| Elfin woods warbler | |
|---|---|
 | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Parulidae |
| Genus: | Setophaga |
| Species: | S. angelae |
| Binomial name | |
| Setophaga angelae | |
 | |
| Range of the elfin woods warbler: Extant (resident) Extant (passage) | |
| Synonyms | |
Dendroica angelae[2] | |
Theelfin woods warbler (Setophaga angelae) is a species ofbirdendemic toPuerto Rico, where it is local and uncommon. Discovered in 1968 and described in 1972, it is the most recently describedNew World warbler (family Parulidae).
The species name,angelae, is a tribute toAngela Kepler, one of its discoverers. These birds areinsectivores, as they feed bygleaning small insects off the habitat leaves.
Due to its small populations and restrictedhabitats, conservation efforts were begun in 1982 to protect this species, but as of 2005, the warbler was still in need of protection. The species is not in immediate danger as the majority of its habitat isprotected forest, butintroduced species (such asrats andsmall Asian mongooses),habitat reduction, and natural disasters represent potential threats to the population.
The elfin woods warbler is one of many species in thegenusSetophaga of theNew World warbler family Parulidae. It was first observed in 1968 by Cameron andAngela Kepler while they were conducting observations on twoPuerto Rican endemic birds, thePuerto Rican amazon and thePuerto Rican tody. On May 18, 1971, a specimen was captured inEl Yunque National Forest, which at the time was believed to be its only location. A year later, Cameron Kepler andKenneth Parkes described the species and named itDendroica angelae, making it the most recently discovered New World warbler. It is the first species described in theCaribbean since 1927 and the first Puerto Rican species described in the 20th century.[2] Although the species was initially placed in the genusDendroica, phylogenetic studies in 2010 usingmitochondrial DNA sequences from New World warblers led to a revision of warbler genera. As a result, the study's authors recommended subsuming the genusDendroica into the genusSetophaga. The same studies showed that the elfin woods warbler is most closely related to thearrowhead warbler, which is endemic toJamaica, and theplumbeous warbler, which is endemic to the islands ofDominica andGuadeloupe.[3] In 2011, theAmerican Ornithologists' Union reorganized the classification of the family Parulidae and transferred species inDendroica toSetophaga.[4][5] This revised classification was subsequently adopted by theInternational Ornithologists' Union.[5]
The genus name is a combination of theAncient Greek wordsses, meaning "moth", andphagos, meaning "eating".[6] Thespecific name,angelae, is a tribute to Angela Kepler.[2] Elfin-woods warbler is an alternative spelling, andReinita de Bosque Enano is theSpanish name.[7][8]
The elfin woods warbler is a smallpasserine, averaging 12.5 cm (5 in) in length and 8.4 g (0.30 oz) in weight.[9] Its upperparts are predominantly black with white areas, and its underparts are white with black streaks. Other identifying characteristics are dark brown eyes, white patches on its ears and neck, an incomplete white eyering, a white eyestripe, and two white spots on its outer tail feathers.[10] Like otherAntillean warblers (Adelaide's warbler,Saint Lucia warbler, plumbeous warbler, and arrowhead warbler), it has a longbill and short, roundwings (53.8 mm or 2.12 in average). AmongSetophaga species, only Adelaide's warbler has a shorter average wing length.[2]Juveniles differ from adults, retaining a grayish-green back for approximately a year and partiallymolting from July to October.[9]
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The elfin woods warbler can be confused with theblack-and-white warbler, a non-breeding visitor that occurs in Puerto Rico from mid-September to early May. The main physical distinction between the two is in the face. The elfin woods warbler has an incomplete whiteeye-ring, while the black-and-white warbler has a bold whitesupercilium above the eye, and the lower half of a white eye-ring. The elfin woods warbler has an entirely blackcrown while the black-and-white warbler's is bisected by a white stripe. The latter species tends to forage on larger branches, while the elfin woods warbler forages in the canopy and on smaller branch tips.[11]
| Songs and calls |
The elfin woods warbler'ssong and call are difficult to hear. The species has a subtle voice and its call and song resemble those of thebananaquit, the most abundant bird in Puerto Rico. The song is a series of "short, rapidly uttered, rather unmusical notes on one pitch, swelling in volume and terminating with a short series of distinct double syllables sounding slightly lower in pitch"[12] while the call has been described as "a single, short, metallicchip".[12]
The elfin woods warbler breeds from March to June. Both parents are involved in the construction of thenest and in feeding thechicks. Nests are built close to thetree trunk within dry aerial leaf litter, usuallyCecropia leaves (a material used by no otherParulidae species), inBulbophyllumwadsworthii trees. Nests are well-concealed and located 1.3 to 7.6 meters (4.3 to 24.9 ft) above ground level.[13] In 2003 a nest with four chicks was found inside a tree stump of Colorado tree,Cyrillaracemiflora, at Maricao. The nest was at about 15 feet above ground level, with little cover in a secondary forest area. Nests are cup-shaped and made from smallroots andtwigs, dry leaves ofChusqueaabietifolia andB. wadsworthii, and dryPanicummaximum leaves. The interior is made from fibers ofC. abietifolia, dry leaves and other plant matter.[14] Females lay two or three white eggs with red-brown spots.[15] The chick's diet consists of insects—parents have been observed offeringlepidopteran andorthopteran adults and lepidopteran larvae to hatchlings.[14]
