers (Scolopacidae) often use tactile probing, inserting their bills deeply into sediment to detect buried invertebrates via mechanoreceptors at the bill tip; godwits (Limosa spp.) perform a characteristic stitching motion during this probing.^[14] These behaviors are synchronized with tidal cycles, as waders typically forage during low tide when intertidal zones expose prey-rich substrates.^[40] Dietary composition shifts with seasonal demands, particularly during migration when high-energy needs drive fat accumulation. Migratory waders increase consumption of energy-dense bivalves during pre-migratory fuelling phases, as seen in larger species wintering in coastal archipelagos, while smaller ones favor polychaetes for similar purposes.^[38] Daily variations may occur based on prey availability, but overall intake prioritizes accessible, high-biomass invertebrates to meet metabolic requirements.^[40] As key predators in intertidal ecosystems, waders influence benthic community structure through selective predation on dominant invertebrates, potentially mediating trophic cascades that enhance wetland resilience.^[41] Their foraging reduces densities of prey like polychaetes and bivalves, altering sediment dynamics and promoting biodiversity in mudflat habitats.^[42]

Breeding biology and reproduction

Waders exhibit diverse mating systems, with most species forming seasonal monogamous pairs that facilitate biparental care during breeding.^[43] This monogamy is prevalent across families like Charadriidae (plovers) and Scolopacidae (sandpipers), where pairs defend territories and share reproductive duties to maximize offspring survival. However, exceptions occur in phalaropes (Phalaropodidae), which display sequential polyandry; females are larger and more colorful, competing aggressively for mates while males perform all incubation and chick-rearing, allowing females to lay multiple clutches in a season.^[44] Similarly, jacanas (Jacanidae) show sex-role reversal, with polyandrous females defending large territories and males assuming primary parental roles.^[45] Nesting in waders typically involves simple ground scrapes, shallow depressions formed by the birds' bodies with minimal lining of vegetation, pebbles, or shells for camouflage.^[46] Clutch sizes generally range from 2 to 5 eggs, with many species like plovers laying a characteristic 4-egg clutch adapted to their environment's predation pressures.^[47] Incubation periods last 20-30 days, often biparentally in monogamous species through alternating shifts, though in polyandrous taxa such as phalaropes, males incubate alone to enable female remating.^[48] Parental care is predominantly biparental, involving both sexes in guarding and leading precocial chicks—which hatch fully feathered and mobile, capable of foraging independently shortly after emerging.^[49] In sex-role reversed species like jacanas, males provide sole post-hatching care, brooding and protecting chicks from threats. Breeding success is heavily impacted by high nest predation rates, often reaching 50% in open habitats, mitigated by cryptic plumage for concealment and distraction displays where adults feign injury to lure predators away.^[50]^[51]

Migration patterns

Many wader species, comprising approximately 80% of the global total, are long-distance migrants that undertake extensive journeys between high-latitude breeding grounds and tropical or subtropical wintering areas.^[52] For instance, the bar-tailed godwit (Limosa lapponica) is renowned for its non-stop flights exceeding 11,000 km, such as from Alaska to New Zealand or Tasmania, covering up to 13,560 km in juveniles over 11 days without feeding or resting.^[53] These migrations often span hemispheres, with birds navigating via innate orientation, celestial cues, and geomagnetic fields to complete annual cycles twice yearly.^[54] Principal migration routes follow established flyways, including the East Atlantic Flyway, which channels birds from European and western Asian breeding sites to sub-Saharan African wintering grounds, and the East Asian-Australasian Flyway, linking Arctic and subarctic breeders to Southeast Asia, Australia, and New Zealand.^[55]^[56] Stopover sites along these pathways, such as coastal wetlands, are essential for refueling, where waders can regain up to 50% of their body mass in days through intensive foraging before resuming flight.^[57] Physiological adaptations enable these feats, with pre-migratory hyperphagia—intense feeding—allowing birds to nearly double their body mass in 2-3 weeks by accumulating fat reserves that fuel extended flights.^[58] During migration, waders achieve sustained airspeeds of 40-60 km/h, often in cohesive flocks that enhance aerodynamic efficiency through V- or echelon formations, reducing individual energy costs by up to 20-30%.