Earlier we wrote a story how we were fortunate to have a nesting pair of White Collard Seedeaters right outside of the bunkhouse at Lower Dover Belize Jungle Lodge. This kind of seedeater is very common in the fields and along forest edges throughout the Cayo District.
Female White Collared Seedeater photograph in bamboo
While on a bird watching hike along the Belize River, we spotted this female White-Collared Seedeater perched on a bamboo thistle overhanging the confluence of Barton Creek and the Belize River.
Bird Photography in Belize at Lower Dover Jungle Lodge
In the absence of the clearly marked male nearby, we identified this female jungle bird by it’s buff to whitish wingbars thanks to Birds of Belize, by H. Lee Jones.
Clearly marked wingbars make this female bird easy to identify
Lower Dover Field Journal 
It’s possible that this bird is a female Variable Seedeater, based on the prominent tail stripe on your bird. There is a good photo of a female similar to yours at: http://www.birdforum.net/opus/Variable_Seedeater.
I am enjoying your blog. If I ever get to Belize again, I would love to visit your place to see all the great wildlife that you’ve written about. Thanks!