How a mother Tree Swallow's brooding behavior changes as her young grow.

Tree swallow females supply heat to small young that the young must have to sustain growth. Once a brood of nestlings has reached a certain size and have grown feathers, they can maintain their own heat and no longer need a mother's daytime brooding.
Video from Francois Paquette of QC. Edited by Chris Gates of NY.
For more on tree swallow care of younger nestlings see:
treeswallowprojects.com/cgrowt...