The great bustard, otis tarda, is the heaviest flying bird in the world. Its closest rivals for this title are the mute swan, cygnus olor, and the kori bustard, ardeotis kori. Along with the swan and the peacock, weighing in between 18 - 25kg, this bird was considered suitable fare for the nobility at banquets in the 15th Century. Both the swan and the bustard were the most expensive of birds to supply.

Description

• The adult male stands at around a metre tall, with the female smaller at 75cm.

• The head and stout neck are pale blue-grey. There are small ear tufts. The back and tail are beige-gold, barred with black. The under-parts and most of the wings are white. The wings have black tips.

• Females and juveniles are paler and drabber.

• Breeding males have a chestnut breast band at the lower neck and a white whisker 'moustache', either side and just below the beak, up to 18cm long.

• The legs are grey-brown.

• The three toes all point forward. Without a talon at the back the bird cannot perch, so it is essentially ground-dwelling.

Behaviour

Great bustards are shy, wary and mainly terrestrial, frequenting extensively cultivated fields and grassy plains. They prefer to hide away rather than fly.

They have an upright stance and deliberate walk and gather in flocks, called droves. These consist mainly of females and juveniles.

When they do fly they have a strong slow powerful flight, appearing similar to an eagle, with the end feathers of the wings flaring, though their trajectory is low and never soaring. The neck and legs are outstretched in flight. An adult male may have a wingspan of two and-a-half metres.

They are omnivorous, eating seeds, fruit and plants all year, but in summer their diet is supplemented with insects, small reptiles and mammals such as voles.

Breeding

Open grasslands are used for the mating displays, and grassland and arable crops for nesting.

The mating display takes place on an area known as a lek¹. These are 50 or so metres apart and are used from late March to early June, depending on the breeding area.

The males put back their heads, inflate their necks with an internal pouch, their whiskers stand upright and they turn their wings to display the white secondary feathers. The whole bird appears to be a large white balloon or powder puff. Usually the bird is fairly stationary, just stomping the ground during this display, which can last up to two minutes.

Females usually nest close to the lek of their mate, but have been known to lay as far away as ten kilometres. Some pairs are monogamous, but luckily for the future survival of the bird, others are not.

Two to three eggs, weighing approximately 150g each are laid at intervals of up to two days apart in a depression in crops or short grass during mid April to late June. Pale green, buff or grey with brown blotches, these blend in well with the few stalks that the female may use to define the nest.

After 21 to 28 days of incubation the chicks, weighing in at 100g, hatch. The mottled brown and buff hatchlings are fed by the mother on insects initially. Able to leave the nest immediately, they peck at small stones which they ingest to aid the digestion in the gizzard. Returning to the female for brooding they take around 35 days to mature to independence, although they may flock with their mother for a year or more.

The females reach breeding age at three to four years old, but the males take a further couple of years to reach full maturity. The rate of reproduction is low. Breeding is followed by a moult.

Calls

The young have a high whistle among their many noises. Apart from the breeding season, when snores, rattles and whines have been recorded, the adults are generally quiet for the rest of the year.

Distribution

The breeding range is from the plains of the Alentejo in Portugal and the Estramadura in Spain to north-east China and Mongolia. The largest populations are in Spain and Russia. Smaller populations are found in China, Mongolia, Portugal and Iran. A few may still breed in Morocco.

They move around often over large tracts of land in their droves of varying size. This makes them difficult to count accurately. The world population of great bustards is generally in decline. It is officially classified as 'vulnerable'.

A factor in their decline is the current use of large agricultural machinery, such as wide harrows and rotovators, and intensive farming techniques, which indiscriminately destroy nests in the vast crop fields.

Reintroduction

The Great bustard used to breed in the British Isles, but since 1830 only a few vagrants² have been noted.

Once the county bird of Wiltshire, it is depicted in the county arms³, other Wiltshire groups, such as the girl guides, and pub signs.

Attempts have been made to reintroduce the great bustard, centered at Porton Down, but these have proved unsuccessful due to the chicks imprinting on humans, making them unable to survive in the wild. Other factors have been the infertility of the adults and very low survival rate of the chicks.

In the summer of 2004, a planned reintroduction onto Salisbury plain was attempted, using chicks recovered from nests abandoned or damaged in Russia. Special techniques and feeding puppets have been developed to avoid direct human contact.

Let us hope that this will be as successful as the reintroduction of the osprey, avocet and black-tailed godwit into the British Isles.

References

• The Great Bustard Group web site - reintroducing the Great Bustard into the British Isles.
• Global alliance of Conservation organisations.
• BBC News Article - Reintroduction of the Great Bustard to Wiltshire in 2004.
• Collins - A Field Guide to the Birds of Great Britain and Europe