Red Warbler
Encyclopedia
The Red Warbler is a small passerine
bird endemic to the highlands of Mexico
, north of the Isthmus of Tehuantepec
. It is closely related to, and forms a superspecies
with, the Pink-headed Warbler
of southern Mexico and Guatemala. There are three subspecies
, which are found in disjunct populations. They differ primarily in the color of their ear patch and in the brightness and tone of their body plumage. The adult is bright red, with a white or gray ear patch, depending on the subspecies; young birds are pinkish-brown, with a whitish ear patch and two pale wingbars.
Like all New World warbler
s, the Red Warbler is an insectivore
. It gleans primarily in understory shrubs. Breeding typically occurs between February and May. The female lays 3–4 eggs in a domed nest, which she builds on the ground. Though she alone incubates the eggs, both sexes feed the young and remove fecal sacs from the nest. The young fledge within 10–11 days of hatching.
. Over the next half century, other naturalists moved it to Cardellina, with the Red-faced Warbler
, and to the widespread tropical warbler genus Basileuterus
– as well as to the Old World
warbler genus Sylvia
and the Old World tit genus Parus
. In 1873, naturalists Philip Lutley Sclater and Osbert Salvin
moved the species to its current genus, Ergaticus
.
There are three subspecies, which differ slightly in appearance:
The Red Warbler forms a superspecies
with the Pink-headed Warbler
of Chiapas
and Guatemala
, to which it is closely related. Despite their disjunct ranges and considerably different plumages, the two have sometimes been considered conspecific. Conversely, it has also been suggested that the Red Warbler should be split into a northern gray-eared species (E. melanauris) and a southern white-eared species (E. ruber).
The Red Warbler's common name is a straightforward reference to its color. The genus
name Ergaticus is a Latinized version of the Ancient Greek
ergatikos, meaning "willing or able to work", while its specific name, ruber, is Latin
for "red".
shows a dark tip. The feathers of this species contain alkaloid
s, which render the bird unpalatable; humans find it inedible.
As a juvenile, the Red Warbler is pinkish-brown with a whitish auricular patch. Its darker wings and tail show pinkish-cinnamon edges, with two paler wingbars on the former.
zone, it tends to sing only during bright morning hours during the breeding season
; regardless of season, it does not sing – and even its calling frequency decreases – in cloud
y weather.
: from southwestern Chihuahua to northern Nayarit, from southern Jalisco and southern Hidalgo to Oaxaca, and from Guerrero
into southern Oaxaca in the Sierra Madre del Sur
. It is fairly common to common in the interior and on adjacent slopes, where it occurs at elevations ranging from 1800 to 3900 m (5,905.5 to 12,795.3 ft) above sea level. It is an altitudinal migrant, moving from higher humid or semi-humid pine
, pine-oak
and fir
forests in the breeding season to lower elevations, often in oak forests, in the winter. It is among the most common of the small birds in its woodland habitat, second only to the Golden-crowned Kinglet
in fir forests in one study and the third most common warbler in oak-conifer woodlands in another.
Though the species was reported to have been collected
in Texas
in the late 19th century, the record's location was not widely believed, and there is no strong evidence that it ever occurred there.
. It gleans
primarily in understory
shrubs at low to middle levels, moving slowly and deliberately through more open areas of the vegetation, and feeding with quick jabs into cracks in bark
and pine needle clusters. It sometimes hover gleans to feed at pine needle clusters. Though it lacks any obvious adaptations for climbing, it regularly does so in its search for prey items on bark and epiphyte
s on branches, often hanging head-down as it probes. In areas of deciduous
growth, it typically flycatches, making brief aerial sorties from a perch in pursuit of flying insects. While it seldom associates with mixed-species flocks, it feeds alongside other birds with no signs of conflict, displaying no hostility towards other species with which it competes. Its foraging area is quite small, often amounting to only a few dozen square meters (several hundred square feet) per day. Late in the afternoon, its rate of foraging declines, and it rests, often taking brief naps, in the forest understory. Though it does not generally feed after sunset, it may do so to take advantage of transient food sources, such as hatching Neuroptera
.
