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Stone-curlew
Stone-curlew
Stone-curlew
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Stone-curlews
Temporal range: Late Oligocene–Present
Bush stone-curlew, Burhinus grallarius
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Suborder: Charadrii
Family: Burhinidae
Mathews, 1912
Genera
modern range

The stone-curlews, also known as dikkops or thick-knees, consist of 10 species within the family Burhinidae, and are found throughout the tropical and temperate parts of the world, with two or more species occurring in some areas of Africa, Asia, and Australia. Despite the group being classified as waders, most species have a preference for arid or semiarid habitats.

Taxonomy

[edit]

The family Burhinidae was introduced in 1912 for the stone-curlews by Australian ornithologist Gregory Mathews.[1][2] The family contains three genera: Hesperoburhinus, Burhinus and Esacus.[3] The name Burhinus combines the Ancient Greek bous meaning "ox" and rhis, rhinos meaning "nose" (or "bill").[4]

Molecular phylogenetic studies have shown that the family Burhinidae is sister to a clade containing the sheathbills in the family Chionidae and the Magellanic plover in its own family Pluvianellidae. The stone-curlews are not closely related to the curlews, genus Numenius, that belong to the sandpiper family Scolopacidae.[5]

Description

[edit]

They are medium to large birds with strong black or yellow black bills, large yellow eyes—which give them a reptilian appearance—and cryptic plumage. The names thick-knee and stone-curlew are both in common use. The term stone-curlew owes its origin to the broad similarities with true curlews. Thick-knee refers to the prominent joints in the long yellow or greenish legs and apparently originated with a name coined in 1776 for B. oedicnemus, the Eurasian stone-curlew. Obviously the heel (ankle) and the knee are confused here.[6]

Behaviour

[edit]

They are largely nocturnal, particularly when singing their loud, wailing songs, which are reminiscent of true curlews.[7] Their diet consists mainly of insects and other invertebrates. Larger species also take lizards and even small mammals.[7] Most species are sedentary, but the Eurasian stone-curlew is a summer migrant in the temperate European part of its range, wintering in Africa.

Species

[edit]

The earliest definitive stone-curlew is Genucrassum bransatensis from the Late Oligocene of France.[8] Wilaru, described from the Late Oligocene to the Early Miocene of Australia, was originally classified as a stone-curlew, but was subsequently argued to be a member of the extinct anseriform family Presbyornithidae, instead.[9][10] The living species are:

Picture Name Binomial name
Double-striped thick-knee Hesperoburhinus bistriatus
Peruvian thick-knee Hesperoburhinus superciliaris
Eurasian stone-curlew Burhinus oedicnemus
Indian stone-curlew Burhinus indicus
Senegal thick-knee Burhinus senegalensis
Water thick-knee Burhinus vermiculatus
Spotted thick-knee Burhinus capensis
Bush stone-curlew Burhinus grallarius (formerly B. magnirostris).
Great stone-curlew Esacus recurvirostris
Beach stone-curlew Esacus magnirostris

References

[edit]
[edit]
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Stone-curlew

View on Grokipedia
from Grokipedia
Stone-curlews, also known as thick-knees, are wader-like birds in the Burhinidae, comprising 10 found mainly in tropical and temperate regions of , , and . They are characterized by large heads, prominent yellow eyes, and cryptic for in open habitats. The (Burhinus oedicnemus), also known as the Eurasian thick-knee, is a distinctive member of this , renowned for its mottled brown-and-buff that provides superb against open, arid ground. Measuring 38–46 cm in length with a of 76–88 cm and weighing 290–535 g, it features a strong yellow-and-black bill and, in flight, reveals striking black-and-white patterns on its wings. This nocturnal or crepuscular inhabits dry, sparsely vegetated landscapes such as lowland heaths, grasslands, steppes, deserts, sand dunes, and arable fields near human , where it forages for , gastropods, small reptiles, amphibians, and occasionally . Native to a vast range spanning (from Iberia and the eastward to the , , and the ), , and southwestern Asia—an extent of occurrence covering 27,000,000 km²—the is a partial migrant, with northern populations wintering in southern parts of its range and from to . In the , where it is a rare summer visitor concentrated primarily in eastern and including the Breckland region, breeding populations have shown recovery through targeted conservation, rising from lows in the 1980s to approximately 350 pairs as of 2025, though overall global numbers are estimated at 360,000–590,000 mature individuals (as of 2012) and appear to be decreasing due to loss from agricultural intensification. Behaviorally, the is largely ground-dwelling and elusive, relying on stillness during the day to evade predators while becoming active at with its haunting, wailing calls that echo across its . Breeding occurs from February to June in warmer regions like the and April onward in the UK, with pairs forming scrapes on bare ground lined minimally with grass or stones to lay clutches of two large, well-camouflaged eggs (about 54 mm × 38 mm), which both parents incubate for 24–26 days. The precocial chicks leave the nest soon after hatching and are cared for by adults for 36–42 days until fledging, with the species normally reaching breeding age at around three years (though capable from ) and capable of living up to 22 years in the wild. Classified as Least Concern on the (as assessed in 2018), the faces ongoing threats from habitat degradation but benefits from protective measures in key areas, highlighting its role as an indicator of healthy, open ecosystems.

