Actitis
Encyclopedia
Actitis is a small genus
of wader
s, comprising just two very similar bird
species
:
These are both small migratory
waders, greyish brown on top and white underneath, with a distinctive stiff-winged flight low over the water. The plumage
s are very similar, apart from Spotted Sandpipers' distinctive breeding plumage, and suspected out-of-range vagrants
must be carefully observed for identification to species.
Both species have short yellow or yellowish legs and a medium bill
. These are not gregarious birds and are seldom seen in large flocks.
They nest on the ground, and their habitat
is near fresh water
. These birds forage
on the ground or in water, picking up food by sight. They may also catch insect
s in flight. They eat insects, crustacean
s and other invertebrate
s.
Actitis is part of the shank
-tattler
-phalarope
clade
and less closely related to the calidrid
sandpipers. Based on the degree of DNA sequence
divergence and putative shank and phalarope fossils from around the Oligocene
/Miocene
boundary some 23-22 million years ago, presumably Actitis diverged from its closest relatives in the Late Oligocene; given the much higher diversity of the prehistoric members of the group in Eurasia
it is likely that they originated there, possibly being isolated as the remains of the Turgai Sea
dried up, which happened just around this time.
The Late Pliocene fossil
described as Actitis balcanica appears to be actually from some indeterminate charadriid
.
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...
of wader
Wader
Waders, called shorebirds in North America , are members of the order Charadriiformes, excluding the more marine web-footed seabird groups. The latter are the skuas , gulls , terns , skimmers , and auks...
s, comprising just two very similar 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...
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...
:
- Common SandpiperCommon SandpiperThe Common Sandpiper is a small Palearctic wader. This bird and its American sister species, the Spotted Sandpiper , make up the genus Actitis. They are parapatric and replace each other geographically; stray birds of either species may settle down with breeders of the other and hybridize...
, Actitis hypoleucos, of EurasiaEurasiaEurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres... - Spotted SandpiperSpotted SandpiperThe Spotted Sandpiper is a small shorebird, 18–20 cm long. Together with its sister species, the Common Sandpiper they make up the genus Actitis...
, Actitis macularia of North AmericaNorth AmericaNorth America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
These are both small migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
waders, greyish brown on top and white underneath, with a distinctive stiff-winged flight low over the water. The plumage
Plumage
Plumage refers both to the layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage vary between species and subspecies and can also vary between different age classes, sexes, and season. Within species there can also be a...
s are very similar, apart from Spotted Sandpipers' distinctive breeding plumage, and suspected out-of-range vagrants
Vagrancy (biology)
Vagrancy is a phenomenon in biology whereby individual animals appear well outside their normal range; individual animals which exhibit vagrancy are known as vagrants. The term accidental is sometimes also used...
must be carefully observed for identification to species.
Both species have short yellow or yellowish legs and a medium bill
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...
. These are not gregarious birds and are seldom seen in large flocks.
They nest on the ground, and their 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...
is near fresh water
Fresh Water
Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
. These birds forage
Forage
Forage is plant material eaten by grazing livestock.Historically the term forage has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used more loosely to include similar plants cut for fodder and carried to the animals, especially...
on the ground or in water, picking up food by sight. They may also catch insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s in flight. They eat insects, crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s and other invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s.
Actitis is part of the shank
Tringa
Tringa is a genus of waders, containing the shanks and tattlers. They are mainly freshwater birds, often with brightly coloured legs as reflected in the English names of six species, as well as the specific names of two of these and the Green Sandpiper. They are typically associated with northern...
-tattler
Tattler (bird)
The tattlers are the two very similar bird species in the shorebird genus Tringa. They formerly had their own genus, Heteroscelus. The old genus name means "different leg" in Greek, referring to the leg scales that differentiate the tattlers from their close relatives, the shanks.The species are:*...
-phalarope
Phalarope
A phalarope or wadepiper is any of three living species of slender-necked shorebirds in the genus Phalaropus of the bird family Scolopacidae. They are close relatives of the shanks and tattlers, the Actitis and Terek Sandpipers, and also of the turnstones and calidrids...
clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
and less closely related to the calidrid
Calidrid
The calidrids or typical waders are a group of Arctic-breeding, strongly migratory wading birds. These birds form huge mixed flocks on coasts and estuaries in winter. They are the typical "sandpipers", small to medium-sized, long-winged and relatively short-billed.Their bills have sensitive tips...
sandpipers. Based on the degree of DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
divergence and putative shank and phalarope fossils from around the Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
/Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
boundary some 23-22 million years ago, presumably Actitis diverged from its closest relatives in the Late Oligocene; given the much higher diversity of the prehistoric members of the group in Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
it is likely that they originated there, possibly being isolated as the remains of the Turgai Sea
Turgai Sea
The Turgai Sea or Turgai Strait, also known as the West Siberian Sea, was a large shallow body of salt water of the Mesozoic and Cenozoic Eras...
dried up, which happened just around this time.
The Late Pliocene fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
described as Actitis balcanica appears to be actually from some indeterminate charadriid
Charadriidae
The bird family Charadriidae includes the plovers, dotterels, and lapwings, about 64 to 66 species in all.- Morphology :They are small to medium-sized birds with compact bodies, short, thick necks and long, usually pointed, wings, but most species of lapwing may have more rounded wings...
.