Body measurements for all 11,000 bird species released in open-access database

Body measurements for all 11,000 bird species released in open-access database - Imperial College London

A new database called AVONET contains measurements of more than 90,000 individual birds, allowing researchers to test theories and aid conservation.

Before and after: Dr Joe Tobias at the start of data collection (with Undulated Antpitta, Ecuador, 1991) and after finalising the AVONET dataset (with Blue-moustached Bee-eater, Ghana, 2021) © Imperial College London.

AVONET was collated by a team of international researchers, led by Dr Joseph Tobias, from the Department of Life Sciences at Silwood Park at Imperial College London. In a special issue of the journal Ecology Letters, edited by Dr Tobias, he and researchers from across the world present the first iteration of the complete AVONET database and some initial findings using the data.

Hayley Dunning talked to Dr Tobias about why such a database is needed, how it came about, and what it has already uncovered about the evolution and ecology of birds worldwide.

What bird traits are recorded in AVONET, and why are they important to study?

For each individual bird, we measured nine ‘morphological’ traits, related to physical aspects of their bodies: four beak measurements, three wing measurements, tail length, and tarsus length (lower leg). AVONET also includes body mass and hand-wing index, which is calculated from three wing measurements to give an estimate of flight efficiency, and so the ability of a species to disperse or move across the landscape.

The final version contains measurements from 90,020 individual birds at an average of around nine individuals per species.

These measurements have been shown to correlate with important ecological features of species, including what they eat and how they search for food. Previous studies have most often used rather broad categories, such as habitat, life history or main food type, but these can be crude and relatively uniform across species. Some studies have included estimates of body size, but clearly the connection between body size and ecological function is relatively weak – for example, hawks and ducks have similar body masses but this says very little about their roles in the ecosystem.

Measurements of beaks, wings and legs provide much richer information, for example about the species’ place in the local food web, how they move about, and how far they travel. Combinations of these traits can predict key functional characteristics of bird species, such as their precise diet and their foraging behaviour, with much greater accuracy than body mass alone.