Post by Eaglehawk on Dec 20, 2019 4:23:27 GMT
Least Flycatcher - Empidonax minimus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Tyrannidae
Genus: Empidonax
Species: Empidonax minimus (Baird, 1843)
The least flycatcher (Empidonax minimus), (also called chebec, or chebecker, after the sound it makes), is a small insect-eating bird. It is the smallest Empidonax flycatcher in eastern North America.
Taxonomy
The closest relative to the least flycatcher was long thought to be the Hammond's flycatcher based on similarities in their songs and appearances. However, mitochondrial DNA analysis has revealed that the least flycatcher diverges significantly from its congeners and does not possess any sister taxa.
Description
The least flycatcher is hard to distinguish from the other birds of its genus. The bird is one of the smallest of the genus Empidonax, measuring 12 to 14 cm in height with a wingspan of 19 to 22 cm and weighing approximately 10.3 g. Its plumage is dull olive-gray on its back and whitish on its belly, notably brighter than the other Empidonax birds. The least flycatcher's wings are lined with two white bars, and white rings contour its eyes. Its beak is short and the lower mandible is yellowish. The juveniles look similar to the adults except that their wing bars are slightly darker, with tawny/olive hues. Because other flycatchers also have those field marks, the best way to identify the least flycatcher is by its call and habitat.
Distribution and habitat
The least flycatcher inhabits the Eastern Rockies of Canada, and the Central-North and Northeastern United-States. During winter, they migrate to Central America and establish themselves from Mexico to Panama.
Geographical distribution of Least flycatcher. Breeding Migration Nonbreeding
The least flycatcher lives in aspen clusters, orchards, shade trees and open woods. They breed in deciduous or mixed forests and occasionally in coniferous groves. They tend to prefer breeding sites near clearing or edges but can also nest in dry woods. They spend the winter in Central America where they nest in forest edges and second growth.
The least flycatcher also made its way in the open country. They often live in villages or city parks, nesting in shade trees and orchards, or along rural roads and forest edges.
Behaviour: vocalization, diet and reproduction
Call
The vocalization of the least flycatcher is often characterized as being dry and sounding like a piercing «che-bec» pushed with strength, the second syllable being louder than the first. During the hottest days of the summer, they often call incessantly.
Singing is essential to the least flycatcher to establish and defend their territory. While the female remains quietly in the nest, the male sings from several perches some distance away from the nest, and a few kilometers above the level of the nest. From there, he sings the Che-bec repeatedly and rapidly during the morning (about 60 times per minute), losing some speed and regularity throughout the day. All of the males in a same area seem to sing in unison. This singing fervor gradually decreases throughout the summer, as the breeding cycle reaches an end.
The female sings rarely. She instead uses a call-note that Macqueen (1950) describes as sounding like «Chweep». She sometimes calls while feeding her nestling, or to her partner when he leaves and returns to the nest. She also uses her chweep-note in outbursts when defending her nest.
Diet
The least flycatcher, as its name indicates, feeds on flies but includes many other items in its diet. They mainly eat insects such as many small wasps, winged ants, beetles, caterpillars, midges, a few true bugs, grasshoppers, spiders and other small invertebrates. They also occasionally eat berries.
To forage, the least flycatcher mainly catches its insects mid-air, but they also catch some insects from the vegetation. When foraging, the bird watches from a perch and flies out to catch the insects that pass by. The Least flycatcher is considered a slow searcher in comparison to other birds, switching perch around 10 times/minute and frequently turning around on its perch to get a 360° view. Least flycatchers rarely glean but hover extensively in comparison to its congeners. Those perches are mainly dead twigs of the bottom part of a tree located in opened patches of the forest. In short, Robinson and Holmes (1982) determined that the least flycatcher attacks 81.1% of their preys by hovering, 9.6% by hawking, 6.2% by flush-chasing and 3.1% by gleaning.