Taxonomy and Evolution

Taxonomy

The stone-curlew (Burhinus oedicnemus), also known as the Eurasian thick-knee, is classified within the family Burhinidae, a group of nocturnal waders distinguished by their thickened leg joints and cryptic plumage. Its full taxonomic hierarchy is Kingdom: Animalia; Phylum: Chordata; Class: Aves; Order: ; Family: Burhinidae; Genus: Burhinus; Species: B. oedicnemus. The family Burhinidae encompasses 10 species divided between two genera: Burhinus (eight species, primarily thick-knees) and Esacus (two species, larger beach thick-knees), all adapted to dry, open habitats across tropical and temperate regions. A 2023 phylogenetic study proposed resurrecting Hesperoburhinus for the two New World thick-knees (B. bistriatus and B. superciliaris), reducing Burhinus to six species, though this change is not yet universally adopted. First described by in 1758 as Charadrius oedicnemus in , the species was later reclassified into the genus Burhinus established by Johann Illiger in 1811. The genus name Burhinus derives from bous () and rhis (nose or snout), alluding to the bird's robust, wedge-shaped bill that resembles an ox's muzzle. The specific epithet oedicnemus combines Greek oidēma (swelling) and knēmē (leg or shin), referencing the swollen tarsal joint typical of thick-knees, which gives the family its alternative common name. The common name "stone-curlew" reflects the species' affinity for stony, barren landscapes where its mottled brown plumage provides camouflage, combined with its eerie, whistling call reminiscent of true curlews (Numenius spp.). Several subspecies are recognized, including the nominate B. o. oedicnemus (Europe and northwest Africa), B. o. harterti (Middle East to Pakistan), and B. o. insidiosus (Central Asia), differentiated by subtle variations in size and plumage tone. Historically, the closely related Indian thick-knee (Burhinus indicus) was treated as a subspecies of B. oedicnemus, but molecular and morphological evidence supports its status as a distinct species since the early 2000s. The Burhinidae family itself remains stably placed within Charadriiformes, though phylogenetic studies confirm its basal position relative to plovers and allies.

Fossil Record

The fossil record of the Burhinidae is sparse, with definitive records limited to a handful of taxa from the late Oligocene and Miocene epochs, reflecting the family's low diversity and specialized habitats that may have hindered fossil preservation. No unambiguous burhinid fossils are known from the Paleocene or Eocene, suggesting that the lineage likely originated in the early Cenozoic but left no trace until the late Oligocene. The earliest recognized burhinid is Genucrassum bransatensis, described from a distal humerus and proximal ulna collected from the late Oligocene (approximately 23 million years ago) deposits at Bransat, France. This small species, roughly comparable in size to the extant collared pratincole, exhibits plesiomorphic humeral features such as a less developed ventral supracondylar process, distinguishing it from modern burhinids while confirming its placement within the family based on shared derived traits like the expanded pneumatic fossa. Its discovery extends the European fossil record of Burhinidae back by several million years and supports an Old World origin for the group during the Oligo-Miocene radiation of charadriiform birds. In the early (late Hemingfordian, approximately 18–16 million years ago), Burhinus lucorum was documented from multiple skeletal elements, including a complete , collected in the Sheep Creek Formation of Sioux County, Nebraska, . This , similar in size to the modern , represents the earliest North American record of the family. The associated and paleoclimate indicate a more mesic, woodland-edge than the arid environments preferred by most extant , implying greater ecological flexibility in early burhinids. Additional fragmentary burhinid remains have been reported from Miocene sites in (e.g., ) and (e.g., ), but these lack formal species designations and contribute little to resolving phylogenetic relationships. An early report of a potential burhinid (Wilaru tedfordi) from late /early strata in , based on pelvic and leg elements, was subsequently reclassified as a presbyornithid anseriform, highlighting diagnostic challenges in distinguishing early charadriiforms from stem waterfowl. No burhinid fossils are confirmed from the , though late records exist, bridging a smaller gap to the ten extant species that persist today.

