What are Great Bustards?
The Great Bustard (Otis tarda) is a large bird in the Bustard family, unrelated to other large bird species such as turkeys or geese. Great Bustards can (and do) fly, despite being the heaviest flying animal alive today. Great Bustards can be found across Europe, as far south as Spain and as far to the north as the Russian steppes. Most members of the Bustard family are smaller than the Great Bustard which is dwarfed only by the Kori Bustard. Male Great Bustards grow about 30% larger than the females, reaching up to 1 meter tall and weighing up to 16Kg (the heaviest recorded Great Bustard weighed in at 21Kg). The conservation status of the Great Bustard is listed as vulnerable, with populations in many countries being in decline and having been extinct in the UK for over 180 years.
Appearance
Huge, heavily built and robust but stately in appearance, adult bustard males can be identified by their bulging neck, heavy chest and characteristically cocked tail which adds to their stocky appearance. Shape is similar to a large goose, but the bustard is much larger with considerably longer legs and a straighter neck.
The head and neck are a pale blue-grey, the body and tail rufous brown with black bars, and underparts white. The wings of the Great Bustard are mostly white with dark secondary feathers.
Males in breeding plumage grow large white moustachial whiskers (20 cm) and become more vividly coloured on their back and tail, also developing a band of russet coloured feathers on their lower neck and breast, amount dependent on age.
Size
There is a marked difference in size between male and females, termed sexual size dimorphism. Great Bustards actually exhibit the largest sexual size dimorphism of any bird species and even most other mammals, birds, reptiles, amphibians, and fishes! Female Great Bustards can be as much as 50% smaller than males.
Males: Standing height 90-105 cm. Wingspan 210-250 cm. Weight 8-16 kg
Females: Standing height 75-85 cm. Wingspan 170-190 cm. Weight 3.5-5 kg.
Voice
Adults usually silent but males can sometimes be heard when fighting in breeding season. They use a variety of gruff nasal barks and also a soft “umb, umb” sound sometimes heard as the gular (throat) pouch is inflated and deflated during display. The young also have a number of calls including a high plaintive whistle, first heard from the egg prior to hatching which continues until chicks are several months old.
Nominate form
Otis tarda tarda Linnaeus, 1758. Iberia, Morocco, Turkey, and central and south-east Europe east to central Siberia.
Extralimital form
Otis tarda dybowskii Taczanowski, 1874.East Asia, from the eastern Altai and Lake Baykal to northern China. Order: Gruiformes (12 Families) Family: Otididae (Bustards) – 25 species in 9 genera.
Common name
It is thought that ‘Bustard’ is derived from ‘Bustarde’ and ‘Bistard’ which date back to at least the fourteenth century, having been recorded as a surname in 1391. Most sources state that this is derived from the Latin avis tarda c.77, meaning slow bird. This became abetarda or betarda in Portuguese, avutarda in Spanish, ottarda in Italian and oustarde and bistarde in Old French. It is suggested that the English is derived from a blend of the two French words with the form Bistard found in some 16th and 17th century sources. Great Bustards had traditional local names in different parts of the country such as Sussex where they were called ‘Shepherds Wild Turkey’.
Scientific name
The name Otis is Greek for ear, as in ear of wheat or barely. Each spring male Great Bustards grow whiskers which closely resemble the ears of wheat. The name, tarda, is Latin, meaning slow. The Great Bustard is often stately but the word tarda is rather surprising as this species is actually rather fleet of foot and has a surprisingly fast flight. In their first official list of British birds, published in 1883, the British Ornithologists Union state that tarda is a “Celtic or Basque word, bearing no relation to tardus = slow”, although, they do not say what the word means. It is possible that tarda is in fact the original name from a language spoken in Spain before the arrival of Romans. On being taken into Latin, it naturally seemed to mean slow.
Population & distribution
Great Bustards can be found worldwide, though in some locations, their numbers are scarce. The world Great Bustard population is estimated at 43,500 – 51,200 individual birds. They have undergone a long-term and marked decline, especially since early 19th century that continues virtually across entire range except in Iberia where populations are considered stabilised and west Russia where an increase in population has been reported.