Reproduction
The least flycatcher breeds in spring in highly clumped groups. The proximity of neighbors even appears to be more important than habitat quality when the bird is selecting its breeding site. The advantage that could explain such a behavior remains unclear and has been the subject of many studies. Some of the hypothesis the scholars explored include: clustering to take advantage of heterogeneous resources, to deter predators, or to keep away other species with similar resource requirements.
The courtship behavior of the least flycatcher remains largely unknown but it is thought to involve the male chasing the female through trees. The males are aggressive and sing incessantly until pairs form. Once pairs form, the female starts building their nest on either the forks of small trees like maples, birches, or ashes, or on the top of a large branch. The average height of the nest is 12 to 25 inches above the ground, but can vary from 2 to 65 inches depending on the habitat. The female builds the nest by weaving fine pieces of grass, strips of bark, twigs, lichen, spider and caterpillar webs, animal hairs and feathers, and other plant-derived materials together to form a tidy cup, a process that takes her about five days.
The female least flycatcher typically lays three to five creamy-white colored eggs, with a strong tendency towards four. The female incubates the eggs for a period of 13 to 16 days while the male remains in the area and occasionally feeds her. The eggs hatch together in June over a period of one to three days. Once the eggs hatch, both parents bring food to their newborns. The nestlings fly for the first time at the age of 12 to 17 days. They typically remain being fed by their parents for another 2 to 3 weeks.
Territoriality
The couple spends most of its time in their chosen breeding site. Their average defended territory size is 0.18 acres (8036.8 feet square), with an average distance between congener's nests of 175 feet. Both parents become particularly aggressive and territorial to both intra- and heterospecific intruders. If another least flycatcher intrudes their territory, the resident male quickly reacts, uttering a sharp note and adopting a threat-display. In its threat-display, the male attempts to look bigger by “fluffing out its breast feathers, raising its chest, extending, vibrating and bending the wings, spreading and flicking the tail up and down, and crouching”. This display lasts only a second or two before the male flies off to chase the trespasser away. If the intruder is too persistent, the resident male engages in a fight and usually wins.
Females can also engage in territorial defenses in certain occasions. If the trespasser comes in a radius of about 20 feet surrounding her nest, the female reacts. If her partner is absent, she flies off to chase the intruder and attacks if necessary. She can also work in tandem with her partner to defend their territory in scenarios where there are more than one intruder at a time. In that case, they both cooperate and chase them away, although the male is always first to react.
Migration
Least flycatchers’ age and sex groups migrate at different intervals. In Fall, adult males leave the breeding ground first, followed by adult females about a week later. The younger ones only join the rest of the group a month later. Fall migration occurs in July and early August, peaking in late-August.
In the Fall migration, it has been reported that populations living in the west first migrate east before heading south. From the East, they then fly down to the Tropics. A few of them establish themselves for the winter in southern Florida, but most of them choose to spend their winter on the coasts of Central America. Once in that region, they inhabit wooded ravines of the Pacific slope or the dense bushes and wooded edges habitats of the Caribbean side.
The least flycatcher leaves its wintering ground relatively early in comparison to other birds, arriving back north in late April to mid-May. It is thought that they can afford to arrive so early because they can subsist on small-sized insects which are out early in spring. They might also arrive early because of their highly competitive breeding site selection – a product of their habit to breed in clustered distribution.
The least flycatcher spends its breeding season in southern Yukon to central Quebec and Maritime Provinces, in Wyoming Indiana, New Jersey and in the mountains of North Carolina. The breeding season only last about 64 days, after which they return south in the Tropics.
The adult least flycatcher molts after migrating to its wintering ground, which differs from most other passerines The juveniles, on the other hand, molt prior and throughout their Fall migration. The reason why the molt of the adults is delayed remains unclear, but might be due to the highly competitive site selection of winter habitat, where the first to arrive are the first to be served.
