Geronticus
Encyclopedia
The small bird
genus
Geronticus belongs to the ibis
subfamily (Threskiornithinae). Its name is derived from the Greek gérontos (γέρωντος, "old man") in reference to the bald head of these dark-plumaged birds; in English they are called bald ibises.
Geronticus contains two living species
. The Northern Bald Ibis
(G. eremita) has a neck crest of elongated feather
s. It is a Critically Endangered
species found around the Mediterranean. Its range had expanded after the last glacial to Alps
of Germany
and even a bit further north, but it was rendered extinct there mainly due to habitat destruction
and unsustainable hunting
. The Southern Bald Ibis
(G. calvus) with a red crown patch but no crest is classified as Vulnerable
and found in subtropical southern Africa
.
Like most ibises, they gregarious long-legged wading birds with long down-curved bills
; they form one subfamily of the Threskiornithidae
, the other subfamily being the spoonbill
s. The two Geronticus species differ from other ibises in that they have unfeathered faces and heads, breed on cliffs rather than in trees, and prefer arid
habitats to the wetlands used by their relatives. Their food contains fewer aquatic animals and more terrestrial
ones; they are known to gather together and feed on locust
swarms, killing many of these notorious pests. This has also contributed to their decline however, as they were much affected by indiscriminate pesticide
spraying in the mid-late 20th century, leading to their disappearance from many regions they used to inhabit.
assigned to the present genus. It is known only from a piece of distal right humerus
, found at Sansan
(France
) in Middle Miocene
rocks of the Serravallian
faunal stage MN 6 (about 12-14 mya). It was initially considered to be a heron
and placed in the genera Ardea
and Proardea
. More plesiomorphic than the living species, it seems to represent an ancient member of the Geronticus lineage, in line with the theory that most living ibis genera seem to have evolve
d before 15 mya.
Geronticus apelex is apparently the direct ancestor of the Southern Bald Ibis. Its remains were found in Early Pliocene deposits near Langebaanweg
(South Africa
) which date back about 5 million years.
What may be an ancestral Europe
an form, Geronticus balcanicus, was found in a Late Pliocene deposit near Slivnitsa
(Bulgaria
). It is hitherto only known from one left and one right carpometacarpus
piece (NMNHS 14 and NMNHS 453, respectively) which are almost alike those of living bald ibises. Contemporaneous with these during the early MN18 faunal stage
– about 2 million years ago (mya) – birds entirely indistinguishable from the modern Northern Bald Ibis inhabited at least Spain
, if not the whole western Mediterranean region already. Thus, the extinct species may be the immediate ancestor of G. eremita, which would have originated at the western extent of its range. Some authors even include the Bulgarian population in G. eremita, but most are more cautious. G. balcanicus may also represent a lineage related but not ancestral to the Northern Bald Ibis, which inhabited the inland regions northeastwards of the European Alpides and – like the immediate ancestor of G. eremita in this scenario – was isolated from the ancestors of G. calvus when gene flow
across tropical Africa ceased.
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...
genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Geronticus belongs to the ibis
Ibis
The ibises are a group of long-legged wading birds in the family Threskiornithidae....
subfamily (Threskiornithinae). Its name is derived from the Greek gérontos (γέρωντος, "old man") in reference to the bald head of these dark-plumaged birds; in English they are called bald ibises.
Geronticus contains two living 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...
. The Northern Bald Ibis
Northern Bald Ibis
The Northern Bald Ibis, Hermit Ibis, or Waldrapp is a migratory bird found in barren, semi-desert or rocky habitats, often close to running water. This 70–80 cm glossy black ibis, which, unlike other members of the ibis family, is non-wading, has an unfeathered red face and head, and a long,...
(G. eremita) has a neck crest of elongated feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
s. It is a Critically Endangered
Critically Endangered
Critically Endangered is the highest risk category assigned by the IUCN Red List for wild species. Critically Endangered means that a species' numbers have decreased, or will decrease, by 80% within three generations....
species found around the Mediterranean. Its range had expanded after the last glacial to Alps
Alps
The Alps is one of the great mountain range systems of Europe, stretching from Austria and Slovenia in the east through Italy, Switzerland, Liechtenstein and Germany to France in the west....
of Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
and even a bit further north, but it was rendered extinct there mainly due to habitat destruction
Habitat destruction
Habitat destruction is the process in which natural habitat is rendered functionally unable to support the species present. In this process, the organisms that previously used the site are displaced or destroyed, reducing biodiversity. Habitat destruction by human activity mainly for the purpose of...
and unsustainable hunting
Hunting
Hunting is the practice of pursuing any living thing, usually wildlife, for food, recreation, or trade. In present-day use, the term refers to lawful hunting, as distinguished from poaching, which is the killing, trapping or capture of the hunted species contrary to applicable law...
. The Southern Bald Ibis
Southern Bald Ibis
The Southern Bald Ibis is a large bird found in open grassland or semi-desert in the mountains of southern Africa.This large, glossy, blue-black ibis has an unfeathered red face and head, and a long, decurved red bill. It breeds colonially on and amongst rocks and on cliffs, laying 2-3 eggs which...
