Arxiu de la categoria: BIRDS

Feathered dinosaurs: the origin of birds

The presence of feathers is one the main characteristics of modern birds. Currently many dinosaur fossils show us that feathers appeared long before birds. Yet the feathers that those Mesozoic animals had weren’t exactly the same as the ones current birds have. The evolution of feathers was a long and gradual process, and in this entry we’ll review the most important evolutionary stages that brought those dinosaurs to develop anatomically modern feathers.

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Today’s feathers

Feathers are fundamental structures for the life of modern birds. Feathers help them insulate from cold and hot weather, make them waterproof, camouflage, allow them to fly and in many species, feathers are very important in the mating rituals. In many birds, plumage allows us to differentiate between different species, telling a male and a female apart, and even allows us to know the age of an individual.

Chrysolophus_pictus_walkingMale golden pheasant (Chrysolophus pictus) photographed at Kuala Lumpur’s Bird Park, showing us different types of feathers. Photo by Bjørn Christian Tørrissen.

Feathers are the most complex integumentary structures found in vertebrates. These are formed in the epidermis, in little follicles which produce keratin. The β-keratin of the bird’s feathers, claws and beak is much more folded than the α-keratin found in mammalian’s hair, hooves or horns, making the first a much stronger structure. Feathers are resistant and light structures, but in many birds they correspond to a third of their body weight.

Modern feathers have a central shaft divided into two parts: the proximal part which inserts to the body called the calamus, and the rachis, the distal part from which the laminar part of the feather appears. This is called the vane and is disposed on both sides of the rachis. The laminar part is made of parallel ramifications called barbs, which have ramifications called barbules which also have ramifications in the shape of small hooks called barbicels that make barbules cross-attach to each other. The superior end of the vane (pennaceous part) barbules are perfectly arranged by the barbicels, while in the inferior end (plumulaceus part) barbules lack barbicels and so they float free from each other.

Parts_of_feather_modified

Parts of a feather:

  1. Vane
  2. Rachis
  3. Pennaceous barbs
  4. Plumulaceous barbs or afterfeather
  5. Calamus

According to its structure, in current birds we can find two main types of feathers:

Contour feathers: These are the feathers that make up the shape of the bird. These are long, flat feathers with a well-developed rachis and well-arranged barbs. These can be further classified into generic contour feathers, which cover the head, neck, trunk and limbs of the animal, and the flight feathers, called rectrices the ones in the tail (symmetric) and remiges the ones in the wings (asymmetric).

Parrot-featherFeathers of a macaw. Photo by Jörg Gorβ.

Down feathers: These are found forming a second layer under the contour feathers. These are feathers with a short rachis and with disordered barbs floating freely. Its main function is to thermally insulate the bird. Natal down feathers covering most bird hatchlings in some time of their lives are called “neossoptilus”.

Young_barn_owl_(Tyto_alba_pratincola)Barn owl hatchling (Tyto alba) covered in down feathers. Photo by Maxgreen.

Apart from these two types, there are other kinds of feathers in birds, such as the semiplumes (with an intermediate structure between contour and down feathers) and the bristles and filoplumes (with few barbs and mainly with a sensory function).

Tipos_de_plumasDifferent types of feathers we can find on modern birds, drawings by Osado. From left to right: Rectrix (tail), remex (wing), generic contour feather, semiplume, down feather, bristle and filoplume.

Origin and evolution of feathers

Probably dinosaurs develped the first feathers as a system to avoid the loss of body heat. Having a covering feathers, a layer of warm air becomes trapped around the animal, making its body temperature more stable. That’s why some scientists think that many dinosaur species had an almost endothermic metabolism (mesothermy), with high and constant body temperature. Nevertheless, primitive feathers or “protofeathers” were very different from modern feathers.

Deinonychus_im_NHM_WienReconstruction of Deinonynchus by Stephen Czerkas, at the Natural History Museum of Vienna. Photo by Domser.

As we will now see, protofeathers went through different evolutionary stages before becoming modern feathers. Even if here we present you these stages linearly, it doesn’t mean that when a new kind of protofeather appeared the previous one disappeared. Just like modern birds sport different kinds of feathers, many dinosaurs presented different combinations of protofeathers, which only represented different levels of specialization.

Stage 1: A single filament

Feather_evolution_StageI_v2Drawing about the origin and formation of the first protofeathers. Extracted from Prum & Brush (2002).

The first known protofeathers were nothing more than a cylindrical hollow spine-like filament, which formed on a follicle’s collar. Even though feathers and protofeathers are typically exclusive characteristics of theropods, this first protofeathers have also been found in two groups of non-theropod dinosaurs. These are the Heterodontosauridae and Psittacosauridae families, many species of which had spines homologous to stage 1 protofeathers which probably also served to retain body heat.