The East Asian population is thought to total 3,500 – 4,700 although some of these belong to the separate sub-species Otis tarda dybowskii. This sub-species was first described in 1874, differing from the nominate Otis tarda tarda by having slightly paler head and neck, broader more well defined black markings on back, greater number of white tail feathers, and the whiskers on adult males connected by short bristle-like feathers on central chin.
| Countries with current breeding records | Number of Great Bustards |
|---|---|
| Austria | 175 |
| Bulgaria | 0 |
| China (NW Xinjiang) | 2,000 – 3,000 |
| Czech Republic | 1 – 6 |
| Germany | 110 |
| Hungary | 1,353 |
| Iran | 89 – 161 |
| Kazakhstan | 0 – 50 |
| Moldova | 0 |
| Mongolia (NE China & SE Russia) | 1,500 – 1,700 |
| Morocco | 91 – 108 |
| Portugal | 1,399 |
| Romania | 0 – 4 |
| Russia (European) | 8,000 – 11,000 |
| Serbia & Montenegro | 35 – 40 |
| Ukraine | 500 – 850 |
| Slovakia | 8 – 16 |
| Spain | 27,500 – 30,000 |
| Turkey | 764 – 1,250 |
Population estimates from:
Palacin & Alonso (2008):
An updated estimate of the world status and population trends of the Great Bustard
Ardeola 55(1) p13-25
Distribution
Great Bustards have a patchy distribution across Eurasia, from Portugal and Spain in the west through Europe and the Russian Federation to Mongolia and China in the east. There are probably small populations in North Africa and the Middle East although their continued existence is uncertain.
Their range undoubtedly expanded, with probable maximum extension in the 18th century, after extensive clearance of forests by man. A subsequent marked and rapid decline in numbers and increasing fragmentation of populations has occurred and continues with conversion of steppe and dry meadows to arable fields, agricultural intensification and persecution.
Behaviour
Great Bustards are highly gregarious birds that form social units termed ‘droves’. Males and females live in separate droves and there is a tendency for birds of the same age to keep together. Large, often loose, flocks form in winter, which may wander in search of food, sometimes joining up with other flocks. Female droves visit groups of displaying males briefly during the breeding season.
Gait is slow and deliberate but bustards are capable of surprisingly fast dashes. Feeding action is a swift pick-up of food from the ground and fast ‘snatching’ of vegetation, often done with apparent petty scrutiny. They have a very wary nature, and will often withdraw into tall vegetation but never into bushes or trees. They are unable to perch, so are only ever seen on the ground. Flight between 30-100 m above ground, action noticeably regular and uninterrupted, never glides, beats slow and majestic, but progress rapid. Wings long and deeply ‘fingered’ appearing mostly white. Silent, unless flushed or threatened at very close range then nasal bark sometimes heard. Lack of an opposable hind claw means they cannot perch, so they are a completely ground-dwelling bird. Great Bustards are notoriously shy and wary birds, often taking cover when alarmed but sometimes flying away. This type of behaviour makes them very difficult to observe.
Food
The Great Bustard is omnivorous, meaning it eats both animal and plant matter. Diet is mainly plants in Spring, Autumn and Winter. Typically takes young shoots, leaves, flowers, ripe and unripe seeds but occasionally rhizomes, bulbs, berries and fruits. Proportion of animal food varies with season, locality, age and sex of bird. Mostly carnivorous in summer. Insects and their larvae predominate but small vertebrates such as voles and lizards also taken. Has been observed taking items not normally taken by other birds such as poisonous seeds of Hemlock, unripe seeds, beetles with unpleasant taste or defensive chemicals and caterpillars with warning colouration. Young are chiefly insectivorous, but as they grow they increase the proportion of plants eaten.
Movements
Populations are migratory in east, dispersive or resident elsewhere. Iberian population shows least movement although local movements do occur. In central Europe mainly resident but will undergo movements of several hundred km in severe winters with heavy snow. Wintering grounds often established in areas with extensive cultivation of crops such as Oil Seed Rape. Degree of cold-weather movements not always directly correlated with depth or duration of snow cover and not every hard winter leads to extensive emigration.
