- Taxon: Bird
- Range: Puerto Rico
- Status: Threatened
The elfin-woods warbler is one of over 120 species of New World warblers, or wood-warblers, found only in Puerto Rico. It was discovered in 1968 and has been a candidate for Endangered Species Act (ESA) listing since 1999, which means listing was warranted but precluded by higher priority listing actions for other species. In 2016, the elfin-woods warbler was listed as threatened under the ESA with a Section 4(d) rule providing exemptions for certain agriculture and forestry activities that may benefit the species.
The elfin-woods warbler is about 4.9 inches in length and weighs about a third of an ounce (8 grams). The adult’s upper body is predominantly black and white, with white patches on ear-covers and neck, incomplete eye ring, and black crown. Immature elfin-woods warblers and adults have similar patterns but differ in coloration. Juveniles have grayish-green and yellowish-green color on the head and underparts while adults are black and white. Its calls are a series of short, rapidly uttered, unmusical notes in one pitch, increasing in volume and ending with a short series of distinct double notes.
Its breeding season extends from March to June. Pairs of elfin-woods warblers weave a cup nest of rootlets and fibers lined with leaves of grasses and down feathers. The warbler’s nest is found entangled on vines and branches or inside tree cavities.
Elfin-woods warblers live in forests with high rainfall, high humidity, low insolation, low temperatures, and constant winds. As its name suggests, this warbler inhabits elfin or montane dwarf forest with dense stands of short, small diameter, twisted trees and shrubs, but it is not exclusive to those areas. This warbler can also live in montane wet forest, and ranges to lower-elevation wet forest.
The elfin-woods warbler forages for insects at heights between 10 and 50 feet; in areas with dense foliage cover, they mainly forage at heights of approximately 26 feet to avoid competition with other insectivorous birds. It eats a large variety of insects, such as moths and dragonflies.
When the species was discovered in 1968, the elfin-woods warbler was thought to occur only in the Luquillo Mountains at El Yunque National Forest in eastern Puerto Rico. During the early 1970s the warbler was reported in the Maricao Commonwealth Forest in western Puerto Rico, Toro Negro Commonwealth Forest in the central mountain range of the Island, and in the Carite Commonwealth Forest in east-central Puerto Rico. Only one record of the elfin-woods warbler exists for the Toro Negro Commonwealth Forest, and more than 15 years have passed since the warbler was seen in the Carite Commonwealth Forest.
The Elfin-woods warbler is currently only found in Puerto Rico in El Yunque National Forest in eastern Puerto Rico, and in Maricao Commonwealth Forest and adjacent private lands in western Puerto Rico. Its habitat is humid montane forests with high rainfall, high humidity, low insolation, low temperatures, and constant winds. It is found on the summits of the mountains and its habitat is composed of dense stands of short, small diameter and twisted trees and shrubs.
Threats to the elfin-woods warbler include habitat loss, fragmentation, and degradation in private lands adjacent to the Maricao Commonwealth Forest, particularly from sun-grown coffee plantations and small residential development. Hurricanes, climate change, and human-induced fires also threaten the warbler’s survival. Hurricanes in El Yunque National Forest are cited as a factor in the warbler’s decline in that forest. However, there are no specific studies indicating that hurricanes are the main cause for elfin-woods warbler population declines. These threats might be worsened by the limited distribution of this bird. Although these threats may act in isolation, it is likely that two or more of these stressors act simultaneously or in combination resulting in cumulative impacts to populations of this species.
Partnerships, research and projects
In 2014, the Service, the Puerto Rico Department of Natural and Environmental Resources (PRDNER), and the U.S. Forest Service signed a Candidate Conservation Agreement (CCA) to work together to conserve the elfin-woods warbler and restore suitable habitat in the El Yunque National Forest and Maricao Commonwealth Forest. The parties agreed to promote, develop, and implement best management practices to avoid any potential threat to suitable and occupied warbler habitat and populations.
Other conservation actions benefitting the elfin-woods warbler include agreements with private landowners through the Natural Resources Conservation Service’s Farm Bill Programs, and the Service’s Partners for Fish and Wildlife and Coastal Programs to implement habitat conservation and restoration practices on agricultural lands adjacent to the Maricao Commonwealth Forest. Between 2007 and 2014, about 1,290 acres of tropical upland forest, and 13 miles of riverbank buffers were conserved and restored through the Partners for Fish and Wildlife Program in collaboration with Natural Resources Conservation Service, Farm Service Agency, PRDNER, Envirosurvey, Inc., and other partners.
More on-going conservation actions
- Establishing additional agreements and partnerships with landowners near Maricao Commonwealth Forest to protect elfin-woods warbler habitat.
- Protecting existing shade-grown coffee plantations, and restoring sun-grown coffee into shade-grown coffee plantations in areas where the warbler has been recorded near the Maricao Commonwealth Forest.
- Implementing habitat restoration projects to provide effective corridors for the warbler dispersal throughout the central mountains of Puerto Rico.
- Promoting the need to conduct additional landscape surveys to identify additional areas where the bird occurs in Puerto Rico.
- Continuing an investigation into the possible causes of the warbler’s declining status at El Yunque National Forest.
How you can help
- Promote local shade-grown coffee and encourage the creation or restoration of shade grown coffee plantations.
- Learn more about the 350 species of birds in Puerto Rico. Of those, more than 100 make their nests and raise their young here in the many habitats Puerto Rico offers.
- If you are a landowner with land near the Maricao Commonwealth Forest or the El Yunque National Forest, please contact the Service’s Caribbean Ecological Field Office at Post Office Box 491, Boquerón, Puerto Rico, 00622, or contact deputy field supervisor Marelisa Rivera at (787) 851-7297, or email@example.com to learn what you can do to provide warbler habitat.
Subject matter experts
- José Cruz-Burgos, firstname.lastname@example.org, 787-851-7297
- Maritza Vargas, email@example.com, 787-851-7297
Federal Register notices
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