Newly discovered retinal structure may enhance vision for some birds
Date: December 18, 2019
Source: Purdue University
A newly discovered retinal structure in the eyes of certain kinds of songbirds might help the animals find and track insect prey more easily.
The foundation of avian vision rests on cells called cone and rod photoreceptors. Most birds have four cone photoreceptors for color vision, a fifth cone for non-color-related tasks, and a rod for night vision. Each cone photoreceptor cell contains a spherical structure called an "oil droplet," which filters light before it is converted to electrical signals by the visual pigments, enhancing color discrimination.
However, the researchers have discovered a never-before-seen type of cone structure in the retina of a group of small songbirds, called flycatchers. Instead of an oil droplet, it contains a high- energy-producing cellular structure called "megamitochondria" surrounded by hundreds of small, orange-colored droplets. The researchers named this novel cellular structure a megamitochondria-small oil droplet complex, or MMOD-complex.
The discovery, made at Purdue University, is detailed in a paper that appeared in the journal Scientific Reports, as part of a collaboration with the State University of New York at Plattsburgh, the University of Wisconsin-Madison, and the University of California, Davis.
The researchers studied this retinal structure using light microscopy, transmission electron microscopy and a technique called microspectrophotometry, which measures the wavelengths of light that these structures absorb the most. The MMOD-complex works as long-pass filters, letting light with wavelengths longer the 565 nanometers -- or yellow, orange and red -- pass through, and absorbing the shorter wavelengths of green, blue and violet.
Traditional cones were present throughout the retina of these flycatchers, and their density decreased moving away from the center toward the periphery. However, the MMOD-complex photoreceptors were present only in the central region of the retina, an arrangement that could help birds detect flying insects, said Esteban Fernandez-Juricic, a professor of biological sciences at Purdue.
"The retina of flycatchers, which are sit-and-wait predatory birds, evolved a novel cellular structure in a photoreceptor that may allow them to detect, track and capture fast-moving prey, like insects," he said.
The paper's lead author was Luke Tyrrell, a former Purdue doctoral student and now an assistant professor of biological science at SUNY Plattsburgh.
"This new cone organelle has not been reported before in this form in any other vertebrate retina and may allow these birds to see their world in a different way from other animals," Tyrrell said.
A complete listing of the paper's authors is available in the abstract, and the paper is available online here. The research was funded by the National Science Foundation. Future research will be aimed at establishing the function of this structure and assess the ability of flycatchers to catch prey under different ambient light conditions.
Story Source: Purdue University. "Newly discovered retinal structure may enhance vision for some birds." ScienceDaily. www.sciencedaily.com/releases/2019/12/191218090216.htm (accessed December 19, 2019).
Journal Reference:
Luke P. Tyrrell, Leandro B. C. Teixeira, Richard R. Dubielzig, Diana Pita, Patrice Baumhardt, Bret A. Moore, Esteban Fernández-Juricic. A novel cellular structure in the retina of insectivorous birds. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-019-51774-w
Abstract
The keen visual systems of birds have been relatively well-studied. The foundations of avian vision rest on their cone and rod photoreceptors. Most birds use four cone photoreceptor types for color vision, a fifth cone for achromatic tasks, and a rod for dim-light vision. The cones, along with their oil droplets, and rods are conserved across birds – with the exception of a few shifts in spectral sensitivity – despite taxonomic, behavioral and ecological differences. Here, however, we describe a novel photoreceptor organelle in a group of New World flycatchers (Empidonax spp.) in which the traditional oil droplet is replaced with a complex of electron-dense megamitochondria surrounded by hundreds of small, orange oil droplets. The photoreceptors with this organelle were unevenly distributed across the retina, being present in the central region (including in the fovea), but absent from the retinal periphery and the area temporalis of these insectivorous birds. Of the many bird species with their photoreceptors characterized, only the two flycatchers described here (E. virescens and E. minimus) possess this unusual retinal structure. We discuss the potential functional significance of this unique sub-cellular structure, which might provide an additional visual channel for these small predatory songbirds.
www.nature.com/articles/s41598-019-51774-w
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Tyrannidae
Genus: Empidonax
Species: Empidonax minimus (Baird, 1843)
The least flycatcher (Empidonax minimus), (also called chebec, or chebecker, after the sound it makes), is a small insect-eating bird. It is the smallest Empidonax flycatcher in eastern North America.