Physical Description

Morphology

Stone-curlews, or thick-knees (family Burhinidae), are medium to large terrestrial wading birds with a morphology adapted for life in open, arid, or semi-arid environments, combining features of both shorebirds and ground-dwelling species. They exhibit a robust build with long, sturdy legs that enable efficient walking and running on flat terrain, often far from . The inter-tarsal is notably swollen and knobby, creating the appearance of "thick knees" that inspired one of their common names. These birds have three short toes on each foot, lacking a hind toe, which supports their primarily lifestyle. The head is relatively large and rounded, featuring a short, straight, and pointed bill suited for capturing surface-dwelling by pecking or probing. The bill measures around 45–53 mm in like the bush stone-curlew (Burhinus grallarius), and is generally less elongated than in typical curlews or plovers. Prominent among their features are the large, eyes, which are laterally placed in the and provide a wide essential for nocturnal and vigilance; the eye-bill-tip in alert posture is typically 15°–20° below horizontal, with minimal amplitude. Eyes in Burhinus lack a but exhibit a pale pink , enhancing low-light vision. Plumage is cryptic and mottled, predominantly in shades of brown, gray, buff, and white, offering effective against stony or sparsely vegetated ground where the birds often freeze motionless when threatened. In the bush stone-curlew, for instance, the upperparts are heavily streaked, with a pale and throat, while the breast and underparts show barring or streaking that blends with dry leaf litter. Wings are long and rounded, with 10 primaries, allowing for strong, when flushed, though the birds prefer to run or hide rather than take wing. The tail is short and square-ended, typically comprising 12 feathers, contributing to their overall streamlined yet stocky form. Body size varies across the family's 10 species, with lengths ranging from approximately 32 cm in the collared thick-knee (Burhinus recollectus) to 59 cm in the beach stone-curlew (Esacus giganteus), and weights from 0.3 kg to over 1 kg; for example, the bush stone-curlew reaches 55–60 cm in length and 50–60 cm in height, with a of 80–100 cm. is minimal, with males and females similar in size and coloration, though some species show subtle differences in bill length or eye ring intensity during breeding. The (Burhinus oedicnemus), the focus of this article, measures 38–46 cm in length, with a of 76–88 cm and weight of 290–535 g. It shares the family's general morphology but is adapted to temperate and Mediterranean environments.

Plumage and Camouflage

The (Burhinus oedicnemus) exhibits cryptic characterized by streaky brown tones on the upperparts, with a paler underbelly and subtle buff and white streaking that creates a mottled, sandy appearance overall. This patterning is accented by darker streaks on the head and neck, a pale , and a finely barred crown, while the wings display a distinctive black-and-white pattern visible primarily in flight. The bill is yellow with a black tip, and the large yellow eyes and legs provide contrast but are subdued against the dominant earthy hues. This plumage serves as highly effective camouflage in the bird's preferred open, arid habitats such as stony heathlands, dry grasslands, and sparsely vegetated steppes, where the streaky brown and sandy colors blend seamlessly with the substrate of rocks, , and sparse . During the day, when the stone-curlew is largely inactive and roosts on the ground, it adopts a rigid, motionless posture that enhances its inconspicuousness, making it extremely difficult for predators to detect amid the similar-toned surroundings. There is no significant in plumage, allowing both sexes to rely on this shared cryptic coloration for evasion. In chicks, the plumage is even more subdued with pale dorsal tones, further aiding concealment in the nest vicinity.