The elfin woods warbler is commonly foundforaging the middlecanopy for insects.[9] While searching for food it oftenflocks with other birds, such as black-and-white warblers,Puerto Rican tanagers andLesser Antillean pewees. Three maneuvers used for catching prey—gleaning, sally-hovering and probing—have been described.[9] Gleaning is described as a hunting maneuver made by a standing or moving bird.Sally-hovering is a hunting maneuver made by a bird in flight. Probing is a maneuver in which the bird, by digging with its beak, forages thesubstrate looking for food in a manner similar to chickens.[9] Gleaning, especially off leaves, is the maneuver used with more frequency by the elfin woods warbler while probing is the least used.[9]
When first discovered, the elfin woods warbler was believed to exclusively occur in the high elevation, from 640 to 1,030 meters (2,100 to 3,380 ft), dwarf orelfin forests of the El Yunque National Forest in eastern Puerto Rico. The wind-clipped trees in these forests rarely exceed 5 meters (16 ft) in height and are characterized by stiff, thick twigs, leathery leaves and impenetrable, denseundergrowth ideal for hiding frompredators. Later studies showed that the speciesmigrated to lower elevations, between 370 and 600 meters (1,210 and 1,970 ft), inTabonuco andPalo Colorado forests.[16] Three more populations were discovered in theMaricao State Forest (1972, largest known population), theCarite State Forest (1977) and theToro Negro State Forest (late 1970s).[13]
The species is presumed extirpated from two locales, occurring only at El Yunque National Forest and the Maricao State Forest.[17] The elfin forest at El Yunque National Forest is characterized by high rainfall and humidity, low temperatures and insolation, and constant winds. It is found at mountain summits and is primarily composed of dense shrub and small trees withmoss andepiphyte growth in its plants and floor. The species richness is low when compared to other types of forests (tabonuco, palo Colorado andpalma sierra forests) found in theLuquillo Mountains. The elfin forest at the Maricao State Forest, located in western Puerto Rico, receives an annual average rainfall of 2,250 millimeters (90 in), a high amount considering that a rainforest, by definition, receives a minimum of 1,700 millimeters (67 in) annually. Since its soil has low water-holding capacity its vegetation is morexeric than expected. The species's highest density occurs inPodocarpus forests in the Maricao State Forest. Little information is available on the elfin forests at Toro Negro and Carite.[16]
In September 1989,Hurricane Hugo struck the central and eastern region of Puerto Rico, affecting three of the four known populations of the elfin woods warbler; the El Yunque National Forest, Toro Negro, and Carite populations were all impacted. A survey conducted two years later in the Toro Negro Forest, located in theCordillera Central, did not find any individuals.[18] Surveys conducted since then suggest that, for reasons yet unknown, the populations at Carite and Toro Negro were likelyextirpated.[13] Continued monitoring of the elfin woods warbler populations is achieved through bird counts performed every three to four years by the Puerto RicanBreeding Bird Survey (PRBBS). A survey conducted in 2001 found three individuals at the Maricao State Forest. AnIUCN assessment of the elfin woods warbler, prepared in 2000, estimated astable population of 600 mature individuals.[19] In 2020 the population was estimated to comprise at least 1800 mature individuals, a figure which equates to at least 2700 individual birds.[1][20]
The elfin woods warbler faces two main threats: predation, and the destruction or alteration of suitable habitat. Thepearly-eyed thrasher, thePuerto Rican sharp-shinned hawk and thenow extirpatedwhite-necked crow are all confirmed native predators. Unconfirmed but potential native predators include two endemic snakes and severalcarnivores known fromfossil records. Introduced species, such as domestic cats and dogs, black rats, andsmall Asian mongooses, are also potential nest predators.[14] These introduced species have proliferated in the Maricao State Forest and El Yunque National Forest due to the presence of facilities built mainly for communication purposes. Both natural and human factors contribute to the destruction of the elfin woods warbler's habitat. The construction of communication towers,logging, and the expansion of roads and trails have all caused habitat destruction within the warbler's range.Natural disasters such asforest fires andhurricanes have also decimated habitat.[12]
The elfin woods warbler was placed on the United States federal candidate list for theEndangered Species Act in 1999, and the announcement was published on the Federal Register of October 25, 1999, Volume 64, No. 205, pages 57535–57547. The USFWS started to consider the need to protect the elfin woods warbler in 1982.[21] In 2005, a group of scientists, scholars, artists and environmentalists petitioned theBush administration to admit 225 species, including the elfin woods warbler, to Endangered Species Act protections.[22]
TheInternational Union for Conservation of Nature (IUCN) first evaluated the status of the elfin woods warbler in 1988. At the time, it was given a classification oflower risk/least concern. Its status was changed to lower risk/near threatened in 1994, tovulnerable in 2000, and toendangered in 2017. The organization justified the warbler's move to endangered status due to the combination of its very small range and its continuing decline due to habitat destruction and degradation.[1]
Media related toSetophaga angelae at Wikimedia Commons
Data related toSetophaga angelae at Wikispecies