FruitadensReconstruction of a heterodontosaurid named Fruitadens. Drawing by Smokeybjb.

In theropods, feathers appeared in a group named Coelurosauria, which includes animals like the tyrannosaur, the velociraptor and modern birds. The oldest feathered coelurosaur known is Sciurumimus, which literally means “squirrel mimic”. This fossil got its name for its fully feathered tail, covered in filamentous protofeathers similar to a squirrel’s.

sciurumimus_skeleton_by_franz_josef73-d5osy3yReconstruction of a juvenile Sciurumimus based on the skeleton found in Bavaria. Drawing by Franz Joseph.

Stage 2: A plumulaceous protofeather

Feather_evolution_Stage2_v2Second stage in the evolution of feathers, in which a division in the follicle produces various barbs with a single origin. Extracted from Prum & Brush (2002).

The next step on the evolution of feathers was the division of the cellular collar of the follicle, which brought the branching of the filament. The result is a plumulaceous protofeather with unbranched barbs originating in a calamus. Stage 2 protofeather are similar to down feathers of current birds and have been found in a wide variety of theropod fossils.

These protofeathers provided a better insulation, helping the animal to keep its body heat. It is also believed that it’s likely that the smallest dinosaurs were more fully covered in protofeathers, since smaller animals loose heat faster than bigger animals and so, they need more mechanisms to retain body heat. Bigger coelurosaur species like Tyrannosaurus may have lost their protofeathers much like modern elephants have lost almost all their body hair. Yet, it is possible that some species presented protofeathers after birth and during the first stages of life, and after growing up they would either loose them or only present them on some body parts.

Juravenator_by_Tom_ParkerReconstruction of a juvenile Juravenator in which we can appreciate how it was covered both with protofeathers and scales. Drawing by Tom Parker.

Yet in a Chinese paleontological site, the two biggest feathered dinosaurs known were discovered. The first to be discovered was Beipiaosaurus, a strange looking coelurosaur of about 3 metres long with long claws, which presented protofeathers both filamentous (stage 1) and plumulaceous (stage 2). This species shared its habitat with Yutyrannus, a 9 metre-long animal up to 1400 kilos of weight, which had almost all its body covered in plumulaceous protofeathers. These two animals probably lived in a humid and cold environment, and their coat of protofeathers helped them to keep their warmth when temperatures would fall.

dino-herdReconstruction of four Yutyrannus and a pair of Beipiaosaurus on their habitat. Drawing by Brian Choo.

Stage 3: Fusion and branching

Feather_evolution_Stages1to3bDrawing of the evolution of feathers from stage 1 to 3. Extracted from Sues (2001).

The third stage in the evolution of feathers gave rise to a protofeather with a central rachis made from the fusion of some barbs (3a) and a protofeather with barbules branching from the main barbs (3b). The combination of these two characters produced a pennaceous, vaned protofeather similar to the ones found in modern birds but less firm, as it lacked the hooked barbicels of modern feathers.

Feather_evolution_StageII_IIIa_v2Fossils of stage 3a protofeathers where we can see a central rachis from which various barbs extend. Extracted from Perrichot (2008).

Stage 4: Hooks to maintain order

Feather_evolution_3-5_v2Modified drawing from Prum & Brush (2002) of the apparition of hooks on the barbules of the stage 4.

It is in this stage where we can start talking about present day feathers. The stage 3 structure with a rachis, barbs and barbules, developed small hooks on the barbules which made them cross-attach and keep the vane together. These feathers were like the ones found in modern birds, the contour feathers, which present a central shaft and a symmetric vane.

Anchiornis_martyniukReconstruction of the troodontid called Anchiornis, where the wide cover of feathers it presented can be seen. Drawing by Matt Martyniuk.

These feathers are found in many different dinosaurs, many of which had begun to develop adaptations for flight, or at least gliding. Despite this, we can also find them in typically running dinosaurs like Velociraptor, a terrestrial predator about the size of a turkey, with a long mouth and a sickle-shaped claw on its hind legs. This claw is thought to be used mainly to kill their prey, but some scientists think that they used their claw to climb trees and ambush their prey from above. Maybe their feathers served them to make more controlled leaps when they fell on their victims.

Velociraptor_restraining_an_oviraptorosaur_by_durbedDrawing of a velociraptor attacking an oviraptotosaur. Drawing by Durbed.

These feathers are also found in the oviraptorosaurs, a coelurosaurian group with beak and few or no teeth. Even if they couldn’t fly, they probably used their arm feathers to incubate their eggs (like the Avimimus genre) and the ones on the tail for display and communication with other members of their species (like the Caudipteryx, and Nomingia genera).

