Great bustard

The genus name Otis was introduced in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae; it came from the Greek name ōtis used for this species taken from Natural History by Pliny the Elder published around 77 AD which briefly mentions a bird like it, it was also given the name ōtidos and the Latin mentioned by the Pierre Belon in 1555 and Ulisse Aldrovandi in 1600. The specific epithet tarda is Latin for "slow" and "deliberate", which is apt to describe the typical walking style of the species. == Description ==

The adult male great bustard is amongst the heaviest living flying birds. A male is typically tall, with a length of around and has a wingspan. The male can range in weight from . The heaviest verified specimen, collected in Manchuria, was about , In a study in Spain, one male weighed as much as . Larger specimens have been reported but remain unverified. Average male weights as reported have been fairly variable: in Russia, males weighed a median of ; in Spain, males weighed a mean of during breeding season and during non-breeding; in Germany, males weighed a mean of ; and the Guinness World Records has indicated that male bustards in Great Britain weighed an average of . Average weight of males is almost an exact match to that of male Kori bustards. Among all flying animals and land birds, male Andean condors (Vultur gryphus) may match or exceed the mean body masses of these male bustards but not their maximum weights. Furthermore, male swans of the two largest species (trumpeter and mute) may attain a similar average mass depending on season and region. The female is about a third smaller in linear dimensions, typically measuring in height, about in length and across the wings. Overall, the female's weight can range from . Like male weights, females weights are quite variable as reported: in Germany, females had a mean weight of , in Spain, females had a mean weight of and in Russia, females reportedly had a median weight of . The latter figure indicates that eastern birds (presumably O. t. dybowskii) are considerably less sexually dimorphic in body mass than in other populations. Perhaps because of this physical sexual dimorphism, there is a skewed sex ratio of about 1.5:1 female to male. An adult male is brown above, barred with blackish colouration, and white below, with a long grey neck and head. His breast and lower neck sides are chestnut and there is a golden wash to the back and the extent of these bright colours tending to increase as the male ages. In the breeding season, the male has long white neck bristles, which measure up to in length, continually growing from the third to the sixth year of life. In flight, the long wings are predominantly white with brown showing along the edges of the lower primary and secondary feathers and a dark brown streak along the upper-edge of the wing. The breast and neck of the female are buff, with brown and pale colouration over the rest of the plumage rendering it well camouflaged in open habitats. Immature birds resemble the female. The eastern subspecies (O. t. dybowskii) is more extensively grey in colour in both sexes, with more extensive barring on the back. The great bustard has long legs, a long neck and a heavy, barrel-chested body. It is fairly typical of the family in its overall shape and habitat preferences. Three other bustard species overlap in range with this species: the MacQueen's (Chlamydotis macqueenii), houbara (Chlamydotis undulata) and little bustards (Tetrax tetrax). However, none of these attains the plumage coloration nor approach the body sizes of this species. Thus, the great bustard is essentially unmistakable. Male droppings are considerably heavier and bulkier than those of females. The weight, volume, and density of droppings also vary depending on the season and their composition, which is influenced by diet. Fecal steroid analyses can be particularly useful for determining sex and also for characterizing the endocrine status of individuals. ==Distribution and habitat==

These birds' habitat is grassland or steppe defined by open, flat or somewhat rolling landscapes. They can be found on undisturbed cultivation and seem to prefer areas with wild or cultivated crops such as cereals, vineyards and fodder plants. However, during the breeding season, they actively avoid areas with regular human activity and can be disturbed by agricultural practices. Great bustards are often attracted to areas with considerable insect activity. The breeding range of the great bustard currently stretches from Portugal to Manchuria, though previously the species bred even further east in Russian Primorsky Krai. As a result of population declines across much of the range, more than half of the global population is now found in central Spain with around 30,000 individuals.The spanish region of Castile and Leon is home to around 30% of the great bustard global population. Smaller populations are in southern Russia and the Great Hungarian Plain. In Iran, the species survives only in a small area in the Boukan region of West Azerbaijan province, where a census in January 2025 recorded just 19 individuals remaining. In 2024, conservation efforts in Boukan led to the successful hatching of the first great bustard chick in captivity in Iran. ==Behaviour and ecology ==

