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Elfin-woods Warbler

2007 Schools Wikipedia Selection. Related subjects: Birds

               iElfin-woods Warbler

                             Conservation status

   Vulnerable (VU)
            Scientific classification

   Kingdom:   Animalia
   Phylum:    Chordata
   Subphylum: Vertebrata
   Class:     Aves
   Order:     Passeriformes
   Family:    Parulidae
   Genus:     Dendroica
   Species:   D. angelae

                                Binomial name

   Dendroica angelae
   Kepler and Parkes, 1972
   Range of the Elfin-woods Warbler
   Range of the Elfin-woods Warbler

   The Elfin-woods Warbler (Dendroica angelae), or Reinita de Bosque Enano
   (Spanish name), is a bird endemic to the Caribbean island of Puerto
   Rico where it is a local and uncommon species. Discovered in 1968 and
   described in 1972, it is the most recently described species of New
   World warbler (Parulidae family). The species name, angelae, is a
   tribute to Angela Kepler, one of its discoverers. An insectivore, it
   feeds by gleaning small insects off leaves.

   Due to its small populations and restricted habitats, 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 is protected forest,
   but introduced species, such as rats and mongooses, habitat reduction,
   and natural disasters represent potential threats to the population.

Discovery

   The Elfin-woods Warbler is one of 29 species in the Dendroica genus of
   the Parulidae family, the New World Warblers. It was first observed in
   1968 by Cameron and Angela Kepler while conducting observations on two
   Puerto Rican endemic birds, the Puerto Rican Parrot and the Puerto
   Rican Tody. On May 18, 1971, a specimen was captured in the Caribbean
   National Forest, which at the time was believed to be its only habitat.
   A year later Kepler and Parkes described and named the species making
   it the most recent warbler ( Dendroica spp.) discovered in the New
   World. Also, it is the first species described in the West Indies since
   1927 and the first Puerto Rican species described in the 20th century.

Physical description

   The Elfin-woods Warbler's upper body is predominantly black with white
   areas while 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. Characteristic of Antillean
   warblers ( D. adelaidae, D. delicata, D. plumbea and D. pharetra), the
   species features a long bill and short, round wings (53.8 mm average).
   Among Dendroica spp., only D. adelaidae has a shorter wing length
   average (50 mm) than the Elfin-woods Warbler. Juveniles differ from
   adults, retaining a grayish-green back for approximately a year and
   partially moulting from July to October. The Elfin-woods Warbler's
   average mature length is 12.5  cm (4.9  in) and its average weight is
   8.4  grams. Sexual dimorphism is not present in this species.
   Black-and-white Warbler, a species commonly mistaken for the
   Elfin-woods Warbler.
   Enlarge
   Black-and-white Warbler, a species commonly mistaken for the
   Elfin-woods Warbler.

   The Elfin-woods Warbler is often confused with the Black-and-white
   Warbler (Mniotilta varia), a non-breeding species in the Caribbean
   occurring in Puerto Rico from mid-September to early May. The main
   physical distinction resides in the eyes. The Elfin-woods Warbler has
   an incomplete white eyering and the Black-and-white Warbler has a white
   band across the eye and a white lower half of the eyering. Another
   distinction is found in the crown, with the Elfin-woods's being
   entirely black and the Black-and-white's having a white band across.

Population and distribution

   When first discovered, the Elfin-woods Warbler was believed to
   exclusively occur in the high elevation, from 640 to 1,030  meters
   (2,099 to 3,378  feet), elfin or dwarf forests of the Caribbean
   National Forest in eastern Puerto Rico. The wind-clipped trees in these
   forests rarely exceed 5 m in height and are characterized by stiff,
   thick twigs, leathery leaves and impenetrable, dense undergrowth ideal
   for hiding from predators. Three more populations were later discovered
   in the Maricao State Forest (1972, largest known population), the
   Carite State Forest (1977) and the Toro Negro State Forest (late
   1970s). Also, studies showed that the species migrated altitudinally to
   lower elevations, from 370 to 600 metres (1,213 to 1,968 feet),
   tabonuco and palo colorado forests.
   Bird count of the Elfin-woods Warbler (2001)
   Enlarge
   Bird count of the Elfin-woods Warbler (2001)

   In September 1989, Hurricane Hugo struck the central and eastern region
   of Puerto Rico affecting three (the Caribbean National Forest, Toro
   Negro and Carite populations) of the four known populations of the
   Elfin-woods Warbler. A survey conducted two years later in the Toro
   Negro Forest, located in the Cordillera Central, did not find any
   individuals. Recent surveys suggest that, for reasons yet unknown, the
   populations at Carite and Toro Negro were likely extirpated. Continued
   monitoring of the Elfin-woods Warbler populations is achieved through
   bird counts performed every 3 to 4 years by the Puerto Rican Breeding
   Bird Survey (PRBBS). The last survey was conducted in 2001 in which 3
   individuals were observed at the Maricao State Forest. IUCN's last
   assessment of the Elfin-woods Warbler, prepared in 2000, estimated a
   stable population of 600 mature individuals.

