The Great Bustard is a bird of superlatives. Males of this species reach 21 kg (45 lbs), making them the heaviest birds capable of flight. Females, however, weigh only 5-7 kg (11-15 lbs). Key to this dramatic difference - the most extreme sexual size difference seen in birds - is the unusual mating system of the Great Bustard.
Female bustards choose a mate on the basis of his appearance and mating display, which is performed at traditional sites each spring. The result of generations of female-choice? Super-sized males with striking red coloration, capable of performing a complex display involving contortion of the body and inflation of a specialized throat sac.
Unfortunately, severe population declines over the past 100 years mean that few people now observe the intricate display of the Great Bustard. The species has declined across its range, becoming extinct in some European countries.
The Asian subspecies of Great Bustard, found only in Mongolia, China, and Russian South Siberia, is of special concern. Though few surveys have been undertaken in Mongolia, the population has been estimated at just 1500 birds. These bustards are particularly at risk as Mongolia transitions from communism to a free-market economy, replete with road construction, increased natural resource development, and land privatization.
Threats to the Great Bustard are numerous. Bustard nests, simple scrapes in the ground, are destroyed by the activity of agricultural machinery in the fields they inhabit. The insect food base so important to the rapid growth of chicks is eliminated with pesticides. Though they are strong fliers, heavy-bodied bustards are not maneuverable enough to avoid collisions with powerlines. And though now illegal, hunting by humans also plays a role in these declines. Our team is working to quantify the risks to bustards in Central Asia, and we communicate with local people and conservation agencies to develop conservation plans.