Отправлено: 06.06.22 17:17. Заголовок: Fauna of Pacific Islands
I'm making this new topic to discuss the animals living in the Pacific islands. Since there is so many islands in the world, I believe that discussing about them in only one topic would be confusing. So, for the sake of organization, I'll leave the other topic that I did to discuss only the fauna of Atlantic islands. To start this topic, I want to talk about the Easter Island. I believe that it would have an interesting fauna, with a combination of species introduced by the humans here and those from the close Eonesia. For example, the Chilean tinamou (Nothoprocta perdicaria) that was introduced here could have a flightless descendant in the Neocene of the island.
Good point. I was thinking that this bird could move like the Harris' hawk when hunting. They have sharp talons, but still can move well on land. I think that the caracara would land, chase after the prey, fly again and land. Repeating this process during the hunt.
Отправлено: 12.06.22 19:36. Заголовок: By the way, I finish..
By the way, I finished another description.
White crested pigeon (Lophocolumba elegans) During the Holocene, the man introduced many species to other continents. Those that were able to survive left descendants in the Neocene. The white crested pigeon is one of them. This species is a descendant of the rock pigeon (Columba livia) which was introduced by the humans in Easter Island. This species now inhabits all areas of the Island, being one of the members of its endemic fauna. The white crested pigeon has 40 cm of length and 72 cm of wingspan. The head, back and rump are slate-gray. The tail is dark gray with white tips. Their main characteristic is the pure white crest coming from the cere to the forehead. Their neck, chest and belly are also white, while the wings are iridescent green. The beak is red, while the legs and feet are pale pink. The male has a bright blue cere, while it's pale in the females and subadults. These birds are omnivorous, but prefer plant matter: chiefly fruits and grains. They forage both in open areas and in trees. Larger flocks of white crested pigeons can be seen feeding on fruits at trees. The white crested pigeon is gregarious, forming flocks of 20 to 50 individuals. Such groups can become larger when there is too much food. They are socially monogamous, but extra-pair matings do occur, often initiated by males. This bird breeds at any time of the year, but peak times are spring and summer. Nesting sites are along coastal cliff faces, sometimes close to the colonies of seabirds. Due to their ability to produce crop milk, pigeons can breed at any time of year. During courtship, the male will stay on the top of a tree cooing loudly. If a female is interested, she will land in a branch near to him. Then, he will start to puff up the feathers on his neck to appear larger, while flapping his iridescent wings. At first, the female invariably flies a short distance away and the male follows her until she stops. At this point, he repeats the same ritual in front of her. The male then proceeds to feed the female by regurgitating food, as they do when feeding the young. The male then mounts the female. The mating is very brief, with the male flapping his wings to maintain balance on top of the female. The nest is a flimsy platform of straw and sticks, laid on the ledge of rocks, under cover, often on cliffs. Two white eggs are laid; incubation, shared by both parents, lasts 19 days. The newly hatched nestling has pale yellow down and a flesh-coloured bill with a dark band. For the first few days, the chicks are tended and fed exclusively on "crop milk". The pigeon milk is produced in the crops of both parents. The fledging period is about 30 days. They reach sexual maturity with 2 years and have a lifespan of 19 years, but many are killed early by predators.
Отправлено: 16.06.22 03:24. Заголовок: I was thinking if Eo..
I was thinking if Eonesia could have some species of passerines that have great sexual dismorphism, like the birds-of-paradise. They could also be descendants of South American Thraupidae. Or perhaps of the Pipridae (manakins).
Отправлено: 16.06.22 05:48. Заголовок: In one article I had..
In one article I had seen an info on the opposite trend in the evolution of island-dwelling birds. Lesser species variety lowers the competition, so the features of sexual dimorphism are less expressed in island species compared to its mainland relative.
Отправлено: 16.06.22 17:12. Заголовок: Автор пишет: Lesser..
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Lesser species variety lowers the competition, so the features of sexual dimorphism are less expressed in island species compared to its mainland relative.
This is interesting. What if this descendant of the Thraupidae have both males and females with similar appearance and doing elaborated mating rituals together?
Yes, and they may look like female more probably JOrnitho пишет:
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doing elaborated mating rituals together?
here I have lots of serious doubts. If the coloration turns duller, the mating ritual seems to tend to simplification compared to mainland species. Mating ritual is an energy-demanding action, and in island conditions (= limited resources) it seems to be less profitable for survival, than in conditions of strict competition of mainland habitats.
Отправлено: 17.06.22 00:37. Заголовок: Автор пишет: If the..
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If the coloration turns duller, the mating ritual seems to tend to simplification compared to mainland species.
I understand. Would be possible for the males of these birds to have complex songs? They could still use it for attract females and to show that they are health.
