Great bustard
The great bustard is a bird in the bustard family, and the only living member of the genus Otis. It breeds in open grasslands and farmland from northern Morocco, South and Central Europe to temperate Central and East Asia. European populations are mainly resident, but Asian populations migrate farther south in winter. Endangered as of 2023, it had been listed as a Vulnerable species on the IUCN Red List since 1996.
Portugal and Spain now host about 60% of the world's great bustard population. The species was extirpated in Great Britain in the 19th century, when the last bird was shot in 1832. Since 1998, The Great Bustard Group have helped reintroduce it to England on Salisbury Plain, a British Army training area. Here, the lack of public access and disturbance allows them the seclusion they desire as a large, ground-nesting bird.
Taxonomy
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 ὠτίς 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 ωτιδος ōtidos and the Latin aves tardas 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. The Latin phrase avis tarda "slow bird" is the origin of the word bustard, via Old French bistarda.
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, a world record for heaviest flying bird. 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 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 may attain a similar average mass depending on season and region. Among both bustards and all living birds, the upper reported mass of this species is rivaled by that of the kori bustard, which, because of its relatively longer tarsi and tail, is both longer and taller on average and is less sexually dimorphic. In terms of weight ranges reported, the great Indian bustard also only lags slightly behind these species.The great bustard is also arguably the most sexual dimorphic extant bird species, in terms of the size difference between males and females. Adult male great bustards measured in Spain weighed on average 2.48 times more than females. Going on mass, the only known bird with a higher dimorphism is the green peafowl as the males are apparently near four times as heavy as females. 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 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 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, houbara and little bustards. However, none of these attains the plumage coloration nor approach the body sizes of this species. Thus, the great bustard is essentially unmistakable.
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. 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, which can reach a trotting speed of. Both sexes are usually silent but can engage in deep grunts when alarmed or angered. The displaying adult male may produce some booming, grunting and raucous noises. The female may utter some guttural calls at the nest and brooded young make a soft, trilling call in communication with their mothers.Migration
Some individuals in Iberian populations make short seasonal movements of, particularly males which appear to move in response to higher summer temperatures. 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. No population is known to use the same grounds for wintering and summering. Great bustards are strong fliers and reach speeds of during migration.
Reproduction
The great bustard breeds in March, and a single male may mate with up to five females. Before mating, the males moult into their breeding plumage around January. Males establish dominance in their groups during winter, clashing violently by ramming into and hitting each other with their bills. Like other bustards, the male great bustard displays and competes for the attention of females on what is known as a lek. In this species, the male has a flamboyant display beginning with the strutting male puffing up his throat to the size of a football. He then tilts forwards and pulls his head in so that the long whiskery chin feathers point upwards and the head is no longer visible. He next cocks his tail flat along his back, exposing the normally hidden bright white plumage then he lowers his wings, with the primary flight feathers folded but with the white secondaries fanning out. The displaying males, who may walk around for several minutes at a time with feathers flared and head buried waiting for hens to arrive, have been described as a "foam-bath" because of their appearance.One to three olive or tan coloured, glossy eggs are laid by the female in May or June. The nests, which are shallow scrapes made by the female on dry, soft slopes and plains, are usually situated close to the prior lek location. Nests are situated in sparse clusters, with a study in Inner Mongolia finding nests at a minimal apart from each other. In the same study, nests were placed at mid-elevation on a hill, at about. Nesting sites are typically in dense grassy vegetation about, likely for protection against predation, with extensive exposure to sunlight. 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.