Distribution and Habitat

Geographic Distribution

The stone-curlews, comprising the family Burhinidae, exhibit a distribution, primarily occurring in open, dry habitats across , , , , and the , with no native populations in the polar regions or dense forests. The family includes six in the genus Burhinus (mostly Old World), two in Esacus (Old World), and two in Hesperoburhinus (New World), reflecting a division between and lineages, though some Burhinus bridge continents. Their ranges often align with semi-arid to arid zones, influenced by historical biogeographical patterns that likely originated in the Old World during the . In the , the Eurasian thick-knee (Burhinus oedicnemus) has the broadest range, breeding across southern Europe (from to ), the , and (extending to and northwestern ), while wintering in sub-Saharan (from to ) and parts of the . The Indian thick-knee (Burhinus indicus) is resident in the (, Pakistan, , , , ) and extends into (, , , , ). African species include the (Burhinus capensis), widespread in sub-Saharan savannas from to ; the thick-knee (Burhinus vermiculatus), distributed along waterways from to and south to ; and the thick-knee (Burhinus senegalensis), found from eastward to and , with southern extensions to . The bush thick-knee (Burhinus grallarius) is endemic to and southern , occupying coastal and subcoastal regions across much of the continent except the far southwest and . The great thick-knee (Esacus recurvirostris) inhabits riverine and coastal areas from through southern (, , , , , , , , southern ), while the beach thick-knee (Esacus magnirostris) ranges along coasts, including (), , , , , the , , , , , and (all mainland states and territories except ). In the , the double-striped thick-knee (Hesperoburhinus bistriatus) occupies grasslands and savannas from southern through (to ) and into northern (, , , northern , with vagrants to the including and ). The Peruvian thick-knee (Hesperoburhinus superciliaris) is restricted to the Pacific coastal slope from southern through to northern , favoring arid shrublands and agricultural areas. These American distributions suggest a relatively recent divergence from ancestors, with limited overlap across the Atlantic. Overall, while most species are sedentary or undertake short local movements, some like the Eurasian thick-knee show partial migration, contributing to seasonal range expansions in .

Habitat Preferences

Stone-curlews of the family Burhinidae primarily occupy semi-arid to arid environments with open, dry landscapes and low or sparse vegetation cover, which supports their terrestrial lifestyle and camouflage. These habitats often include steppes, dry grasslands, deserts, heathlands, and coastal shores, where bare ground or minimal plant cover predominates to allow for effective foraging and nesting on the surface. The family's preference for such areas stems from their need for unobstructed visibility and space, as dense vegetation hinders their ground-based activities and increases predation risk. While most species favor inland dry terrains, habitat selection varies across genera and regions. For instance, the (Burhinus oedicnemus) thrives in lowland heaths, semi-natural dry grasslands, infertile agricultural fields, and steppes on poor soils, adapting to short-cropped arable lands like those with or where vegetation remains under 20 cm. In contrast, waterside species such as the water thick-knee (Burhinus vermiculatus) and thick-knee (Burhinus senegalensis) select riverbanks, sandbars, and semi-arid wetlands, often near seasonal water sources in savannas or deserts. Coastal and island-dwellers like the beach thick-knee (Esacus magnirostris) utilize sandy or rocky shores, intertidal zones, and mangroves, while the great thick-knee (Esacus recurvirostris) prefers rocky riverbanks and muddy lake edges in tropical regions. Nesting and foraging sites emphasize open, flat ground with minimal disturbance; nests are simple scrapes, often ringed with stones or debris for camouflage, placed in areas of bare soil or short grass (5-20 cm height) to enable quick escape and chick mobility. Many species show adaptability to human-modified landscapes, such as grazed pastures or fallow fields, but require structural diversity like plowed patches for enhanced suitability. Overall, these preferences reflect an evolutionary adaptation to environments where arthropod prey is abundant on the ground surface, though intensification of agriculture and habitat fragmentation pose ongoing challenges.

