Choker

Choker
Kangaroo eagle (light morph)
Systematics
Order : Birds of prey (Accipitriformes) Family : Hawk species (Accipitridae) Subfamily : Harpiinae Genre : Morphnus Type : Choker
Scientific name of the  genus
Morphnus
Dumont , 1819
Scientific name of the  species
Morphnus guianensis
( Daudin , 1800)

The crested eagle ( Morphnus guianensis ) is a large bird of prey from the hawk family . The species, which is widespread in the tropical forests of the American continent, was first described scientifically in 1800 by the French zoologist François-Marie Daudin . The crested eagle is currently the only representative of the genus Morphnus .

Description and behavior

features

Despite its size and conspicuous appearance, the crested eagle is a species that has not been researched so far, so detailed descriptions are only available for a small number of specimens. As with many birds of prey, the females are significantly larger and heavier than their male counterparts. While adult females can weigh 1850 to 1975 g, males only reach a weight of 1200 to 1275 g. However, there is no more extensive sexual dimorphism . The average height is between 79 and 89 cm. Distinctive features of the crested eagle are its downwardly curved, matt black beak and the conspicuous hood on the back of the bird's head. The strong, featherless legs and toes are yellowish in color and end in black claws. Wax skin and reins are dark gray, but the iris of the eye is brown. The species shares its habitat with the harpy eagle , with which it is occasionally confused due to the similar coloring of the plumage. Harpies, however, are again considerably larger and more massive than strangled eagles. Furthermore, the significantly longer tail of the crested eagle can be used as a clear distinguishing feature.

Regardless of gender or geographical distribution, the species has a pronounced dimorphism . The plumage of the more common, light Morph is pale brown to grayish in color on the head, neck and upper chest area, the throat is white. In the lower chest area and on the stomach, the white is criss-crossed with narrow, cinnamon-colored stripes. The elongated feathers of the hood have a white base that becomes darker towards the tip. The back and shoulders are colored black, the contour feathers there show white tips. This pattern is continued on the control feathers, but there are also three gray, mousy brown speckled bands. Towards the wings, the color of the contour feathers changes to brown and gray tones, interspersed with blackish stripes. The wing feathers are predominantly blackish, with brown speckles and darker tips. The darker or "striped" morph is a melanistic form and differs from the light morph by a blackish basic color with white banding in the lower chest and stomach area. Furthermore, this shape has white contour feathers with black stripes on the lower wings. Some sources also differentiate another, "extremely dark" morph for individuals with particularly pronounced melanism.

Young crested eagle in Darién , Panama

Juvenile crested eagles are initially uniform in color and are more similar in color to the light morph. The birds need four years until their plumage corresponds completely to that of the adult birds. The development towards the dark morph is only visible after the first full moult on the basis of darker feathers on the head and chest as well as less contrasting contour feathers on the wings. Until the first moult, the young birds are predominantly whitish in color, the wing feathers are darker, with pale spots and stripes. The tail feathers show gray and brown tones, with seven to ten narrow, black stripes. With advancing age, the plumage of all forms takes on an increasingly darker color.

behavior

The general behavior of the species outside of the breeding season has been little researched. It is known that the birds lead a largely solitary way of life and only come together in pairs to reproduce. Black-necked eagles need very large territories of at least 100 km², over which they can occasionally be observed while gliding. The active defense of the territory against conspecifics apparently does not take place. Threatening gestures by nesting females and young birds towards vultures flying by could, however, indicate possible territorial behavior towards other species. The species is a resident bird in its entire range .

nutrition

The idol snake ( Boa constrictor ) is one of the largest prey of the strangler

Corded eagles feed on a purely carnivorous diet and, due to their size, can hunt a wide range of prey. These include above all snakes (mainly green dog-headed snakes , idol snakes and chicken-eaters ) and tree-dwelling, mostly nocturnal mammals with a head-trunk length of around 20 to 35 cm, including Central American tree prickles , wrinkled bears , various opossums and small bears . During several months of observation of a nest in the Guatemalan Tikal National Park , a 126 × 8 cm idol snake was the largest animal captured by the adult birds. In addition, smaller monkeys such as common squirrel monkeys and young red-faced spider monkeys are regularly attacked. When appropriate, other birds are also accepted as part of the diet. In Brazil, kangaroo eagles have been seen ambushing shako chickens and trumpeter birds under trees with lots of fruit . The hunting behavior of the species is variable, the birds often circling alone or in pairs at great heights above the forest looking for prey. Another regularly used method is to wait in a seat control room directly below the canopy. If the prey is spotted on the ground or in the trees, the birds rush down on them and hit them with their claws. Juvenile strangler eagles are also known to search tree hollows and holes in the ground for food. To do this, they put their head or a leg into the opening and try to grab the prey with their beak or claws. This behavior has not yet been directly observed in adult birds, but the fact that nesting kangarooses brought their young carcasses of nocturnal animals during the daytime, which usually spend the day in their burrows, suggests that this hunting method can also be used in adulthood is still applied. In addition, strangled eagles plunder the nests of other, smaller birds of prey and prey on their nestlings.