containing young has been found as late as the end of June. The female alone builds the nest, a task which typically takes 4–6 days. She chooses a sunlit area, such as an area of windfall, the brushy edge of a trail or water course, or a small clearing, for its location. Tightly woven of plant material, the nest is hidden in ground vegetation and anchored to the stalks of surrounding vegetation. Bulky and untidy on the outside, it is typically constructed primarily of dead pine needles and dead grass, though gray lichen
s, green moss, dead leaves, shreds of bark and tips of fern fronds are also used; most of these materials are gathered from the ground close to the nest, though some is picked from low branches or further away. The nest, which is usually oven
-shaped with a side or upward-facing entrance, measures roughly 6 in (15.2 cm) wide by 7 in (17.8 cm) long by 4.5 in (11.4 cm) high. A small number of nests are only cups, lacking the roof of the more typical structures. Inside, the nest is tidy and compact, lined with fine grasses and plant fluff, which is generally gathered some distance from the nest.
Early in the breeding season, as many as 11 days may transpire between the completion of the nest and the laying of the first egg
. Later in the season, this time decreases so that the first egg is laid as soon as the nest is ready. The female normally lays three eggs, though clutches
of up to four have been recorded. The eggs, which are variously described as pale pink with evenly distributed brown spots or white with cinnamon and rust spots densely ringing the larger end of the egg, measure 16–17 mm (0.62992125984252–0.669291338582677 in) by 13 mm (0.511811023622047 in) and weigh 1–1.4 g (0.035273962105112–0.0493835469471567 oz). The female alone incubates
the eggs for 16 days; the male does not even approach the nest until several days after the eggs hatch. She sits facing the back wall of the nest, with her head and body sheltered by its roof and her tail sticking out the opening. She sits tight at the approach of danger, typically not flying until a potential predator actually makes contact with the nest.
Both adults feed the nestlings and remove fecal sac
s, though the female removes far more than the male does. The pair move deceptively when approaching the nest, foraging – or pretending to forage – in nearly vegetation. They stay only a few seconds in any one spot, including at the nest, making it more difficult for a predator to locate the young. The nestlings, which make a rapid, high-pitched peeping call as an adult approaches carrying food, fledge within 10–11 days of hatching.
by the International Union for the Conservation of Nature. Though there is evidence that its numbers are decreasing, the decline has not been precipitous, and the population remains quite large, with estimates ranging from 50,000 to 499,999 birds. The forested areas in which it occurs, however, include some of the most threatened habitats in Mexico, with logging, agricultural expansion, firewood
gathering, road building, tourist development, overgrazing
and intensive urbanization among the many things contributing to the destruction of the forests. There is some evidence that selective logging in pine forests may actually favor this species, which prefers more open, sunlit areas in which to breed.
Passerine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
bird endemic to the highlands of Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, north of the Isthmus of Tehuantepec
Isthmus of Tehuantepec
The Isthmus of Tehuantepec is an isthmus in Mexico. It represents the shortest distance between the Gulf of Mexico and the Pacific Ocean, and prior to the opening of the Panama Canal was a major shipping route known simply as the Tehuantepec Route...
. It is closely related to, and forms a superspecies
Superspecies
A superspecies is a group of at least two more or less distinctive species with approximately parapatric distributions. Not all species complexes, whether cryptices or ring species are superspecies, and vice versa, but many are...
with, the Pink-headed Warbler
Pink-headed Warbler
The Pink-headed Warbler is a small passerine bird found in the southwestern highlands of Guatemala and the central and southeastern highlands of the Mexican state of Chiapas. The adult is primarily red, with a silvery-pink head and chest...
of southern Mexico and Guatemala. There are three subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
, which are found in disjunct populations. They differ primarily in the color of their ear patch and in the brightness and tone of their body plumage. The adult is bright red, with a white or gray ear patch, depending on the subspecies; young birds are pinkish-brown, with a whitish ear patch and two pale wingbars.
