Chestnut Sided Warbler
Birds of Panama - large bird photo gallery
The Chestnut-sided Warbler (Setophaga pensylvanica) breed in eastern North America and in southern Canada westwards to the Canadian Prairies. These birds are migratory, wintering in Central America south to northern Colombia. For more details from Wikipedia about the Chestnut Sided Warbler please see this page here.
This Chestnut Sided Warbler image was taken in Altos del Maria.