Behavior and Ecology

Activity Patterns and Migration

The Eurasian stone-curlew (Burhinus oedicnemus) is predominantly crepuscular and nocturnal, with foraging and ranging activities peaking at and dawn to exploit low-light conditions while minimizing predation risk during daylight hours. Its large eyes adapt it for vision in dim light, enabling efficient hunting of on the ground. During the day, individuals typically remain motionless in camouflaged positions within open habitats like riverbeds or stony plains, where nearly all diurnal locations are recorded in suitable breeding territories. Nocturnal ranging extends beyond these core areas, with about two-thirds of fixes still in river gravels but some venturing into adjacent fields. Migration in the is characterized by partial migration, where only portions of populations undertake short-distance movements within the Mediterranean basin, while others remain resident. Inter-population variability is pronounced, with continental Italian populations (e.g., Taro and Piave rivers) showing higher migration rates (up to 70%) compared to Mediterranean ones (e.g., and , around 30%), influenced by climatic differences. Migrants from winter in sites like , , , and , covering average distances under 1000 km. Intra-population variability also occurs, with some individuals skipping migration altogether. Migratory timing reflects energy and time minimization strategies, with autumn departures from breeding grounds occurring from late October to early January—25 days earlier for continental birds than Mediterranean ones. Spring returns happen from early February to early , with Mediterranean populations arriving 10 days sooner, and continental birds traveling longer routes. In North African stopover sites like northwest , pre-breeding gatherings form in late , followed by final departures in the first half of . Flights are predominantly nocturnal, more so in autumn than spring, aligning with the species' overall activity patterns.

Diet and Foraging

The (Burhinus oedicnemus) is a ground-foraging that exhibits a predominantly insectivorous diet, supplemented by other and occasionally small vertebrates. Its behavior is largely nocturnal or crepuscular, allowing it to exploit prey in low-light conditions while minimizing predation risk and competition. Adults and chicks typically hunt by scanning the ground from an upright posture and pecking at detected items, often in open habitats with sparse vegetation such as grasslands, arable fields, or steppe-like areas. This method enables efficient capture of mobile prey like , with foraging ranges extending up to approximately 3 km from nesting sites and home ranges averaging around 30 hectares during the breeding season. The diet consists mainly of soil-surface arthropods, earthworms, and molluscs, which together form the bulk of intake for both adults and dependent chicks. In southern England populations, earthworms constitute a significant portion when soil moisture is high, but their prevalence decreases during dry periods, shifting reliance toward arthropods and molluscs. Analysis of prey items reveals a focus on invertebrates typically 5–15 mm in length, reflecting the bird's ability to handle small to medium-sized food sources. Parents actively provision chicks with similar prey, leading them to foraging grounds shortly after hatching to encourage independent feeding. In Mediterranean habitats like the Doñana region of southern Spain, the diet is even more heavily skewed toward insects, comprising about 97% of identified prey items from fecal analyses, with beetles (Coleoptera) dominating at around 70%, particularly weevils (Curculionidae) and jewel beetles (Buprestidae), alongside ants (Formicidae) at 21%. Orthopterans such as grasshoppers (Acrididae) make up a smaller fraction, while non-insect prey like snails, amphibians, and small passerine birds or their eggs are rare, occurring in less than 2% of samples. Foraging here targets seasonally abundant, aggregated prey in dry marshlands, with birds consuming large numbers of ants when encountered, adapting to local invertebrate booms for nutritional efficiency.

Reproduction and Parental Care

The (Burhinus oedicnemus) is typically monogamous, with pairs forming during the breeding season and both sexes participating in reproductive activities. The breeding season varies by region but generally occurs in spring across its temperate range, from early to or early in , with some populations starting as early as in subtropical areas like the . In more arid or southern populations, such as in , breeding begins in late and peaks in late to early . Nests are simple ground scrapes, often on bare soil or , sometimes lined with minimal or surrounded by stones for . Females usually lay a of two eggs, though single-egg clutches occur due to replacement laying after loss; eggs are large, cryptically colored in shades of stone with dark spots or blotches to blend with surroundings. Egg dimensions average approximately 54 mm × 38 mm. Incubation begins with the first and lasts 24–27 days, shared equally by both parents, who take turns to ensure continuous coverage and protection from predators and environmental extremes. Parents exhibit vigilant behaviors, including retrieval if displaced; for instance, one observed female retrieved a displaced by rolling it back to the nest using her after detecting its absence through soft calling and inspection. The chicks are precocial, covered in downy plumage and capable of following parents shortly after hatching, but they receive extensive care from both adults. Parents lead to areas, providing initial food by regurgitation or direct feeding via beak-to-beak transfer during the first few days, while also defending against threats through displays. Chicks fledge after about 35–42 days and remain dependent on parents for up to two months post-fledging, during which time the family group stays together for protection and learning skills. Typically, only one successful brood is raised per year, though replacement clutches may be attempted if the first fails.

