The Birders’ Dozen Profile 10: Hooded Warbler
Dr. Jessica Outcalt
Welcome to the Birders’ Dozen! Over the next three issues we are going to continue introducing the last few birds from Forestry for the Birds. The Birders’ Dozen are forest birds that can benefit from targeted management practices, as most are declining due to habitat loss. We’ve curated this list to cover a wide range of habitat types, from young to mature forest, open to closed canopy, or dense to non-existent shrub layers. Our goal is to engage landowners and foresters in the process of managing forests for wildlife, or “forests for the birds.”
Most of the birds we’ve met in this series have been selected because their populations are rapidly declining and conservation action is needed to keep them from becoming threatened or endangered. The Hooded Warbler is one of the exceptions to this pattern, however. These brightly patterned yellow and black birds are gap specialists, which means they benefit from disturbances like treefalls or harvesting within mature forest landscapes, and their populations are actually increasing in many places. They’ve earned a place in our list despite this because they can serve as useful indicators of healthy forests—a sign that a mature forest has structural diversity enough to support these tiny birds.
Natural History
Male Hooded Warblers are conspicuously colored, with bright yellow feathers and a distinct black “hood” on their head. Adult females may also show this coloration, though it is less distinct than the males. The Hooded Warbler is unique, however, in that sexes not only look different, but defend and occupy territories in distinct wintering habitat types. When wintering in the Caribbean and Central America, male Hooded Warblers occupy mature forests, while female warblers occupy shrubby and disturbed areas.
Hooded Warblers likely make long flights across the Gulf of Mexico while migrating between wintering and breeding habitats. They typically utilize edge or shrubby areas during migratory periods, likely due to food availability and more available shelter from predators. Migrating at night like most songbirds, Hooded Warblers most likely take a loop migration route directly across the Gulf of Mexico in spring—when timing is important to reach breeding territories—and longer routes around the Gulf in fall—when energy efficiency is more important.
During the breeding season, Hooded Warblers occupy a range of forested habitats, from tree fall gaps in large forest areas to edges of small, isolated fragments. High shrub density is one of the most important characteristics of nesting sites, often fruit-bearing shrubs like blackberry and gooseberry. Shrubby habitats rich in food resources, such as regenerating clearcuts, are also used heavily during the post-fledging period. Though the Hooded Warbler uses shrubby edge habitats, it is typically found within or near large tracts of mature forest.
Hooded Warblers are socially monogamous, as they form pairs during the breeding season, but promiscuity outside of pairs is common. This allows Hooded Warbler populations to become more genetically diverse. Females build nests in dense shrub patches within forests, generally 1-4 feet above ground. Clutches of 3-4 cream-colored eggs are incubated by females, though both parents feed the young once hatched, which fledge around 10 days old. Brown-headed Cowbird parasitism is common for Hooded Warblers, especially in recent decades as fragmentation has become more common.
Hooded Warbler, photo courtesy Matt Williams Nature Photography
Habitat Management
This warbler is a relatively common species in its range, and has been increasing by approximately 2% per year in the Central Hardwoods region. However, presence of Hooded Warblers in a forest patch can be considered an indicator of a healthy managed forest. Forest management that creates gaps and edges can provide beneficial nesting and foraging habitat for these warblers, as well as other species that occupy similar niches.
Hooded Warblers are unique, as they’re gap and edge-dependent mature forest birds. While habitat fragmentation—an increase in edge habitat due to loss from factors such as road building—is detrimental to many mature forest birds, its effect on Hooded Warblers is nuanced. Creation of gaps through treefalls, small-scale harvests, or development can provide breeding habitat for these birds. However, this may also introduce threats from Brown-headed Cowbirds, which thrive in edge habitats.
As with many situations, management techniques will likely depend on the larger context in which they take place. If you have a large, unbroken mature forest patch, creation of small gaps and dense shrub patches within the overall forest area will be greatly beneficial to breeding Hooded Warblers. If you have small woodlots instead, focusing on techniques such as invasive species removal and improving shrub layers can benefit breeding and migratory populations of these charismatic yellow birds.
Conclusion
A mature forest bird that specializes in dense, shrubby areas is a unique one on our list of the Birders’ Dozen, but nonetheless highlights the importance of structural diversity in a healthy forest. Management techniques that foster growth of shrub patches within a mature forest landscape can be beneficial for many birds in Indiana, and particularly for this brightly colored little warbler. Diversity may be a buzzword in many situations, but it’s an important trait of a healthy ecosystem: creating a structurally diverse forest allows a diverse community of wildlife to thrive, including birds such as the Hooded Warbler.
Special thanks to the Alcoa Foundation, the Indiana Forestry Educational Foundation, and The Nature Conservancy for their support and leadership of Forestry for the Birds.
Jessica Outcalt is an independent consulting biologist who worked with The Nature Conservancy to develop the “Birders’ Dozen Profiles.” She is now a Natural Resources Training Specialist with Purdue University’s Department of Forestry and Natural Resources. She completed her BS in biology at Taylor University, her PhD in wildlife ecology at Purdue University, and is passionate about birds and getting people involved in conservation and scientific processes.
References
Chiver, I., L. J. Evans Ogden, and B. J. Stutchbury (2020). Hooded Warbler (Setophaga citrina), version 1.0. In Birds of the World (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.hoowar.01
Vitz, Andrew C., and Amanda D. Rodewald. 2007. “Vegetative and Fruit Resources as Determinants of Habitat Use by Mature-Forest Birds During the Postbreeding Period.” The Auk 124 (2): 494–507. https://doi.org/10.1093/auk/124.2.494.