Arxiu de la categoria: BIRDS

Is it a stork? Is it an eagle? It is… the secretarybird!

Tall and stylish, at first sight the secretarybird reminds us of a stork or a crane: black and white plumage, long legs… but the beak and claws betray it. Beyond that they are all birds, they have little in common. Find out more about this especial bird of prey!

BIRDS OF PREY

Curved and powerful beaks, curved claws, carnivorous feeding… we all know how to recognize an eagle, a vulture, a hawk or an owl when we have them in front of us. Birds of prey, raptors or predatory birds are specialized in hunting live animals, except vultures (which are scavengers) and the palm-nut vulture (Gypohierax angolensis) which feeds, along with other things, on the fleshy husks of oil palm and raffia palm fruits. Raptors sometimes also steal prey from other raptors, hence their name. Once they have killed the prey, they try to avoid the indigestible parts, but it is inevitable that they ingest skin, hair, nails, teeth, bones… all these elements of difficult digestion will be regurgitated out of the beak after a few hours in the shape of a bolus, called pellet.

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Pellets of some owls and their content. Source

REPRODUCTION

Depending on the species, raptors build the nest on the ground, trees or rocks, except for falconidae and nocturnal raptors which do not build nests (they use those of other species or put their eggs in holes in trees or rocks). As a general rule, the larger ones are sexually mature after several years and lay a single egg, while the smaller ones are sexually mature after a year and lay more than one egg. The females of the hunter raptors are usually larger than the male and unlike the nocturnal ones, in the diurnal raptors the male also participates in the incubation.

SENSES

It is estimated that diurnal birds of prey see up to 8 times more in detail than a human and in color, so they can spot prey or carrion at great distances. By contrast, hearing is the most developed sense of the nocturnal raptors, with a hearing acuity 50 times higher than ours and black and white vision. As in the rest of the birds, the smell is not very good, except for the turkey vulture (Cathartes aura).

THE SECRETARYBIRD: A DIFFERENT BIRD OF PREY

The secretarybird (Sagittarius serpentarius) is of the same order (Accipitriformes) as ospreys, New World vultures, kites, hawks, buzzards and eagles. It is the only representative of the Sagittariidae family. In flight or at a distance, it looks more like a crane than a bird of prey. It has long, bare legs and shorter, not-so-curved fingers.

Secretarybird in Serengeti’s National Park. Photo: Yoky

It has a crest of black feathers. The flight feathers are also black and the rest of the body is gray and whitish, both in males and females. In the center of the tail it has two longer feathers. In males the feathers of the crest are slightly longer. His orange plucked face and its long lashes strongly attract our attention (in young secretarybirds the color is more yellowish than orange-reddish). It can weigh up to 4.5 kg, measure 1.5 m in height (it is the highest and longest raptor) and measure 2.2 m of wingspan.

Up-close of the secreatrybird. Photo: unknown

The origin of his name is not clear: it was believed it was because of the crown of 20 feathers that remind of the feathers attached to the hair of the British secretaries of the nineteenth century, or to the scribes of the Middle Ages, who carried the feathers behind the ear. Most likely, its name derives from a bad French translation of its Arabic name: saqr-et-tair (hunting bird).

FEEDING

Although its diet includes large insects, small mammals, frogs, lizards and turtles, it also preys on snakes, including cobras and vipers.

Secretarybird eating a whole snake. Source

Although it can fly, it prefers walking and running. Unlike most raptors, it does not look for prey from the air. Adults usually hunt in pairs and are able to walk up to 25-30 kms a day through the African savannah in search of their prey. Once a snake is detected, the secretary kicks the grass and pursues it until it catches it. Like all raptors, it does not attack its prey with its beak, but with its claws: first it kills it or stuns it with strong kicks, with an equivalent force of up to 5 times its weight and then swallow it whole (reference). In addition, unlike other birds, it keeps its eyes open during the attack, which allows to hit with precision the head and neck of its prey. Do you remember the cassowary, another bird capable of fatal kicks?

Do not miss this video in which you can see a couple of secretarybirds with their chicks and their impeccable way of hunting in slow motion:

REPRODUCTION

Secretarybirds are quite social. They can live in groups of 2 to 5 individuals, although they may be lonely occasionally. The mating ritual includes undulating flights by the male and falls, together with guttural calls. Male and female also chase each other with open wings similar to when they hunt. They form monogamous couples for life. Mating occurs on the ground and occasionally on the top of the trees, preferably between August and March.

Secretarybird in tis nest with two eggs. Photo: Hispalois

They build the nest in the acacia branches, which they can reuse year after year until it is too heavy. They put from 1 to 3 eggs of greenish-white color in intervals of 2 or 3 days, although the weakest chick usually dies. The eggs are incubated mainly by the female, although the male can participate in the incubation, and lasts about 42-46 days. The chicks will stand up at 6 weeks and after a short time their parents will teach them to hunt. Their plumage is darker and in successive moults they will obtain the color of adults. They will live up to 15 years old at the most in the wild.

Secretarybird chicks. Source

In this video made with a hidden camera in a nest you can observe how the secretary regurgitates the food to feed his chick:

DISTRIBUTION, THREATS AND CONSERVATION

The secretarybird distributes across the savanna and open African pastures (south of the Sahara) and it is not migratory. It is classified as vulnerable by the IUCN Red List and appears in Appendix II of CITES.

Sagittarius serpentarius distribution map
Distribution of the secretarybird. Source: IUCN

Although some individuals live in protected areas such as natural parks, their population is probably declining due to habitat degradation, alteration, poisoning, hunting and capture for trade. The natural predators of chicks are ravens, crows, tocos and hornbills, large owls and kites.