^[59] Post-flight, birds rapidly metabolize these reserves, sometimes losing half their mass in days upon arrival.^[60] Waders exhibit strong philopatry, with high site fidelity to breeding, stopover, and wintering locations, where adults often return to the same territories year after year, promoting population stability but potentially increasing vulnerability to localized habitat loss.^[61] However, climate change is disrupting these patterns, with many species arriving earlier at breeding grounds—advances of 1-5 days per decade noted since the 1990s—due to warmer temperatures altering food availability and wind patterns along flyways.^[62] This temporal shift risks phenological mismatches, such as breeding before peak invertebrate prey emerges.^[63]

Conservation and threats

Population status

Wader populations worldwide have shown concerning declines over recent decades, with over half of species exhibiting downward trends based on available data. In North America, for instance, more than half of the 52 regularly breeding shorebird species have experienced population reductions of 50% or more since the late 20th century, with declines accelerating for 13 species. In Europe, the Eurasian Curlew (Numenius arquata) has declined by approximately 50% since the 1990s, reflecting broader patterns among breeding waders. These trends are particularly pronounced among migratory species, where habitat pressures along flyways contribute to reduced abundance, though specific migration dynamics are addressed elsewhere.^[64]^[65]^[66] Global estimates indicate that migratory wader populations number in the tens of millions annually, supporting vast flyway networks, but many species face critically low numbers. For example, as of the 2024 IUCN assessment, the Critically Endangered Spoon-billed Sandpiper (Calidris pygmaea) is estimated to have 330–550 mature individuals (approximately 165–275 breeding pairs) at the end of the breeding season. Such vulnerable taxa highlight the fragility of certain wader groups, with scolopacids (sandpipers and allies) showing disproportionate declines compared to other families.^[67]^[68]^[69] According to the 2024 IUCN Red List update, approximately 15% of shorebird species (21 out of about 140) are classified as globally threatened (Vulnerable, Endangered, or Critically Endangered), while 19% (26 species) are Near Threatened, leaving approximately 66% (93 species) as Least Concern among those assessed, with 16 migratory shorebird species uplisted to greater threat levels in the 2024 assessment alone. This breakdown underscores the elevated risk for waders, with scolopacids overrepresented in higher threat categories due to their reliance on dynamic coastal habitats.^[5]^[70] Population status is monitored through coordinated international efforts, such as the International Waterbird Census (IWC), which involves annual volunteer-led surveys at over 25,000 wetland sites across 143 countries to track abundance and distribution changes in waders and other waterbirds. These site-based counts provide essential data for detecting trends and informing conservation priorities, with regional programs like the UK's Wetland Bird Survey contributing to flyway-scale analyses.^[71]^[72]

Major threats

Habitat loss due to coastal development and wetland drainage poses the most significant threat to wader populations worldwide, particularly by destroying critical stopover sites along migration routes. In the East Asian-Australasian Flyway, reclamation projects have led to the loss of over 65% of intertidal mudflats in the Yellow Sea since the 1950s, severely impacting species like the bar-tailed godwit and great knot that rely on these areas for refueling during long-distance migrations.^[73] Similarly, wetland drainage in Europe and North America has degraded up to 50% of key coastal habitats, forcing waders to use suboptimal sites with reduced food availability and increasing energy costs during migration.^[74] Climate change exacerbates these pressures through sea-level rise, which erodes breeding islands and intertidal foraging areas essential for wader reproduction and survival. Projections indicate that a 1-meter rise could inundate 20-30% of global coastal wetlands by 2100, directly threatening Arctic and temperate breeding grounds for species such as the dunlin and red knot.^[75] Additionally, warming temperatures cause phenological mismatches, where altered timing of invertebrate prey emergence disrupts food webs and leads to lower chick survival rates in breeding populations.