[CT Birds] Response to Question about the Blue-winged/Golden-winged hybirds

sean graesser sgraesser13 at me.com
Wed May 9 15:26:39 EDT 2012

I have had a decent amount of experience with these birds in the past,  
so here are my thought on them. I have seen the Hybrids establish  
territories, but it seems that they do not come back to these  
territories from year to year. This is also through banding  
information collected. I have banded a number of Hybrid individuals  
that were confirmed breeding, but was not able to obtain these birds  
again in years following this. Now this is obviously not an exact  
science due to some individuals possibly eluding nets, but is has  
happened at multiple locations. I have banded a few hybrids here in CT  
they are found during the breeding up in the northwest corner pretty  
easily. It is also interesting to look at historic shifts in  
populations. When you have a GWWA territory that has been slowly taken  
over by BWWA you run across hybrids more frequently for the first few  
years predominately F1 Brewster Warblers. Than you will see F2  
Brewster with "pure" BWWA and a few LAWA. You than see the final shift  
to "pure" BWWA with a few hybrids popping up every so often. This is  
talked about in the Peterson's guide to warblers.

As mentioned about the genetic difference being very slight is almost  
an understatement. When you have a Hybrid and want to know what its  
potential parent species are, so far it has been found to be almost  
undeterminable with using markers. They are very difficult bird to do  
genetic work on.

Another thing to take note of in the region is most "Pure" birds in  
regions were historic hybridization is occurring most likely are not  
pure. When these hybrid birds breed with pure parents species or other  
hybrids you run across individuals being born looking pure again.  
There are sometimes small things you can look at to see seemingly pure  
birds having recessive genes from earlier backcrosses. Some things to  
look for in BWWA's is the appearance of spiked lores were the line at  
the beginning has a small diagonal line that comes down. Also looking  
at the white wing bars and if they are tipped yellow. Now this needs  
to be done with some caution because of HY's having a yellow wash to  
there secondary coverts. GWWA it has to do with the completion of the  
white supercillium and if it makes it all the way across with out  
meeting the yellow from the crown.

If you want to learn more about this Hybridization I suggest reading  
The Genetics of the Golden-winged X Blue-winged Warbler Complex by  
Kenneth C. Parkes it was published in Wilson and is easily found online.

I also have some degree of experience with them and can shed more  
light on things if anyone is interested.

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