Although traditionally admired in Africa, for its conservation there are proposed measures such as a surveillance program to obtain an estimate of the population and the monitoring of the trend of the species. It is also proposed in the areas where the species is decreasing, to increase the awareness of the threats among the local population, in particular the farmers. There also propositions to face the capture and trade of the species.

As a final curiosity, the secretary is the emblem of the Republic of Sudan, it appears on the coat of arms of South Africa and on many stamps of different African countries.

Sudan emblem. Source

 

South Africa coat of arms. Source

REFERENCES

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Animal genitalia: birds and fish

The function of the reproductive system is apparently simple: to transmit the genes to the next generation. Why does it has so different and curious shapes in all kinds of animals? Would not  be enough with a simple sperm-emitting channel and a simple receiver? Find out in this post different shapes and reproductive strategies of birds and fish. If you want to learn about amphibia, reptile and mammal genitalia, click here.

ANIMALS’ SEX LIFE

Animals have different breeding strategies. In elementary school we learned that the fertilization can be:

  • External (outside the female’s body)
  • Internal (inside the female’s body)

And according to where the embryo develops the species are:

  • Oviparous: in an egg hatching outside the mother’s body (most fish, amphibians and reptiles)
  • Ovoviviparous: in an egg that hatch inside the mother’s body (sharks, vipers, boas…)
  • Viviparous: in a womb inside the body of the mother.

In high school we learned that there are strategists species:

  • r-strategists: they do not care for the offspring, which suffers a high mortality at birth. To compensate, they lay lots of eggs. They are usually short-live animals that quickly reach sexual maturity (invertebrates, fish, amphibians …)
  • K-strategists: they dedicate more energy to the care of the breeding, reason why they assure their survival and therefore the number of offspring in each laying or delivery is lower. Usually they are animals of longer life (dog, elephant, human …).

But if we analyze the reproduction in detail, it is not as simple as this. The sexual life of invertebrates is full of unlikely strategies to ensure fertilization, but we will talk about them another time and now we will focus on birds and fish.

THE EVOLUTION OF GENITALIA

The reproductive organs seem to have been the most diverse and most rapidly changed throughout evolution, giving rise to structures of almost every shape and size imaginable. If we believe that the only function is to give sperm, to receive it and to transport it to the ovule, we may be surprised by such diversity. In fact, the reproductive apparatus does much more than that and that is why the anatomy is so different between different animal groups.

Some insects, for example, use their penis for courtship, others use it to make sound and transmit vibrations to the female during mating. If the female likes the music, she will allow the male to take care of her offspring. Females also have adaptations to administer the sperm, like some flies, that can keep the sperm of different males in different receptacles of his reproductive apparatus.

Penis with bristles of the beetle Acanthoscelides obtectus. Source

The use of the penis in courtship and mating by the male and the administration of sperm in females would be two reasons that would explain the complexity of animal genitalia. The competition to ensure that a male’s sperm is actually the one that fertilizes all the female eggs would be another, with strategies as radical as plugging the ducts of the female once inseminated so that no other male can access it.

We will focus on this article on the genitals of fish and birds, do not miss the following post on amphibians, reptiles and mammals.

FISH GENITALIA

Although in most fish the fertilization is external, some have structures or pseudopenises to put the sperm inside the female.

SHARKS AND RAYS

They have the pelvic fins modified into two appendages called pterigopods or claspers, with which they introduce the sperm into the female.

Male shark (left) and female shark (right). Source

During copulation only one is used, which is filled with water thanks to a structure called siphon to expel it under pressure mixed with the sperm. According to the species, the young can be born from the mother’s body or from an egg.

Birth of a shark and fertilized egg. Source

POECIILIDAE FISH

Fish of the family Poeciliidae (guppys, mollys, platys, xhipos…), well known in aquarism, have the anal fin modified in a copulatory structure called gonopodium. They do not lay eggs, but the offspring are born directly from the mother’s body.

Male and female guppy. Source

PRIAPIUM FISH

It is a family of fish (Phallostethidae) that present the copulatory organ under the head. They mate face to face with the female, a thing almost unique in animals that live underwater. With the priapium they are anchored to the female and fertilize the eggs internally for a longer time than usual in other species.

Phallostethus cuulong male, discovered in Vietnam.. Source

Other curiosities in fish are possession of both sexes (hermaphroditism) or sex change, as in clown fish.

LOPHIIFORMES FISH

The best known representative of the Lophiiformes is the monkfish. In this order of fish, males are much smaller than females and they latch to females with their teeth, because of the difficulty of finding a mate in the abyssal bottoms. As time passes by, the male is physically fused to the female. He loses its eyes and its internal organs, except the testicles. A female may have six or more males (pairs of testicles) fused in her body.

Lophiiforme with a fused male. Source

BIRD GENITALIA

Most bird species (97%) do not have a penis and fertilization is performed with cloaca-cloaca contact (cloacal kiss, or cloacal apposition), a conduit that is used both as a reproductive and excretory system.

Left: urogenital apparatus of the male: F) testis, B) vas deferens, A) kidney, E) ureter, C) urodeum of the sewer. Right: urogenital apparatus of the female: A) ovary with mature follicle, F) infundibulum, E) oviduct, B) kidney, C) ureter, D) cloacal urodeum.Source

There are different hypotheses by which birds are believed to have lost their penis during evolution (since their reptilian ancestors did have it): to lighten the weight during flight, to avoid infections, by chance during the evolutionary process or to the females had better control over whom to reproduce. It seems that the latter would be the most accepted, since for example ducks fly long distances and have large and heavy penises.

But some birds do have a penis, which unlike mammals and reptiles, goes into erection by filling it with lymph, not blood.

WATERFOWL GENITALIA

Ducks, geese and swans are among the few birds that have a penis. The vagina of the ducks is shaped like a spiral clockwise, so when the male penetrates the female with his penis also spiral counterclockwise, if she is not interested flexes his vaginal muscles and penis leaves her body.

