Mauritius Kestrel
Encyclopedia
The Mauritius Kestrel is a bird of prey
from the family Falconidae
endemic to the forests of Mauritius
, where it is restricted to the southwestern plateau
's forests, cliffs, and ravines.
It is the most distinct of the Indian Ocean kestrels
. It colonized its island home to evolve
into a distinct species
probably during the Gelasian
(Late Pliocene
).
It is the most distant living species among the western Indian Ocean kestrels
(Groombridge et al. 2002, qv Réunion Kestrel
).
s. The lifespan is 15 years in captivity. The Mauritius Kestrel hunts by means of short, swift flights through forests. It is carnivorous, eating gecko
s, dragonflies
, cicada
s, cockroach
es, cricket
s, and small bird
s.
in the 18th century and by cyclone
s. But the most severe decline was in the 1950s and 1960s due to indiscriminate DDT
use and invasive species
like cat
s, mongoose
s and Crab-eating Macaque
s which killed the kestrels and their eggs. What was probably this species' closest relative in recent times, the Réunion Kestrel
, became extinct around 1700 for fairly mysterious reasons.
The recorded population dropped to an all-time low of only 4 individuals in 1974 and it was considered the rarest bird in the world. Stanley Temple
from Cornell University
studied this species for two years and the first attempt in 1973 to breed the birds in captivity failed because the hatchling died when the incubator had a breakdown. Though conservation measures were immediately undertaken with the help of a breeding program by the Jersey Zoo (now called Durrell Wildlife) the efforts to rescue this species initially failed because the eggs were not fertile.
In 1979 a new attempt was undertaken. With the help of Gerald Durrell
, the Welsh
biologist Carl G. Jones established a wildlife sanctuary on Ile aux Aigrettes. He climbed on the trees and removed the eggs from the nests. This time the eggs were fertile, and Jones was able to rear the hatchlings in incubators. The wild kestrels' diet was supplemented so they would be able to lay a new egg after the first one was removed, averting any negative impact on the wild population. Slowly the population increased and during a census in 1984 50 individuals were estimated. Techniques for breeding, release, and "hacking
" of young birds were improved, the captive breeding center becoming a pioneering research institution for tropical raptor
and small falcon conservation. The captive breeding programme was scaled back in the early 1990s as a self-sustaining population was established. Since 1994, the programme serves only as a safeguard, should some catastrophe befall the wild population, and other rare endemics are now being cared for at the station (such as the Pink Pigeon
or the Mauritius Fody
).
Today there are more than 800 mature birds, with numbers rising; it is estimated that the remaining habitat allows for a carrying capacity
of maybe 50-150 more (BirdLife International 2006a,b). They occur in the remaining forests of the island, especially in the Black River Gorges region. The species was downlisted to Vulnerable
by the IUCN in 1994 as releases of captive-bred birds became unnecessary. Little conservation action was deemed necessary only a two decades - in Mauritius Kestrel terms, a long lifetime or maybe 4-5 generation
s - after the species had stood at the very brink of extinction. Today, apart from routine monitoring to be able to assist individual couples that fail to establish breeding territories for lack of nesting facilities - a major limiting factor, the ongoing control of introduced predators is basically all that is being done to assist the species' survival (BirdLife International 2006a,b).
While some apparent inbreeding depression
was noted in the captive birds, it was certainly lower than might be expected given that the effective population size
was maybe 5 individuals during the mid-1970s. It is known that several genetic lineages of Mauritius Kestrels have disappeared entirely during the 20th century population decline. However, the debilitating effects of DDT accumulation on the birds' health, and not inbreeding, are considered to have been the major cause for the failure of Temple's breeding program.