Nomingia_gobiensisReconstruction of the oviraptorosaurian Nomingia, in which we can see the fan of feathers on its tail. Drawing by Smokeybjb.

Other dinosaurs like Scansoriopteryx had an arboreal lifestyle, and the feathers on its arms allowed it to glide from one tree to the other both to hunt and to escape predators. A relative of this animal called Epidexipteryx, even though not having feathers on its arms (as far as is known) presented long vaned feathers on the tail, probably to send visual signals to other members of its species.

Epidexipteryx_NTReconstruction of Epidexipteryx in which the long vaned tail feathers can be appreciated. Reconstruction by Nobu Tamura.

Stage 5: Asymmetry brings flight

Amber_feathersDrawings and fossils of all the different stages of the evolution of feathers. Extracted from McKellar et al (2011).

Finally the last stage in the evolution of feathers is the appearance of asymmetric feathers, with a displaced rachis making one half of the vane wider than the other. These feathers are the remiges found on the wings of birds, which not only increase drag during gliding, but also allow the animal to leave the ground and fly.

poecile-montanus-kittila-85459_1920Photo of a Willow tit (Poecile montanus) taking flight, where we can perfectly see the asymmetric remiges on its wings. Photo by David Mark.

Even if it’s generally assumed that apart from birds no other dinosaur group accomplished powered flight, there’s one group which got really close. The microraptorians were a group of small feathered dinosaurs characterized by presenting flight feathers, not only on their front limbs but also on their hind limbs. The most famous of them, Microraptor, had asymmetrical flight feathers on its arms, legs and, unlike modern birds, on its tail.

Microraptor4Drawing of the silhouette of Microraptor gliding. Extracted from Xu et al.

Even if it’s usually considered a glider, some authors argue that possibly Microraptor was capacitated to fly. Some skeletal characteristics indicate that some microraptorians may have been better suited for flight than Archaeopteryx, the ancestor of modern birds. For example, Microraptor presented a fused more developed sternum than Archaeopteryx, which would have made for a major anchor point for the flight muscles.

Video from the American Natural History Museum of the reconstruction of the appearance of Microraptor.

Nevertheless, Archaeopteryx is still considered the nearest to the ancestor of modern birds that, even if it wasn’t a great flier, it already had the different kinds of feathers found on current birds. Probably many more dinosaurs were covered with feathers or protofeathers, but in this entry we have only seen the species which show irrefutable evidence of having them. As we have seen, the road to reach modern feathers was long and gave rise to a wide diversity of dinosaur species, but after a meteorite practically extinguished life on Earth 65 million years ago, only one group of feathered dinosaurs survived and thrived.

This is labeled USNM# 4178. The original fossil is at Humboldt Museum, East Be rlin. The rock was found in Solnhofn, West Germany, and it is from the Jurassi c period.Fossil of Archaeopteryx lithographica from the late Jurassic found at southern Germany. Photo by James L. Amos.

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References

The next sources have been consulted during the elaboration of this entry:

Meet present velociraptors

There are some stories about eagles who kidnap children, movies about murderer birds… But it really exist a bird which can kill a person? Are birds of prey the most dangerous birds? Keep reading to find out more.

THE CASSOWARY

According to the Guinness Book of Records, the most dangerous bird in the world is the cassowary. Cassowaries (family Casuariidae), like the emu (with whom it is related) and the ostrich, are flightless birds and good runners (up to 50 km/h). They are also good swimmers and can jump up to almost 2 meters. They live in New Guinea, north of Australia (Queensland) and neighboring islands (Ceram, Aru).

Casuario (casuarius unnapendiculatus). Foto de Quartl
Northern cassowary (Casuarius unnapendiculatus). Photo by Quartl

There are three species: the Southern cassowary (Casuarius casuarius), the Dwarf cassowary (Casuarius bennetti) and the Northern cassowary (Casuarius unappendiculatus). The largest of all is the Sourthern cassowary, in which we will focus in this article. Its name comes from Papua and means “horned head”.

Besides the size (1.80 m tall and weighing 70 kg, females are larger than males), highlighting the Southern cassowary is their blue and red neck, plucked, with two hanging pieces of skin (wattles), along with a casque that crowns the head, which is higher in the female. This casque is made up of trabecular bone (spongy bone) covered with hard skin (keratinized), which helps make their way through the dense vegetation of the rainforest where they live or for sexual attraction. It can also be a sign of the age, health and status of the animal respect their peers. It is estimated that they can live up to 12 to 19 years in the wild.

Primer plano de un casuario. Foto de Nick Hobgood.
Foreground of a Southern cassowary (Casuarius casuarius). Photo by Nick Hobgood.