Vagina (left) and penis (right) of Mallard (Anas platyrhynchos).Source

The vertebrate with the longest penis in proportion to its body is precisely a duck, the Argentine diving duck (Oxyura vittata). He keeps it rolled up inside, but in erection he can be twice as long (42.5 cm) as his body (20 cm).

Oxyura vittata male with penis out. Unknown author

Duck penises, in addition to their different sizes and curvatures, can be smooth or have spines or furrows. This variability is due to the competitive pressure to overcome the females’ vagina. Both genitals are a clear example of coevolution. If you want to know more about coevolution visit this post.

Vaginas with blind ducts, penises with spines to extract sperm from previous copulations… ducks have a real “war” for reproductive control. In monogamous species such as geese and swans, the reproductive apparatus is not so complex, but in more promiscuous species, such as ducks, they are more complex and with longer penises so that it can be guaranteed that the male who has fertilized the eggs is the one who will take care of the chicks.

RED-BILLED BUFFALO WEAVER GENITALIA

This African passerine (Bubalornis niger) has a pseudopenis 1.5 cm long. It does not have blood vessels nor spermatozoa, reason why apparently its function is to give pleasure to the female and to favor the attraction of the male. Males in colonies have longer pseudopenises than those living alone, so the evolution of this appendix could also be explained by male-male competition.

Red-billed buffalo weaver. Photo by Reg Tee

OSTRICHES AND RELATIVES

African ostriches (Sthrutio camelus) are from the Ratites family, which also includes kiwis, rheas (American ostriches), tinamous, emus and cassowaries. All of them have a penis, and except for tinamu, they are running birds.

Ostriches about to mate. Source

The genitalia of the cassowary are really very peculiar. We have already discovered in this post how exceptional this animal is. Both sexes have a phallic appendage, but it is not connected to any reproductive organ. In the case of males, it is invaginated in a sort of “vaginal cavity”. At the moment of the copulation, it comes out (as if we turned out the finger of a glove), but the sperm leaves the cloaca, that is, from the base of this pseudopenis, not from the tip. In the case of females, the phallic appendage (sometimes referred to as clitoris) is a little smaller than in males.

Cassowaries mating. You can watch the video here

These male-female characteristics have given rise to rituals and beliefs in the folklore of New Guinea. They consider the cassowary an androgynous creature of mixed genders, therefore powerful because they have the attributes of both sexes. The remote Bimin-Kuskusmin tribe (Central New Guinea) celebrates rituals where intersexual people are considered representatives of these animals, so they are revered and powerful. On the other hand, Mianmin people tells stories about a human woman with a penis that became a cassowary.

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REFERENCES

The blue-footed bird that fascinated Darwin

Blue-footed booby (Sula nebouxii) was studied by Charles Darwin during his trip to the Galapagos Islands. Definitely, this bird is a wonder of the evolution of the species. We will know more about this amazing bird that is increasingly threatened.

1. WHERE TO FIND IT AND HOW TO RECOGNIZE IT

The Blue-footed booby (Sula nebouxii) is a species of bird of the order Suliformes (gannets and other related birds), family Sulidae (gannets or piqueros), from the American Pacific. They are medium-large-sized coastal birds that feed on catching fish diving on the water. It is distributed along the coasts between Peru and the Gulf of California, and the Galapagos Islands.

map-blue-footed-booby-160-2999-cb1447107513_national geographic
Picture 1: Blue-footed booby distribution map. Source: http://www.nationalgeographic.com

Blue-footed booby is unmistakable for its curious and striking bright blue paws, as its name suggests. However, this characteristic is only present by adult birds, since when they have not yet completed their development the chickens have pale legs as part of their survival strategy to avoid drawing attention to possible predators. To differentiate between adult males and females, we must look at two characters: size, males are smaller than females; and the unmistakable difference in their pupils, larger in females.

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Picture 2: Blue-footed booby male (on the left) and female (on the right), can be observed the difference in the size of their pupils. Source: www.stillnotgrowup.com

They feed mainly on pelagic fish such as pilchards (Sardinops caeruleus), chub mackerel (Scomber japonicus) and flying fishes (Exocoetus sp.). It is fascinating to watch the activity of these birds while they feed: they fly over the sea and dive from the air after their prey, entering the water at high speed, reaching speeds of up to 96 km / hour. This same technique to obtain food is carried out by all the pikemen and gannets. It is a gregarious species both for breeding and feeding, so it is common to see groups of birds hunting in the sea.

pesca_Tui De Roy_Miden Pictures
Picture 3: Group of blue-footed booby feeding on the sea by the diving technique. Source: Roy Tui via Miden Picture.

2. WHY GANNETS AND OTHER CURIOSITIES

Blue-footed booby is a bioindicator species, reflecting both oceanic conditions and marine productivity. They change their diet and growth rate of the chicks according to the available food (Maccall,1982; Ricklefs et al., 1984; and Jahncke and Goya, 2000), as well as their distribution pattern in the marine region during the breeding season (Valle Castillo, 1984; Hayes and Baker, 1989; Tershy et al., 1991).

piquero-patas-azules-683d83b718edc1575315599068d5f46d
Picture 4: Bird resting on rocks in Puerto Ayora, Ecuador. Source: Emilio, Erasmus Photo Puerto Ayora

Courting behavior is very complex (Parkin et al., 1970, Nelson, 1978, Rice, 1984), and its striking blue paws play a very important role. The male shows his legs to the female during the ritual, as it is one of the characters that the female takes into account in the choice of her partner. The color of the legs is due to the accumulation of carotenoids obtained from their diet, which is used as a breeding strategy: it reflects the health status of the individual and increases the chances of success. However, it has been shown that this strategy is not limited to a preference of the females for males with brighter blue paws, but also males show preference for females with brighter colored legs and thus, they may have a higher probability of interactions with other males other than his partner (Torres and Velando, 2003), despite being a monogamous species.