Species

Genera Overview

The family Burhinidae, commonly known as stone-curlews or thick-knees, encompasses three genera: Hesperoburhinus, Burhinus, and Esacus, comprising a total of 10 distributed across tropical and temperate regions worldwide. These genera are distinguished by recent phylogenetic analyses that resolved longstanding taxonomic uncertainties, revealing deep divergences dating back over 30 million years and supporting separations based on molecular, morphological, and characters. The genera reflect adaptations to diverse terrestrial habitats, with shared traits including large yellow eyes suited for nocturnal activity, robust bills, and cryptic patterning for . Hesperoburhinus, a recently erected for the Neotropical thick-knees, contains two : the Double-striped Thick-knee (H. bistriatus) and the Peruvian Thick-knee (H. superciliaris). Endemic to arid and semi-arid regions of Central and , from to northern , these birds are characterized by prominent superciliary stripes extending to the neck sides, a feature unique among burhinids, along with 55 single-nucleotide synapomorphies and distinct patterns such as bold facial stripes and barred underparts. They exhibit a more slender build compared to congeners, with bills adapted for probing sandy or rocky substrates. Burhinus, the most speciose with six , is predominantly found in the , ranging from and to and . Representative include the Eurasian Thick-knee (B. oedicnemus), widespread in dry grasslands and farmlands; the (B. capensis) of ; and the Bush Thick-knee (B. grallarius) of . These birds feature a combination of Greek-derived ("ox-nose" for their sturdy bills) and morphological uniformity, including long legs with thickened tarsi (hence "thick-knee") and mottled brown-gray plumage for blending into stony environments. Phylogenetic data place Burhinus as sister to Esacus, with divergences supported by vocalization differences and preferences for inland arid zones rather than coastal areas. Esacus comprises two large coastal species: the Beach Thick-knee (E. magnirostris) of and , and the Great Thick-knee (E. recurvirostris) from to . These are the largest burhinids, with heavier bills recurved at the tip for capturing crustaceans and insects along shores, and bolder black-and-white head patterns distinguishing them from the more uniformly cryptic Burhinus. Their distribution is limited to and estuarine habitats, reflecting specialized adaptations to intertidal foraging. Overall, the genera highlight the family's across continents, with Hesperoburhinus representing an ancient lineage isolated early from its relatives.

List of Species

The family Burhinidae, commonly known as stone-curlews or thick-knees, includes 10 extant species distributed across three genera: Esacus (2 species), Burhinus (6 species), and Hesperoburhinus (2 species). This classification reflects recent phylogenetic revisions, which separated the Neotropical species into Hesperoburhinus based on genetic and morphological analyses. The species are primarily tropical and subtropical waders, with ranges spanning , , , and the .
GenusCommon NameScientific Name
EsacusBeach Thick-kneeEsacus magnirostris
EsacusGreat Thick-kneeEsacus recurvirostris
BurhinusEurasian Thick-kneeBurhinus oedicnemus
BurhinusIndian Thick-kneeBurhinus indicus
BurhinusSenegal Thick-kneeBurhinus senegalensis
BurhinusWater Thick-kneeBurhinus vermiculatus
BurhinusBurhinus capensis
BurhinusBush Thick-kneeBurhinus grallarius
HesperoburhinusDouble-striped Thick-kneeHesperoburhinus bistriatus
HesperoburhinusPeruvian Thick-kneeHesperoburhinus superciliaris

