I was fortunate to run into this female Black-throated Blue Warbler at Sabine Woods on 20 October 2003. The pictures were taken in very low light and suffer from a long shutter-speed and wobbly hands.  Still, you should be able to pick up on the field marks.  This bird was found only after seven visits to the upper texas coast in a 17-day period where I was expressly looking for this species.