The evolutionary history of the birds seems to hold clues as to why (Groombridge et al. 2002): Mauritius is a volcanic island, and although the colonization of the island by kestrels cannot be dated with high precision, it was almost certainly some time before volcanic activity died down. The Mauritius Kestrel population seems to have survived a prolonged period of volcanic activity, which must have kept the population small and fluctuating as habitat
, food, and kestrels were destroyed by volcanic eruptions time and again. As near-panmictic conditions were sustained for many generations, allele
s that might cause inbreeding depression
were steadily removed by means of natural selection
. The phenomenon that effective population sizes as low as 4-5 can be tolerated without pronounced inbreeding depression is also known from other small-island birds, such as Petroica traversi or the Laysan Duck
.
The classification as a Vulnerable species is due to the same fact: on an island as small as Mauritius, chance events like volcanic eruptions (hardly likely in our time) or storms (common and possibly increasing in frequency and strength) can always wipe out major parts of a species' population (BirdLife International 2006a,b). The IUCN classification VU D1+D2 reflects this, translating into a population size of less than 1000 mature individuals, and less than 20 km² of occupied habitat.
Bird of prey
Birds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as birds that primarily hunt vertebrates, including other birds. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh....
from the family Falconidae
Falconidae
The falcons and caracaras are around 60 species of diurnal birds of prey that make up the family Falconidae. The family is divided into two subfamiles, Polyborinae, which includes the caracaras and forest falcons, and Falconinae, the falcons, kestrels and falconets.-Description:Falcons and...
endemic to the forests of Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...
, where it is restricted to the southwestern plateau
Plateau
In geology and earth science, a plateau , also called a high plain or tableland, is an area of highland, usually consisting of relatively flat terrain. A highly eroded plateau is called a dissected plateau...
's forests, cliffs, and ravines.
It is the most distinct of the Indian Ocean kestrels
Indian Ocean kestrels
Isolated on various islands around the Indian Ocean, kestrel populations evolved into different species, like Darwin's finches. Behaviour remains similar to other small species of Falco except on forested Mauritius where kestrels hunt arboreally more like hawks...
. It colonized its island home to evolve
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
into a distinct species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
probably during the Gelasian
Gelasian
The Gelasian is an age in the international geologic timescale or a stage in chronostratigraphy, being the earliest or lowest subdivision of the Quaternary period/system and Pleistocene epoch/series. It spans the time between 2.588 ± 0.005 Ma and 1.806 ± 0.005 Ma...
(Late Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
).
It is the most distant living species among the western Indian Ocean kestrels
Indian Ocean kestrels
Isolated on various islands around the Indian Ocean, kestrel populations evolved into different species, like Darwin's finches. Behaviour remains similar to other small species of Falco except on forested Mauritius where kestrels hunt arboreally more like hawks...
(Groombridge et al. 2002, qv Réunion Kestrel
Réunion Kestrel
The Réunion Kestrel is an extinct bird of prey which belongs to the falcon family. It inhabited the Mascarene island of Réunion and was part of the Western Indian Ocean radiation of kestrels....
).
Description
It can reach a size between 26 and 30.5 cm. The weight is up to 250 grams. The males are slightly smaller than the females. The wing is approximately 45 cm and are rounded, unlike those of other falconFalcon
A falcon is any species of raptor in the genus Falco. The genus contains 37 species, widely distributed throughout Europe, Asia, and North America....
s. The lifespan is 15 years in captivity. The Mauritius Kestrel hunts by means of short, swift flights through forests. It is carnivorous, eating gecko
Gecko
Geckos are lizards belonging to the infraorder Gekkota, found in warm climates throughout the world. They range from 1.6 cm to 60 cm....
s, dragonflies
Dragonfly
A dragonfly is a winged insect belonging to the order Odonata, the suborder Epiprocta or, in the strict sense, the infraorder Anisoptera . It is characterized by large multifaceted eyes, two pairs of strong transparent wings, and an elongated body...
, cicada
Cicada
A cicada is an insect of the order Hemiptera, suborder Auchenorrhyncha , in the superfamily Cicadoidea, with large eyes wide apart on the head and usually transparent, well-veined wings. There are about 2,500 species of cicada around the world, and many of them remain unclassified...
s, cockroach
Cockroach
Cockroaches are insects of the order Blattaria or Blattodea, of which about 30 species out of 4,500 total are associated with human habitations...
es, cricket
Cricket
Cricket is a bat-and-ball game played between two teams of 11 players on an oval-shaped field, at the centre of which is a rectangular 22-yard long pitch. One team bats, trying to score as many runs as possible while the other team bowls and fields, trying to dismiss the batsmen and thus limit the...
s, and small bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s.
