Puerto Rican Wood Warbler
| Puerto Rican Wood Warbler | ||||||||||||
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Puerto Rican Wood Warbler ( Setophaga angelae ) |
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| Setophaga angelae | ||||||||||||
| ( Kepler & KC Parkes , 1972) |
The Puerto Rican wood warbler ( Setophaga angelae , Syn . : Dendroica angelae ), also known as the angela wood warbler , is a rare and endemic bird of the Caribbean island of Puerto Rico . The species was discovered in 1968 and described scientifically for the first time in 1972. This makes it the youngest species to be discovered in the wood warbler family . The art epithet honors ornithologist Angela Kepler , who was involved in the first scientific description. The Puerto Rican wood warbler is an insectivore that picks small insects from leaves.
Because of the small population and the limited habitat , protective measures were taken in favor of this bird species as early as 1982. Also in 2005 this species was classified as still in need of protection. Species introduced to Puerto Rico such as rats and mongooses are threatening the population of this bird species . The largest part of its range is today in protected forest areas. However, because the population is small, natural disasters that destroy these forests can lead to a collapse in the numbers.
Discovery of the species
The Puerto Rican wood warbler is one of 29 species that belong to the genus Dendroica in the wood warbler family. The ornithologist Cameron and the naturalist and botanist Angela Kepler first observed this species when they carried out observations in forest areas on the bird species Puerto Rican amazon and yellow flank todi, which are also endemic to Puerto Rico . On May 18, 1971, they caught a specimen in the Caribbean National Forest . At the time it was believed that this forest was the only range of the species. In 1972 the two scientists described the species and named it Dendroica angelae . The bird is the first species to be described in the West Indies since 1927 and as the only representative of the wildlife for Puerto Rico in the 20th century.
Appearance
The upper side of the body of the Puerto Rico wood warbler is predominantly black feathered and has only a few irregular white feathers. The underside of the body, on the other hand, is mostly white with black dashes. The characterizing features of this species are the dark brown eyes, white feathers on the ears and on the neck as well as an interrupted white eye ring, white eyebrows and two white spots on the outer tail feathers. As is typical for the wood warbler of the Antilles - in addition to the Puerto Rico wood warbler, these are the Antilles wood warbler , Saint Lucia wood warbler , gray wood warbler and wood warbler - the Puerto Rico wood warbler has a long beak in relation to its head size and short, round wings. On average, they are 53.8 millimeters long. Only the Antilles warbler has even shorter wings with an average of 50 millimeters.
Juveniles of the Puerto Rican wood warbler differ from adult birds by their gray-green body surface. They show this up to about twelve months after hatching. They molt into the plumage of adult birds from July to October. The plumage of both sexes is identical. When fully grown, Puerto Rican wood warblers are approximately 12.5 centimeters long and weigh an average of 8.4 grams.
There is a risk of confusion of this species with the climbing forest warbler ( Mniotilta varia ). Although this species does not breed in Puerto Rico, it occurs there from mid-September to early May. The most striking difference between these species is the fletching around the eyes. While the Puerto Rico wood warbler has an interrupted, white eye ring, the treecreeper wood warbler has a white bridle over the eye. Another white spring band is located below the eye. The top of the head is also different. With the Puerto Rico wood warbler this is completely black feathered, while with the climbing wood warbler a white band runs over the top of the head.
Existence and distribution
After its discovery, it was believed that the Puerto Rico wood warbler basically only occurs at altitudes between 640 and 1030 above sea level . Its only distribution area appeared to be the coppice of the Caribbean National Forest. The wind-ruffled trees in this forest region rarely grow taller than five meters and are characterized by thick, stiff branches, leathery leaves and an impenetrable undergrowth, which offers small bird species such as the Puerto Rican wood warbler ideal protection from predators. Another population was discovered in the Maricao State Forest as early as 1972 , which is still considered to be the one with the highest numbers. Puerto Rico wood warbler was discovered in 1977 in the Carite State Forest and in the late 1970s in the Toro Negro State Forest . Studies also showed that this species by no means only occurs at altitudes between 640 and 1030 meters. Depending on the season, these birds migrate to lower-lying areas and then stay in regions between 370 and 600 meters above sea level.