The plumage is black, shiny and loose, giving it an aspect like hair. The tips are sharp and used as a defense. But the real danger of the cassowary falls upon its legs and feet, as one of its three fingers has a claw of about 10-12 cm long.

pies, peus, garra, uña, casuario, feet, foot, cassowary
Cassowary feet, in which can be seen its inner finger modified as a powerful claw. Photo by Christian Ziegler

DIET

The cassowary feeds mainly on fruits in the ground, which are swallowed whole. This makes them important seed dispersers, up to 70 different species. Their diet is completed with invertebrates such as insects, small vertebrates and fungi.

quandong, cassowary, eating, fruit
Cassowary eating quandongs, one of its favorite fruits. Photo by Christian Ziegler

REPRODUCTION

Cassowaries are birds of solitary habits, they meet only in breeding season (June to October). The female is dominant over the male and can mate with several males, putting different clutches on the floor.

cassowary, eggs, huevos, casuario, ous, casuari
Cassowary eggs are green coloured. Foto de Christian Ziegler

The males are responsible for incubating the eggs (4-8) for 50 days and take care of the chicks up to one year and four months. These have a plumage with brown, black and white stripes, they turn brown at 5 months of age. The final color and helmet appear when they are between 2 -4 years old.

casuario, pollitos, chicks, cassowary, casuari, pollets, iphone photo
Cassowary with its chicks. Photo by Kaisa Breeden

BEHAVIOUR

They are quiet and peaceful but highly territorial birds. When disturbed or threatened, they do not hesitate to violently attack with their powerful legs and beak. They attack like it is believed Velociraptors did: cassowaries make big jumps and kick their opponents eviscerating them with their powerful claw as if it were a dagger, and causing internal injuries because of blows. The cassowary has killed at least two people in Australia (2009 data) and probably some more that has not been documented in native populations. There have also been cases of bone fractures in people, such as ribs, legs …

In this video you can see how a cassowary attacks:

CONSERVATION AND THREATS

Although they are not dangerous to humans unless they are bothered, the main threat cassowaries suffer is the destruction of their habitat (replacement of the forest by cultivated fields) and forest fragmentation, which prevents access to food and other reproductive groups. There are also frequent car accidents in Australia and attacks of domestic dogs to cassowary chicks. Finally they are also victims of uncontrolled hunting in the area of New Guinea.

Australia, señal de tráfico, casuario, cape tribulation, cassowary, traffic signal
Traffic signal in Cape Tribulation, Australia, warning of the presence  of cassowaries. Photo by Mireia Querol

The Southern cassowary is classified as Vulnerable in the UICN Red List as well as the Northern cassowary. The dwarf cassowary is near threatened. Cassowaries in Australia live in protected areas, and there are also specific conservation plans by Queensland Parks and Wildlife Service. There are no reliable population data in New Guinea.

As we have seen, the cassowary is a spectacular bird that arouse great respect but is in danger. We encourage you to leave your comments and your experiences about it if you have traveled to their habitat and have been lucky enough to see one in the wild.

REFERENCES

 MIREIA QUEROL ALL YOU NEED IS BIOLOGY

Homosexuality is so animal

Fortunately for LGTB collective, greater and greater countries and societies understood that homosexuality is something natural and that it is not an illness. Anyway, despite this is true, it is also true that it is necessary to work hard to achieve equality on lesbian, gay, transexual and bisexual rights and to eradicate the false belief that homosexuality is unnatural. In the next weeks, in cities all over the world like Barcelona and Madrid will take place LGTB Pride parties. For this reason, this article hope to show clear examples that homosexuality is not exclusive of human, but present in many animals. So, there is no reason to continue believing in the argument that homosexuality is unnatural! 

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INTRODUCTION

Homosexuality is a fact present in many animal species. In fact, it has been documented in 1,500 of the more than 1 million described animal species (Bagemihl, 1999). Without going any further, a study of the California University demonstrated that in all the analysed species there were some individuals with homosexual traits or behaviours, including worms, flies, birds, dolphins and chimpanzees, among others.

In the animal kingdom, the concept “homosexuality” refers to any sexual behaviour between same sex animals, like copulation, flirt, mating, genital stimulation and young breeding. In the case of humans, it is more complex than this because there is much more factors and feelings are involved in this.

