They very much breed and their mixed genes introgress readily back into
both parental species. As such, you have to go to the very far edges of
both species' ranges to find ''pure" Golden-winged and Blue-winged
Warblers. In fact, a study conducted in Ontario actually found that
hybrids had a slightly higher fitness than pure Golden-winged Warblers!
More and more Brewster's and Lawrence's warblers are being found further
north and the Blue-winged Warbler is slowly outcompeting the Golden-winged
Warbler, both through direct competition and 'genetic pollution'.

Do a google scolar search on these birds and my friend Rachel Vallender
who studies these birds at Cornell to learn more.

Frode Jacobsen
Windsor Mill, MD 21244


> does anybody know if brewster's and lawrence's warblers can breed or are
> they sterile like mule's are?
>
>