^[76] Illegal hunting remains a pervasive issue, especially in Africa and Asia, where unregulated shooting and trapping target migratory waders during stopovers. In West Africa, sites like the Banc d'Arguin serve as wintering grounds for over 2 million birds, with illegal hunting contributing to regional declines in species like the ruff and little stint. In Asia, similar practices along the flyway involve mist nets and shotguns despite legal protections. Recreational disturbances from human activities, such as beach walking and dog exercise, further compound this by reducing foraging efficiency; studies show that even low levels of disturbance can decrease intake rates by 25-30% through repeated flushing events.^[77]^[78] Pollution from oil spills contaminates foraging habitats, leading to direct mortality and long-term bioaccumulation in food chains that affects wader health and reproduction. The 2010 Deepwater Horizon spill, for instance, oiled thousands of shorebirds in the Gulf of Mexico, with lingering effects on species like the American oystercatcher persisting years later.^[79] Increased predation due to invasive species, such as red foxes expanding into Arctic nesting areas amid climate-driven habitat changes, has raised nest failure rates to over 70% in some regions, decimating local populations of ground-nesting waders like the semipalmated sandpiper.^[80] These combined threats have driven widespread population declines, underscoring the urgent need to address their cumulative impacts.^[6]

Conservation measures

Conservation efforts for waders encompass a range of international and local initiatives aimed at safeguarding their migratory habitats and populations. The Ramsar Convention on Wetlands plays a pivotal role, designating 2,531 sites worldwide (as of February 2025) that cover more than 2.6 million square kilometers and include critical stopover points along major flyways for wader species.^[81] These wetlands provide essential foraging and resting areas, with many sites specifically supporting high concentrations of shorebirds during migration. Additionally, the Wadden Sea, recognized as a UNESCO World Heritage Site since 2009, spans the coasts of Denmark, Germany, and the Netherlands, offering protected intertidal habitats vital for millions of waders breeding in the Arctic and wintering in Africa.^[82] The site's management through the Trilateral Wadden Sea Cooperation ensures coordinated conservation across borders, including restrictions on development to maintain ecological integrity.^[83] Legal frameworks further bolster wader protection by regulating human activities that impact these birds. In the United States, the Migratory Bird Treaty Act of 1918 prohibits the take, possession, or commerce of protected migratory birds, including numerous wader species such as plovers, sandpipers, and curlews, without permits.^[84] This act implements bilateral treaties with Canada, Mexico, Japan, and Russia, enforcing hunting seasons and habitat safeguards. Internationally, the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA), effective since 1999, covers 255 wetland-dependent species, many of which are waders, across 118 countries from Africa to Eurasia.^[85] AEWA's Action Plan promotes sustainable hunting practices, habitat restoration, and transboundary cooperation to mitigate threats like illegal take.^[86] Research and restoration projects address specific declines through targeted interventions. For instance, habitat rehabilitation in Europe often employs managed realignment, where coastal defenses are removed or breached to allow saltwater inundation and recreate intertidal zones, benefiting wader foraging areas; notable examples include the Medmerry project in the UK, which restored 184 hectares of habitat since 2013.^[87] Regarding critically endangered species, the Eskimo Curlew's recovery strategy includes recommendations for captive breeding programs should viable populations be rediscovered, with advisory groups emphasizing genetic research on proxy species to inform potential reintroduction efforts.^[88] Community-driven initiatives enhance conservation by linking local economies with biodiversity protection. In Delaware Bay, eco-tourism programs highlight the interdependence of red knots and horseshoe crabs, generating $7–10 million annually in visitor spending while raising awareness; these efforts support regulated horseshoe crab harvests to ensure egg availability for migrating waders.^[89] Complementary measures, such as volunteer monitoring and advocacy, help reduce bycatch in fisheries that inadvertently affect wader habitats and food sources in the region.^[90]

References

[1]
Wading birds found in UK wetlands - WWT
The group commonly known as 'waders' in the UK (or shorebirds in the US) are typically long-legged and long-billed, often seen half-submerged at shorelines, ...
