Is it possible the yellow color is pollen?  We saw two hummers in AZ 
whose bills were half yellow.  We thought we had 2 immature Berylline 
Hummers, but after much asking around, we were shown photos of young 
Beryllines and had to accept that we had pollen-billed Rufous Hummers.

Georgia McDonald     Towson,  Balt Co.

Les Roslund wrote:
>     Talbot Bird Club member Margie Steffens who lives in St Michaels, MD
> had an immature Ruby-throated Hummingbird feeding at a Mexican Sage bush in
> her yard from Oct 7 through Oct 12.  This bird also carried a yellow mark on
> its bill, as if marked for some kind of Hummingbird Study.  Does anyone know
> of such study? Perhaps somewhere there are researchers who would like to
> know where this little bird has spent much of the past week.
>  
> Les Roslund
> HYPERLINK "mailto:[log in to unmask]"
> Talbot County
> Easton MD 21601
>  
>
>