Taxonomy
The closest relative to the least flycatcher was long thought to be the Hammond's flycatcher based on similarities in their songs and appearances. However, mitochondrial DNA analysis has revealed that the least flycatcher diverges significantly from its congeners and does not possess any sister taxa.
Description
The least flycatcher is hard to distinguish from the other birds of its genus. The bird is one of the smallest of the genus Empidonax, measuring 12 to 14 cm in height with a wingspan of 19 to 22 cm and weighing approximately 10.3 g. Its plumage is dull olive-gray on its back and whitish on its belly, notably brighter than the other Empidonax birds. The least flycatcher's wings are lined with two white bars, and white rings contour its eyes. Its beak is short and the lower mandible is yellowish. The juveniles look similar to the adults except that their wing bars are slightly darker, with tawny/olive hues. Because other flycatchers also have those field marks, the best way to identify the least flycatcher is by its call and habitat.
Distribution and habitat
The least flycatcher inhabits the Eastern Rockies of Canada, and the Central-North and Northeastern United-States. During winter, they migrate to Central America and establish themselves from Mexico to Panama.
Geographical distribution of Least flycatcher. Breeding Migration Nonbreeding
The least flycatcher lives in aspen clusters, orchards, shade trees and open woods. They breed in deciduous or mixed forests and occasionally in coniferous groves. They tend to prefer breeding sites near clearing or edges but can also nest in dry woods. They spend the winter in Central America where they nest in forest edges and second growth.
The least flycatcher also made its way in the open country. They often live in villages or city parks, nesting in shade trees and orchards, or along rural roads and forest edges.
Behaviour: vocalization, diet and reproduction
Call
The vocalization of the least flycatcher is often characterized as being dry and sounding like a piercing «che-bec» pushed with strength, the second syllable being louder than the first. During the hottest days of the summer, they often call incessantly.
Singing is essential to the least flycatcher to establish and defend their territory. While the female remains quietly in the nest, the male sings from several perches some distance away from the nest, and a few kilometers above the level of the nest. From there, he sings the Che-bec repeatedly and rapidly during the morning (about 60 times per minute), losing some speed and regularity throughout the day. All of the males in a same area seem to sing in unison. This singing fervor gradually decreases throughout the summer, as the breeding cycle reaches an end.
The female sings rarely. She instead uses a call-note that Macqueen (1950) describes as sounding like «Chweep». She sometimes calls while feeding her nestling, or to her partner when he leaves and returns to the nest. She also uses her chweep-note in outbursts when defending her nest.
Diet
The least flycatcher, as its name indicates, feeds on flies but includes many other items in its diet. They mainly eat insects such as many small wasps, winged ants, beetles, caterpillars, midges, a few true bugs, grasshoppers, spiders and other small invertebrates. They also occasionally eat berries.
To forage, the least flycatcher mainly catches its insects mid-air, but they also catch some insects from the vegetation. When foraging, the bird watches from a perch and flies out to catch the insects that pass by. The Least flycatcher is considered a slow searcher in comparison to other birds, switching perch around 10 times/minute and frequently turning around on its perch to get a 360° view. Least flycatchers rarely glean but hover extensively in comparison to its congeners. Those perches are mainly dead twigs of the bottom part of a tree located in opened patches of the forest. In short, Robinson and Holmes (1982) determined that the least flycatcher attacks 81.1% of their preys by hovering, 9.6% by hawking, 6.2% by flush-chasing and 3.1% by gleaning.