Отправлено: 21.06.22 17:48. Заголовок: I finished the descr..
I finished the description of some of the Eonesian tanagers.
Atarapan symphonic tanager (Paratangara atarapaensis) With the passing of the Holocene to the Neocene, the movements of tectonic plates caused the changes in the disposition of the continents and the appearance of new islands. The islands of Eonesia are some of these that appeared during this new geological period. These new habitats gave opportunity for the animals that could reach them. There they found new resources and evolved into new species. The symphonic tanager of the Genus Paratangara, part of the Family Thraupidae, is endemic to the islands. Their ancestors reached Eonesia coming from Central America. The type species of the genus is the Atarapan symphonic tanager, an endemic species to the forests of the Atarapa islands. The Atarapan symphonic tanagers have 15 cm of length and 27 cm of wingspan. These birds have a bright red plumage on the head, neck, back and rump. The chest and belly are bright green. The wings, ear-coverts and tail is black. While there wasn’t a great sexual dismorphism, the females' plumage is a bit duller. The beak and legs are dark gray. These birds eat mainly fruits and small buds. The fruits are usually swallowed whole, with the seeds being regurgitated. Insects are also taken, mainly from the underside of branches. The Atarapan symphonic tanager is usually found in pairs, but sometimes small groups are formed. The males have elaborate songs that they use to attract the females. This species is monogamous, with pairs staying together for the rest of their lives. While they are mostly silent, the females will vocalize with the males. They form a "duet" that is used to strengthen the pair's bond. When they are in a flock, the birds will vocalize in such a way that reminds of a natural symphony. The parents work together to build the nest, but only the female incubates them. One to three, usually two, dark-marked whitish to gray-green eggs are laid in a deep cup nest in a high tree fork. Incubation lasts for 14 days with the chicks fledging after 17 days. They reach sexual maturity with 11 months and have a lifespan of 12 years. The Genus Paratangara have other two species that also inhabits Eonesia:
Burotu symphonic tanager (Paratangara burotuensis) This species inhabits the Burotu islands. They have 13 cm of length and 25 cm of wingspan. These birds have a bright orange plumage on the head, neck, back and rump. The chest and belly are bright green. The wings, ear-coverts and tail is black. Their song is also different of the Atarapan species.
Fisaga symphonic tanager (Paratangara fisagaensis) This species inhabits the Fisaga islands. They have 16 cm of length and 31 cm of wingspan. These birds have a bright yellow plumage on the head, neck, back and rump. The chest and belly are bright bluish-green in the males, with the females being a duller green. The wings, ear-coverts and tail is black. Their song is also different from the other previous species.
Отправлено: 22.06.22 06:40. Заголовок: I finished the descr..
I finished the description of the owl-like harrier of Eastern Island.
Owl-harrier (Strigocircus solitarius) The human actions during the Holocene caused the collapse of many ecosystems. Easter Island was one of these cases. This place was completely deforested and many of its endemic species perished. However, with the arrival of the Neocene it was able to recover, developing a new endemic fauna. One of the species that is now living here is the owl-harrier, a descendant of the cinereous harrier (Circus cinereus) that reached the island after the disappearance of humanity. When their ancestors reached the island, they found that no species of owl lived here. This way the owl-harrier evolved to fill the niche of these birds. This bird is crepuscular, being more active during the dusk and early hours before dawn. The female of the owl-harrier is larger than the male with an average size of 46 cm compared to the male's 40 cm. The wingspan is 90 to 115 cm. Both sexes have a 40 cm long tail. Morphologically, these birds are similar to an owl. They have large eyes that allow them to see during the night and a good hearing. Their plumage is dark grey above with black wingtips and a dark brown rump. The underparts are pale grey, with a rufous streaked belly. The face is chestnut brown with a black border. The beak and legs are dark grey. This species eats mainly rodents and bats, but also birds that are sleeping in branches during the night. Insects are also eaten, but more occasionally. While being monogamous and sharing a territory, the pair stays separated during most of the year, with only some occasional meetings happening. They come together durig their breeding season, which starts during the summer. During this period, males and females reforce their bond by engaging in nocturnal aerial courtship displays and chatter very loudly. This is the only period that they vocalize more frequently, being silently birds most of the time. The nest is built hidden in rock crevices. Nests are made of sticks and are lined inside with grass and leaves. Four to eight whitish eggs are laid by the female, who incubates them for 32 days. When incubating eggs, the female sits on the nest while the male hunts and brings food to her and the chicks. The male will help feed chicks after they hatch, but does not usually watch them for a greater period of time. The male usually passes off food to the female, which she then feeds to the young, although later the female will capture food and simply drop into the nest for her nestlings to eat. The chicks fledge at around 36 days old, though breeding maturity is not reached until 2 years in females and 3 years in males. Their lifespan is of 22 years.
