Illinois Natural History Survey - University of Illinois

Prothonotary Warbler


Susan Post


If I owned a paint store one of the colors I would offer would be prothonotary yellow. It is the color of the male Prothonotary Warbler’s head. It is the same color as the first dandelions of spring—orange-yellow centers that grade to bright yellow. This color lets you know spring is here and brightens the wet woods where the warbler occurs.  One ornithologist eloquently described the bird as “an animate mote of golden sunlight moving through dark swamps.”

The Prothonotary Warbler, Protonotaria citrea, breeds across much of the eastern United States. From April to August in Illinois it is commonly found in the swamps of southern Illinois. By late September the warblers have migrated to the mangrove forests of Central and South America.

Prothonotary Warblers are heavy-bodied and short tailed. They are approximately 14 cm (5.5 inches) long and weigh 15 g (about half an ounce). The male’s head, neck, and body are a rich saffron or orangey-yellow, while females are bright yellow with no orange hues. Their black bills and eyes stand out against the plain yellowish heads. Bluish wings and tails complete the picture.

Just as the cardinal gets its name from the red worn by Roman Catholic cardinals, the Prothonotary Warbler gets its name from the eighteenth century Louisiana Creoles who thought the bird’s plumage resembled the golden robes of the protonoarius (papal clerk), a Catholic Church official who advised the Pope. Its nickname is the golden swamp warbler, for its affinity for swamps and bottomland forests.

Prothonotary Warblers are found in deciduous swamps, backwater sloughs, wet woodlands without a dense understory, and along slowly moving rivers and streams. This attraction to water may be due to a higher number of decaying trees with nest cavities in flooded areas and the added benefit of lower predation by mammals when the nest site is located over water.

These birds are one of two warbler species that nest in cavities, and the availability of suitable nesting cavities is one of the most critical habitat requirements for them. While abandoned Downy Woodpecker holes are common nest sites, a variety of natural cavities are used, and the birds will readily use nest boxes, preferring those with a smaller internal volume than Bluebird boxes. Since 1994, hundreds of milk cartons have been used in a southern Illinois warbler study by the Illinois Natural History Survey.

Males establish territories around one or more suitable nest sites and place moss inside the cavities before the female arrives. The male displays at each cavity and the female selects from among those available. The nest site is almost always over or within 5 m (16.4 feet) of standing water or in a low-lying easily flooded area. While the male initially places moss in potential nest sites, once a site is chosen the female constructs the remainder of the nest. Prothonotary Warblers are one of the few cavity-nesting species that use large amounts of moss in their nesting. The nests are a combination of moss, grass, sedges, and even fishing line.

After finishing the nest, the female lays 4–6 brown-spotted eggs which hatch after 12–14 days of incubation by the female. Primary predators of eggs and nestlings are rat snakes and raccoons.  Ten days after hatching the young leave the nest (fledge), but the parents will continue to feed the birds for up to 35 days. While the nest’s proximity to water might deter predators, if the water rises and floods the nest, the hatchings will drown. However, fledging birds can swim.

The warbler forages by hopping on branches, stumps, trees, and the ground, looking for a variety of insects and small mollusks. Caterpillars, flies, midges, spiders, and mayflies make up the bulk of their diet during breeding season.

To chase away the winter grays, head to the swamps of southern Illinois (Heron Pond or LaRue Pine Hills) during April and May for a glimpse of this feathered sunshine.


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