FIGURE 2 Diagram of linear measurements of avian morphology presented in AVONET. (a) Resident frugivorous tropical passerine (fiery-capped manakin,Machaeropterus pyrocephalus) showing four beak measurements: (1) beak length measured from tip to skull along the culmen; (2) beak length measured from the tip to the anterior edge of the nares; (3) beak depth; (4) beak width. (b) Insectivorous migratory temperate-zone passerine (redwing, Turdus iliacus) showing five body measurements: (5) tarsus length; (6) wing length from carpal joint to wingtip measured on the unflattened wing; (7) secondary length from carpal joint to tip of the outermost secondary; (8) Kipp's distance, measured directly or calculated as wing length minus first-secondary length; (9) tail length. Protocols for measuring these traits are provided in Supplementary material. AVONET also includes body mass, and Hand-wing index (calculated from 6 to 8), making 11 traits in total. Illustration by Richard Johnson