Отправлено: 06.07.22 04:29. Заголовок: Beyond working in id..
Beyond working in ideas for plants of Easter Island, I also thought about some other animals that could fill some niches here: a hamster-like rat eating fallen fruits and tubercules (sweet potato and yam), a parakeet to eat fruits of palm trees, a wren or warble to eat insects, an aquatic rallid and a dwarf descendant of the chicken to eat in the forest floor. Is it too much for the island? With its size, the false-nandu would be capable to reach food in places that the dwarf chicken couldn't and the hamster-like rat would be the prey of the owl harrier.
Rapa Nui thrush (Turdus leucourus) The human actions during the Holocene caused the collapse of many ecosystems. Easter Island was one of these cases. This place was completely deforested and many of its endemic species perished. However, with the arrival of the Neocene it was able to recover, developing a new endemic fauna. One of the species living here is the Rapa Nui thrush, a descendant of birds that arrived on the island from South America. The Rapa Nui thrush has 23 cm of length and a wingspan of 42 cm. This species has a brownish-black plumage in the upperparts and wing, while the chest and belly are creamy. Their tails have white tips. The beak is yellow in the males and light gray in the females. Both sexes have pale gray legs and feet. This species is a generalist feeder, principally foraging for invertebrates but also taking fruits. It tends to swallow fruits whole, but can peck those that are too large. Activity peaks are at dawn and dusk. The nesting season of the Rapa Nui thrush occurs during the spring. The male will find a suitable territory to build a nest and will sing constantly to attract the female. This bird is a polygamous species, with the male mating with two females, usually one older than the other. Differently of other polygamous birds, all of them raise the young. Together, the three birds build an open-cup nest, usually 4 to 5 meters above ground. Inside it both females will lay two to three creamy white eggs, with the older female being the first to lay them. During 13 days, the females will share the incubation while the male defends the territory. The female that isn’t busy incubating, will help the male in his task. Together they will vocalize in duet to show that the territory is theirs. The nestlings are attended by the three birds. They fledge within 12 days, but continue receiving food from the adults for more three weeks. After that they are expelled from the territory. Once the young leave, the bond between the adults is broken. However, they will usually come together once again during the next nesting season. Sexual maturity is reached with 2 months and they have a lifespan of 8 years.
Heavy-billed parrot (Lophopsitta rhyncogravis) The human actions during the Holocene caused the collapse of many ecosystems. Easter Island was one of these cases. This place was completely deforested and many of its endemic species perished. However, with the arrival of the Neocene it was able to recover, developing a new endemic fauna. One of the species living here is the heavy-billed parrot. Its closest relatives are the parrots that live in Eonesia. This bird is found widespread throughout the island. The heavy-billed parrot has 28 cm of length and 57 cm of wingspan. The plumage is mainly green, except for the blue crown and reddish-orange in the face, neck and upper chest. The primaries and secondary feathers are violet. The tail is rounded with yellow tips. These birds have a large, heavy and strong beak. The beak is black, while the legs are pale gray. This species feeds on a number of fruits and seeds. They use their strong beak to break the hard shell of the Rapa Nui coconut, a descendant of the coconut that was introduced by the humans in the island. The heavy-billed parrot is a gregarious bird, forming flocks of 15 to 40 individuals. These birds are monogamous breeders who nest in tree cavities. Each mated pair of parrots needs their own tree for their nest. The female lays two to four eggs, which she incubates for 30 days while being fed by her mate. The adults defend their nesting sites. The chicks require feeding and care from their parents in the nest. The parents take care of them until 5 weeks after they are fledged. Young leave the nest at the age of 12 weeks and reach sexual maturity with 2 years. They have a lifespan of 32 years, but many are killed by the Rapa Nui caracaras before reaching this age.
Timid rail (Pardirallus timidus) The human actions during the Holocene caused the collapse of many ecosystems. Easter Island was one of these cases. This place was completely deforested and many of its endemic species perished. However, with the arrival of the Neocene it was able to recover, developing a new endemic fauna. One of the species living here is the timid rail, a descendant of the plumbeous rail (Pardirallus sanguinolentus) that arrived in the island coming from South America and evolved here to this new species. This species lives close to freshwater reservoirs, hidden among the reeds. The timid rail has 27 cm of length with very reduced wings, making it impossible for them to fly. It has a long, downward curving pale gray bill and is grayish brown with a pale chestnut breast and conspicuous whitish rump patch. This plumage allows these birds to camouflage in the reeds. The legs are dark gray. These birds are omnivorous, feeding on invertebrates and plant material. When foraging, they rarely leave the cover of reeds and bushes, hoping to avoid the attack of flying predators. The timid rail is a mostly solitary bird, with only pairs living together. Due to staying hidden in the reeds and bushes during most of the time, it's most common to hear their loud callings. The pair build the nest together and share the incubation of the eggs. The structure is made of branches and pieces of grass, constructed among the vegetation. The female lays a clutch of 7 white eggs with brown spots. The eggs are incubated for 14 days. The brown, downy precocial chicks soon leave the nest but are fed and protected by the parents. Fledging occurs after four to five weeks. They reach sexual maturity with 18 months and have a lifespan of 15 years.
