Here is a page with all the aging and sexing of RT Hummingbirds.
I think you are seeing pollen on the bill perhaps.
Date: Thu, 26 Aug 2010 17:32:42 -0400
From: Maeve Kim <[log in to unmask]>
Subject: hummingbird bills?
Hummingbirds are clearly preparing for their long journeys, often
spending as long as two minutes at one feeder perch - very unlike
their eat-and-run habits of earlier in the summer. The birds that
I've identified as juveniles all have a great deal of white at the
base of their bills, extending more than a third of the way along the
bill. I don't see this in Sibley or the National Geographic bird
guide. Has anyone else noticed white bills?
Vermont Center for Ecostudies
PO Box 420 • Norwich, VT 05055