Birds vs bats


Birds vs bats

In this rare frame you see Jay ( Garrulus glandarius ), Which caught a bat. The victim of a successful hunter was watery night ( Myotis daubentonii ) Or pond ( Myotis dasycneme ). The picture was taken at the end of April this year in the Moscow region.

Birds and bats (Chiroptera) are the only modern vertebrates capable of active flight, the former mainly leading a daytime lifestyle, and the latter being nocturnal. This separation most likely arose more than 50 million years ago. It can be assumed that it helps the two groups to avoid competition for airspace, but several facts speak against this hypothesis at once. For example, ecological niches insectivorous bats and birds do not intersect so much that they needed to be "bred" in time. Competition with birds also cannot explain the nocturnal 3–3–343 lifestyle. Birds of the Air and fruit-eating bats from the family leafy (Phyllostomidae), because they eat fruits that are available at any time of the day.

Today, scientists consider a more plausible alternative explanation, according to which bats are nocturnal, so as not to become prey for birds. Bats could encounter this problem already at the first stages of evolution, in the early 3-3-3351. Eocene 3-3-33334. . Then many groups of insectivorous birds, including swifts and swallows, have not yet appeared, so that competition with them could not prevent the bats from occupying the niche of daytime insect hunters. However, they were not allowed to do this by the time predatory and omnivorous birds appeared by that time. For some reason, the threat posed by them was so great that the early bats had to become nocturnal.

This hypothesis is supported by the fact that on some oceanic islands, where birds of prey and omnivorous birds are few or absent, bats carry a daily life. One of these species is Azores party ( Nyctalus azoreum ), Endemic Azores archipelago . On its native islands coronal and falconous do not nest at all, from hawk-like occurs. only endemic subspecies Buzzard ( Buteo buteo rothschildi ), And from owls - long-eared owl ( Asio otus ). On the island San Miguel also inhabited now extinct scoop Otus frutuosoi , but she most likely flew badly and ate insects. Some island populations of widespread species of bats also switched to daylight activity, for example, Indian horseshoe raccoons (3-3-33337. 3-3-338. Rhinolophus lepidus 3-3-33334. 3-3-33338.) From the Malay island of Tioman (3-3-3391. Tioman Island 3-3-33333. Hipposideros ruber [/i]) From the island Sao Tome off the west coast of Africa. Similar examples exist among winged birds: a subspecies of the Nicobar flying fox ( Pteropus melanotus natalis ) With lead a daily lifestyle. Christmas Island and Samoan flying fox ( Pteropus samoensis ) from the archipelago Samoa .


Birds vs bats

Azores Vespers - one of the few bats that lead a daytime lifestyle. Photo © stefanvanschaik from flickr.com


If bats really became nocturnal due to birds, then this strategy still works successfully: with the exception of most owls, representatives of species potentially dangerous for bats mostly hunt during the day. Nevertheless, from time to time, winged mammals are still 3–3–3137. become victims of diurnal birds. They are especially vulnerable if they leave the shelter at a wrong time, where they spend daylight hours. This is exactly what happened with the nightlight from the main photo. She rested in an abandoned quarry, but during the day something disturbed her and made her fly out. I noticed a disoriented bat, caught in the air and ate a jay. Like all corvids, this bird will never give up easy prey.


Birds vs bats

Jay cracking down on an unfortunate nightlight. Photo © Alexandro Pedrovich , Moscow region, April 2020


However, sometimes even a shelter cannot protect bats from birds. In 2009 German scientists published article , which described the unusual hunting tactics 3-3-3167. great tits (3-3-33337. Parus major 3-3-33338.) From the 3-3-3171 massif. Bukk in northeast Hungary. These birds learned to kill and eat bat dwarf ( Pipistrellus pipistrellus ), Wintering in the local cave Ishtallosh-Kyo .

Observations from 2004–2006 showed that in winter days, flocks of tits regularly look for food near the entrance to the cave. Hearing the squeak of an awakened bat, they penetrate inside and carefully examine the crevices in the walls and ceiling in search of its source. The bird kills the discovered bat with its beak, carries it out and pecks on the nearest tree, eating the brain, meat and internal organs. Given that the weight of the dwarf bat does not exceed 8 g, this is easy prey for the great tit (weighs from 14 to 21 g).

Over two years of research, scientists have recorded 18 cases of successful hunting of tits for bats. They also found out that birds attack bat only during the period of non-feeding. When a feeding trough was hung near the cave, tits chose to feed on it and hunted bats much less often.