Conservation

Status and Threats

The stone-curlews, belonging to the family Burhinidae, exhibit varied conservation statuses across their 10 , with most classified as Least Concern by the , reflecting their relatively large ranges and stable or moderately sized populations in some regions. However, several face ongoing declines, including the Beach Thick-knee (Esacus magnirostris), assessed as Near Threatened due to a global population of 4,100–8,000 mature individuals that is decreasing, particularly in and . Similarly, the Great Thick-knee (Esacus recurvirostris) is Near Threatened, with populations undergoing moderately rapid declines driven by habitat pressures, while the Eurasian Thick-knee (Burhinus oedicnemus) remains Least Concern despite an overall decreasing trend estimated at 360,000–589,999 mature individuals. The Bush Thick-knee (Burhinus grallarius) is also Least Concern but suspected to be declining, with 10,000–15,000 mature individuals affected by regional threats in . Primary threats to stone-curlews stem from habitat loss and degradation, particularly through agricultural intensification, urban development, and coastal tourism, which fragment open grasslands, drylands, and riverine areas essential for breeding and foraging. For instance, the Beach Thick-knee suffers from coastal development that destroys nesting beaches, while the Bush Thick-knee faces clearance for agriculture and pastoralism in Australia, compounded by the removal of fallen timber that provides nesting cover. Human disturbance, including recreational activities like off-road vehicle use and beach-going, leads to breeding failures by causing nest abandonment, as seen in coastal populations of the Eurasian Thick-knee. Additionally, introduced predators such as feral cats, dogs, foxes, pigs, and rats pose significant risks to eggs and chicks across multiple species, with the Bush Thick-knee particularly vulnerable to red fox predation. Other pressures include direct mortality from road collisions, collisions with fences or wires, and localized or , especially during migration for species like the Eurasian Thick-knee in the Mediterranean region. and poisoning affects foraging birds, notably the Bush Thick-knee in agricultural landscapes, while exacerbates vulnerabilities through sea-level rise and increased storm frequency impacting coastal breeders like the Beach Thick-knee. Poor juvenile recruitment and nesting success further hinder population recovery, underscoring the need for targeted habitat protection to mitigate these cumulative threats.

Conservation Efforts

Conservation efforts for stone-curlews (family Burhinidae) focus primarily on habitat restoration, predator control, and population reintroduction programs, as many species face declines due to agricultural intensification and . Globally, the family includes species of varying conservation concern, with initiatives often led by organizations like and regional . These efforts emphasize collaborative partnerships with landowners and governments to implement agri-environment schemes that create suitable nesting and foraging areas. In the , the Royal Society for the Protection of Birds (RSPB) launched a targeted recovery program for the (Burhinus oedicnemus) in 1985, when the population had plummeted to fewer than 150 breeding pairs nationwide due to loss of grassland and heathland habitats. This initiative, supported by and involving over 57 farms and landowners in eastern (, , and ), has created 305 specialized nesting plots on light, stone-based soils, alongside the restoration of hundreds of hectares of semi-natural grass heathland. By 2024, these measures resulted in 226 breeding pairs in the region, representing a more than twofold increase from the 1985 low of under 100 pairs, with over 365 pairs UK-wide; notably, 70% of confirmed breeding attempts in occurred on government-funded nesting plots. The program's success led to the species' downgrading from "Red" (high conservation concern) to "Amber" status on the UK Birds of Conservation Concern list in 2009. Additional actions include volunteer-led nest monitoring and protection from disturbance, contributing to stable or increasing short-term trends in despite ongoing global declines. For the bush stone-curlew (Burhinus grallarius) in , conservation efforts center on , reintroduction to predator-free sites, and habitat management to counter threats from es, cats, and habitat clearance. Programs in southeastern states, including Victoria, , and , have involved multiple projects since the early , such as fox control trials and the creation of secure release areas like and Mt Rothwell Biodiversity Reserve. Organizations like the Penguin Foundation and have released captive-bred individuals, with initiatives like the Odonata Foundation's breeding program providing birds for translocation; for instance, in 2024, releases aimed to establish self-sustaining s and restore ecological roles in woodlands. These actions have contributed to a significant population increase over the last 15 years, from critically low numbers to an estimated 10,000–15,000 mature individuals, though the species remains decreasing overall and listed as Endangered in several states. Landholder agreements promote the retention of fallen timber and reduced grazing to enhance juvenile survival and recruitment. The Peruvian thick-knee (Burhinus superciliaris), classified as Vulnerable due to its small, declining population in coastal shrublands of southern and , benefits from broader habitat protection efforts under national biodiversity plans, though species-specific actions are limited. Monitoring and studies on and molt patterns support potential future interventions, but intensified agriculture continues to pose risks without expanded site safeguards. Across the family, international agreements like the CMS Appendix II for several species facilitate cross-border cooperation, while proposed measures include standardized population monitoring and enforced regulations against hunting and collisions.