[2]
Waders or Shorebirds (order Charadriiforme) - Earth Life
Jul 12, 2023 · This bird is quite unmistakable. The adult is grey with a white belly, red legs and long down curved bill, and a black face and black breast ...
[3]
Identify waders | The Wildlife Trusts
Description: A fairly large, distinctive glossy black-and-white bird, with pink legs and a bright orange-red beak. They also have a red eye with a red ring ...
[4]
[PDF] Lesson 1: What is a Shorebird?
Shorebirds are a diverse group of birds in the order Charadriiformes, including sandpipers, plovers, avocets, oystercatchers, and phalaropes.
[5]
Multilocus perspectives on the monophyly and phylogeny of the ...
Mar 8, 2007 · In particular, 1) Charadriiformes are comprised of three suborders, Lari, Scolopaci, and their sister Charadrii, 2) Alcidae is nested well ...
[6]
Pratincoles and Coursers (Family Glareolidae) - iNaturalist
Glareolidae is a family of birds in the wader suborder Charadri. It contains two distinct groups, the pratincoles and the coursers.
[7]
Multilocus perspectives on the monophyly and phylogeny of the ...
Mar 8, 2007 · Hypotheses of non-monophyly and sister relationships of shorebirds are tested by multilocus analysis. The monophyly of and interfamilial ...
[8]
Bird Academy's A-to-Z Glossary of Bird Terms
Sep 9, 2016 · Ornithologists in Britain and the British Commonwealth, except Canada, speak of shorebirds as “waders.” siblicide: The killing of one's ...A · P · S
[9]
Phylogenetic relationships and divergence times of Charadriiformes ...
Comparative study of character evolution in the shorebirds is presently limited because the phylogenetic placement of some enigmatic genera remains unclear.
[10]
Early Eocene fossils elucidate the evolutionary history of the ...
Jul 1, 2023 · We report charadriiform and charadriiform-like birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK).
[11]
[PDF] Evolution of Foraging Strategies in Shorebirds
Results from our ecomorphological and evolution- ary analysis support the hypothesis by Zweers and co-workers on the evolution of feeding mechanisms in ...
[12]
Account – Charadriiformes - Bird Families of the World
Family #045. Sandpipers and Allies (Scolopacidae). Species: 97 (5 extinct); Distribution: Global; wf251 status: 100% members ticked; OH: 63 seen, 55 ...
[13]
Charadriiformes) based on nuclear DNA sequence data - PMC
Jul 23, 2003 · For example, the Scolopacidae was found to be monophyletic in the analyses of Strauch [3] and Sibley and Ahlquist [8], while Chu [6] and ...Missing: polyphyletic | Show results with:polyphyletic
[14]
The effect of the global warming on waders - Leica Nature Blog
Oct 21, 2024 · 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 ...
[15]
Little Stint Bird Facts | Calidris Minuta - RSPB
Habitats Marine and Intertidal, Wetland, Grassland ; UK passage 770 ; UK wintering 14 birds ; Weight 20-40g ; Wingspan 34-37cm ...
[16]
Eurasian curlew (Numenius arquata) - Thai National Parks
This is the largest wader in its range, at 50 - 60 cm in length, with an 89 - 106 cm wingspan and a body weight of 410 - 1360 g. It is mainly greyish brown ...
[17]
[PDF] Build-A-Shorebird Adaptations Lessons
Long legs help shorebirds to wade through water or mud while keeping their body dry. 8. Long Toes (Drinking Straws): Because shorebirds are often walking.Missing: morphology | Show results with:morphology
[18]
[PDF] RED-NECKED PHALAROPE ASSESSMENT | Maine.gov
Mar 15, 1997 · Their toes are extensively webbed at the bases with scalloped lateral flanges (Terres 1980, Paulson. 1993), adapting phalaropes for wading and ...
[19]
Eye size, foraging methods and the timing of foraging in shorebirds
Mar 21, 2006 · We found that shorebirds that forage at night were more likely to have large eyes, but species using vision to detect their prey did not have larger eyes.
[20]
Cretaceous origins of the vibrotactile bill-tip organ in birds - PMC - NIH
Dec 2, 2020 · The most obvious difference between these two groups is that Herbst corpuscles are embedded within bony pits in the beaks of birds with bony ...