Like all New World warbler
New World warbler
The New World warblers or wood-warblers are a group of small, often colorful, passerine birds restricted to the New World. They are not related to the Old World warblers or the Australian warblers....
s, the Red Warbler is an insectivore
Insectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
. It gleans primarily in understory shrubs. Breeding typically occurs between February and May. The female lays 3–4 eggs in a domed nest, which she builds on the ground. Though she alone incubates the eggs, both sexes feed the young and remove fecal sacs from the nest. The young fledge within 10–11 days of hatching.
Taxonomy
When he first described the Red Warbler in 1827, naturalist William John Swainson assigned it to the genus Setophaga – the same genus as that of the American RedstartAmerican Redstart
The American Redstart is a New World warbler. It is the only member of its genus and is unrelated to the Old World redstarts. It derives its name from the male's red tail, start being an old word for tail.-Description:...
. Over the next half century, other naturalists moved it to Cardellina, with the Red-faced Warbler
Red-faced Warbler
The Red-faced Warbler is a species of New World warbler.Mature Red-faced Warblers are small birds, 14 cm long. They are light gray on top with a white rump and a white underside. The face, neck, and upper breast are all bright red, while the crown and sides of the head are black...
, and to the widespread tropical warbler genus Basileuterus
Basileuterus
Basileuterus is a genus of New World warblers, best represented in Central and South America. This is one of only two warbler genera that are well represented in the latter continent...
– as well as to the Old World
Old World
The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....
warbler genus Sylvia
Sylvia
Sylvia may refer to:* A feminine given name of Latin origin, also spelled Silvia. The French form is Sylvie.* Sylvia, Kansas, a town in Kansas-Persons:*Saint Silvia*Queen Silvia of Sweden*Sylvia , American country singer born Sylvia Jane Kirby...
and the Old World tit genus Parus
Parus
Parus is a genus of Old World birds in the tit family. As defined here, it contains the following species:* Genus Parus** White-shouldered Tit Parus guineensis, sometimes separated in Melaniparus...
. In 1873, naturalists Philip Lutley Sclater and Osbert Salvin
Osbert Salvin
Osbert Salvin FRS was an English naturalist, best known for co-authoring Biologia Centrali-Americana with Frederick DuCane Godman. This was a 52 volume encyclopedia on the natural history of Central America....
moved the species to its current genus, Ergaticus
Ergaticus
Ergaticus is a genus of New World warblers — small passerine birds found only in the Americas. The name is the Latinized version of the Ancient Greek ergatikos, meaning "willing or able to work"...
.
There are three subspecies, which differ slightly in appearance:
- E. r. ruber, described by Swainson in 1827, has white ear patches and is found from southern JaliscoJaliscoJalisco officially Estado Libre y Soberano de Jalisco is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is located in Western Mexico and divided in 125 municipalities and its capital city is Guadalajara.It is one of the more important states...
and southern Hidalgo to OaxacaOaxacaOaxaca , , officially Estado Libre y Soberano de Oaxaca is one of the 31 states which, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided into 571 municipalities; of which 418 are governed by the system of customs and traditions...
. - E. r. melanauris, which was described by Robert Thomas MooreRobert Thomas MooreRobert Thomas Moore was an American businessman, an independent ornithologist, a philanthropist, and the founder and for some years the editor-in-chief of the Borestone Mountain Poetry Awards...
in 1937, has dark gray ear patches and somewhat more scarlet upperparts than E. r. ruber. It is found from southwestern Chihuahua to northern NayaritNayaritNayarit officially Estado Libre y Soberano de Nayarit is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 20 municipalities and its capital city is Tepic.It is located in Western Mexico...
. - E. r. rowleyi was described by R. T. Orr and J. D. Webster in 1968. It has white ear patches and ruby-red upperparts (brightest of the three subspecies), and is found in the Sierra Madre del SurSierra Madre del SurThe Sierra Madre del Sur is a mountain range in southern Mexico, extending from southern Michoacán east through Guerrero, to the Istmo de Tehuantepec in eastern Oaxaca.-Geography:...