The great bustard is gregarious, especially in winter when gatherings of several dozen birds may occur. Male and female groups do not mix outside of the breeding season. The great bustard has a stately slow walk but tends to run when disturbed rather than fly. Running speeds have not been measured but adult females have been known to outrun red foxes (Vulpes vulpes), which can reach a trotting speed of . European populations are sedentary or make irregular movements in response to severe winter weather. Populations breeding along the Volga in Russia migrate around to spend the winter season in Crimea and Kherson Oblast. Populations breeding in northern Mongolia migrate over to Shaanxi Province of China. Great bustards often gather in larger numbers at pre-migratory sites in order to move collectively to winter grounds. In the Iberian Peninsula, migrating great bustards seem to choose different periods for movements based on sex. Eggs weigh about and are on average tall by wide. The female incubates the eggs alone for 21 to 28 days. The chicks almost immediately leave the nest after they hatch, although they do not move very far from their mother until they are at least 1 year old. Young great bustards begin developing their adult plumage at about 2 months, and begin to develop flying skills at the same time. They practice by stretching, running, flapping, and making small hops and jumps to get airborne. By three months they are able to fly reasonable distances. If threatened, the young stand still, using their downy plumage, mainly sepia in colour with paler buffy streaks, as camouflage. Juveniles are independent by their first winter, but normally stay with their mother until the next breeding season. Males usually start to mate from 5 to 6 years of age, although may engage in breeding display behaviour at a younger age. Females usually first breed at 2 to 3 years old. Great bustards sometimes eat toxic blister beetles of the genus Meloe to self-medicate, increasing sexual arousal of males. There are some differences between the diets of female and male bustards as a result of sexual dimorphism in weight, one of the highest in birds. Foraging In winter the feeding intensity increased and then decreased through the morning in both sexes, and was lower in flocks of males than in flocks of females. This sexual difference is greater where legume availability was smaller in central Spain. that would allow them to obtain enough food relative to their absolute daily energy requirements. The size of morning foraging area is smaller in sites with more legume availability, likely because legumes are the most preferred substrate type. Predation on adult male great bustards has been reportedly committed by white-tailed eagles (Haliaeetus albicilla) while golden eagles (Aquila chrysaetos) are potential predators and eastern imperial eagles (Aquila heliaca) have been known to prey on great bustards (but not likely to include adult males). Great bustards of unspecified age and sex have been found amongst Eurasian eagle-owl (Bubo bubo) prey remains in Bulgaria. The bold, conspicuous behaviour of the breeding adult male bustard may attract the same large mammalian predators that predate chicks, such as wolves and lynx, while the more inconspicuous female may sometimes be attacked by various predators. However, predation is generally fairly rare for adults because of their size, nimbleness and safety in numbers through social behaviour. Occasionally, other natural causes may contribute to mortality in the species, especially starvation in harsh winter months. However, major causes of mortality in recent centuries have been largely linked to human activity, as described below. ==Population distribution==

As of 2008, the global population numbered between 44,000 and 51,000 birds (Palacin & Alonso 2008), about 38,000 to 47,000 in Europe, with 30,000 or more than half in Spain. Hungary had the next largest Great Bustard population with about 1,555 in the year 2012, followed by Ukraine and Austria. Between 4,200 and 4,500 were found in east Asia. Elsewhere, the populations are declining because of habitat loss throughout its range. A sizeable population also exists in Hungary (1,100–1,300 birds) where the Eastern European steppe zone ends, near Dévaványa town and also in the Hortobágy National Park, Nagykunság and Nagy-Sárrét regions. The population is down from a population of 10,000–12,000 before the Second World War. Agroenvironment schemes as unirrigated legumes fostered a population increase of great bustards in Castilla y Leon, central Spain. ==Threats and conservation status==

The great bustard is classified as endangered at the species level. There are myriad threats faced by great bustards. Increasing human disturbance could lead to habitat loss caused by the ploughing of grasslands, intensive agriculture, afforestation, increased development of irrigation schemes, and the construction of roads, power lines, fencing and ditches. Mechanisation, chemical fertilizers and pesticides, fire and predation by dogs are serious threats for chicks and juveniles, and hunting of adults contributes to high mortality in some of their range countries. Agricultural activity is a major disturbance at nest and, in Hungary, few successful nests are found outside of protected areas. Bustards are also occasionally killed by collisions with automobiles or by entanglement in wires. Bewick's prediction was correct; the great bustard was hunted out of existence in Britain by the 1840s. In 2004, a project overseeing the reintroduction to Salisbury Plain in Wiltshire using eggs taken from Saratov in Russia was undertaken by The Great Bustard Group, a UK Registered Charity that aims to establish a self-sustaining population of great bustards in the UK. The reintroduced birds have laid eggs and raised chicks in Britain in 2009 and 2010. Although the great bustard was once native to Britain, great bustards are considered an alien species under English law. In Hungary, where the species is the national bird, great bustards are actively protected. The Hungarian authorities are seeking to preserve the long-term future of the population by active protection measures; the area affected by the special ecological treatment had grown to by the summer of 2006. Under the auspices of the Convention on Migratory Species of Wild Animals (CMS), also known as the Bonn Convention, the Memorandum of Understanding (MoU) on the Conservation and Management of Middle-European Populations of the Great Bustard was concluded and came into effect on June 1, 2001. The MoU provides a framework for governments, scientists, conservation bodies and others to monitor and coordinate conservation efforts in order to protect the middle-European populations of the great bustard. ==Notes==