[21]
Dunlin Identification, All About Birds, Cornell Lab of Ornithology
### Dunlin Plumage Summary
[22]
Ruddy Turnstone Identification - All About Birds
Breeding females are paler than males. Nonbreeding adults have brown ghosting of the breeding plumage pattern. Juveniles look similar to nonbreeding birds, but ...Missing: belly | Show results with:belly
[23]
Killdeer Identification, All About Birds, Cornell Lab of Ornithology
### Killdeer Plumage Summary (Focus on Rufous in Breeding)
[24]
[PDF] A Shorebird MAnAgeMent MAnuAl - Manomet
Jan 20, 2021 · taxonomic families of the 81 shorebird species of the Americas. Some shorebirds are difficult to identify, and this is compounded by ...
[25]
Scolopacidae | Encyclopedia MDPI
Oct 30, 2022 · Within species there is considerable variation in patterns of sexual dimorphism. Males are larger than females in ruffs and several ...
[26]
Field Identification - Red-necked Phalarope - Phalaropus lobatus
Reversed sexual dimorphism video : female brighter and plumage less variable than male during breeding season (Reynolds 1987a ...
[27]
Feather Moult and Migration - Space for Shorebirds
Nov 15, 2022 · Along with adult birds, juveniles will also moult their first plumage in autumn, but they will keep their flight feathers until the following ...
[28]
Shorebird habitat selection and foraging behaviour have important ...
Mar 19, 2024 · Shorebirds are attracted to large areas of potential habitat (bare mud, sand, shallow water), which should be maximised at non-breeding ...
[29]
[PDF] Energetic Constraints on the Non-breeding Distribution of Coastal ...
Jan 1, 1996 · On the basis of general habitat preferences, coastal shorebirds usually occur in open and exposed areas, whether during the breeding season ...
[30]
[PDF] Effects of climate variation on the breeding ecology of ... - ARCUS
A total of about 35 shorebird species have their main distribution within Arctic tundra habitat, and a further c. 15 extend their distribution from more.
[31]
Mapping wader biodiversity along the East Asian—Australasian flyway
Jan 25, 2019 · The study is conducted to facilitate conservation of migratory wader species along the East Asian-Australasian Flyway
[32]
Wilson's Plover Charadrius Wilsonia Species Factsheet
Taxonomy. Order. Charadriiformes. Family. Charadriidae. Authority. Ord, 1814. Taxonomic sources ... Shorebirds: An Identification Guide to the Waders of the World ...
[33]
Breeding ecology of a high-altitude shorebird in the Qinghai ...
Mar 21, 2024 · We provide the first detailed investigation of a high-altitude nesting shorebird in the Qinghai–Tibetan Plateau, the Tibetan Sand Plover Charadrius atrifrons.Missing: altitudinal | Show results with:altitudinal
[34]
Global changes in coastal wetlands of importance for non-breeding ...
Feb 1, 2023 · We analyzed habitat changes of 907 coastal wetlands important for shorebirds. There was an expansion of marshland and urban areas, and a decline of barren land.Missing: diversity hotspots
[35]
Seasonal Variation in the Diet of Migratory Shorebirds Wintering in ...
Mar 28, 2024 · The diet of the smaller species was composed mainly of polychaetes, contributing 83% to the diet of Curlew Sandpiper, and close to 70% in ...
[36]
Long-billed Dowitcher | Audubon Field Guide
In migration and winter also eats mollusks, marine worms, crustaceans. At times, may feed heavily on seeds of grasses, bulrushes, pondweeds, other plants.Missing: omnivory | Show results with:omnivory
[37]
The Relationships between Morphological Characteristics and ... - NIH
Therefore, this study aims to determine the significant relationships between morphological characters and foraging behavior adapted by shorebird and water ...
[38]
Shorebirds Affect Ecosystem Functioning on an Intertidal Mudflat
Aug 24, 2020 · Mud snails can compensate for the loss of higher predators on intertidal mudflats (Hamilton et al., 2006; Cheverie et al., 2014). This ...