Reproduction

Unlike other aspects of its behavior, the species' reproduction is relatively well documented. After the animals come together in pairs, copulation usually takes place in March, the actual breeding process begins in April or May. A pronounced courtship behavior taking place in the run-up to the mating could not be determined. For the construction of the nest, particularly tall trees are typically selected that protrude over the general canopy and thus offer a good all-round view. The nest is created in a fork of branches and constructed from dead branches up to one meter long. A clutch size of two eggs is typical in the wild, but three or four eggs can also be found in captivity. However, the actual rearing of more than one young bird per clutch has not yet been observed. The eggs have a matt, creamy white color without any further markings. Their average size is around 60 × 50 mm, with a weight of around 90 g immediately after oviposition. They are almost exclusively incubated by the female adult bird, while the male is responsible for providing food during this time. The exact time until the young hatch has not yet been determined, but based on observations in related species such as the harpy eagle or the great hooded eagle, it is estimated to be around 48 to 51 days. After hatching, the female remains at the nest almost continuously for about a month and hoards the young bird. While the male adult bird continues to bring food, this is only passed on to the young by the female, and the cleaning of the nest takes place exclusively by the female. The male only spends a few minutes at the nest. After about 30 days the young bird can move around in the nest, another ten days later it begins to utter vocalizations in response to "threats" from birds flying past. At around 80 days of age, the young learns to eat food independently; the entire nestling period can last between 100 and 110 days. Even after they have fledged, the offspring do not leave the immediate vicinity of the nest for a long time and remain dependent on the care provided by their parents. Young crested eagles only become truly independent after up to 16 months, which means that successful couples can only raise a young every two to three years.

In 2004, researchers observed a female crested eagle near Quintín, Panama , who was involved in the rearing of a nestling of harpy eagles over an extended period of time and brought it multiple food. This behavior was apparently tolerated by the nestling's parents, although harpies usually actively defend their territory against other birds of prey. The nestling did not behave any differently towards the strangler than towards its own parents. The reasons for this behavior - which is also not unknown in other species - are not fully understood, but one possible explanation is that the female gobble eagle recently lost its own brood and had transferred its breeding behavior to the harpy cub.

Vocalizations

The strangler's eagle is generally considered to be a less vocal species. Its most frequently heard call is said to be similar to that of the black buzzard ( Buteogallus urubitinga ), which has a similar distribution area. It is described as a "high- pitched , high - pitched whistle" that repeats itself several times and is intended to sound like wheyr - wheyr - wheyr - wheyr - wheyr - wheyr - br , with the emphasis on the short, last syllable. During the breeding season, this call is also used by the male bird as a contact call when it approaches the nest to bring prey. The female responds with a high, high-pitched wee - hee and the flapping of her wings.

Spread and endangerment

The crested eagle prefers large, pristine rainforests as a habitat , but may be able to get along in drier and more open areas as long as there is sufficient forest for the birds to hunt. The species is more of a lowland inhabitant and avoids higher regions, but occurs occasionally up to heights of over 1000, in Ecuador also up to 2200 m. The range includes large parts of South and Central America, but is not contiguous. In Central America it extends from northern Guatemala via Belize to northern Honduras . Apparently only isolated island populations exist in Nicaragua and Costa Rica . Further noteworthy evidence of the strangler eagle was found in eastern Panama and western Colombia . The largest contiguous area extends in a wide, crescent-shaped arc from central Colombia over the east of Ecuador and Peru , the north of Bolivia and Amazonia to the Atlantic coast in Suriname , Guyana and in the extreme east of Venezuela . It also occurs in parts of Paraguay and Argentina . In the 2010s, some relic populations were also found in the fragmented Atlantic forests of Brazil, where the species had been considered extinct since the 19th century. Basically, the species is considered rare, which is also related to the size of the territories of individual individuals. Due to their way of life and their extensive space requirements, kangaroos are one of the species that are particularly threatened by habitat loss and fragmentation due to increasing deforestation. Furthermore, direct hunting and hunting pressure on potential prey by humans also represent a threat. Researchers assume that the population of the species has been declining continuously for several decades. However, observations from southern Mexico , Nicaragua and Costa Rica show that the species has apparently recently colonized regions in which it could not be detected in the past. Overall, the IUCN lists the crested eagle as near threatend as of 2017, i.e. does not consider the long-term conservation of the species to be assured. Furthermore, the kangaroo is mentioned in Appendix II of the Washington Convention on the Protection of Species , so commercial trade with representatives of the species is restricted and only permitted after appropriate testing.