Conservation
The story of this bird is one of the most remarkable conservation stories. In pre-colonial time the population was estimated between 175 and 325 breeding pairs. This small population was caused most likely by deforestationDeforestation
Deforestation is the removal of a forest or stand of trees where the land is thereafter converted to a nonforest use. Examples of deforestation include conversion of forestland to farms, ranches, or urban use....
in the 18th century and by cyclone
Cyclone
In meteorology, a cyclone is an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterized by inward spiraling winds that rotate anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth. Most large-scale...
s. But the most severe decline was in the 1950s and 1960s due to indiscriminate DDT
DDT
DDT is one of the most well-known synthetic insecticides. It is a chemical with a long, unique, and controversial history....
use and invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
like cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...
s, mongoose
Mongoose
Mongoose are a family of 33 living species of small carnivorans from southern Eurasia and mainland Africa. Four additional species from Madagascar in the subfamily Galidiinae, which were previously classified in this family, are also referred to as "mongooses" or "mongoose-like"...
s and Crab-eating Macaque
Crab-eating Macaque
The Crab-eating macaque is a cercopithecine primate native to Southeast Asia. It is also called the "long-tailed macaque", and is referred to as the "cynomolgus monkey" in laboratories.-Etymology:...
s which killed the kestrels and their eggs. What was probably this species' closest relative in recent times, the Réunion Kestrel
Réunion Kestrel
The Réunion Kestrel is an extinct bird of prey which belongs to the falcon family. It inhabited the Mascarene island of Réunion and was part of the Western Indian Ocean radiation of kestrels....
, became extinct around 1700 for fairly mysterious reasons.
The recorded population dropped to an all-time low of only 4 individuals in 1974 and it was considered the rarest bird in the world. Stanley Temple
Stanley Temple
Stanley A. "Stan" Temple is an American avian ecologist and wildlife biologist. He is the Beers-Bascom Professor in Conservation, Professor of Wildlife Ecology and Professor of Environmental Studies at the University of Wisconsin–Madison....
from Cornell University
Cornell University
Cornell University is an Ivy League university located in Ithaca, New York, United States. It is a private land-grant university, receiving annual funding from the State of New York for certain educational missions...
studied this species for two years and the first attempt in 1973 to breed the birds in captivity failed because the hatchling died when the incubator had a breakdown. Though conservation measures were immediately undertaken with the help of a breeding program by the Jersey Zoo (now called Durrell Wildlife) the efforts to rescue this species initially failed because the eggs were not fertile.
In 1979 a new attempt was undertaken. With the help of Gerald Durrell
Gerald Durrell
Gerald "Gerry" Malcolm Durrell, OBE was a naturalist, zookeeper, conservationist, author and television presenter...
, the Welsh
Welsh people
The Welsh people are an ethnic group and nation associated with Wales and the Welsh language.John Davies argues that the origin of the "Welsh nation" can be traced to the late 4th and early 5th centuries, following the Roman departure from Britain, although Brythonic Celtic languages seem to have...
biologist Carl G. Jones established a wildlife sanctuary on Ile aux Aigrettes. He climbed on the trees and removed the eggs from the nests. This time the eggs were fertile, and Jones was able to rear the hatchlings in incubators. The wild kestrels' diet was supplemented so they would be able to lay a new egg after the first one was removed, averting any negative impact on the wild population. Slowly the population increased and during a census in 1984 50 individuals were estimated. Techniques for breeding, release, and "hacking
Hack (falconry)
Hacking is a training method that helps young falcons reach their hunting potential by giving them exercise and experience. This technique is used to prepare the falcon to become an independent hunter. The sequence of the procedure includes captivity, releasing, flight, and either the falcon will...
