the kentucky warbler , oporornis formosus , is a small species of new world warbler .
the kentucky warbler , like all members of the genus oporornis , is a sluggish and heavy warbler with a short tail , preferring to spend most of its time on or near the ground , except when singing .
adult kentucky warblers are about 13 cm (5 to 6 inches) long .
they are mostly an olive-green in color on their back and nape , and a brilliant yellow below from their throat to their belly .
they have a small tinge of black on their crown , and a large black mask with a yellow pattern that runs from the beak and encircles the eyes , resembling a pair of spectacles .
female kentucky warblers have slightly less black on the sides of their head , and immature birds may have almost no black at all .
the kentucky warbler is a very common bird with a large range , frequenting moist deciduous forests .
it is migratory , spending summer in the central and eastern united states , often ranging as far north as wisconsin to pennsylvania .
come fall and winter the kentucky warbler will migrate back to the yucatn peninsula and the many islands of the caribbean , flying non-stop across the gulf of mexico .
kentucky warblers nest on the ground hidden at the base of a shrub or in a patch of weeds in an area of ample vegetation .
the female will lay between 3 to 6 eggs , which are white or cream-colored and specked with brown .
incubation is done by the female only , and lasts for about 12 days .
the young kentucky warblers usually leave the nest about 10 days after hatching .