, from GuerreroGuerreroGuerrero officially Estado Libre y Soberano de Guerrero is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 81 municipalities and its capital city is Chilpancingo....
to southern Oaxaca.
The Red Warbler forms a superspecies
Superspecies
A superspecies is a group of at least two more or less distinctive species with approximately parapatric distributions. Not all species complexes, whether cryptices or ring species are superspecies, and vice versa, but many are...
with the Pink-headed Warbler
Pink-headed Warbler
The Pink-headed Warbler is a small passerine bird found in the southwestern highlands of Guatemala and the central and southeastern highlands of the Mexican state of Chiapas. The adult is primarily red, with a silvery-pink head and chest...
of Chiapas
Chiapas
Chiapas officially Estado Libre y Soberano de Chiapas is one of the 31 states that, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 118 municipalities and its capital city is Tuxtla Gutierrez. Other important cites in Chiapas include San Cristóbal de las...
and Guatemala
Guatemala
Guatemala is a country in Central America bordered by Mexico to the north and west, the Pacific Ocean to the southwest, Belize to the northeast, the Caribbean to the east, and Honduras and El Salvador to the southeast...
, to which it is closely related. Despite their disjunct ranges and considerably different plumages, the two have sometimes been considered conspecific. Conversely, it has also been suggested that the Red Warbler should be split into a northern gray-eared species (E. melanauris) and a southern white-eared species (E. ruber).
The Red Warbler's common name is a straightforward reference to its color. The genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
name Ergaticus is a Latinized version of the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
ergatikos, meaning "willing or able to work", while its specific name, ruber, is Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
for "red".
Description
The Red Warbler is a small passerine, measuring 12.5–13.5 cm (4.9–5.3 in) in length, and weighing from 7.6 to 8.7 g (0.268082111998851 to 0.306883470314474 oz). As an adult, it is red overall, with either a white or dark gray (depending on the subspecies) auricular patch on each side of its head. Its slightly darker wings and tail are edged in pinkish-red. Its legs are flesh-colored, and its flesh-colored billBeak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
shows a dark tip. The feathers of this species contain alkaloid
Alkaloid
Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms. This group also includes some related compounds with neutral and even weakly acidic properties. Also some synthetic compounds of similar structure are attributed to alkaloids...
s, which render the bird unpalatable; humans find it inedible.
As a juvenile, the Red Warbler is pinkish-brown with a whitish auricular patch. Its darker wings and tail show pinkish-cinnamon edges, with two paler wingbars on the former.
Voice
The Red Warbler has several common calls, including a high, thin tsii and a stronger pseet. Its song is a mix of short trills and richer warbles, interspersed with high-pitched chips. Unlike other species in the same habitatHabitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
zone, it tends to sing only during bright morning hours during the breeding season
Breeding season
The breeding season is the most suitable season, usually with favourable conditions and abundant food and water, for breeding among some wild animals and birds . Species with a breeding season have naturally evolved to have sexual intercourse during a certain time of year in order to achieve the...
; regardless of season, it does not sing – and even its calling frequency decreases – in cloud
Cloud
A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...
y weather.
Habitat and range
Endemic to the highlands of Mexico north of the Isthmus of Tehuantepec, the Red Warbler has three disjunct populationsDisjunct distribution
In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but widely separated from each other geographically...
: from southwestern Chihuahua to northern Nayarit, from southern Jalisco and southern Hidalgo to Oaxaca, and from Guerrero
Guerrero
Guerrero officially Estado Libre y Soberano de Guerrero is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 81 municipalities and its capital city is Chilpancingo....
into southern Oaxaca in the Sierra Madre del Sur
Sierra Madre del Sur
The Sierra Madre del Sur is a mountain range in southern Mexico, extending from southern Michoacán east through Guerrero, to the Istmo de Tehuantepec in eastern Oaxaca.-Geography:...