Dwarf junglefowl (Nanogallus carunculatus) During the Holocene, the man introduced many species to other continents. Some only because of their ornamental value, while others were introduced because they were useful for agriculture. The domestic chicken (Gallus domesticus) was introduced in several parts of the world. With the disappearance of humanity, they survived and continued to evolve. The chickens that were introduced in Eastern Island evolved in isolation, giving rise to the dwarf junglefowl. This species lives widespread across the island, but prefers to stay in areas with shrub cover to avoid being attacked by Rapa Nui caracaras. The dwarf junglefowl have 34 cm of length, with males being slightly larger than females. The wingspan is 42 cm. This species still has the ability of flying, but rarely does it. The lack of ground predators in Easter Island makes the ability of flying irrelevant. The plumage of this species is a mix of brown, cream and grey. The breast and back are mottled in dark brown, chestnut, and cream colours, with grey spots on the flanks and above. The breast and neck is reddish-brown. The males have bright red bare skin in the face and an elongated red fleshy wattle that dangles from its throat. They also have iridescent green feathers in the tail. The females lack the wattles and iridescent feathers, with their tails being dark brown. The legs of males are red and have spurs while the yellow legs of females usually lack spurs. Both sexes have dark grey beaks. This species spend most of their time foraging for food by scratching the ground for various seeds, fallen fruit, and insects. During the night, rather than perching in a tree, they search for an area with dense shrubs to rest. This way they avoid the attack of the owl-harriers. The dwarf junglefowl have a polyandric reproductive strategy, with a female being linked with two or three males that form a pride of sorts. These males are usually siblings. The female pairs with the alpha male of the pride and nests on the ground, hidden among the bushes. Her eggs are cream with a yellow or pink tint with purple spots. The hen incubates her eggs, while the alpha male guards her nest from a nearby perch during the nesting season. The other males remain in close proximity, and guard the nesting territory from intruders or potential predators, such as rival males, or predatory birds. The eggs are incubated for 18 days. As soon as the chick hatches, they are already capable of leaving the nest. Chicks fledge in about 4 to 5 weeks, and at 12 weeks old they are chased out of the group by their mother. At this point they start a new group or join an existing one. Sexual maturity is reached at 5 months, with females taking slightly longer than males to reach maturity. They have a lifespan of 13 years.
Rapa Nui rat (Geomurinus brachyurus) While humans purposefully introduced some species in new habitats, others were inadvertently introduced. The rats (Rattus) followed the humans to several places, benefiting from their presence. When they were extinct, some of these rodents were able to survive and continue their evolution. In Easter Island, the populations of rodents that survived evolved into an endemic species, the Rapa Nui rat. The Rapa Nui rat has 13 cm of body length, with a short tail of 5 cm. Their physical appearance reminds that of a Cricetidae hamster, with them having a fossorial lifestyle. They have strong forelimbs that are used to excavate the ground to make tunnels to be used as their dens. It has reddish-brown fur with a white underside and three black stripes on the back. This species feeds mostly on fruits, roots and seeds. Insects and eggs are eaten very occasionally. They spend the day on their dens, only leaving to forage at night. The Rapa Nui rats are very territorial and intolerant of each other, with attacks against each other being commonplace. Exceptions do occur, usually when a female and male meet when the female is in heat, but even so, the female may attack the male after mating. Even siblings, once mature, may attack one another. Same-sex groups of siblings can stay with each other until they are about eight weeks old, at which point they will become territorial and fight with one another, sometimes to the death. Infanticide is not uncommon among females, usually due to stress from the environment. They also eat their dead young. These rodents mark their burrows with secretions from special scent glands on their hips. The males in particular lick their bodies near the glands, creating damp spots on the fur, then drag their sides along objects to mark their territory. Females also use bodily secretions and feces. They can have two to four litters per year. The Rapa Nui rat has a gestation of 15 days, giving birth to a litter of 1 to 12 that wean after three weeks of pregnancy. It communicates by squeaking or with ultrasound. The females are sexually mature with eight weeks, while the males only become mature with six months. Their lifespan is 3 years, but many are killed by predators, such as the owl-harrier.
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