Relationships between morphological parameters in birds with different flying habits.

1. Data on morphological and physiological parameters from 346 species of birds were collected from diverse sources. 2. The observed relationships among some pairs of variables showed differences between the five flight styles into which the studied birds were classified. 3. The characteristic kind of flight for each species is related to four easily obtainable non-invasive parameters: body weight (BW), wing area (WA), wing span (WS) and boyd length (BL). 4. Wing-loading index (BW2/3/WA) gives the most effective variable to describe the flying habits of any species.