[39]
Shorebirds-driven trophic cascade helps restore coastal wetland ...
Dec 6, 2023 · Also, at larger scales, simulating predators' non-consumptive effects using predator mimics, sounds, or cues may be more feasible. We suggest ...
[40]
Mating system and timing of breeding in Holarctic waders
Mating system and parental care system were strongly related, with all polygamous species being uniparental and monogamous species being biparental. It is ...
[41]
Wilson's Phalarope Overview, All About Birds, Cornell Lab of ...
There they spin round and round in the nutrient-rich waters, creating whirlpools that stir up invertebrates that will fuel their migration to South America.Missing: feet adaptation
[42]
[PDF] Division of labour in parental care behaviour of a sex-role-reversed ...
We studied the division of labour between the two sexes in parental care of the eggs and chicks in wattled jacanas, Jacana jacana, in the Republic of Panama.
[43]
Bird nests - Avian Biology
Scrape nests are simple depressions in the ground (sometimes with a few stones added) or in the leaf litter. Such nests are used by some penguins, shorebirds, ...Missing: habits | Show results with:habits
[44]
Willet Life History, All About Birds, Cornell Lab of Ornithology
Nesting Facts ; Clutch Size: 4 eggs ; Number of Broods: 1 brood ; Egg Length: 1.9-2.4 in (4.9-6.2 cm) ; Egg Width: 1.3-1.6 in (3.4-4 cm) ; Incubation Period: 22-29 ...Nesting · Behavior · Conservation
[45]
Long-term decline in nest survival of a ground-nesting shorebird on ...
Kentish plovers typically incubate their clutch for 25 days before eggs hatch and at first discovery of a clutch, eggs were floated in a jar filled with water ...Missing: habits | Show results with:habits
[46]
The causes and implications of sex role diversity in shorebird ...
Oct 11, 2023 · After hatching, parents care for their chicks which are typically precocial (self-feeding chicks, e.g. plovers, sandpipers and jacanas) or ...
[47]
(PDF) Vegetation structure influences predation rates of early nests ...
Predation rates of wader nests in South Iceland were ca 50% for a study conducted in 2015-2016 that monitored a total of 469 nests (Laidlaw et al.
[48]
linking distraction behavior with nest survival in a ground-nesting bird
Other studies reveal that flushing behavior of incubating shorebirds influenced nest survival (Koivula and Rönkä 1998; Amat and Masero 2004a; Gómez-Serrano and ...Missing: habits | Show results with:habits
[49]
The conservation of migratory shorebirds needs to account for the ...
Migratory shorebirds are experiencing rapid population decline. Monitoring programs along shorebird flyways provide information on their population dynamics ...
[50]
Juvenile bar-tailed godwit "B6" Sets World Record - USGS.gov
A four-month-old bar-tailed godwit known as B6 set a new world record by completing a non-stop 11-day migration of 8,425 miles from Alaska to Tasmania, ...
[51]
Migration Distance and Body Condition Influence Shorebird ...
Jul 8, 2019 · This study shows that migratory behavior of shorebirds has predictable patterns based on migration distance that are moderated by body condition of individuals.
[52]
East Atlantic Flyway - Wadden Sea Quality Status Report
This thematic report provides a summary of the trends in bird numbers, distribution patterns and pressures along the flyway.
[53]
[PDF] EAST ASIAN — AUSTRALASIAN FLYWAY PARTNERSHIP (EAAFP)
The East Asian–Australasian Flyway (EAAF) is one of the largest flyways and it stretches from the Russian. Far East and Alaska, southwards through East and.
[54]
Annual Patterns of Shorebird Migration and Habitat Use at ... - BioOne
Mar 6, 2025 · Due to the great distances covered in their migration routes, shorebirds use stopover sites to replenish energy and rest to prepare for further ...
[55]
(PDF) Seasonal changes in body mass, body composition and food ...
Within a 2-3-week period before migration they may double in total body mass, but after 2-3 d of flight return to starting mass (Davidson & Evans, 1988; ...
