Figure 2.

The percentage of threatened species in different behavioural categories: (a) foraging behaviour (1 foraging generalist, 2 bark gleaning, 3 aerial screening, 4 aerial sallying, 5 arboreal gleaning, 6 ground foraging, 7 aquatic plunge, 8 aquatic dive, 9 aquatic surface); (b) mating behaviour (1 monogamy with infrequent polygyny, 2 monogamy with frequent polygyny, 3 monogamy, 4 polygyny), (c) migratory behaviour (1 migrant, 2 partial or short-distance migrant, 3 sedentary); (d) breeding system (1 cooperative, 2 non-cooperative); (e) territoriality (1 weak, 2 strong, 3 none); (f) nest placement (1 cavity, 2 exposed elevated, 3 exposed ground). The width of each segment indicates the proportion of all species (n = 9576) in each behavioural category. Segment heights indicate the percentage of species threatened in each category. Colours indicate threat level (Critically endangered (CR), Endangered (EN), Vulnerable (VU) and Near Threatened (NT)).