From the biological point of view, it is supposed that the goal of any species is its perpetuation. So, which is the function of homosexuality? There are many theories about it and they are not particular because for each species there is one explanation or another. Let’s explain three of them! Marelen Zuk, professor in biology at the University of California, propose that not producing their own offspring, homosexuals could help to breed and take care of their relatives, what also contributes to genetic pool. According to the biologist and phsycologist Janet Mann from the Georgetown University, it is a way of creating links and alliances between individuals. Finally, in the case of fruit fly and other insects, the evolutionary biologist Nathan Bailey suggest that the reason of their homosexuality is the lack of the gene that let them to distinguish between both sex. There is also the possibility that homosexuality doesn’t have any function. At any rate, homosexual behaviour may have evolutionary consequences, but it is still being studied.

PINGUINS

On February 2004, New York Times published that Roy and Silo, two male chinstrap penguins (Pygoscelis antarctica) from the Central Park Zoo, coiled their necks, vocalized one to other and had sex. When they were exposed to females, they rejected them. Moreover, zookeepers gave them a fertile egg in order they incubate them and when the little penguin was born they feed her until she was able to live by herself. This is not an isolated case because it have happened more in this and other zoos, like in Bremerhaven Zoo (Germany), Faunia (Spain) and Dingle Ocean World (Ireland).

But this is not exclusive of captive animals. A research done on Adélie penguin (Pygoscelis adeliae) found homosexual behaviours in some of their young individuals. Another research was carried on king penguin (Aptenodytes patagonicus), in which it was observed that 28.3% of males flirted with other males. The reason in this case seems to be an excess of males or high testosterone levels. Anyway, it was found two partners (male-male and female-female) in which one knew the vocalization of the other.

Los pingüinos son un claro ejemplo de aves con comportamientos homosexuales (Foto de Listverse).
Penguins are a good example of birds with homosexual behaviours (Picture from Listverse).

BONOBOS

The bonobo (Pan paniscus), apes very close to humans, are a good example of homosexual behaviours. They are so sexual. It has been observed that, in captivity or free, half of their sexual relationships are with same sex animals. In addition, females have sex with other females almost every hour. The main function of this is to strengthen links between animals. In the case of males, in order to reduce the stress after a fight, a penis fight takes place, that consists on rubbing their genitals together.

En los bonobos, las relaciones con seres del mismo sexo podrían servir para hacer los vínculos más fuertes (Foto de BBC).
In bonobos, same sex relationships may be done to strengthen social links (Picture from BBC).

KILLER WHALES

Homosexual interactions between male killer whales (Orcinus orca) are an important part of their social life. When resident groups join together during summer and autumn to feed, males show flirting, affectionate and sexual behaviours between them. Normally, interactions take place one to one and lasts for an hour, but it can be longer. In this interactions, they caress, chase and carefully push one to the other. Another amazing behaviour is the beak – genital orientation, but it also take place between males and females. Just under the water surface, one male swims in an upside down position, touching the genital zone of the beak. Then, they dive together in a double helix spiral. This happens several times, but they interchange their positions. It is not strange to see them with the erected penis during this interaction. Despite it happens in all ages, it is specially abundant in young animals.

Las orcas (Orcinus orca) son cetáceos con comportamientos homosexuales habituales (Foto de WorldPolicy)
Killer whales (Orcinus orca) are cetaceans with homosexual behaviours (Picture from WorldPolicy)

GUPPIES

A research made on guppies (Poecilia reticulata) demonstrated that the lack of females in the environment during a long period of time produce that males prefer other males even when there are females in the environment. Not only this. When males that had been with females during a long period of time are deprived from females for a short time (two weeks) they prefer males instead of females.

Los machos de guppy preferían otros machos cuando no había hembras en su ambiente durante largos períodos de tiempo (Foto de GuppyFish).
Male guppies prefer other males when there is no females in the environment during a long period of time (Picture from GuppyFish).

DRAGONFLIES

Some studies lay bare that there is a high rate of mating between same sex individuals in dragonflies. The reasons could be the lack of individuals of the other sex or that female tricks to avoid sexual advances of males could produce that males look for same sex individuals. One specific example is blue-tailed damselfly (Ischnura elegans), in which 17% of males of wild populations prefer male partners.

Los machos del cola azul (Ischnura elegans) prefieren a otros machos cuando son alojados en ausencia de hembras (Foto: L. B. Tettenborn, Creative Commons).
17% of male blue-tailed damselfly (Ischnura elegans) prefer other males (Picture: L. B. Tettenborn, Creative Commons).

SOME EXAMPLES MORE

  • Studies on wild occidental gull (Larus occidentalis) show that between 10 and 15% of females are homosexual. It has been seen that they show flirting rituals between them and that they set nets together. They only copulate with males to produce fertile eggs, but then go with their initial partner.
  • On domestic sheep, 8% of males from a flock prefer other males despite the presence of females. But this could benefit other males because they can present the same genes and pass to next generation. But this also benefits females by doing them more fertile.
  • The king of savannah, the lion, also have homosexual behaviours. It has been observed wild male and female lions with this behaviour, include mating.