In 1989, Hurricane Hugo devastated the interior and the eastern parts of Puerto Rico. With the Caribbean National Forest, Toro Negro and Carite State Forest, three of the distribution areas of the Puerto Rico wood warbler were affected by this natural disaster. No representative of this bird species was observed in a bird census in the Toro Negro Forest two years after the hurricane. In the later inventories in the Carite State Forest and the Toro Negro State Forest, no Puerto Rico wood warblers were counted either. A bird census in 2001 in the Maricao State Forest found three individuals of this species. The IUCN estimated the population in 2000 to be a stable population of 600 adult birds.
It is now assumed that the Puerto Rican wood warbler was limited in its range to moist mountain forests and has recently only occurred in four isolated areas. It is now considered extinct in two of these distribution areas. Its distribution area is limited to the Caribbean National Forest and the Maricao State Forest. The region within the Caribbean Nation Forest, in which the Puerto Rican wood warbler can be observed, is characterized by high humidity and rainfall as well as comparatively low temperatures. They are also very exposed to wind. The distribution area seems to be limited to the summit regions of the mountains, whose vegetation consists of dense undergrowth and small trees with high epiphyte growth . The biodiversity of these forests is low compared to other Puerto Rican forests. The distribution areas in the Maricao State Forest are also very rainy. They have an average rainfall of 2250 millimeters. This amount of precipitation is very high if one takes into account that forest areas with an annual average rainfall of 2000 millimeters are already considered to be rainforest. Since the soil in these forest areas has only a limited retention capacity for the amount of precipitation, the vegetation is more drought-resistant than the amount of precipitation suggests. The highest population density of Puerto Rico wood warblers has so far been found in the Podocarpus forests of the Maricao State Forest. Little has been published about the characteristics of the earlier distribution areas in Toro Negro and Carite.
Behavior and diet
The Puerto Rican wood warbler is most commonly seen hunting insects in the central treetop area. He is usually in association with other birds such as the climbing Warbler ( Mniotilta varia ), the Puerto Rican Tanager ( Nesospingus speculiferus ) and the Small Antilles Schnäppertyrann ( Contopus latirostris to see). So far, three different food acquisition strategies have been observed and described. Most commonly, the Puerto Rican Wood Warbler pick up insects in the foliage of trees as they move along the branches, scare away or spot insects. This is a form of food acquisition that can be seen regularly in Central Europe, for example, with blue tits or golden chickens . The Puerto Rican wood warbler also masters a form of hunting flight in which it remains in one place in the air and from this position flies forward quickly to pick up any insects it has discovered from leaves or branches. Occasionally the bird also examines the substrate for insects with its long beak. However, this form of food acquisition is the least frequently observed.
The singing and calls of the Puerto Rican wood singer are very difficult to hear in the forests of Puerto Rico. They are only performed very quietly and also resemble those of the Bananaquit , one of the most common bird species in Puerto Rico. The singing is described as "short, fast and rather unmusical performed short whistles on one pitch". The volume of the whistles increases in volume during the singing; the chant ends with a short series of two-syllable whistles that are slightly lower in pitch. The call, on the other hand, is a short, metallic-sounding “chip”.
Reproduction
The Puerto Rican wood warbler breeds from March to June. Both parents are involved in both nest building and feeding the young.
For the nest building, mostly dry remains of leaves are used and the nest is built near the tree trunk. Nesting trees mostly belong to the species Bulbophyllum wadsworthii . The nests are well hidden and are usually built in the places where dried-up remains of the species Cecropia have accumulated in forked branches . The nests are between 1.3 and 7.6 meters above the ground and are cup-shaped. For construction, Puerto Rican wood warblers use small roots and twigs, as well as dry leaves of Chusquea abietifolia and Bulbophyllum wadsworthii . Of Panicum maximum only dry leaves are installed. The inside of the nest is lined with plant fibers from Chusquea abietifolia and dry leaves from other plant species. The females lay two to three white eggs with small reddish brown spots. The young are fed insects by their parents. Parent birds have been observed feeding butterflies and jumping fright as well as caterpillars to their young.
Predators and population threats
Hunting pressure and the destruction and change of its habitat threaten the continued existence of the Puerto Rican wood warbler as a species.