3. THE BLUE-FOOTED BOOBY IN YEARS OF CHANGES

‘El Niño’ is a cyclical climatic phenomenon (every 2-7 years) that wreaks problems worldwide, with the most affected areas being South America and the areas between Indonesia and Australia, causing water warming and huge changes in climate, as it causes severe droughts and floods. Its origin is related to the level of the oceanic surface and its thermal anomalies. The ‘El Niño’ phenomenon reverses the Humboldt current, which brings cold, nutrient-rich water from Antarctica, and warm equatorial water arrives instead, decreasing the number of birds that may depend on marine life.

el-niño
Picture 5: ‘El Niño’ phenomenon process. Source: http://www.ecuadordelsur.blogspot.com.es

In years of the ‘El Niño’ phenomenon, the blue-footed booby modifies its habits feeding on coastal fish almost exclusively (Carboneras 1992, Jancke and Goya 2000). In addition, it has been observed that this phenomenon influences its reproduction being negatively affected parameters such as laying size, hatching, success in flying chicks, … related to the low ocean productivity that causes this phenomenon (Wingfield, 1999).

Blue-footed Booby
Picture 6: Laying and hatching of eggs. Source: http://www.darwinfoundation.org

Currently, scientists have shown that due to global warming the frequency of El Niño has increased, and this seriously threatens the survival of the species in Galapagos since it may assume that there is not enough time for the species to recover, leading to their populations to very low populations and even to extinction.

4. A HARD START FOR CHICKS

The blue-footed booby lays 1-3 eggs incubated for 41 days. Chicks fly about 102 days and parents continue to feed them until their full independence.

pollosyprogenitor_Tui de Roy_Miden Pictures
Picture 7: Father and chicks. Source: Tui de Roy, Miden pictures

In clutches, usually two chickens, a hierarchy is usually established in which the first-born chicken is dominant in front of its smaller brother and receives more food from the parents. It is a species that can present or not the phenomenon of reduction of the clutch by means of the fraticide (Anderson, 1989, Anderson and Ricklefs, 1992), causing the older brother the death of the smaller one. In one way or another, the brother born last will have a difficult beginning because he will have to compete with his older brother for food in a continuous struggle for survival.

Blue-footed Booby
Picture 8: Clutches are usually of two chickens and the older brother shows dominance over the small. Source: http://www.darwinfoundation.org

5. REFERENCES

  • CONABIO – www.biodiversidad.gob.mx
  • Effect of food deprivation on dominance status in blue-footed booby (Sula nebouxii) broods – Miguel A. Rodriguez-Girones,” Hugh Drummond,b and Alex Kacelnik’ – Behavioural Ecology, 1996
  • Male preference for female foot colour in the socially monogamous blue-footed booby, Sula nebouxii – Animal Behaviour, 2005 – Roxana Torres, Alberto Velando.
  • Maternal investment in eggs is affected by male feet colour and breeding conditions in the blue-footed booby, Sula nebouxxi – Behavioral Ecology and Sociobiology, 2008 – Fabrice Dentressangle, Lourdes Boeck and Roxana Torres
  • The Effects of an “El Niño” Southern Oscillation Event on Reproduction in Male and Female Blue-Footed Boobies,Sula nebouxii – John C. Wingfield, Gabriel Ramos-Fernandez, Alejandra Núñez-de la Mora, Hugh Drummond – General and Comparative Endocrinology, 1999
  • http://www.lareserva.com/home/Alcatraz_patas_azules
  • http://www.iucnredlist.org/
  • Cover photo: Credit Asahi Shimbum vía Getty Images

Sara de la Rosa Ruiz

Parent love? Costs of parental care in birds

Parental care is an evolutionary adaptation, widespread in a large number of species, in which parents try to increase the chances of success of their children. However, there are decisions that parents must make and they will directly affect the survival not only of their descendants, but of themselves and their own species. We will see what happens in the case of birds.

1. PARENTAL INVESTMENT

According to the Theory of parental investment (Trivers, 1972), the animals that reproduce sexually must assess the cost to them to invest in their children.

Reproduction is costly, and individuals are limited to what they can devote time and resources to raising and growing their offspring, and such an effort can be determinant in their survival and future reproductive activities. According to the Principle of Allocation, the energy that an individual obtains must be distributed among the requirements derived from its maintenance, growth and reproduction. Extra energy being channeled to any of these activities will result in less energy available to the remaining ones.

imagen_energia
Principle of assignment. Source: Introduction to the science of animal behavior. Carranza.

Caring for the offspring consists of a series of activities carried out by the parents and an increase in the probabilities of survival of offspring, effects that will be considered as benefits. At the same time, these activities will have negative consequences on the parents, affecting their survival and the probability of producing new offspring in the future, since they involve an expense of time and energy or costs. Each individual must consider both, costs and benefits, to make the most beneficial choice.

cocodrile
Breeding of broad-snouted caiman (Caiman latirostris) in the mouth of his mother. Photo: Mark MacEwen

2. FORMS OF PARENTAL INVESTMENT

Parental investment must be considered from the beginning of reproduction, and not only from the birth of offspring.

We can distinguish different stages in the parental investment of birds:

Investment prior to fertilization: birds need to establish nesting and feeding grounds with conditions conducive to raising their offspring, such as the availability of food. In addition, once the territory is selected, they will have to choose a safe place for predators to set up their nest. In some cases they will also dedicate energy to the construction of the same, adding costs to the parental investment. The production of gametes is another process that supposes an energetic expense for the individual.