  • In some species of seahorse, homosexual behaviours between females are frequent, more than heterosexual.

CONCLUSION

Homosexual behaviours are no only in humans, but they are more complex in people. The reason that lead to the development of these behaviours in animals are several: lack of females, to stablish harder links… but there are some examples in which the behaviour is permanent. Moreover, it has been seen that this behaviours are not artificial due to the captivity of animals, like humans in prison, but they haven in wild animals too. So, homosexuality happens in many animals and cannot be considered unnatural. In addition, if it is the result of natural forces it cannot be considered immoral. 

gay-friendly

REFERENCES

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Bearded vulture: conservation of a unique bird

Last month a bearded vulture was born for the first time in Spain of parents bred in captivity and reintroduced into the wild. The bearded vulture is the only bird in the world that feeds almost exclusively on bones. Like the Iberian lynx, it is one of the emblematic animals of the Iberian Peninsula and it is endangered, so it is subject to various conservation and reintroduction programs. In this article, we encourage you to find out more about the bearded vulture and the spanish conservation projects.

DESCRIPTION

The bearded vulture (Gypaetus barbatus) is a diurnal bird of prey popularly included in what is called vultures, scavenger and ghoul birds (they feed on dead animals). However, the bearded vulture is quite different from other vultures:

Quebrantahuesos (Gypaetus barbatus) adulto. )Foto de Jose Luis Ojeda)
Adult bearded vulture (Gypaetus barbatus). (Photo by Jose Luis Ojeda)

 

  • It is so highly specialized that 85% of their diet are bones (osteophague) of dead mammals such as wild ungulates (chamois) and domestic cattle (goats, sheep). It can swallow bones up to 25 cm, and if they are too large catches them, rises them to 20-40 m and crashes bones against the rocks into smaller pieces that can swallowIt also uses the same technique to break tortoise shells.
  • It is very large, with a wingspan up to 2.8 meters and a weitgh up to 7 kg.
  • In general it isn’t noisy: it just whistles if it is excited or during the mating season.
  • It hasn’t the typical plucked vulture head. Vultures have a few or no feathers on their heads to maintain an optimum hygiene after putting their head in dead animals. Due to its peculiar diet, the bearded vulture has more feathers on head and neck, with its characteristic beard” below the peak.
  • The plumage is the same for both sexes but changes with age. The typical reddish and yellowish adults plumage is due to their habit of bathing in mud rich in iron oxides, otherwise they will had a white breast.
Fases del plomatge del trencalòs, segons Adam i Llopis (2003). (Imatge de © X. Parellada.)
Plumage phases of the bearded vulture, Adam and Llopis (2003). (Image by © X. Parellada.)

In this video (5 minutes, catalan) you can see bearded vultures in flight, breaking bones, engulfing them, raising a chick in the nest and bathing in mud.

REPRODUCTION

Bearded vultures nests on ledges and natural rock caves in the mountainous and rugged areas where they live. They have stable partner for life from age 7 and the reproductive cycle has different stages:

  • Pre-laying (September to November): nest building (covering it with branches, wool, feathers, bones ), defense of territory and sexual activity.
  • Incubation (December-February): they lay one or two eggs with a time difference of 6 days. Both sexes participate in the incubation for 53 days.
  • Nurturing (March-August): the largest chick kills his brother (fraticidal violence) to ensure survival. Parents provide food and when the chick leaves the nest (June-July), learn from them to find and prepare food until their emancipation.
  • Emancipation (January): displacement (thousands of kilometers) and dating back to the land where it was born to breed (philopatric instinct).
Seguimiento de nidos naturales mediante cámaras. (Foto: FCQ)
Tracking of natural nests with cameras. (Photo: Foundation for the Conservation of the Bearded Vulture)

DISTRIBUTION

Subspecies Gypaetus barbatus meridonalis is distributed by the South and East Africa, while Gypaetus barbatus barbatus by North Africa and parts of Eurasia (see map).

In the Iberian Peninsula is found naturally only in the Pyrenees (Catalonia, Aragon and Navarra). Spain is the European country with more breeding couples registered (about 130, 2014 data).

gypaetus barbatus, quebrantahuesos, trencalòs, berded vulture distribution, distribución
Bearded vulture distribution. In red, areas in which has been reintroduced . (Image by Mario, Wikimedia).

