I wonder if there is a really tiny GPS device that can be mounted on passerine birds (or circa 10 grams birds) without affecting their flight. This web site shows information for bat’s GPS. But it also only last for 24 hours. I wonder if there is some lightweight and long battery life about 2–5 grams. I found this also, but haven’t found if it contains a long battery life.
Is there a study on GPS tracking small birds?