Placement and incubation: The laying of the eggs implies a great investment for the female, who is the one who does it. In relation to egg production, the energy investment of the female will vary depending on the development of the chicken at birth. In precocial birds or nidifugous (that present a state of advanced development at birth and can leave the nest, being able to move and Regulate its own temperature), the percentage of yolk will be greater and therefore, the greater the energy demand in its production. On the other hand, in altricial birds (born in premature developmental state, with eyes and ears not developed, body without feathers and without capacity to move), the percentage of yolk has been seen that is smaller and with this also the energy investment of the female. However, this initial differential investment may be later compensated for in the parental care necessary after hatching, which will be higher in altricial birds.

ovos_
Percentage of yolk in eggs of different species of altricial and precocial birds. 1. Bohemian waxwing (Bombycilla garrulus), 2. Ruddy duck (Oxyura jamaicensis), 3. Malleefowl (Leipoa ocellata), and 4. North Island brown kiwi (Apteryx mantelli). Source: Sotherland & Rahn, 1987

Once the female makes the egg laying, a very delicate stage begins in which the correct development of the embryo will be determined by the incubation conditions: temperature, humidity, ventilation and egg turnover.

Care after birth. After the hatching of the eggs, the offspring will need food, temperature regulation, and protection, by the parents. But this care will vary depending on their development at birth, being smaller in the precocial than in the altricial.

altricial_precocial
Difference between chickens of altricial (left) and precocial (right) birds at birth. Photo: Bloomsbury Publishing

Precocial and superprecocial birds are characterized by patterns of simple parental care, with minimal assistance in the nest. As an example are galliformes and anseriformes, who seek their own food since they are born, but will depend on their parents to protect themselves. At the other extreme, altricial species are characterized by sophisticated parental care, with a high level of offspring assistance. These features associated with altricial development are also related to an increase in the variety of flight styles, flight speed, and ecological habits (Dial, 2003).

desenvolvimento_altricia_precocial
Relationship between parental investment and mobility / ecological habits. Source: Dial, 2003.

Finally, we can find different models of parental care according to the individuals involved in the care of the young. In breeding parasitism, individuals try to reduce the costs of parental care by involving other individuals in caring for their offspring. (Lying birds: Brood parasitism in birds, the continual struggle for survival). Another possibility is that only one member of the pair, male or female, cares for the offspring; Or that both engage in that task (male and female). Finally, cooperative breeding is a system in which adult individuals (assistants) provide parental care, such as feeding, thermoregulation, grooming and advocacy, to juveniles who are not their direct descendants. If only a pair is reproduced, it will be cooperative breeding, if they reproduce more, it is called communal breeding.

birds-parental-care
In emperor penguin (Aptenodytes forsteri), all individuals in the group create a circle around the young to keep warm. Source: http://www.pinguinopedia.com

3. SEX CONFLICT

The conflict of interests between males and females begins in the production of gametes. The male gametes, smaller and simpler, need less investment on the part of the individual. In contrast, as we have seen, female gametes need more investment of female resources.

From the point of view of the male, the most advantageous would be to fertilize as many females as possible and let them be the ones who would care for the young, while he is engaged in seeking and fertilizing more females. On the contrary, the most advantageous for a female would be for the males she mates to take care of the pups so that she could devote her time, energy and resources to mating again and producing more pups.

However, the choice of one or another strategy will be determined mainly by several factors: physiological limitations, types of life cycles and ecological factors. According to the balance of costs and benefits for males and females in each ecological context, each sex will try to maximize its reproductive success, even at the expense of the reproductive interests of the other sex.

shorebird_parental_care2
Distribution of parental care between females and males. From left to right: greater painted-snipe (Rostratula benghalensis), wattled jacana (Jacana jacana), eurasian stone-curlew (Burhinus oedicnemus), Eurasian oystercatcher (Haematopus ostralegus), white-rumped sandpiper  (Calidris fuscicollis), and ruff (Philomachus pugnax). Source: Szekely et al. (2006)

The conflict between the sexes in parental care can be explained through the classic Maynard-Smith model (1978), represented by the Matrix of Game Theory, which will determine the parents’ decisions about whether or not to care for their offspring as a function of Success or benefit they obtain. Success will depend on the number of offspring produced (W), their chances of survival when they receive more or less parental care (P), and the male’s chances of mating again if he deserts (p).

matriz
Matrix of game theory that represents the conflict between both parents on whether or not to care for offspring. Source: Maynard-Smith, 1977

The selection will favor the desertion of one of the progenitors when the progenitor has a high probability of re-pairing, when the desertion has a small effect on the survival of the offspring and when the contribution of this progenitor is small (Lazarus, 1989). Even when both parents care for the offspring, there are conflicts of interest with respect to the level of investment that males and females provide, so that what each sex is willing to invest will depend in part on their partner’s level of investment.

REFERENCES

  • Birkhead, T.(2016) The art of hatching and egg.
  • Carranza, J. (1994). Ethology. Introduction to the Science of Behaviour.
  • Gill, Frank B (2007). Ornithology. New York: W. H. Freeman & Company. 758p
  • Kenneth P. Dial (2003). Evolution of avian locomotion: correlates of flight style, locomotor modules, nesting biology, body size, development, and the origin of flapping flight The Auk, 120 (4)
  • Sotherland, P., & Rahn, H. (1987). On the Composition of Bird Eggs The Condor, 89 (1)

Sara de la Rosa Ruiz

Invasive species. A threat to biodiversity.

If you are thinking of giving an animal as a pet, be responsible: an animal is not a toy. In addition, you have to keep in mind that many animals that we find in the stores and that are called exotic species, may in the long term pose a great environmental problem, so think about it because you are sure to find other alternatives in your gifts. In this article I will tell you what damage these animals can cause in our fauna, in particular, exotic birds, when they stop being “pets” to become “invasive species“.

WHAT IS AN INVASIVE SPECIES?