Natural predators that are native to Puerto Rico include the pearl-eye mockingbird ( Margarops fuscatus ), corner-tailed cattle ( Accipiter striatus ) and the Antilles crow ( Corvus leucognaphalus ), which has now become extinct in Puerto Rico . Two species of snake endemic to Puerto Rico and several carnivores are also considered to be potential predators for the Puerto Rican wood warbler. Hunting pressure on this species of bird has increased from human introduced species such as the house cat, rats, and little mongoose. These species are potential nest predators and enter the distribution areas of the Puerto Rico wood warbler with humans. Although the current distribution areas are mainly in protected forest areas, a number of buildings have been erected in these forests. Most of these are transmission masts and facilities that are necessary for the maintenance of these masts. The spread of rats, cats and mongooses in the protected forest areas mostly originates from these facilities.
Logging also contributes to changes in the habitat of the Puerto Rico wood warbler. Among other things, it goes hand in hand with the construction of roads and paths as well as the construction of logging camps or storage areas for felled wood. These facilities are also sources of inspiration for neozoa, which increase the hunting pressure on this bird species. Similar to other endemic species with small populations - well-known examples are the Mauritius hawk , the Puerto Rican amazon or the island cape fox - natural disasters such as hurricanes or forest fires or even just a deviation in annual rainfall can lead to a complete population collapse.
Protective measures
The Puerto Rico wood warbler was placed on the "United States federal candidate list for Endangered Species Act" in 1982. This list suggests the species to which the protection afforded by the Endangered Species Act should be extended. In 2005, a group of scientists, artists, and environmentalists contacted the Bush administration to extend the protection of this legislation to a total of 225 species on this list, including the Puerto Rican wood warbler. This has not happened until now. Similar to the Puerto Rican wood warbler, more than a third of the 225 species has been on the suggested list for 20 years or longer. More than half have been on the proposal list for 10 years. Several studies have indicated that 114 species native to the United States have become extinct since the Endangered Species Act was created in 1973. A number of environmental organizations and scientists see the cause of the disappearance of many of these species in a lack of habitat protection on the part of the federal authorities in the USA.
The IUCN assessed the status of the Puerto Rican wood warbler for the first time in 1988. At that time, the species was classified in the category of "lower risk / least concern". In 1994 the status was changed to "lower risk / near threatened" due to new inventories. As the inventory situation has since continued to deteriorate, the species is since 2000 in the category "endangered" ( vulnerable ) out. The IUCN justified this classification with "... there is no direct or immediate threat. However, the combination of a very small distribution area and a small inventory has serious implications for the long-term survival of this kind. "2017, the status was" "(critically endangered endangered ) changed.
References and comments
- ^ Victor, M. Cuevas: Wildlife Facts - January 2002 - Elfin-woods Warbler . USDA Forest Service. Found March 19, 2006. January 2002. Retrieved November 10, 2010.
- ↑ Kepler, CB and Parkes, K .: A New Species of Warbler (Parulidae) from Puerto Rico . In: The Auk . 89, No. 1, January 1972, pp. 1-18. Retrieved June 18, 2006.
- ↑ Cruz, Alexander and Delannoy, Carlos A .: [ Ecology of the Elfin-woods Warbler ( Dendroica angelae ) II ( Memento from February 25, 2009 in the Internet Archive ) Ecology of the Elfin-woods Warbler ( Dendroica angelae ) II .] In : University of Colorado . August, pp. 152-162.
- ↑ Anadón Irrizary, Verónica (2006). Distribution, habitat occupancy and population density of the Elfin-woods Warbler ( Memento of the original from July 24, 2006 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. . MS thesis. University of Puerto Rico at Mayagüez.
- ^ Bryan Arroyo Vázquez: Observations of the breeding biology of the Elfin Woods Warbler . In: The Wilson Bulletin . 104, No. 2, June 1992, pp. 362-365.
literature
- Jon Curson, David Quinn, David Beadle: New World Warblers. Helm, London 1994, ISBN 0-7136-3932-6 .
Web links
- Setophaga angelae inthe IUCN Red List of Threatened Species 2019.2. Listed by: BirdLife International, 2017. Retrieved October 15, 2019.