Burhinus

The genus Burhinus was erected by the German zoologist Johann Karl Wilhelm Illiger in 1811 with the bush stone-curlew as the type species. The name combines the Ancient Greek bous meaning "ox" and rhis, rhinos meaning "nose" (or "bill"). Determining the correct placement of this family can be difficult as they are very ancient species. Burhinus are best placed in Charadriiformes. They resemble bustards (family: Otididae) and have been previously classified with them in Gruiformes. Their placement in Gruiformes is considered convergent evolution, as both orders have the same lifestyle and biotopes. Comparisons made of skeleton, biochemistry and parasites plus down on young, confirm Burhinus as a charadriiform. They have some similarities to Glareolidae and some phylogenies do place them as a sister clade to this family. however this is also considered convergent evolution. Burhinus and Chionis together are sister to the rest of the Charadriidae. A phenotypic study of Charadriiformes suggests that Burhinidae should consist of three genera – Esacus, Burhinus plus resurrected Orthorhampus. In this model, the bush stone-curlew would be removed from Burhinus and placed in a subfamily Esacinae with Esacus. This subfamily would be known as the greater thick-knees, while the remainder of the genus Burhinus would fall into Burhininae, the lesser thick-knees. This is based on character analyses of skeletons, skin and natal patterns. It is possible that the population of Eurasian stone-curlews on the Canary Islands should also be split in this way as this population shows very little genetic variation. In IOC 14.1, the double-striped thick-knees were transferred to the newly described genus Hesperoburhinus. The bush stone-curlew has had a confusing history of classification. This species has previously been considered two species and B. magnirostris has at times been used for this species, with the same specific epithet now used for the beach stone-curlew in the sister genus Esacus, leading to much confusion. There are three fossil species known: • Burhinus lucorum Bickart, 1981 from the Early Miocene of Nebraska • Burhinus aquilonaris Feduccia, 1980 from the Pleistocene of Kansas • Dwarf thick-knee, Burhinus nanus Brodkorb, 1959 from the Late Pleistocene of The Bahamas == Description ==

Burhinus are a genus of long-legged, large-eyed, terrestrial waders with eerie nocturnal calls. They range from 32 cm (Senegal thick-knee) to 59 cm (bush stone-curlew). Burhinus’ secondary feathers are usually not replaced in one season, with the inner and outer feather being shed first. A pre-breeding moult may just be the head and neck and sometimes not at all. Once they have fledged, juvenile Burhinus will moult only their head and body, some wing-coverts and central tail. Juveniles will moult their secondary wing feathers after their first winter. This can be helpful when estimating the age of young birds. == Distribution and habitat ==

Burhinus species are found in the tropics and sub-tropics of the Old World, with one species found in Australia. They are generally sedentary and can live their whole lives within a few kilometres of hatching site. Eurasian stone-curlews are the exception, breeding in temperate areas and migrating south to avoid the northern winter. Birds from Britain and France will migrate to Italy, Greece, and Turkey and further. Double-striped, Peruvian and the spotted thick-knees are rarely seen outside breeding areas while Senegal thick-knees will move based on rains in north. Burhinus are generally timid and wary, though in some case they may live close to humans using resources from dung and crops, as well as nesting on rooftops. == Behaviour and ecology ==

