In a group of birds (passerines and non-passerines) body weight was found to be highly correlated with the length of the humerus and with the area of the foramen magnum. In addition, body weight was highly correlated with humerus length in 58 specimens of streak-necked fly-catcher, Mionectes striaticollis, suggesting a possible use of this measurement to estimate body weight of individuals in a single species. Body weight was not correlated with foramen magnum area in 25 specimens of savannah sparrow, Ammodramus sandwichensis.