In former USSR often considered truly migratory, except in southern Ukraine where resident. Ukraine population boosted by up to 10,000 birds in the winter, mostly from Russian Federation. However, recent winter observations of birds wintering in Russia at -30C and deep snow cover suggests that even in hard winters not all migrate. Great Bustards have been reported from Syria and Iraq in winter but whether birds still breed in these countries is unknown.
Habitat
Traditionally a bird of expansive grass plains (steppe), they have adapted well to modern agricultural landscapes. They are frequently found in semi-cultivated/managed grasslands, arable farmland and traditional lowland hay meadows. Below are pictures of some real Great Bustard habitats:
Great Bustards most likely evolved in dry tropical grassland plains but since man’s extensive forest clearances and cultivation of land, open habitat has increased and Great Bustards are now found across continental middle latitudes, especially the steppe zone, but penetrate into temperate, Mediterranean, marginal boreal zones, and oceanic climates. They favour lowlands, river valleys, and undulating open country, avoiding steep or rocky terrain, deserts, wetlands, forests, and savannas or parklands with more than isolated or small clumps of trees. Arable fields bearing crops such as Oil Seed Rape, Kale and Lucerne now apparently appear to be more attractive than natural steppe although farmland areas with high agricultural disturbance near human settlements are often avoided.
Breeding
Females typically become sexually mature from two years of age and males typically from five or six years. Great Bustards have a mating system termed ‘lekking’. It is a system in which males compete for females with an elaborate visual display. Females appear to visit several males before copulating and appear to be very selective in their choice of mate. Mating success is strongly skewed, with the majority of matings performed by a small proportion of males at a lek site. No pair bonds are formed and pairings may differ from year to year. During the display, males appear to grow in size and change colour from brown to white. This is done by ruffling the feathers and inflating a special balloon-like structure in the neck with air, called the gular pouch. The wing feathers are twisted forward and fan out, and the tail is cocked right up and over onto the back. The head is drawn onto the back also, as the gular pouch is inflated, pushing the white whiskers upwards. The displaying male usually stands still or tramples with his feet and swings his inflated neck.
Nesting and Young
After mating, females disperse to lay their eggs – they do not form nesting colonies. Males play no part in the nesting or care of the young. The incubation and rearing of chicks is carried out by the female alone and the young birds will stay with their mother for at least the first winter.
Great Bustards nest on the ground, making a small depression and sometimes lining it with a few bits of vegetation. Two eggs are normally laid, although occasionally only one or even three are laid. Eggs weigh about 150 g and are on average 79.4 mm tall by 56.8 mm wide. They vary in colour from grey to green or brownish, with darker blotches. The eggs take three to four weeks to hatch. Newly hatched chicks are about 20 cm long and weigh about 100g. They are a greyish colour with dark brown or black markings. The chicks are nidifugous, meaning they are capable of looking after themselves soon after hatching and able to leave the nest site. Although they can walk almost immediately, the chicks cannot feed themselves for the first few days so the mother feeds them insects bill to bill.
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. Juveniles are independent by their first winter, but normally stay with their mother until the next breeding season.
Mortality
The natural mortality of Great Bustards in the wild is over 80 % in the first year. As ground-dwelling birds with a reluctance to fly, they are susceptible to a certain level of predation when feeding, nesting and roosting. Predators of eggs and hatchlings include avian predators such as raptors and corvids (crows) and mammals such as foxes, badgers and hedgehogs. Chicks grow incredibly quickly and by six months are approximately three-quarters full size. The number of predators reduces by this time to typically include foxes and where they occur, wolves and large raptors such as White-Tailed Eagle. Full grown adults, especially those in groups, are normally capable of scaring off, or fleeing safely from these predators.
They are long-lived birds, so those that do make it through the first year usually live on for another 15 or 20 years. In adults, males have a higher mortality rate than females, probably due to fighting during the breeding season and being typically bolder in character.