Invasive alien species (IAS) are one of the main causes of biodiversity loss in the world. An exotic invasive species is one that is outside its natural range, past or present, thus assuming some kind of human intervention that translates into its transfer through a biogeographic barrier that otherwise could not have been overcome . The introduction of exotic species has been carried out for many years both voluntarily and accidentally, many from the pet trade. The problem arises when some of these species establish, reproduce successfully and disperse from the introduction zone causing true pests.

Some of these species are especially known for the economic damages they generate, such as the zebra mussel in the Lower Ebro in Spain (2 million euros per year). But they also pose a threat to our biodiversity, because of the impacts they cause on native or indigenous species (species that are within their natural range, past or present, or within their potential dispersal area, that is, to which it can reach by its own means) by competition, predation, hybridization, introduction of diseases and parasites.

HOW DOES AN AVE BECOME AN INVASIVE SPECIES?

As we have seen, invasive alien species have only managed to occupy areas outside their natural distribution through human intervention. Depending on the intentionality of this intervention, the introduction can be of three types:

  • Intent or deliberate: when the introduction of the species into the natural environment is premeditated, for use in biological production systems, or for recreational purposes.
  • Accidental: Occurs when there is escape or release of the animal that was kept in captivity.
  • Involuntary or accidental: inadvertent introduction of species through means of transport or communication.

When an exotic species is released into the natural environment, different stages take place (introduction, establishment and expansion) until it finally becomes an invasive species and represents a real risk.

In the case of birds, the introduction of these species is usually due to releases from individuals who have been held captive, mostly from the purchase in pet stores.

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Picture 1: Argentine parrot (Myiopssita monachus) in captivity – Photo: http://www.animalesmascotas.com

INVASIVE BIRDS IN THE WORLD

The Argentine or gray parrots (Myiopsitta monachus) originally inhabited forests, shrub steppes, savannahs, cultivated areas, parks and cities in south-central South America: Argentina, Paraguay, Uruguay, Bolivia and Brazil. It is appreciated as a pet, so it has been marketed worldwide, managing to escape and adapt to new areas, becoming an invasive species that causes huge problems in countries around the world. It is currently present in asilvestrada in North America, Europe and Asia.

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Picture 2: Distribution map of the Argentine parrot – Photo: http://www.researchgate.net

It has been demonstrated that the sounds emitted by these birds have negatively affected the reproduction of insectivorous passeriformes, because they interfere in their pre-nuptial communication and in their reproduction habitat, being displaced by the parrots. Also magpies (Pica pica) have been affected due to the pressure exerted directly on them, displacing them physically, and indirectly, competing for resources. In addition, they cause significant damage to trees and crops, such as almonds (Prunus dulcis), which have seen damage during flowering and then immature almonds. According to SEOBirdLife, the spanish population of this species is estimated at about 20,000 individuals.

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Picture 3: Group of argentine parrots established as invasive species in a city park – Photo: http://www.higieneambiental.com

A similar situation has occurred with the Kramer parrot (Psittacula krameri), estimating its populations in Spain in 3,000 individuals.

The common coral beak (Estrilda astrild), from South Africa; Or the black swan (Cygnus atratus) are also examples of species that were transported to our country to be kept in captivity and eventually ended up being introduced accidentally.

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Species such as the wild pigeon (Columba livia) and sparrow (Passer domesticus) are invasive species in America and pose a major problem in the continent’s Biosphere Reserves, especially in Argentina, where these species are displacing native species in environments Urbanized or in the process of urbanization. On the other hand, reserves located in insular ecosystems are especially sensitive and both their integrity and their endemic species (a species or taxon originating in a determined and limited geographic area, which is only present in that area) are threatened by an abundant community of invasive species. To control the situation, management and eradication programs are maintained, however, prevention is a fundamental pillar in the control of these populations.

WHAT MEASURES CAN BE ADOPTED?

There are numerous global and regional initiatives for information and management on invasive alien species, including the Global Invasive Species Program (GISP), the IUCN-ISSG Invasive Alien Species Specialist Group (IUCN-ISSG), the Global Information Network on Invasive Alien Species (GISIN) and the Global Invasive Species Program of The Nature Conservancy (TNC-GISI), among others.

The prevention strategy is fundamental to minimizing the impact of invasive species and is based in full on the guiding principles of the Convention on Biological Diversity (CBD, 2002), reaffirmed in the European Strategy on Invasive Alien Species (Genovesi & Shine, 2004) , Adopted by the Standing Committee of the Berne Convention in December 2003.

The key elements taken into account in the invasive species prevention strategy are:

  • Prediction of the invasive potential of an alien species requires knowledge and assessment of a broad spectrum of variables dependent on the species’, vector and host ecosystem’s biological characteristics that may affect its establishment, impact.
  • A hierarchical approach in three stages: first, to prevent the entry of the invasive species (exclusion), to detect it quickly and eradicate it upon entry (early detection and rapid response, and finally to minimize its impact if eradication fails).

On a personal level, you can contribute to prevention taking into account some Good Practices:

  • If you observe an animal with similar characteristics to the invasive alien species in a new area, you must communicate it as soon as possible.
  • When traveling to another country, do not transport animals, plants or seeds.
  • If you are thinking of buying a pet of exotic origin do it in specialized stores. It is necessary to obtain the documents proving that the copies are duly certified, legally imported and free of parasites and diseases.
  • Collect and demand information about your pet: From what geographical area does it come? In what type of habitat do you live in your place of origin? What do you eat and how do you behave in freedom? What is its scientific name? This information will help you take better care of it and indirectly protect the natural environment around you.
  • Do not ever abandon it or release it in nature.