Burhinus are terrestrial and often only fly when surprised, despite being strong flyers. When observed, Burhinus will generally look furtive and secretive and prefer to stay motionless. They roost on the ground during the day beside clumps of vegetation, rock or fallen timber. Most species are active from dusk till dawn. Burhinus can be sociable with non-breeding flocks of dozens to hundreds using traditional sites In Europe, 300 or more Eurasian stone-curlews have been seen together at times, whilst in Tunisia, 150 have been recorded together. Non-breeding spotted stone-curlews can sometimes be found in loose flocks of 50 also during breeding season. Breeding Eurasian stone-curlews are the best-studied species, however what is known about other species aligns with Eurasian information in many instances. Burhinus form monogamous, long-term (probably lifelong) pairs. For the more tropical species, the breeding season is opportunistic, depending on the availability of food and nesting sites, while the temperate species nest in the spring and summer. Generally, nesting will consist of solitary pairs, if possible, but when the population is dense or the habitat restricted, multiple pairs may be found nesting in close proximity, especially double-striped and Senegal stone-curlews. Courtship consists of short runs, skips and leaps with open wings and the black and white wing/tail patches may possibly be important. Displays may be between two birds or in a group. The nest usually consists of a simple scrape that is sometimes lined with stones or shells. If the vegetation becomes too tall, as can occur if nesting occurs within a crop, Burhinus will abandon the nest site. Clutch size is two eggs, rarely three, laid at 2-day intervals. Egg size is specific to species and the eggs are usually rounded ovals, smooth slightly glossy, whitish or buffish with brown spots and mottles. Burhinus’ eggs match with the ground, nesting building and choice of nest substrate preferred by each species and individual variation occurs. This increases crypsis and improves hatching success. Incubation begins when the last egg is laid but sometime just before with synchronous or consecutive hatching. Broken shells are carried away. Minor disturbances will cause parents to quietly leave nest, while more serious threats will cause them to defend the nest. This can include distraction displays and aggressive behaviour, though very occasionally a broken wing display has been observed. The non-incubating parent will spot danger and warn their mate. The alarm is raised with a special posture. The sitting bird will walk away then runs and flies off, while the other bird flies in different direction. They will both turn back and meet, and watch to see what will become of the disturbance. The male will follow intruder if it leaves, whilst the female will carefully return. The pair will attack ground predators, diving, wings out and neck forward. On the other hand, they will stand upright wing fanned against herbivore that may trample the eggs or chicks. If chicks are not lost to the threat, the parents will lead them to a new area. Senegal thick-knees will watch humans at nest and then return quite quickly even if watched. Voice Burhinus are mainly silent during the day, with the majority of call occurring during the night. Their call is penetrating and far-carrying and has been described as eerie, mournful and plaintive. They can produce remarkable vocal performances including wailing and whistling. Eurasian stone-curlews often make short sharp notes like oystercatchers (Haematopodidae), which are repeated, accelerating to up more prolonged curlew like calls and then dies away. The Senegal stone-curlew is more nasal, while the Aborigine name for Bush stone-curlew is "Willaroo" which is onomatopaeic to the long drawn out whistling scream. Several individuals will join in a prolonged chorus, especially at the beginning of breeding season. The role of the calls of Burhinus is poorly understood due to the difficulty of observation of individuals while calling. Eurasian stone-curlews are the best studied and it has been found that: • groups are more vocal than pairs; • vocals may be more important between adjacent pairs than within the pair; • more vocal in pre-lay period, silent when newly arrived in breeding territory, quiet again before chicks arrive and until fledging; • more daytime calling occurs while establishing a territory or from unpaired or non-breeding birds, and these birds are more easily attracted by call playback. Vocalisations usually start approximately thirty minutes after sunset and started by single individual, and then partner and other pairs join in. The birds are quieter in middle of night and finish at sunrise. Adults call more frequently during the spring and summer. Some calls have no context, however a number of calls have been described for Eurasian stone-curlews. Vocalisations for adults include aggression, greeting between pairs or groups of territory holders meeting, specific behaviours like nest scraping and spring displays, distraction behaviours, adults defending their nest with eggs or chicks as well as conversational calls between adults over newly hatched chicks. Calls from chicks and juveniles up to 70 days old have also been documented, with two types completely different to adults. == Status and conservation ==

It is very difficult to know the true status of this genus, as its species are so secretive. There is just enough data to show that most species of Burhinus have been affected by interference. In Britain, sensitive management of grazing in heathlands, setting aside patches within crops, and the protection of nests from predators, machinery and stock has led to a halt of the very sharp decline of the Eurasian stone-curlew, with this population now stable though not increasing. Modelling the habitat required for stone-curlews, as well as the use of ringing recovery, geo-locators and GPS data loggers, has also helped to determine which areas are important to protect for Eurasian stone-curlews in both Britain and Italy. The Bush stone-curlew has contracted in its range, with reduced numbers or local extinction in the south and east. with their surroundings The African thick-knee species will often live alongside people while generally ignoring them. In these places, the populations seem stable and stone-curlews will use the resources associated with humans. Such populations will for instance feed on insects in livestock dung and nest on roofs. Some modification seems to be beneficial where suitable habitat is produced as a result, for example along road-sides for the American species, however this can lead to mortality as well. == Relationship with humans ==

Due to their secretive nature, Burhinus mainly come to the attention of humans through their calls, leading to varied local names. The calls of the bush stone-curlew caused unease to white settlers as well as Aboriginal people in Australia, especially because they are hard to see, which added to the fear and superstition. The main reference in folklore is to a vague, disembodied voice in the night. In some places, the double-striped stone-curlew is kept semi-captive to help keep pests under control. The yellow eyes and bill of the Eurasian stone-curlew was once thought to indicate that they were good treatment for jaundice. == Gallery ==

File:Bush Stone-curlew.jpg|Bush stone-curlew File:Kaptriel - Spotted dikkop - Burhinus capensis.jpg|Cape thick-knee File:Eurasian Thicknee - Along Po river - Italy FJ0A1202 (28252446508), crop.jpg|Eurasian stone-curlew File:Waterdikkop-crop2.jpg|Water thick-knee File:Senegal Thick-knee - Gambia (32528240471), crop.jpg|Senegal thick-knee File:Spotted thick-knee (Burhinus capensis).jpg|Spotted thick-knee == References ==