Systematics

Both the species Morphnus guianensis and the genus Morphnus are currently considered to be monotypic , geographical variations are also missing. The presence of two visually very different morphs meant that they were listed as separate species in the specialist literature for a long time. Daudin described the species for the first time in 1800 under the scientific name Falco guianensis and thus placed it among the falcons , whereby he had a copy of the light morph for his first description . The darker Morphe, however, was initially described as Morphnus taeniatus ( Gurney , 1879) and listed as a separate species. It was not until 1949 that the two ornithologists Carl Eduard Hellmayr and Henry Boardman Conover discovered that both morphs were one and the same species.

literature

• David F. Whitacre, Juventino López, Gregorio López: Neotropical Birds of Prey: Biology and Ecology of a Forest Raptor Community . Ed .: David F. Whitacre. Cornell University Press, Ithaka / London 2012, ISBN 978-0-8014-4079-3 , pp. 164–184 ( limited preview in Google Book search).

Web links

Commons : Red-tailed Eagle ( Morphnus guianensis )  - Collection of images, videos, and audio files

• Recordings of vocalizations at xeno-canto.org

Individual evidence

1. ↑ Whitacre, López & López, pp. 164-165
2. ^ ^{A b} Jedediah W. Smith: Crested Eagle Morphnus guianensis - Appearance. In: birds.cornell.edu. TS Schulenberg, 2012, accessed on February 14, 2020 (English). 
3. ↑ ^{a b c} Felipe Bittioli Rodrigues Gomes, Tânia M. Sanaiotti: A review of the distribution of the Crested Eagle, Morphnus guianensis (Daudin, 1800) (Accipitridae: Harpiinae), including range extensions . In: Revista Brasileira de Ornitologia . tape 23 , no. 1 , 2015, p. 36-63 , doi : 10.1007 / BF03544289 .
4. ^ Jedediah W. Smith: Crested Eagle Morphnus guianensis - Behavior. In: birds.cornell.edu. Cornell Lab of Ornithology, 2012, accessed February 19, 2020 . 
5. ^ Whitacre, López & López, p. 180
6. ↑ Whitacre, López & López, pp. 166-170
7. ↑ Jedediah W. Smith: Crested Eagle Morphnus guianensis - Diet and Foraging. In: birds.cornell.edu. Cornell Lab of Ornithology, 2012, accessed February 19, 2020 . 
8. ↑ ^{a b} Whitacre, López & López, p. 170
9. ^ Whitacre, López & López, p. 172
10. ↑ Jedediah W. Smith: Crested Eagle Morphnus guianensis - Breeding. In: birds.cornell.edu. Cornell Lab of Ornithology, 2012, accessed February 20, 2020 . 
11. ↑ José De Jesús Vargas González, Rodolfo Mosquera, Mark Watson: Crested Eagle (Morphnus guianensis) feeding a post-fledged young Harpy Eagle (Harpia harpyja) in Panama . In: Ornitologia Neotropical . tape 17 , no. 4 , 2006, p. 581-584 .
12. ^ Jedediah W. Smith: Crested Eagle Morphnus guianensis - Sounds and Vocal Behavior. In: birds.cornell.edu. Cornell Lab of Ornithology, 2012, accessed February 20, 2020 . 
13. ↑ Rodrigo Costa Araújo, Luís Fábio Silveira, Daniel Eduardo da Luz: Rediscovery of the Crested Eagle Morphnus guianensis (Daudin, 1800) in the fragmented Atlantic Forest of Bahia, Brazil . In: Revista Brasileira de Ornitologia . tape 23 , no. 1 , 2015, p. 25-28 .
14. ^ Jedediah W. Smith: Crested Eagle Morphnus guianensis - Distribution. In: birds.cornell.edu. TS Schulenberg, 2012, accessed on February 18, 2020 (English). 
15. ^ Crested eagle Morphnus guianensis. In: iucnredlist.org. BirdLife International, 2017, accessed February 18, 2020 . 
16. ↑ Morphnus guianensis. In: cites.org. Retrieved February 18, 2020 . 
17. ^ Whitacre, López & López, p. 165