REFERENCES

  • Biological invasions. Collection Dissemination of the Higher Council of Scientific Research.
  • Exotic Invasive Species. The response of the European Union. Environment, 2004.
  • Legislation on Exotic Birds. Group of Exotic Birds SEO / BirdLife, 2012.
  • Photo cover: http://pajarosdemadrid.blogspot.com.es/

Sara de la Rosa Ruiz

Migratory birds: tireless traveler

Do you realize that some birds appear for certain time and place but suddenly, one day, dissapear again until the next year? Where do they go and why do they decide to fly though thousands of kilometres? Certainly, migration of birds is a phenomenon that has fascinated the human being from the beginning. In this post you will have an overview of the migration and discover fun and interesting facts of these wonderful birds. 

WHAT IS THE MIGRATION?

Migration is a natural phenomenon that happens in different species, but is particularly striking in birds. Requirements of essential resources (food, breeding areas,…), in several phases of their life cycle, is the main reason to start the journey to look for more favourable terms. The migration is a regular seasonal  movement that are performed by birds and coincide with the amount of a resource or different seasons, between breeding and wintering grounds.

Migration of short distance, for example when animals are moving from mountain areas at lower altitudes because of the temperature. On the other hand, migration of long distance when birds are traveling thousands of kilometres  through physical, meteorological and ecological barriers.

From Ice Age, migratory birds have evolved to fly long distances because in this way they are able to occupy different habitats and benefit from season resources in other climates. The migratory behaviour originating from an evolution because of climate changes on the Earth, and it is necessary an animal adaptation to the conditions in the new area. This behaviour was developed in species from more Northern latitudes in the Northern Hemisphere and in southern regions in the Southern Hemisphere.

WHAT TYPES OF MIGRATORY MOVEMENTS ARE THERE?

Migratory birds travel twice per year, in different seasons and times in their annual cycle. In the prenupcial (or spring) migration period birds fly from wintering to breeding areas. In the breeding areas there are enough resources to feed their offspring and safe breeding places. In the postnupcial (or winter) migration period adults and young birds fly to the wintering areas because of the weather and the high resource availability.

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Group of grus in the wintering area where weather and conditions are better than en North of Europe – Photo: Manuel Gómez Calzado

These movements have concrete patterns in each species and develop the different migratory routes, but researches have discovered the routes can be variables.

So, according to the migratory pattern there are longitudinal, altitudinal or latitudinal migrations. It could be variances in migratory behaviour between individuals, including in the same species, according to several factors us age, sex or population.

MIGRATORY ROUTES

Birds use these migratory movements through specific routes, with important features (catchment of a river, mountain ranges, coast,…) and ensure favourable conditions for the journey. Also, the rest areas are used to rest and feed in long routes.

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Migratory routes on the world – Photo: SEO-BirdLife

In the majority of birds from Europe and Asia, such us storks and vultures, spend the winter in the tropical Africa area, crossing their route the Arabian Peninsula and the Suez Canal. Migratory birds from the United States and Canada have their wintering areas in Mexico and Central America, and their routes depend of their area of origin: birds from east cross through the Gulf of Mexico or the Mississippi river basin; birds from west through the Rocky Mountains and Mexico Mountains, and finally, birds from Pacific used the cost or the open sea.

However, the routes can be different and depend of the distribution of birds; for example a bird species from Eurasia that pervaded North America. Their relatives used to spend the winter in Africa, so the population from North America cross Canada, the North Atlantic and Europe to spend the winter in Africa.

Researches show the routes are not so fixed us we though, and they can change according to the requirements of the species and environmental conditions over time. Also, there are fluctuations between different groups in the same species.

HOW DOES MIGRATION HAPPEN?

Human beings have always tried to answer the question ‘how is it possible birds fly so far?’. Several researches shows birds use a mix of mechanisms to migrate: the
Earth’s magnetic field, positions of the Sun, Moon and stars, polarized and ultraviolet light, recognising geographical features, reflected sound waves, taste and smell.

A research showed the migratory birds have proteins on their retina that is like a light-sensitive compass. When it is lightened with sunset light, the CPF molecule reacts and forms other compound that is sensitive to the magnitude and direction of a weak magnetic field. Two electrons rotate in opposite direction because of this chemical reaction, and the bird finds the north and south direction.

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A group of proteins that birds use during the migration – Photo: http://concienciangela.blogspot.com.es/

For some birds, such us the mayority of passerine birds, migration is an innate and individual process and they have special mechanisms to find the right way. In other cases, when birds fly in group, the migratory behaviour is developed through social learning because young birds travel with adults. Birds born of parents with different migratory routes used to choose a middle migratory route.

DISCOVERING SOME CURIOUS FACTS

The bird that travel father is the Arctic tern (Sterna paradisaea) from the Arctic, its breeding area in summer, to Antarctic to find food in winter. This distance is about 80000 km per year, and this species has developed the ability to sleep with a hemisphere off and another on flying directly.

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Arctic stern (Sterna parasidaea) and its migration – Photo: Birdlife

 

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In a research about Alpine swift (Tachymarptis melba), it was showed that this species can stand on the air for 6 months in their migration to Africa. The most interesting is that all vital processes are being on the air.

The migratory bird that flies higher is the common crane (Grus grus) and they can fly over the Himalaya mountain each year carried by the thermal currents. Breeding areas of this species are in the north of Europe and Centre and Northwest of Asia, also there are some groups in southeastern Europe and close to the Caspian and Black Seas. The wintering areas are in Spain, Portugal, north and east of Africa, south of France and south Asia.

REFERENCES

  • “Birds Migratory flyways influence the phylogeography of the invasive brine shrimp Artemia frasciscana in its native American range” – Joaquín Muñoz, Franciasco Amat, Andy J. Green, Jordi Figuerola and Africa Gómez
  • Effect of climate on the migration behavior of the common buzzard Buteo buteo – Martin, Beatriz; Onrubia, Alejandro; Ferrer, Miguel – 2014, Climate Research 60: 187 – 197 (2014)
  • Regional Forest Fragmentation and the Nesting Success of Migratory Birds – Robinson, Scott K.; Thompson III, Frank R.; Donovan, Therese M.; Whitehead, Donald R.; Faaborg, John; – Scientific Journal (JRNL) – 1995

 

 

 

Full colour: Birds and their plumage

The most beautiful characteristic of birds is their different colour patterns between species, genders, ages, and even in individuals. In this post, we will discover some ecological and behavioural factors involved in the variability of colour in different individuals and how they are perceived by the bird eye.

