The huge adult male great bustard is amongst the heaviest living flying animals.
It is also arguably the most sexual dimorphic extant bird species, in terms of the size difference between males and females.
Going on mass, the only known bird with a higher dimorphism is the green peafowl (Pavo muticus) as the males are apparently near four times as heavy as the female.
Among both bustards and all living birds, the upper reported mass of this species is rivaled by that of the kori bustard (Ardeotis kori), which, due to 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 (Ardeotis nigriceps) also only lags slightly behind these species.
A male is typically 90–105 cm (2 ft 11 in–3 ft 5 in) tall, with a length of around 115 cm (3 ft 9 in) and has a 2.1–2.7 m (6 ft 11 in–8 ft 10 in) wingspan.
The male can range in weight from 5.8 to 18 kg (13 to 40 lb).
Average male weights as reported have been fairly variable: in Russia, males weighed a median of 9.2 kg (20 lb); in Spain, males weighed a mean of 9.82 kg (21.6 lb) during breeding season and 10.62 kg (23.4 lb) during non-breeding; in Germany, males weighed a mean of 11.97 kg (26.4 lb); and the Guinness World Records has indicated that prior to their extirpation male bustards in Great Britain weighed an average of 13.5 kg (30 lb).
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.
In a study in Spain, one male weighed as much as 19 kg (42 lb).
The heaviest verified specimen, collected in Manchuria, was about 21 kg (46 lb).
Larger specimens have been reported but remain unverified.

The female is about a third smaller in linear dimensions, typically measuring 75 to 85 cm (2 ft 6 in to 2 ft 9 in) in height, about 90 cm (2 ft 11 in) in length and 180 cm (5 ft 11 in) across the wings.
The females are roughly one-third the weight of the male.
Overall, the female's weight can range from 3.1 to 8 kg (6.8 to 17.6 lb).
Like male weights, females weights are quite variable as reported: in Germany, females had a mean weight of 3.82 kg (8.4 lb), in Spain, females had a mean weight of 4.35 kg (9.6 lb) and in Russia, females reportedly had a median weight of 6 kg (13 lb).
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 12–15 cm (4.7–5.9 in) 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
The huge adult male great bustard is amongst the heaviest living flying animals. It is also arguably the most sexual dimorphic extant bird species, in terms of the size difference between males and females. Going on mass, the only known bird with a higher dimorphism is the green peafowl (Pavo muticus) as the males are apparently near four times as heavy as the female. Among both bustards and all living birds, the upper reported mass of this species is rivaled by that of the kori bustard (Ardeotis kori), which, due to 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 (Ardeotis nigriceps) also only lags slightly behind these species. A male is typically 90–105 cm (2 ft 11 in–3 ft 5 in) tall, with a length of around 115 cm (3 ft 9 in) and has a 2.1–2.7 m (6 ft 11 in–8 ft 10 in) wingspan. The male can range in weight from 5.8 to 18 kg (13 to 40 lb). Average male weights as reported have been fairly variable: in Russia, males weighed a median of 9.2 kg (20 lb); in Spain, males weighed a mean of 9.82 kg (21.6 lb) during breeding season and 10.62 kg (23.4 lb) during non-breeding; in Germany, males weighed a mean of 11.97 kg (26.4 lb); and the Guinness World Records has indicated that prior to their extirpation male bustards in Great Britain weighed an average of 13.5 kg (30 lb). 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. In a study in Spain, one male weighed as much as 19 kg (42 lb). The heaviest verified specimen, collected in Manchuria, was about 21 kg (46 lb). Larger specimens have been reported but remain unverified.
The female is about a third smaller in linear dimensions, typically measuring 75 to 85 cm (2 ft 6 in to 2 ft 9 in) in height, about 90 cm (2 ft 11 in) in length and 180 cm (5 ft 11 in) across the wings. The females are roughly one-third the weight of the male. Overall, the female's weight can range from 3.1 to 8 kg (6.8 to 17.6 lb). Like male weights, females weights are quite variable as reported: in Germany, females had a mean weight of 3.82 kg (8.4 lb), in Spain, females had a mean weight of 4.35 kg (9.6 lb) and in Russia, females reportedly had a median weight of 6 kg (13 lb). 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 12–15 cm (4.7–5.9 in) 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 
Great bustard