Biology
Great bustard from John Gould’s Birds of Great Britain, 1873 © Natural History Museum, London
Breeding
Male bustards first breed at 5–6 years of age, though they can start showing breeding behaviours, such as displaying, sooner. Females first breed at 2–3 years old.
Males moult into their breeding plumage in January, and begin displaying in April. One male may mate several females attracted by his displays, but has no further part in chick-rearing.
Females nest on the ground, in a simple scrape - 2–3 eggs are laid from April to May, or into June in more northern regions.
Eggs are about 80mm long, smooth, glossy and vary in colour, but are typically olive browns or greens.
Eggs are incubated for about 25 days. Chicks fledge at 30–35 days, but remain dependent on the female until they reach full size at about 80–120 days.
Dispersal
Western populations are largely resident, but frequently disperse in winter to find suitable food sources.
Eastern populations are fully migratory.