1. COLOURS IN BIRDS

Different colours of the bird plumage are determinated by the combination of the amount of pigments (melanin and carotene) in feathers, and the specific microestructure in some parts of the feather.

Some pigments, as melanin (eumelanin for black and grey, pheomelanin for brown and beige) are synthesized by birds. There are specific pigments of particular taxa, for example the pigment synthesized by the psittacidae family  (it includes macaws, parakeets and other from Africa and America).

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Macaws – http://www.toonts.com

Other substances, as carotenoids, are assimilated with food. For example, flamingos and roseate spoonbills find this pigments in small crustaceans that they eat. Thus, colours depend on habitat and season.

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Roseate spoonbill (Platalea ajaja) – http://www.merindad.com

Also colours that depend on this pigments, birds have structural colours. On bird feathers can appear an effect, called “dissemination of Rayleigh“,  when rays of light hit the melanin microgranules that reflect short waves (blue) and transmit long waves.

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Structure of feather barb – http://www.wikipedia.es

In some birds, as balb ibis (Geronticus eremita), iridescense is showed under certain lighting conditions with purple and blue colours. This effect is the result of the light incidence in microleaf of the feathers: melanin absorbs light and determines the black colour, and the colours of rainbow are reflected by this microleafs, when microgranules could only reflect the blue colour.

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Iridescense in bald ibis (Genonticus eremita) – http://www.econoticias.com

3. HOW THIS VARIETY OF COLOURS IS PERCEIVED BY BIRDS?

Visual system of birds have anatomical differences to humans system. We are able to see in visible spectrum because we have three cone receptors in our eyes that divide light into three different spectral ranges (blue, red and green). Birds have four cone receptors and also they are able to see the ultraviolet radation.

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Wavelenghts in birds and humans – http://www.todosobrelaevolucion.org.mx
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On the left human vision and on the right ultraviolet vision in birds – http://www.notaculturaldeldia.blogspot.com.es

In addition, birds have special oils on the surface of the cones that improve the colour vision enabling the perception of a colorful world.

3. ECOLOGICAL FACTORS LINKED TO COLOR VARIATION

Plumage colour helps to distinguish different species, between male and female in birds with sexually dimorphic, aged, and can be different between individuals of the same species. But also, in same species,  this variety is related with ecological and ethological factors.

Some studies point out colour is key indicator of birds’ health status and could be important in mate choise. In many species, females prefer to breed with brigher colour males. These preferences are due to brigher colour males show higher quality and a greater capacity to survive. The carotenoids that influence in plumage colour must be supplied by the diet, but also are involved in other vital processes such as inmune process, precursors of vitamins and control of oxidative stress. According this theory, colour is a good indicator of the state of bird health, because if an individual uses carotenoids in plumage colour other vital processes must be covered and this individual has a good health. In a research about mate choise in blue tit (Cyanistes caeruleus) was demonstrated that in brigher colour males the probability of selection is higher and their chicks grow best.

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Blue tit (Cyanistes caeruleus) – Foto: Luis Ojembarrena

On other hand, there is some species with a cryptic plumage that makes observation hard. This kind of plumage is essential in species with high rate of predation because in this way the bird can mingle with the environment and the probability of predation decreases, specially during certain sensitive periods such us females hatching or chicks. An example of cryptic plumage is the nighthawk (Caprimulgus europaeus) that uses its plumage to dissaper in waffle when female is hatching to decrease the risk of predation.

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Nighthaw (Caprimulgus europaeus) hatching – Foto: Victor Guimera

4. SOME ANOMALIES

Some individuals can have anomalies in their plumages due to influence of factors such us genetic variability, environmental pressures and diet. Some of the most common include:

  • Albinism: It consists on the precense of white feather rather than the usual feather due to a genetic change that inhibits the formation of tyrosinase enzyme responsible for the synthesis of the melanin. It is fully expressed when colour feather, soft parts (beak, claws, nails) and eyes reduce melanina.
  • Leucism: It is characterized by reduced pigmentation. A genetic mutation prevents melanin deposited in feathers properly.
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Bird with albinism has changes in its anatomy  (colour of eyes, for example), and in leucism the bird only has decreased pigment – http://www.biodiversidad-bajio-profundo.blogspot.com.es/
  •  Melanism: It is a development of the dark colored pigment melanim in the feathers. It can ocurr partially, with dark marks, or completely if all plumage becames dark.

Negative factors for quality of habitats have shown to have influence in colour birds. In this way, it is possible to study colour patterns in birds to relate them with the state of a population and to promote conservation measures. This methodology will be cheaper and gives us highly valuable information.

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Rural and urban birds – P.Salmon

5. REFERENCES

  • J. Carranza, J. Moreno y M.Soler. “Researches about animal behaviour”. XXV años de la Sociedad Española de Etología (1984-2009)”. Universidad de Extremadura
  • P. Salmón, J.F. Nilsson, A.Nord, S.Bensch, C.Isaksson. “Urban environment shortens telomere length in nestling great tits, Parus major”. The Royal Society Publishing.
  • James Dale, Cody J. Dey, Kaspar Delhey, Bart Kempenaers y Mihai Valcu. “The effects of life history and sexual selection on male and female plumage colouration”. doi:10.1038/nature15509.
  • Cover photo: http://www.hdfondos.es

Sara de la Rosa Ruiz