. It is fairly common to common in the interior and on adjacent slopes, where it occurs at elevations ranging from 1800 to 3900 m (5,905.5 to 12,795.3 ft) above sea level. It is an altitudinal migrant, moving from higher humid or semi-humid pine
Pine
Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...
, pine-oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
and fir
Fir
Firs are a genus of 48–55 species of evergreen conifers in the family Pinaceae. They are found through much of North and Central America, Europe, Asia, and North Africa, occurring in mountains over most of the range...
forests in the breeding season to lower elevations, often in oak forests, in the winter. It is among the most common of the small birds in its woodland habitat, second only to the Golden-crowned Kinglet
Golden-crowned Kinglet
The Golden-crowned Kinglet, Regulus satrapa, is a very small songbird.Adults are olive-gray on the upperparts with white underparts, with thin bills and short tails. They have white wing bars, a black stripe through the eyes and a yellow crown surrounded by black...
in fir forests in one study and the third most common warbler in oak-conifer woodlands in another.
Though the species was reported to have been collected
Bird collections
Bird collections are curated repositories of scientific specimens consisting of birds and their parts. They are a research resource for ornithology, the science of birds, and for other scientific disciplines in which information about birds is useful...
in Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
in the late 19th century, the record's location was not widely believed, and there is no strong evidence that it ever occurred there.
Behavior
Though it sometimes joins mixed-species flocks, the Red Warbler is more typically found alone or in pairs. Youngsters probably choose mates in the autumn of their first year, and pairs remain together year-round, except during severe weather and during post-breeding molt.Food and feeding
The Red Warbler is an insectivoreInsectivore
An insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures. An alternate term is entomophage, which also refers to the human practice of eating insects....
. It gleans
Gleaning (birds)
Gleaning is a term for a feeding strategy by birds in which they catch invertebrate prey, mainly arthropods, by plucking them from foliage or the ground, from crevices such as rock faces and under the eaves of houses, or even, as in the case of ticks and lice, from living animals. This behavior is...
primarily in understory
Understory
Understory is the term for the area of a forest which grows at the lowest height level below the forest canopy. Plants in the understory consist of a mixture of seedlings and saplings of canopy trees together with understory shrubs and herbs...
shrubs at low to middle levels, moving slowly and deliberately through more open areas of the vegetation, and feeding with quick jabs into cracks in bark
Bark
Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...
and pine needle clusters. It sometimes hover gleans to feed at pine needle clusters. Though it lacks any obvious adaptations for climbing, it regularly does so in its search for prey items on bark and epiphyte
Epiphyte
An epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...
s on branches, often hanging head-down as it probes. In areas of deciduous
Deciduous
Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...
growth, it typically flycatches, making brief aerial sorties from a perch in pursuit of flying insects. While it seldom associates with mixed-species flocks, it feeds alongside other birds with no signs of conflict, displaying no hostility towards other species with which it competes. Its foraging area is quite small, often amounting to only a few dozen square meters (several hundred square feet) per day. Late in the afternoon, its rate of foraging declines, and it rests, often taking brief naps, in the forest understory. Though it does not generally feed after sunset, it may do so to take advantage of transient food sources, such as hatching Neuroptera
Neuroptera
The insect order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order contains some 6,010 species...
.
Breeding
The Red Warbler breeds primarily in early spring, from February until May, though at least one nestBird nest
A bird nest is the spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American Robin or Eurasian Blackbird, or the elaborately woven hanging nest of the...
containing young has been found as late as the end of June. The female alone builds the nest, a task which typically takes 4–6 days. She chooses a sunlit area, such as an area of windfall, the brushy edge of a trail or water course, or a small clearing, for its location. Tightly woven of plant material, the nest is hidden in ground vegetation and anchored to the stalks of surrounding vegetation. Bulky and untidy on the outside, it is typically constructed primarily of dead pine needles and dead grass, though gray lichen
Lichen
Lichens are composite organisms consisting of a symbiotic organism composed of a fungus with a photosynthetic partner , usually either a green alga or cyanobacterium...
s, green moss, dead leaves, shreds of bark and tips of fern fronds are also used; most of these materials are gathered from the ground close to the nest, though some is picked from low branches or further away. The nest, which is usually oven
Beehive oven
A beehive oven is an early type of oven. It gets its name from its domed shape, which resembles that of an old-fashioned beehive, and was in common use in the Americas and Europe from the Middle Ages to the advent of the gas and electric ovens. Beehive ovens were common in households used for...