" of young birds were improved, the captive breeding center becoming a pioneering research institution for tropical raptor
Bird of prey
Birds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as birds that primarily hunt vertebrates, including other birds. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh....
and small falcon conservation. The captive breeding programme was scaled back in the early 1990s as a self-sustaining population was established. Since 1994, the programme serves only as a safeguard, should some catastrophe befall the wild population, and other rare endemics are now being cared for at the station (such as the Pink Pigeon
Pink Pigeon
The Pink Pigeon, Columba mayeri, is a species of Columbidae endemic to Mauritius, and is now very rare. It was on the brink of extinction in 1991 when only 10 individuals remained, but its numbers have increased due to the efforts of the Durrell Wildlife Conservation Trust since 1977...
or the Mauritius Fody
Mauritius Fody
The Mauritius Fody is a rare species of bird in the weaver family. It is endemic to the island of Mauritius. It is classified by BirdLife International as being endangered. It is also on the United States' Endangered Species List with an endangered status.This bird is 14 centimeters long...
).
Today there are more than 800 mature birds, with numbers rising; it is estimated that the remaining habitat allows for a carrying capacity
Carrying capacity
The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment...
of maybe 50-150 more (BirdLife International 2006a,b). They occur in the remaining forests of the island, especially in the Black River Gorges region. The species was downlisted to Vulnerable
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
by the IUCN in 1994 as releases of captive-bred birds became unnecessary. Little conservation action was deemed necessary only a two decades - in Mauritius Kestrel terms, a long lifetime or maybe 4-5 generation
Generation
Generation , also known as procreation in biological sciences, is the act of producing offspring....
s - after the species had stood at the very brink of extinction. Today, apart from routine monitoring to be able to assist individual couples that fail to establish breeding territories for lack of nesting facilities - a major limiting factor, the ongoing control of introduced predators is basically all that is being done to assist the species' survival (BirdLife International 2006a,b).
While some apparent inbreeding depression
Inbreeding depression
Inbreeding depression is the reduced fitness in a given population as a result of breeding of related individuals. It is often the result of a population bottleneck...
was noted in the captive birds, it was certainly lower than might be expected given that the effective population size
Effective population size
In population genetics, the concept of effective population size Ne was introduced by the American geneticist Sewall Wright, who wrote two landmark papers on it...
was maybe 5 individuals during the mid-1970s. It is known that several genetic lineages of Mauritius Kestrels have disappeared entirely during the 20th century population decline. However, the debilitating effects of DDT accumulation on the birds' health, and not inbreeding, are considered to have been the major cause for the failure of Temple's breeding program.
The evolutionary history of the birds seems to hold clues as to why (Groombridge et al. 2002): Mauritius is a volcanic island, and although the colonization of the island by kestrels cannot be dated with high precision, it was almost certainly some time before volcanic activity died down. The Mauritius Kestrel population seems to have survived a prolonged period of volcanic activity, which must have kept the population small and fluctuating as habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
, food, and kestrels were destroyed by volcanic eruptions time and again. As near-panmictic conditions were sustained for many generations, allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
s that might cause inbreeding depression
Inbreeding depression
Inbreeding depression is the reduced fitness in a given population as a result of breeding of related individuals. It is often the result of a population bottleneck...
were steadily removed by means of natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
. The phenomenon that effective population sizes as low as 4-5 can be tolerated without pronounced inbreeding depression is also known from other small-island birds, such as Petroica traversi or the Laysan Duck
Laysan Duck
The Laysan Duck , also known as the Laysan Teal because of its small size, is an endangered dabbling duck endemic to the Hawaiian Islands...
.
The classification as a Vulnerable species is due to the same fact: on an island as small as Mauritius, chance events like volcanic eruptions (hardly likely in our time) or storms (common and possibly increasing in frequency and strength) can always wipe out major parts of a species' population (BirdLife International 2006a,b). The IUCN classification VU D1+D2 reflects this, translating into a population size of less than 1000 mature individuals, and less than 20 km² of occupied habitat.