[56]
How a Flock of Birds Can Fly and Move Together | Audubon
They often fly at speeds of 40 miles or more per hour, and in a dense group the space between them may be only a bit more than their body length. Yet they can ...
[57]
Physiomorphic Transformation in Extreme Endurance Migrants
Jun 16, 2021 · Here we document the verity of the proposed physiomorphic changes by comparing organ sizes and body composition of bar-tailed godwits.Missing: pre- | Show results with:pre-<|separator|>
[58]
Site-fidelity in Black-tailed Godwits - wadertales - WordPress.com
May 21, 2018 · Shorebirds are generally philopatric (site-faithful to breeding areas) – youngsters settle to breed in areas near where they were raised and ...
[59]
Bird migration timing skewed by climate, new research finds
Dec 16, 2019 · Temperature and migration timing were closely aligned, with the greatest changes in migration timing occurring in regions warming most rapidly.
[60]
The Influence of Migration Timing and Local Conditions on ... - NIH
Jan 21, 2025 · Our results demonstrate that the timing of nest initiation in Arctic‐breeding shorebirds is influenced by both local conditions and the timing ...
[61]
North American shorebirds are declining faster than we ever imagined
Mar 30, 2023 · A new study, based on nearly 40 years of community science data, shows many shorebird species in North America have declined by half in recent decades.
[62]
A synthesis of Eurasian Curlew (Numenius arquata arquata ...
Jan 26, 2023 · The European population of Eurasian Curlew Numenius arquata arquata, a near-threatened wader subspecies, has undergone pronounced population declines over the ...
[63]
Curlew - BTO
The Curlew (Numenius arquata) is a scarce breeding species with a 51% population decrease from 1995-2023, and a 59k pair population. It has a 18% seasonality.Missing: BirdLife | Show results with:BirdLife
[64]
How many shorebirds use the East Asian-Australasian Flyway?
Feb 10, 2022 · This new study shows that there are at least nine million shorebirds on this flyway. How many more would there have been ten, twenty or fifty years ago?<|control11|><|separator|>
[65]
Demography and Populations - Spoon-billed Sandpiper
May 5, 2025 · A rigorous estimate in 2014 put the global population at 210–228 breeding pairs, with a post-breeding population of adults and immatures of ...
[66]
New estimate of the trend in world population size of the Spoon ...
Aug 1, 2024 · The estimated mean world population size at the end of the breeding season, averaged over the whole survey period, was 443 mature individuals ...
[67]
2024 Red List update reveals migratory shorebirds are declining ...
Aug 5, 2025 · Global Red List status of 137 migratory shorebird species when assessed in 1988 and 2024. ... Key threats to migratory shorebirds include habitat ...
[68]
IUCN Red List: Concerning decline of migratory shorebird species ...
Oct 29, 2024 · The latest IUCN Red List update for birds has revealed a highly concerning downwards trend in migratory shorebird numbers globally, with 16 species moved to ...
[69]
International Waterbird Census
The IWC is a monitoring programme operating in 143 countries to collect information on the numbers of waterbirds at wetland sites.
[70]
Bird monitoring: Wetland Bird Survey (WeBS) - JNCC
Nov 19, 2024 · WeBS is a UK-wide monitoring scheme which targets wildfowl, waders and other waterbirds to produce population abundance and distribution trends
[71]
Muddy business in the Yellow Sea - MAHB
Oct 21, 2014 · The latest assessment of intertidal mudflats in the Yellow Sea has revealed the loss of 65% of their original extent in the 1950s, when they ...Missing: 50%
[72]
Impacts of habitat loss on migratory shorebird populations and ...
Shorebirds of the Yellow Sea–Importance, Threats and Conservation Status. (2002). M. Barter. The Yellow Sea–a vitally important staging region for migratory ...Missing: major | Show results with:major
[73]
(PDF) Global Climate Change and Sea Level Rise: Potential Losses ...
Jul 2, 2025 · Global warming is expected to result in an acceleration in current rates of sea level rise, inundating many low-lying coastal and intertidal ...
