Poor little guy. I feel so sorry for the last ones. From what I've read, hummers try to fatten up before migrating in case they can't find food further along. The last ones to leave are thus the littlest ones that couldn't compete as well for food and have to wait for the others to leave before fattening up.

I increase the sugar content to 2:1 for the stragglers--help them fatten up faster. I know every morning when you find he's still there is gut wrenching. All the advice I can give is that you have to trust in nature. He'll leave when he's ready.

This morning I switched the sugar solution from 1 part sugar/4 parts water to 1 part sugar in 3 parts water. On of my books said that in a lab situation hummingbirds offered free choice of many different ratios chose 65% sugar even though they would never see it in nature. I will wait a day and increase the mix to 50% as you have used. I don't know if the bird looks fatter or if it's just that the feathers are more puffed up. Thanks!

Coopernikus-Update--I think he finally fattened up enough to migrate; haven't seen him for several days, and the last time was in the morning and he was looking pretty chubby.