   Historically, the Elfin-woods Warbler was restricted to humid
   mountainous forests at four distinct locales in Puerto Rico. Presently,
   the species is presumed extirpated from two locales, occurring only at
   the Caribbean National Forest and the Maricao State Forest. The elfin
   forest at the Caribbean 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 with moss and epiphyte growth in its plants
   and floor. The species richness is low when compared to other types of
   forests (tabonuco, palo colorado and palma sierra forests) found in the
   Luquillo Mountains. The elfin forest at the Maricao State Forest,
   located in western Puerto Rico, receives an annual average rainfall of
   2,250 cm (994 in), a high amount considering that a rainforest, by
   definition, receives a minimum of 67 inches annually. However, since
   its soil has low water holding capacity its vegetation is more xeric
   than expected. The species's highest density occurs in Podocarpus
   forests in the Maricao State Forest. Little information is available on
   the elfin forests at Toro Negro and Carite.

Diet and behaviour

   The Elfin-woods Warbler is commonly found foraging the middle canopy
   for insects. While searching for food it often flocks with other birds,
   such as Black-and-white Warblers, Puerto Rican Tanagers and Lesser
   Antillean Pewees. Three maneuvers used for catching prey, gleaning,
   sally-hover and probing, have been described. Gleaning is described as
   a hunting maneuver made by a standing or moving bird. Sally-hover is a
   hunting maneuver made by a bird in flight. Probing is a maneuver in
   which the bird, by digging with its beak, forages the substrate looking
   for food in a manner similar to chickens. Gleaning, especially off
   leaves, is the maneuver used with more frequency by the Elfin-woods
   Warbler while probing is the least used.

   The Elfin-woods Warbler's song and call are difficult to hear. The
   species has a subtle voice and its call and song resemble those of the
   Bananaquit, 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" while the call has
   been described as "a single, short, metallic chip".

   The Elfin-woods Warbler breeds from March to June. Both parents are
   involved in the construction of the nest and in feeding the chicks.
   Nests are built close to the tree trunk within dry aerial leaf litter,
   usually Cecropia leaves (a material used by no other Parulidae
   species), in Bulbophyllum wadsworthii trees. Nests are well-concealed
   and located 1.3 to 7.6 meters above ground level. Nests are cup-shaped
   and made from small roots and twigs, dry leaves of Chusquea abietifolia
   and B. wadsworthii, and dry Panicum maximum leaves. The interior is
   made from fibers of C. abietifolia, dry leaves and other plant matter.
   Females lay 2 to 3 white colored eggs with red-brown spots. The chick's
   diet consists of insects – parents have been observed offering
   lepidopteran and orthopteran adults and lepidopteran larvae to
   hatchlings.

Threats and conservation efforts

   Sharp-shinned Hawk, a natural predator of the Elfin-woods Warbler.
   Enlarge
   Sharp-shinned Hawk, a natural predator of the Elfin-woods Warbler.

   The survival of the Elfin-woods Warbler faces two main threats,
   predation and the destruction or alteration of suitable habitat.
   Confirmed native predators are the Pearly-eyed Thrasher (Margarops
   fuscatus), the Sharp-shinned Hawk (Accipiter striatus) and the
   extirpated White-necked Crow (Corvus leucognaphalus) while unconfirmed
   native predators include two endemic snakes and several carnivores
   (from fossil records). Introduced species, such as cats (Felis
   domesticus), dogs (Canis lupus familiaris), rats (Rattus rattus) and
   small Indian mongooses (Herpestes javanicus) are also potential nest
   predators. These species have proliferated due to the presence of
   human-developed facilities, mainly for communication purposes, in the
   Maricao State Forest and the Caribbean National Forest. Two factors
   contribute to the destruction of the Elfin-woods Warbler's habitat,
   humans and nature. Human-related habitat destruction includes the
   construction of communication towers, acquisition of timber, and
   expansion of roads and trails. Nature's contribution comes from natural
   disasters such as forest fires and hurricanes.

   The Elfin-woods Warbler was placed on the United States federal
   candidate list for Endangered Species Act in 1982. In 2005, a group of
   scientists, scholars, artists and environmentalists petitioned the Bush
   administration to admit 225 species, among these the Elfin woods
   Warbler, to the Endangered Species Act. Of these 225 species, more than
   one third have been on the candidate list for 20 or more years and half
   for 10 or more years. Recent studies also show that since the creation
   of the Endangered Species Act in 1973, 114 United States species have
   become extinct, many because of lack of habitat protection by the
   federal government.

   The IUCN first evaluated the status of the Elfin-woods Warbler in 1988.
   At the time it was given a classification of lower Risk/least concern.
   In 1994, its status was changed to Lower Risk/near threatened and in
   2000, its status was changed to vulnerable, where it remains. The
   justification for maintaining the species' status as vulnerable is that
   "There are no direct or immediate threats, but the combination of a
   very small range and population may have important implications for its
   chances of long-term survival, and this species consequently qualifies
   as Vulnerable".

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   with only minor checks and changes (see www.wikipedia.org for details
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