キイロアメリカムシクイ Setophaga petechia

Typically yellow overall, but some immatures can be almost completely gray. Most males have reddish-brown streaks below; females are plainer and duller yellow. Always looks uniform and plain-faced, with rather stout bill for a warbler. Favors brushy habitats near water, often foraging in shrubs fairly low to the ground. Common and widespread throughout North America; winters in Central and northern South America. “Mangrove” Yellow Warbler, currently considered a subspecies, is found in mangroves and nearby brush from Mexico to Ecuador. Males have a distinctive reddish-brown head.