THREATS

Bearded vulture populations are declining. It is ranked globally asnear threatened” in the IUCN Red List and “endangered” in the Spanish Catalogue of Endangered Species. Current threats they face are:

  • Death by poisoning (illegal baits, poisoned animal consumption, consumption of remains of lead hunting ammunition plumbism).
  • Death by electrocution or collisions with power lines and wind turbines of wind farms.
  • Poaching
  • Habitat loss and decreasing of reproductive efficiency because of the humanization of the medium (urbanisation, adventure sports )
  • Reduction of food (cattle in stables, obligation to bury the corpses )
Quebrantahuesos muerto por envenenamiento. (Foto: DARPAMN)
Bearded vulture dead by poisoning. (Photo: DARPAMN)

CONSERVATION IN SPAIN

Due to the limited distribution of populations, their low number and difficulty to colonize new territories, in 2014 thirteen autonomous communities signed a protocol for the recovery of vultures in Spain. The most prominent action of this protocol is to strengthen the National Strategy for the Conservation of the Bearded Vulture in Spain (started in 2000) and the Programme Captive Breeding (2001), with actions such as the revaluation of rural areas, supplementary feeding and support for traditional farming practices. This strategy also involves the reintroduction in historic areas where the bearded vulture has been extinguished:

WHAT IS HACKING?

Hacking or rural upbringing is a technique that involves the release of captive-bred animals in an area that the bird assimilates as its birthplace. If successful, the bearded vulture returns to settle and breed. This technique did not has a conservationist origin, since it was developed by falconers in the Medieval Age. Falconry (hunting with birds of prey) are also currently used for wildlife control at airports or cities.

In falconry hacking consists in lefting in an elevated cage chicks that can feed by themselves. Falconer feeds them without being seen. After a few days they open the cage, using it as a basis for learning to fly. They are still feeding them until they learn to hunt by themselves and leave the cage. The young ones connect the cage as its birthplace so it will always return.

Alimentación de un pollo con un señuelo para evitar el contacto humano. Foto: Fundación para la Conservación del Quebrantahuesos
Feeding a chick with a decoy to avoid human contact and make its life possible in the wild. (Photo: Foundation for the Conservation of the Bearded Vulture)

The center managed by the Gypaetus Foundation is based on the natural breeding, with minimal human intervention. Parents raise and feed their young from the second week of hatching. To monitor the nests a video surveillance system is used.

Since 2006, 31 bearded vultures have been released from captive breeding and each one is tracked by GPS transmitters. Currently 15 individuals are still sending signals (9 were killed and 7 stopped working). As said in the introduction, the good news is that last month was born the first chick result of released individuals (Tono and Blimunda) by hacking technique.

For more information, check out this documentary (in spanish) about the bearded vulture and its conservation (El bosque protector. Fauna amenazada, El Quebrantahuesos, 29 minutes).

REFERENCES

MIREIA QUEROL ALL YOU NEED IS BIOLOGY

Nocturnal birds of prey: the barn owl, legends and myths

Nocturnal birds of prey have suffered since a long time ago an unfair bad reputation that has led them in some cases to be persecuted and hated. What are these superstitions? Which is their conservation state? What can you do for them? In this article you will discover owls and the barn owl, Tyto albaand the legends associated with them.

GENERAL CHARACTERISTICS OF NOCTURNAL BIRDS OF PREY

As its name suggests, most nocturnal birds of prey (owls, owls, tawny owls) have nocturnal or crepuscular habits. They are carnivorous, with beaks and claws (two toes forward and two backward) adapted to tear flesh from their prey (small mammals, birds, reptiles, large insects ).

HEARING

Owls usually have a rounded shape and apparent large head, with the face feathers forming the so-called facial disk. The facial disc serves as a dish heading sounds towards the ears. The opening of the ear is large, with a fold of skin (preaural halda), which functions as a pinna and is movable as in some mammals.

Oído de lechuza norteña (Aegolius acadicus). (Foto tomada de Jim McCormac).
Norther saw whet owl ear (Aegolius acadicus). (Photo by Jim McCormac).

The position of each ear is asymmetric in some species (one is higher than the other), so some of them -like the barn owl- can locate prey in complete darkness: an ear perceives sound before the other, so their  brain can calculate the exact place where prey is (directional hearing).

Boreal owl skull, cráneo de mochuelo boreal
Boreal owl skull (Aegolius funereus) where can be seen the asymmetric hearing openings and sclerotic eye rings. (Photo taken of Jim Williams)

EYESIGHT

Owl’s vision is highly developed. Eyes, unlike most birds, are in front position, which allows a perfect estimation of depth and three-dimensional vision. On the other hand, eyes are tubular (not spherical like ours) due to the large size of the cornea and lens, which prevents owls from moving them within their sockets. Also they have a protective bone plate around the eyes (sclerotic rings) that also impede movement. To solve this problem, they are able to turn his head 270 degrees. It can be considered that they see in black and white (they best perceive changes in light rather than colors), the pupil dilates a lot in bad light conditions (iris is hidden by dilated pupil) and they are the only birds in which the eyelid closes up to below. They also have a transparent lid” that moistens and protects the eye, called the nictitating membrane.