Reproduction
The least flycatcher breeds in spring in highly clumped groups. The proximity of neighbors even appears to be more important than habitat quality when the bird is selecting its breeding site. The advantage that could explain such a behavior remains unclear and has been the subject of many studies. Some of the hypothesis the scholars explored include: clustering to take advantage of heterogeneous resources, to deter predators, or to keep away other species with similar resource requirements.
The courtship behavior of the least flycatcher remains largely unknown but it is thought to involve the male chasing the female through trees. The males are aggressive and sing incessantly until pairs form. Once pairs form, the female starts building their nest on either the forks of small trees like maples, birches, or ashes, or on the top of a large branch. The average height of the nest is 12 to 25 inches above the ground, but can vary from 2 to 65 inches depending on the habitat. The female builds the nest by weaving fine pieces of grass, strips of bark, twigs, lichen, spider and caterpillar webs, animal hairs and feathers, and other plant-derived materials together to form a tidy cup, a process that takes her about five days.
The female least flycatcher typically lays three to five creamy-white colored eggs, with a strong tendency towards four. The female incubates the eggs for a period of 13 to 16 days while the male remains in the area and occasionally feeds her. The eggs hatch together in June over a period of one to three days. Once the eggs hatch, both parents bring food to their newborns. The nestlings fly for the first time at the age of 12 to 17 days. They typically remain being fed by their parents for another 2 to 3 weeks.
Territoriality
The couple spends most of its time in their chosen breeding site. Their average defended territory size is 0.18 acres (8036.8 feet square), with an average distance between congener's nests of 175 feet. Both parents become particularly aggressive and territorial to both intra- and heterospecific intruders. If another least flycatcher intrudes their territory, the resident male quickly reacts, uttering a sharp note and adopting a threat-display. In its threat-display, the male attempts to look bigger by “fluffing out its breast feathers, raising its chest, extending, vibrating and bending the wings, spreading and flicking the tail up and down, and crouching”. This display lasts only a second or two before the male flies off to chase the trespasser away. If the intruder is too persistent, the resident male engages in a fight and usually wins.
Females can also engage in territorial defenses in certain occasions. If the trespasser comes in a radius of about 20 feet surrounding her nest, the female reacts. If her partner is absent, she flies off to chase the intruder and attacks if necessary. She can also work in tandem with her partner to defend their territory in scenarios where there are more than one intruder at a time. In that case, they both cooperate and chase them away, although the male is always first to react.
Migration
Least flycatchers’ age and sex groups migrate at different intervals. In Fall, adult males leave the breeding ground first, followed by adult females about a week later. The younger ones only join the rest of the group a month later. Fall migration occurs in July and early August, peaking in late-August.
In the Fall migration, it has been reported that populations living in the west first migrate east before heading south. From the East, they then fly down to the Tropics. A few of them establish themselves for the winter in southern Florida, but most of them choose to spend their winter on the coasts of Central America. Once in that region, they inhabit wooded ravines of the Pacific slope or the dense bushes and wooded edges habitats of the Caribbean side.
The least flycatcher leaves its wintering ground relatively early in comparison to other birds, arriving back north in late April to mid-May. It is thought that they can afford to arrive so early because they can subsist on small-sized insects which are out early in spring. They might also arrive early because of their highly competitive breeding site selection – a product of their habit to breed in clustered distribution.
The least flycatcher spends its breeding season in southern Yukon to central Quebec and Maritime Provinces, in Wyoming Indiana, New Jersey and in the mountains of North Carolina. The breeding season only last about 64 days, after which they return south in the Tropics.
The adult least flycatcher molts after migrating to its wintering ground, which differs from most other passerines The juveniles, on the other hand, molt prior and throughout their Fall migration. The reason why the molt of the adults is delayed remains unclear, but might be due to the highly competitive site selection of winter habitat, where the first to arrive are the first to be served.
Newly discovered retinal structure may enhance vision for some birds
Date: December 18, 2019
Source: Purdue University
A newly discovered retinal structure in the eyes of certain kinds of songbirds might help the animals find and track insect prey more easily.
