Galapagos Yellow Warbler

The yellow warbler (Setophaga petechia) is a New World warbler species found in North America, the Caribbean and northern South America with 35 (to 37) subspecies (sometimes some are treated as separate species), depending on the source. All subspecies are very similar, the difference being the males' head color in breeding season. Males in winter, females and immature birds have a greenish-yellow upperside and a duller yellow underside. Young males obtain breast and head coloration. Females are more dull, particularly on the head. The wing and tail feathers are blackish olive with yellow edges. The eyes and short thin beak are dark. The feet are lighter or darker olive-buff. The subspecies can be divided into three (or four) main groups according to the males' head color in breeding season. 

 

One main group is the golden warbler (the petechia group). It has (15, 16 or) 17 subspecies and is found in the mangrove swamps of the West Indies. The adult male has a chestnut crown patch and it is the extent of the patch that varies among the subspecies. The crown patch can be orange to dark chestnut and may be restricted or absent in some individuals. The chestnut in the crown my be indistinct in northern populations and becomes darker to the south. The color of the upperparts and the pattern of chestnut streaking on underparts varies geographically. The chestnut streaking of underparts is more prominent in the western Caribbean. It is non-migratory. 

An illustration of one subspecies of the golden yellow warbler from Birds of the World.

Another main group, the mangrove warbler (The erithachorides group) has (11 or) 12 subspecies and is found in the mangrove swamps of coastal Middle America and northern South America. The adult male usually has an entirely chestnut head (or hood). Subspecies vary in the extent and hue of the hood. The chestnut head ranges from dark and forming a hood in northern birds to paler (no distinct hood) in southern populations from Pacific islands and Caribbean islands off South America. Many females have a chestnut crown and cheeks and streaking on the underparts. The color of the upperparts and the pattern of chestnut streaking on the underparts  varies geographically. Chestnut streaks are narrower in males from norther populations. It is non-migratory. 

An illustration of one subspecies of mangrove yellow warbler from Birds of the World.

An illustration of another subspecies of mangrove yellow warbler from Birds of the World.

The Galapagos yellow warbler, considered a separate group (the aureola group) by some, has one subspecies, the Galapagos yellow warbler. It is the only yellow warbler I've seen so far. It is found in the Galapagos Islands and Cocos Islands. 

An illustration of the Galapagos yellow warbler from Birds of the World.

I saw the Galapagos yellow warbler when we visited the Galapagos Islands in March of 2022. It was on the far western island of Fernandina at Espinosa Point. 

Some lump the Galapagos yellow warbler with the mangrove warbler group and you can see that it does not have a full hood. It has chestnut streaking on the underparts. 

60% of their diet is caterpillars. This one is eating a caterpillar. 

The wings and tail feathers are blackish-olive with yellow edges. A greenish-yellow upperside. 

The other main group, the American yellow warbler (the aestiva group) has 6 subspecies and is yellow headed. It is migratory. They breed in temperate North America and migrate to Central and South America.

An illustration of one subspecies of American yellow warbler from Birds of the World.

An illustration of another subspecies of American yellow warbler from Birds of the World.

The information for this comes from Wikipedia, Birds of the World and iNaturalist.