References

  1. https://animalia.bio/eurasian-stone-curlew/1000
  2. https://datazone.birdlife.org/species/factsheet/eurasian-thick-knee-burhinus-oedicnemus
  3. https://www.bto.org/learn/about-birds/birdfacts/stone-curlew
  4. https://www.rspb.org.uk/whats-happening/news/stone-curlew-projects-anniversary
  5. https://www.animaldiversity.org/accounts/Burhinus_oedicnemus_oedicnemus/classification/
  6. https://avibase.bsc-eoc.org/species.jsp?avibaseid=C7DB323E37CEDBE6
  7. https://www.avespress.com/uploads/downloads/180/file/AS_1_3_PDFA.pdf
  8. https://fatbirder.com/ornithology/burhinidae-thick-knees-and-stone-curlews/
  9. https://www.gbif.org/species/2482100
  10. https://www.monaconatureencyclopedia.com/burhinus-oedicnemus/?lang=en
  11. https://www.fws.gov/taxonomic-tree/1684071
  12. https://birdsoftheworld.org/bow/species/burhin2/cur/introduction
  13. https://www.tandfonline.com/doi/abs/10.1080/02724634.1981.10011902
  14. https://pmc.ncbi.nlm.nih.gov/articles/PMC4785986/
  15. https://doi.org/10.2173/bow.burhin2.01
  16. https://www.rares.world/wp-content/uploads/2019/07/Aves-Burhinidae-Burhinus-grallarius-Bush-stone-curlew-MG2018-v-1.pdf
  17. https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/thick-knees-burhinidae
  18. https://ebird.org/species/eutkne1
  19. http://blascozumeta.com/specie_files/04590_ENG_Burhinus_oedicnemus_aranzadi.pdf
  20. https://digitalcommons.usf.edu/cgi/viewcontent.cgi?article=3229&context=wsg_bulletin
  21. https://datazone.birdlife.org/species/factsheet/indian-thick-knee-burhinus-indicus
  22. https://datazone.birdlife.org/species/factsheet/water-thick-knee-burhinus-vermiculatus
  23. https://datazone.birdlife.org/species/factsheet/senegal-thick-knee-burhinus-senegalensis
  24. https://datazone.birdlife.org/species/factsheet/bush-thick-knee-burhinus-grallarius
  25. https://datazone.birdlife.org/species/factsheet/great-thick-knee-esacus-recurvirostris
  26. https://datazone.birdlife.org/species/factsheet/beach-thick-knee-esacus-magnirostris
  27. https://datazone.birdlife.org/species/factsheet/double-striped-thick-knee-burhinus-bistriatus
  28. https://datazone.birdlife.org/species/factsheet/peruvian-thick-knee-burhinus-superciliaris
  29. https://www.macaronesian.org/assets/files/file-b03604056bdeab.pdf
  30. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1474-919X.2011.01153.x
  31. https://link.springer.com/article/10.1007/s10336-022-02020-0
  32. https://www.researchgate.net/publication/307174070_Spring_migration_and_breeding_biology_of_Stone-Curlews_Burhinus_oedicnemus_on_the_north-west_Atlantic_coast_of_Morocco
  33. https://www.cambridge.org/core/journals/journal-of-zoology/article/habitat-selection-ranging-behaviour-and-diet-of-the-stone-curlew-burhinus-oedicnemus-in-southern-england/71E59AA03E9649A83BDD3E8B8CD60661
  34. https://www.researchgate.net/publication/231898030_Habitat_selection_ranging_behaviour_and_diet_of_the_Stone_Curlew_Burhinus_oedicnemus_in_Southern_England
  35. https://doi.org/10.1017/S095283699900704X
  36. https://www.tandfonline.com/doi/pdf/10.1080/00063658609476898
  37. https://doi.org/10.1080/00063658609476898
  38. https://doi.org/10.3906/zoo-1305-41
  39. https://www.researchgate.net/publication/336530888_Egg_retrieval_by_Eurasian_Stone-curlew_Burhinus_oedicnemus
  40. https://www.birdguides.com/articles/conservation/saving-the-stone-curlew/
  41. https://www.worldbirdnames.org/new/updates/taxonomy/
  42. https://www.sciencedirect.com/science/article/pii/S1055790322002330
  43. https://www.museum.lsu.edu/~Remsen/SACCprop976.htm
  44. https://www.worldbirdnames.org/new/classification/family-index-2/
  45. https://www.bbc.com/news/articles/cx2gjjk0kgjo
  46. https://www.birdlife.org/news/2025/03/18/the-return-of-the-stone-curlew-a-conservation-triumph/
  47. https://penguinfoundation.org.au/whats-new/bush-stone-curlew-reintroduction
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