The foundation of avian vision rests on cells called cone and rod photoreceptors. Most birds have four cone photoreceptors for color vision, a fifth cone for non-color-related tasks, and a rod for night vision. Each cone photoreceptor cell contains a spherical structure called an "oil droplet," which filters light before it is converted to electrical signals by the visual pigments, enhancing color discrimination.
However, the researchers have discovered a never-before-seen type of cone structure in the retina of a group of small songbirds, called flycatchers. Instead of an oil droplet, it contains a high- energy-producing cellular structure called "megamitochondria" surrounded by hundreds of small, orange-colored droplets. The researchers named this novel cellular structure a megamitochondria-small oil droplet complex, or MMOD-complex.
The discovery, made at Purdue University, is detailed in a paper that appeared in the journal Scientific Reports, as part of a collaboration with the State University of New York at Plattsburgh, the University of Wisconsin-Madison, and the University of California, Davis.
The researchers studied this retinal structure using light microscopy, transmission electron microscopy and a technique called microspectrophotometry, which measures the wavelengths of light that these structures absorb the most. The MMOD-complex works as long-pass filters, letting light with wavelengths longer the 565 nanometers -- or yellow, orange and red -- pass through, and absorbing the shorter wavelengths of green, blue and violet.
Traditional cones were present throughout the retina of these flycatchers, and their density decreased moving away from the center toward the periphery. However, the MMOD-complex photoreceptors were present only in the central region of the retina, an arrangement that could help birds detect flying insects, said Esteban Fernandez-Juricic, a professor of biological sciences at Purdue.
"The retina of flycatchers, which are sit-and-wait predatory birds, evolved a novel cellular structure in a photoreceptor that may allow them to detect, track and capture fast-moving prey, like insects," he said.
The paper's lead author was Luke Tyrrell, a former Purdue doctoral student and now an assistant professor of biological science at SUNY Plattsburgh.
"This new cone organelle has not been reported before in this form in any other vertebrate retina and may allow these birds to see their world in a different way from other animals," Tyrrell said.
A complete listing of the paper's authors is available in the abstract, and the paper is available online here. The research was funded by the National Science Foundation. Future research will be aimed at establishing the function of this structure and assess the ability of flycatchers to catch prey under different ambient light conditions.
Story Source: Purdue University. "Newly discovered retinal structure may enhance vision for some birds." ScienceDaily. www.sciencedaily.com/releases/2019/12/191218090216.htm (accessed December 19, 2019).
Journal Reference:
Luke P. Tyrrell, Leandro B. C. Teixeira, Richard R. Dubielzig, Diana Pita, Patrice Baumhardt, Bret A. Moore, Esteban Fernández-Juricic. A novel cellular structure in the retina of insectivorous birds. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-019-51774-w
Abstract
The keen visual systems of birds have been relatively well-studied. The foundations of avian vision rest on their cone and rod photoreceptors. Most birds use four cone photoreceptor types for color vision, a fifth cone for achromatic tasks, and a rod for dim-light vision. The cones, along with their oil droplets, and rods are conserved across birds – with the exception of a few shifts in spectral sensitivity – despite taxonomic, behavioral and ecological differences. Here, however, we describe a novel photoreceptor organelle in a group of New World flycatchers (Empidonax spp.) in which the traditional oil droplet is replaced with a complex of electron-dense megamitochondria surrounded by hundreds of small, orange oil droplets. The photoreceptors with this organelle were unevenly distributed across the retina, being present in the central region (including in the fovea), but absent from the retinal periphery and the area temporalis of these insectivorous birds. Of the many bird species with their photoreceptors characterized, only the two flycatchers described here (E. virescens and E. minimus) possess this unusual retinal structure. We discuss the potential functional significance of this unique sub-cellular structure, which might provide an additional visual channel for these small predatory songbirds.
www.nature.com/articles/s41598-019-51774-w