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From Bob Sargent re Ruby-throateds



Bob Sargent in Alabama sent the following response to my query and gave
permission to forward it to Carolinabirds. He (gently) corrected my
impression that fledglings are a little smaller than adults. (I thought they
were a little thinner and shorter-billed.) I appreciate the observations all
have shared on this question of one versus two broods a year in the piedmont
-- they've really helped me understand the problem. And I'm still looking
out the window trying to figure it out! G.T. in Orange County, NC

From Bob Sargent:
Double brooding is a common occurrence in Ruby-throated Hummingbirds.  The 
second nest is often built by the female as she continues to feed her two 
nestlings in the first nest.  Our banding and color-marking of nesting 
females has shown that some females actually build THREE nest in a single 
season.  In the northern tier of states and southern Canada, we SUSPECT that

some females (maybe most) have only one brood per year because of the 
shortened breeding season.  This is only speculation not proven by banding 
studies.  

You might be interested to know that baby hummers are larger than the female

parent at the time they fledge.  In fact, Martha (my wife) and I banded two 
baby hummers yesterday in the nest that were 8 and 10 days out of the egg.  
The older bird weighed more than an adult female at the time of banding.
You 
may copy this post to Carolina Birds if you wish.

I hope this helps.  God Bless.
Bob Sargent
Trussville, Alabama