-shaped with a side or upward-facing entrance, measures roughly 6 in (15.2 cm) wide by 7 in (17.8 cm) long by 4.5 in (11.4 cm) high. A small number of nests are only cups, lacking the roof of the more typical structures. Inside, the nest is tidy and compact, lined with fine grasses and plant fluff, which is generally gathered some distance from the nest.
Early in the breeding season, as many as 11 days may transpire between the completion of the nest and the laying of the first egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
. Later in the season, this time decreases so that the first egg is laid as soon as the nest is ready. The female normally lays three eggs, though clutches
Clutch (eggs)
A clutch of eggs refers to all the eggs produced by birds or reptiles, often at a single time, particularly those laid in a nest.In birds, destruction of a clutch by predators, , results in double-clutching...
of up to four have been recorded. The eggs, which are variously described as pale pink with evenly distributed brown spots or white with cinnamon and rust spots densely ringing the larger end of the egg, measure 16–17 mm (0.62992125984252–0.669291338582677 in) by 13 mm (0.511811023622047 in) and weigh 1–1.4 g (0.035273962105112–0.0493835469471567 oz). The female alone incubates
Avian incubation
Incubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...
the eggs for 16 days; the male does not even approach the nest until several days after the eggs hatch. She sits facing the back wall of the nest, with her head and body sheltered by its roof and her tail sticking out the opening. She sits tight at the approach of danger, typically not flying until a potential predator actually makes contact with the nest.
Both adults feed the nestlings and remove fecal sac
Fecal sac
A fecal sac is a mucous membrane, generally white or clear with a dark end, that surrounds the feces of some species of nestling birds. It allows parent birds to more easily remove fecal material from the nest...
s, though the female removes far more than the male does. The pair move deceptively when approaching the nest, foraging – or pretending to forage – in nearly vegetation. They stay only a few seconds in any one spot, including at the nest, making it more difficult for a predator to locate the young. The nestlings, which make a rapid, high-pitched peeping call as an adult approaches carrying food, fledge within 10–11 days of hatching.
Conservation and threats
The Red Warbler is currently rated as a species of Least ConcernLeast Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
by the International Union for the Conservation of Nature. Though there is evidence that its numbers are decreasing, the decline has not been precipitous, and the population remains quite large, with estimates ranging from 50,000 to 499,999 birds. The forested areas in which it occurs, however, include some of the most threatened habitats in Mexico, with logging, agricultural expansion, firewood
Firewood
Firewood is any wood-like material that is gathered and used for fuel. Generally, firewood is not highly processed and is in some sort of recognizable log or branch form....
gathering, road building, tourist development, overgrazing
Overgrazing
Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, or by overpopulations of native or non-native wild animals.Overgrazing reduces the...
and intensive urbanization among the many things contributing to the destruction of the forests. There is some evidence that selective logging in pine forests may actually favor this species, which prefers more open, sunlit areas in which to breed.
External links
- Red Warbler photos on the Academy of Natural SciencesAcademy of Natural SciencesThe Academy of Natural Sciences of Drexel University, formerly Academy of Natural Sciences of Philadelphia, is the oldest natural science research institution and museum in the New World...
' Visual Resources for Ornithology website - Red Warbler videos on the Internet Bird Collection website
- Red Warbler vocalizations on the Macauley Library's (Cornell Laboratory of OrnithologyCornell Laboratory of OrnithologyThe Cornell Lab of Ornithology is a member-supported unit of Cornell University in Ithaca, New York which studies birds and other wildlife. It is housed in the Imogene Powers Johnson Center for Birds and Biodiversity in Sapsucker Woods Sanctuary...
) website - Red Warbler vocalizations on the xeno-canto.org website