Visión lechuza, binocular, vista, búho, razces nocturnas
Binocular vison of a nocturnal bird of prey. Humans have a field vision of 180 degrees, 140 of them binocular). (Image by The Owl Pages)

PLUMAGE

Owls, unlike diurnal birds of prey, have a special flight feathers structure, fringed at the top surface and contours. The friction between them and the air is damped, achieving a spectacular silent flight undetectable by preys.

Pluma de lechuza común y autillo, donde se observan las barbicelas. (Foto tomada de Pedro Montoya).
Barn owl feather (Tyto alba) and european scops owl (Otus scops), (Image taken of Pedro Montoya).

THE BARN OWL

The barn owl (Tyto alba), is unmistakable: it has a very well defined and heart-shaped facial disk. The back is gray with golden spots and fine black and white dots.

DISTRIBUTION AND BEHAVIOUR

The barn owl lives all over the world (except Antarctica, north Europe and most Asia) and don’t build a nest, but lays eggs in tree holes, holes in the rock or human buildings (barns, attics, farmhouses, castles, churches ).

Why the barn owl has this negative reputation that caused their persecution in many parts of the world and in Spain? Causes are diverse, all fed by human fear:

  • They can nest in abandoned or sacred locations as churches (some with their own cemetery).
  • Nocturnal habits
  • They are sendentary, they can stay in the same hunting ground for years until food is scarce.
  • Ghostly appearance due to their colors and smooth and silent flight.
  • By their vocalizations (they have 17 different ones) like human screams and peculiar snorts. Listen to some owls making a defense vocalization in the following video:

THE BARN OWL IN THE POPULAR CULTURE. BELIEFS, SUPERSTITIONS, MYTHS AND LEGENDS

In the Iberian Peninsula was believed that owls drank the oil of the lamps in churches, leaving the Saints in the dark (when the real thieves were sacristans). By landing on lamps or touching them and pouring the oil, it was believed that owls hated light, like evil spirits. In spanish and catalan there are sayings that refer to this myth. They were hunted, killed and hanged above the doors of churches and barns to ward off fire and lightning.

The vocalizations of barn owls are also interpreted as announcements of death, and there is a belief (without basis) that if someone hear an owl for several nights (something not difficult given their sedentary habits) a person suddenly will lose life.

Tyto alba, lechuza común, lechuza de campanario
Barn owl (Tyto Alba). (Photo by Kerkuil André).

In other cultures there are also negative legends about owls: in Africa that are sent by sorcerers to kill people or evil demons announcing disasters, in the Argentine pampas that they are sisters of the devil; in Sicily, death or illness for all these reasons they have been killed and tortured.

However, they can also be a good sign (such as guardians of women who die in Australia), but the best known case is the representation of Athena, Greek goddess of wisdom. Currently still appears as a symbol of many institutions and in Greek euro coins.

Euro grecia, euro griego
Greek euro. (Resource: RTVE)

CURRENT STATUS AND THREATS

Nowadays the barn owl is in a state of decline and with an uncertain future due to changes introduced by humans in rural areas, such as changes in cultivation or use of pesticides and rodenticides, which kill their prey (mice) or indirectly birds themselves. The works and renovations of buildings where they used to nest also interfere with reproduction. They also suffer accidents due to the towers and power lines and are often hit by cars. Canary subspecies (Tyto alba gracilirostris) is disappearing due its habitat fragmentation and the low number of individuals in their populations.

Lechuza muerta
Barn owl in a barbed wire. (Photo by PacoT).

It is listed as Endangered in the Red Book of Birds of Spain and included in the National Catalogue of Endangered Species in the category “Special interest“.

WHAT CAN YOU DO FOR OWLS?

Try to find out about these magnificent birds and make them known to your immediate surrounding, banishing misconceptions, especially if you live near their nesting and feeding areas. If you own crops, try to minimize the use of pesticides: a pair of barn owls hunt in average about 2,000 mice a year, being therefore even beneficial to humans.

If you find an owl or wounded bird, you have to pick it carefully (using a towel or a jacket) to avoid hurt it or being hurt, and leave it in a dark, quiet place inside a box pierced so it can breathe. Do not feed it. Then contact a wildlife recovery centre.

REFERENCES

If you enjoyed this article, please share it on social networks to spread it. The aim of the blog, after all, is to spread science and reach as many people as possible. Feel free to share your experience with birds of prey in the comments below. ¿Do you know someone who still believe in this owl legends?

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