Washington Post story.

In the summer of 2007, a team of scientists devoted its mornings for several weeks to attaching tiny data chips encased in clear plastic to the backs of nearly three dozen songbirds they had trapped in northwestern Pennsylvania.

As one researcher held each bird still, another would slide a Teflon loop around one of the animal's legs -- in much the way that a parent slips a backpack over a child's shoulders -- before working a second loop around the other leg and then stitching the chip and loops together with Kevlar thread.