The Great bustard is a member of the bustard family and the only member in the genus Otis. One of the heaviest birds alive today that can fly, it is found across Europe. Huge, robust but stately looking, adult males have a bulging neck and a heavy chest, with a characteristically cocked tail. The breeding plumage of males includes white moustachial whiskers that are 20cm long, and their back and tail become more vividly colored. They develop a band of feathers on their breast and lower neck that are russet colored, becoming brighter and wider as they get older. These birds walk with an upright stance, and fly with powerful and regular wing beats.
Great bustards are endemic to central and southern Europe, where they are the largest bird species, and across temperate Asia. In Europe, populations are mainly resident, while Asian birds travel further south in winter. This species inhabits grassland, steppe, and open, agricultural land. They favor regions for breeding with little or no presence by humans.
These birds are diurnal, and, among vertebrates, have one of the greatest differences in size between the sexes. For this reason, males and females live in separate groups for almost the whole year, except during the mating season. This size difference also affects food requirements as well as breeding, dispersal and migratory behaviors. Females tend to flock together with individuals who are related. They are more philopatric and gregarious than males, and will often remain at their natal area for their entire life. In winter, males establish a group hierarchy, engaging in violent, prolonged fights, stabbing the head and neck of other males, sometimes causing serious injury, behavior which is typical of bustards. Some populations of Great bustards are migratory, gathering at pre-migratory sites in great numbers in order to collectively move to winter grounds.
The Great bustard is omnivorous, it eats vegetation such as grass, legumes, crucifers, grains, flowers and grapes. It also eats rodents, the chicks of other species, earthworms, butterflies, large insects and larvae. Lizards and amphibians are also eaten, depending on the season.
These birds are polygynous, and one male may mate with as many as five females. The males perform spectacular courtship displays, competing in a lekking system, where they gather at a ‘lek’ or small display ground to try to impress the females. The breeding season is in March, and eggs are laid in May-June, depending on the region. Nests are usually close to leks. 2-3 eggs are laid and the female on her own incubates them for about 25 days to a month. Chicks are precocial and can immediately leave the nest. Their mother raises them and they fledge at around 30-35 days. They do not reach full size until 80 to 120 days old, and for about ten months are dependent on their mother.
This species suffers from the fragmentation and loss of its habitat. Increasing land privatization and human disturbance is expected to cause more habitat loss with the plowing of grasslands, afforestation, intensive agriculture, increased use of irrigation schemes, and construction of power lines, roads, fencing and ditches. Chemical fertilizers and pesticides, mechanization, fire and predation are major threats for the chicks and juveniles, while hunting of adult birds causes high mortality in some countries where they live.
According to the IUCN Red List, the total population size of the Great bustard is around 44,000-57,000 individuals. Currently this species is classified as Vulnerable (VU) and its numbers today are decreasing.