[74]
Low migratory connectivity and similar migratory strategies in a ...
Feb 28, 2024 · Migratory shorebird populations are declining worldwide, showing an apparent inability to respond to the interplaying challenges emerging ...
[75]
Hunting poses serious risk to East Asian shorebirds - BirdGuides
May 20, 2020 · As the world looks to tighten up the illegal capture of wildlife in the wake of the coronavirus crisis, a new study by an international team ...
[76]
Change in tidal flats in the Yellow Sea between the 1950s and the...
We estimated that approximately 47,870 shorebirds were killed at 19 stopover sites per year, mainly from hunting and deterrence. Mortalities for 11 shorebird ...
[77]
Assessing the effects of human activities on the foraging ...
Mar 13, 2019 · Our results indicate that even a low density of people and dogs can significantly reduce the foraging opportunities of shorebirds.
[78]
Oiled coasts mean oiled shorebirds: Brazil oil spill impacts shorebirds
Nov 25, 2019 · Oil spills remain a major existential threat to shorebird populations. Spills kill birds outright when they are coated in oil, reduce their ...Missing: invasive foxes
[79]
The Arctic Is No Longer A Safe Haven for Breeding Shorebirds
Nov 13, 2018 · Predators now wipe out 70 percent of shorebird nests in the far north, a shift in historical patterns that scientists pin on climate change.Missing: oil spills invasive
[80]
Press Release: New report reveals plummeting migratory shorebird ...
Oct 28, 2024 · Previously estimated at 49% in BirdLife International's State of the World's Birds 2022, the percentage of extant (i.e. not extinct) bird ...<|control11|><|separator|>
[81]
The Ramsar List
There are over 2,500 Ramsar Sites on the territories of 173 Convention Contracting Parties across the world, covering more than 2.5 million square kilometres.
[82]
Wadden Sea - UNESCO World Heritage Centre
The Wadden Sea is the largest unbroken system of intertidal sand and mud flats in the world. The site covers the Dutch Wadden Sea Conservation Area, the German ...Maps · Documents · Gallery · VideosMissing: waders | Show results with:waders
[83]
Welcome to the Wadden Sea World Heritage | Wadden Sea
For its globally unique geological and ecological values the Wadden Sea is listed by UNESCO as World Heritage. Nowhere else in the world is there such a dynamic ...Protection and management · Wadden Sea Newsletter · Common Wadden Sea...Missing: waders | Show results with:waders
[84]
Migratory Bird Treaty Act of 1918 | U.S. Fish & Wildlife Service
The Migratory Bird Treaty Act (MBTA) prohibits the take (including killing, capturing, selling, trading, and transport) of protected migratory bird species ...Missing: waders | Show results with:waders
[85]
Species Covered by AEWA
The Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) is an intergovernmental treaty dedicated to the conservation of migratory ...Missing: shorebirds | Show results with:shorebirds
[86]
AEWA | Agreement on the Conservation of African-Eurasian ...
The African-Eurasian Migratory Waterbird Agreement (AEWA) is an intergovernmental treaty dedicated to the conservation of migratory waterbirds and their ...About · Species · Agreement Text · AEWA NewsMissing: shorebirds | Show results with:shorebirds
[87]
The Medmerry project for intertidal habitat restoration with managed ...
The largest managed realignment project in open coastal Europe has regenerated 184 hectares of intertidal habitat, restoring wildlife functioning and ...
[88]
Conservation and Management - Eskimo Curlew - Numenius borealis
The Eskimo Curlew Advisory Group suggested a captive breeding program if searches of breeding grounds produce nesting birds. Such a program needs to be ...
[89]
Red Knot and Horseshoe Crabs - Delaware Riverkeeper Network
According to one report, horseshoe crab-dependent ecotourism generates between approximately $7 million and $10 million of annual spending in Cape May, New ...
[90]
Horseshoe Crabs in the Delaware Bay | The Nature Conservancy DE
Horseshoe crab eggs are critical for sustaining migratory birds each year. The threatened red knot, for example, flies from wintering grounds in South America ...