Birds vs bats

Left - Great tit attacked tap dance . Although the titmouse cannot be called a specialized hunter, this aggressive and intelligent bird uses every opportunity to find food, especially in difficult times. Sometimes it even kills birds of a size comparable to it for the sake of their meat (or when competing for hollows - see 3-3-3205. The intensity of competition for nests between titmouse and flycatchers depends on climatic conditions 3-3-33334., "Elements", 02/14/2019). See also 3-3-3207. video (caution, not for the faint of heart). Photo © Lassi Kujala from is.fi . Right - Dwarf-bat, who became victims of tits. Photo © Peter Estok from newscientist.com


One of the authors of the study first observed the hunting of great tit for bat from the cave of Ishtallosh-Kyo in the winter of 1995-1996. Theoretically, this individual could be the ancestor of birds that came to the center of attention of ornithologists ten years later (the average life of tits in the wild is 3–3–3221. 1.5 years 3–3–3334.). Then it can be assumed that the hunting skill of Hungarian tits is not a unique feature of individual individuals, but a real cultural tradition that is transmitted within the population through learning through observation (see 3-3-33223. Cultural traditions in birds are based on social learning and conformism 3-3-33334., “Elements”, 12/08/2014). Perhaps great tits have similar ability in other European countries - at least, unconfirmed reports of their hunting for wintering bats came from Sweden and Poland.

Many species of bats spend daylight hours gathering in large colonies in safe places - for example, in caves, human buildings or the crowns of large trees. However, they become vulnerable when they leave en masse in the evening and morning twilight. places of rest and come back. A live stream, consisting of thousands of individuals, attracts some birds of prey, for whom this is a real buffet, able to satisfy up to half of the daily food requirements. For example, in North America red-tailed ( Buteo jamaicensis ) And Svenson buzzards (3-3-33337. B. swainsoni 3-3-33338.), as well as 3-3-33235. Mexican Falcons ( Falco mexicanus ) Prey on Brazilian folded lips ( Tadarida brasiliensis ) When they fly out of the caves. In South Africa, silver dwarf eagles exhibit similar behavior ( Hieraaetus wahlbergi ), African Goshawks ( Accipiter tachiro ) And wintering tackles ( Falco subbuteo ).

Svenson buzzards prey on the Brazilian clawfish leaving a cave in the desert of the US state New Mexico

For most feathered predators, bats are not the main prey. However, one of their species has become a specialized bat hunter. It's about wide-range kite ( Macheiramphus alcinus ) - a medium-sized bird of prey, different subspecies of which is inhabit tropical Africa and Madagascar, Southeast Asia and Indonesia, as well as 3-3-33273. New Guinea . Contrary to the Russian name, this species is not related to the usual Kite from the genus Milvus : at different times he was brought closer to beetles 3-3-33334. (Perninae) and smoky kites (Elaninae), and today they are considered a relative of harpies ( Harpiinae ).


Birds vs bats

Wide kite. Pay attention to the large eyes, which indicate specialization in hunting at dusk, and a huge section of the mouth, allowing you to swallow the whole prey. These features make the wide-kite kite more similar to Goat or shearing than a bird of prey. Photo © Ian White from flickr.com


Bats weighing 20–75 g make up the majority of the diet of the long-haired kite (besides them it is 3–3–3313. Eats 3–3–3334. Insects and small birds, especially swallows and swifts nesting in caves). Unusual food addictions forced the kite to switch to a twilight lifestyle and acquire a number of useful anatomical devices. For example, huge eyes allow this bird to see prey in low light, and a wide open mouth to swallow caught prey entirely in the air to make better use of the short hours of evening and morning twilight, when bats congregate at resting places, and it is easiest to catch them. Observations 3-3-33315. show , that the prey that fell into the claws of the kite, after six seconds, is in his stomach.

Even the nesting times of wide-necked kites are synchronized with the life cycle of bats. Their egg laying is timed to coincide with the beginning of pregnancy in bats: heavy females are less maneuverable and it is easier to catch them than usual. And the fledglings of kite chicks leave the nests simultaneously with the flight of inexperienced young bats, which not only represent an accessible source of food, but also 3-3-33319. help hone hunting skills.

In Central and South America, another species of bird of prey lives, actively hunting bats, 3-3-3323. evening falcon ( Falco rufigulari ). His Russian name suggests that he often hunts at dusk, and the English - bat falcon - reflects food cravings. Nevertheless, the specialization of this predator did not go as far as that of a wide-kite kite: the main part of its diet is not bats, but birds and insects. Some sources also claim that bats are a favorite prey for 3-3-3327. black and white cyclocaba , or the black and white owl, the owl inhabiting Central and North South America, but in general, data on the diet of this species are contradictory.

It is difficult to say why bats are so vulnerable to birds, especially during daylight hours. However, it is obvious that this did not prevent them from occupying many ecological niches and giving rise to more than 1200 modern species, becoming the second largest detachment of mammals after rodents. Winged animals thrive - even if they have to hide in the light of day.

Photo © Alexandro Pedrovich , Moscow region, April 2020.

Sergey Kolenov

22 май 2020 /
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