(G. calvus) with a red crown patch but no crest is classified as 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:...
and found in subtropical southern Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
.
Like most ibises, they gregarious long-legged wading birds with long down-curved bills
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
; they form one subfamily of the Threskiornithidae
Threskiornithidae
The family Threskiornithidae includes 34 species of large terrestrial and wading birds, falling into two subfamilies, the ibises and the spoonbills. It was formerly known as Plataleidae. The spoonbills and ibises were once thought to be related to other groups of long-legged wading birds in the...
, the other subfamily being the spoonbill
Spoonbill
Spoonbills are a group of large, long-legged wading birds in the family Threskiornithidae, which also includes the Ibises.All have large, flat, spatulate bills and feed by wading through shallow water, sweeping the partly opened bill from side to side...
s. The two Geronticus species differ from other ibises in that they have unfeathered faces and heads, breed on cliffs rather than in trees, and prefer arid
Arid
A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...
habitats to the wetlands used by their relatives. Their food contains fewer aquatic animals and more terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
ones; they are known to gather together and feed on locust
Locust
Locusts are the swarming phase of short-horned grasshoppers of the family Acrididae. These are species that can breed rapidly under suitable conditions and subsequently become gregarious and migratory...
swarms, killing many of these notorious pests. This has also contributed to their decline however, as they were much affected by indiscriminate pesticide
Pesticide
Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...
spraying in the mid-late 20th century, leading to their disappearance from many regions they used to inhabit.
Fossil record
Geronticus perplexus is by far the oldest fossilFossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
assigned to the present genus. It is known only from a piece of distal right humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
, found at Sansan
Sansan
Sansan is a commune in the Gers department in southwestern France.The vicinity of Sansan is known for its Miocene fossil deposits where geologist Edouard Lartet unearthed the jaw of the primate Pliopithecus antiquus in 1837.-Population:...
(France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
) in Middle Miocene
Middle Miocene
The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene....
rocks of the Serravallian
Serravallian
The Serravallian is in the geologic timescale an age or a stage in the middle Miocene epoch/series, that spans the time between 13.65 ± 0.05 Ma and 11.608 ± 0.005 Ma...
faunal stage MN 6 (about 12-14 mya). It was initially considered to be a heron
Heron
The herons are long-legged freshwater and coastal birds in the family Ardeidae. There are 64 recognised species in this family. Some are called "egrets" or "bitterns" instead of "heron"....
and placed in the genera Ardea
Ardea (genus)
Ardea is a genus of herons. Linnaeus named this genus as the Great Herons, referring to the generally large size of these birds, typically 80–100 cm or more in length....
and Proardea
Proardea
Proardea is an extinct genus of heron, containing a single species, Proardea amissa . It stood about 70 cm tall and was very similar to a modern heron in shape...
. More plesiomorphic than the living species, it seems to represent an ancient member of the Geronticus lineage, in line with the theory that most living ibis genera seem to have 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...
d before 15 mya.
Geronticus apelex is apparently the direct ancestor of the Southern Bald Ibis. Its remains were found in Early Pliocene deposits near Langebaanweg
Langebaanweg
Langebaanweg is a town on the southwest coast of South Africa, in Western Cape Province.It is the location of the air force base AFB Langebaanweg l....
(South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
) which date back about 5 million years.
What may be an ancestral Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
an form, Geronticus balcanicus, was found in a Late Pliocene deposit near Slivnitsa
Slivnitsa
Slivnitsa is a town in western Bulgaria, 22 km away from Sofia, lying on the main road connecting the capital with the Bulgarian-Serbian border...
(Bulgaria
Bulgaria
Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...
). It is hitherto only known from one left and one right carpometacarpus
Carpometacarpus
The carpometacarpus is the fusion of the carpal and metacarpal bone, essentially a single fused bone between the wrist and the knuckles. It is a smallish bone in most birds, generally flattened and with a large hole in the middle. In flightless birds, however, its shape may be slightly different,...
piece (NMNHS 14 and NMNHS 453, respectively) which are almost alike those of living bald ibises. Contemporaneous with these during the early MN18 faunal stage
Faunal stage
In chronostratigraphy, a stage is a succession of rock strata laid down in a single age on the geologic timescale, which usually represents millions of years of deposition. A given stage of rock and the corresponding age of time will by convention have the same name, and the same boundaries.Rock...
– about 2 million years ago (mya) – birds entirely indistinguishable from the modern Northern Bald Ibis inhabited at least Spain
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
, if not the whole western Mediterranean region already. Thus, the extinct species may be the immediate ancestor of G. eremita, which would have originated at the western extent of its range. Some authors even include the Bulgarian population in G. eremita, but most are more cautious. G. balcanicus may also represent a lineage related but not ancestral to the Northern Bald Ibis, which inhabited the inland regions northeastwards of the European Alpides and – like the immediate ancestor of G. eremita in this scenario – was isolated from the ancestors of G. calvus when gene flow
Gene flow
In population genetics, gene flow is the transfer of alleles of genes from one population to another.Migration into or out of a population may be responsible for a marked change in allele frequencies...
across tropical Africa ceased.