Great Bustard – Otis tarda

International

The Great Bustard possibly possesses the widest range of any threatened species of bird, distributed as it is from close to the Atlantic seaboard in Iberia and Morocco across to the Pacific coast of China, a distance of about 10,000 km.

The world population currently includes about 31,000 to 36,000 individuals, 34% less than 16 years ago (Palacin & Alonso 2022). Population declines were recorded in 9 out of 17 countries. According to the recent study by Mimi Kessler, the global population consists of an estimated 29,060 - 32,449 individuals (Kessler 2022). The majority of the Great Bustard population, around 27,987 to 30,436 individuals, live in Europe (update on the status of the european Great Bustard population during the MOS5 2023 in Bratislava, Slovakia). Not only the world population but also the european population has declined by 1/3 in 11 years.

An increase in the population was only achieved in Germany, Austria , Slovakia and Hungary through protective measures. The centers of occurrence are in central Spain, in the great Hungarian lowlands and in southern Russia. With 22,000 to 24,000 individuals, more than half of the world population is in Spain. Within the MoU countries (signatory states to the Memorandum of Understanding on the Conservation and Management of the Middle-European Population of the Great Bustard), Hungary has the largest population with a maximum of 1,573 individuals in 2022.

Distribution of the Great Bustard open in Google Earth (requires Google Earth installation)

The Great Bustard (Otis tarda) originates in steppe areas. Fossil finds show that bustards occurred in the "polar steppes" of central Europe in the wake of the last ice age. As forests took over in large areas of Europe, suitable habitat for the species shrank significantly. Then, following extensive medieval deforestation, the Great Bustard became a common sight in European agricultural areas, reaching its widest distribution in the 17th and 18th centuries. Around the year 1800, Great Bustards populated Europe's large-scale agricultural landscapes in abundant numbers, breeding from England and Scotland in the west to Denmark and southern Sweden in the north. In Russia, the northern range limit lay some 500 km further north than it does today.

As the medieval system of cultivating arable land in 3-year rotations came to an end, diversity of food resources for Great Bustards decreased. In modern times, especially from the middle of the 19th century on, intensification of agriculture and later the erection of overhead power lines (medium and high voltage) lead to populations in Europe suffering severe declines and many subpopulations becoming extinct. The first populations to die out were those at the range limits in the west (England 1845) and north (Sweden 1862), where in addition to everything else climatic conditions were unfavourable. England embarked on a large-scale reintroduction programme a few years ago.

Extensive research was carried out at the 7 main study areas Westliches Weinviertel (WW), Marchfeld (MF), Rauchenwarther Platte (RP), Heideboden (HB), Parndorfer Platte (PP), Mosonszolnok (MS) and Hanság (HA).

The West Pannonian population of the Great Bustard showed a marked decline in numbers from a total of at least 3,500 individuals in 1900 to about 130 in 1995. Factors implicated in this decline are habitat changes caused mainly by agricultural transformations and the development of human infrastructures (particularly high and medium voltage power lines), but also hunting pressure. As a result of intensive and cross-border protective measures the population recovered from the low in 1996 to a population of at least 505 individuals in winter 2014/2015.

Within the last years, the West Pannonian population of the Great Bustard has increased significantly. That means the number of females has increased from 80 in 1996 to 310 in 2015.Also the number of males has increased during the same period, from 50 individuals to around 160.

Austria's bustard population is located at the northwestern edge of the third largest European distribution "cluster" of Great Bustards in the Great Hungarian Plain. The Austrian population is centred around the Western Weinviertel, the Marchfeld and the Rauchenwarther Platte in Lower Austria, and the Heideboden, the Parndorfer Platte and the Hanság / Seewinkel in Burgenland.

The total Austrian population declined from 700-800 individuals in the middle of the 20th century (1942) to 150-170 in 1970-72, decreasing further to approximately 100 in 1978, and finally reaching about 60 individuals at the end of the century. Following a slight recovery in numbers and recolonization of "Austrian" breeding sites in the cross-border population from western Hungary, the population was back up to about 320 individuals in the breeding season of 2014.

Since 1995 numerous special Great Bustard protection fields have been created within the framework of ÖPUL (Austrian programme for an environmentally appropriate, extensive and natural habitat friendly agriculture). During the years 1995 to 2000, their extend was around 300 ha and has increased to around 5.000 ha since 2003. Within the last years, also the number of Great Bustards living in Austria has increased to approximately 320 individuals (breeding time 2014).

Overview of Great Bustard numbers (numbers of individuals during the breeding season) in Eastern Austria between 1940 and 2014 (blue column), and the total area of ÖPUL-Great bustard protection fields between 1996 and 2014 (red column); data: Raab et al. (2010) and own data.

In the period since 1990, populations in two Austrian areas increased markedly, in the Heideboden and the Western Weinviertel. In the Hanság, Parndorfer Platte and Rauchenwarther Platte areas the populations remained more or less stable at a low level over the same period. In the Marchfeld area the population decreased drastically from 25 to 6 individuals from 1990 to 2000, subsequently stabilising at a low level and most recently beginning to show a slight upward trend again. In the Vienna basin south of the river Danube small breeding populations persisted into the second half of the 20th century. Only individual breeding occurrences now remain on the Rauchenwarther Platte. Not counting this site, there were more than 100 bustards in the Vienna basin around 1940; numbers dropped to only 2 individuals in 1990 and the population has become extinct since.

Table: Development of Great Bustard numbers (individuals) in Austria by sites.

Source: Raab et al. (2010) and own data.

In December of 2002, around 200 Great Bustards were counted in Austria for the first time in a long period, because part of the Hungarian and Slovakian populations close to the border were staying in the attractive wintering grounds of Burgenland. In January and February of 2004 numbers even rose to 219 birds, 176 out of which were counted in northern Burgenland alone. At the same time a further 32 bustards stayed on the Hungarian side close to the border, making the total for the West-Pannonian population, i.e. the cross-border Austro-Hungarian-Slovak-Czech population 251 Great Bustards in winter 2003/04.

In February 2014 a total of 505 bustards were observed. Winter numbers of the West-Pannonian population therefore increased from 129 in 1995/96 to at least 505 in 2014/15. That many Great Bustards could not be observed in that region for 30 years! During the past winters nearly the whole West-Pannonian population of Great Bustard could be found in the attractive wintering grounds of Burgenland and Lower Austria. Long since a good deal more than 300 bustards could be found in Austria for the last few winters.