The
Sedge Warbler (
Acrocephalus schoenobaenus) is an
Old World warblerThe "Old World Warblers", family Sylviidae are a family of small passerine bird species; the names sylviid warblers or true warblers may be more appropriate. The Sylviidae mainly occur as breeding species, as the name implies, in Europe, Asia and, to a lesser extent Africa...
in the genus
AcrocephalusThe Acrocephalus warblers are small, insectivorous passerine birds belonging to the genus Acrocephalus. Formerly in the paraphyletic Old World warbler assemblage, they are now separated as the namesake of the marsh- and tree-warbler family Acrocephalidae...
. It is a medium-sized warbler with a brown, streaked back and wings and a distinct pale
superciliumThe term supercilium is a name for a plumage feature present on the heads of many bird species. It is a stripe which starts above the bird's loral area, continuing above the eye, and finishing somewhere towards the rear of the bird's head. It is distinct from the eyestripe which is a line which...
. Sedge Warblers are
migratoryBird 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. These however are usually irregular or in only one direction and are termed variously as nomadism, invasions,...
, crossing the
SaharaThe Sahara , , "The Greatest Desert") is the world's largest hot desert. At over 9,000,000 square kilometres , it covers most of Northern Africa, making it almost as large as the United States or the continent of Europe. The desert stretches from the Red Sea, including parts of the Mediterranean...
to get from their
EuropeEurope 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 water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
an and
AsiaAsia is the world's largest and most populous continent, located in the eastern and northern hemispheres. It covers 8.6% of the earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population.Asia is traditionally defined as part of the...
n breeding grounds to spend winter in
AfricaAfrica 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. With a billion people in 61 territories, it accounts for about 14.8% of the...
. The male's song is composed of random chattering phrases and can include mimicry of other species. The Sedge Warbler is mostly
insectivorousAn insectivore is a type of carnivore with a diet that consists chiefly of insects and similar small creatures.Although individually small, insects exist in enormous numbers and make up a very large part of the animal biomass in almost all non-marine environments...
.
Description
This is a medium-sized warbler, long and weighing around 12 g. It has a streaked brown back and wings, and pale underparts. The rump is warm brown and unstreaked, contrasting with the duller wings. The forehead is flattened, there is a prominent whitish
superciliumThe term supercilium is a name for a plumage feature present on the heads of many bird species. It is a stripe which starts above the bird's loral area, continuing above the eye, and finishing somewhere towards the rear of the bird's head. It is distinct from the eyestripe which is a line which...
, the crown is streaked with black, and the bill is strong and pointed. The legs are greyish.
The
plumagePlumage 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...
of the sexes is identical, although they can be told apart when caught for
ringingBird ringing or bird banding is a technique used in the study of wild birds, by attaching a small, individually numbered, metal or plastic tag to their legs or wings, so that various aspects of the bird's life can be studied by the ability to re-find the same individual later...
by the presence of a
brood patchthumb|250px|Brood patch of [[Sand Martin]]A brood patch is a patch of featherless skin that is visible on the underside of birds during the nesting season. This patch of skin is well supplied with blood vessels at the surface making it possible for the birds to transfer heat to their eggs when...
or
cloacal protuberanceIn zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive and urinary tracts of certain animal species. The word comes from Latin, and means sewer...
. Juvenile birds have dark spots on the breast. They can be easier to confuse with
Aquatic WarblerThe Aquatic Warbler, Acrocephalus paludicola, is an Old World warbler in the genus Acrocephalus. It breeds in temperate eastern Europe and western Asia, with an estimated population of 15,000 pairs. It is migratory, wintering in west Africa...
Acrocephalus paludicola due to an apparent pale central crown stripe contrasting with the darker edges. Other similar species include
Moustached WarblerThe Moustached Warbler, Acrocephalus melanopogon, is an Old World warbler in the genus Acrocephalus. It breeds in southern Europe and southern temperate Asia with a few in north-west Africa. It is partially migratory...
A. melanopogon and Pallas's Grasshopper-warbler
Locustella certhiola. The oldest recorded Sedge Warbler was a bird ringed in
FinlandFinland , officially the Republic of Finland
, is a Nordic country and democracy situated in the Fennoscandian region of northern Europe. It borders Sweden on the west, Russia on the east, and Norway on the north, while Estonia lies to its south across the Gulf of Finland...
which reached the age of 10 years, 1 month. The typical lifespan is 2 years.
Taxonomy
The Sedge Warbler was first described by
Carolus LinnaeusCarl Linnaeus was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature...
in his
Systema naturae in 1758 (British ornithologists did not distinguish the species from the Eurasian Reed Warbler until the 18th Century). Its scientific name is derived from the
GreekGreek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical...
akros, meaning 'pointed', and
kephale ('head'),
skhoiniklos ('reed') and
baino ('to walk'). It is monotypic.
Distribution and habitat
The Sedge Warbler has a large range and an estimated Global Extent of Occurrence of 10 million square kilometres, with a large global population including between 8.8 million and 15 million birds in
EuropeEurope 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 water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
. Data analysis by the
British Trust for OrnithologyThe British Trust for Ornithology is an organisation founded in 1932 for the study of birds in the British Isles.-Activities:The BTO carries out research into the lives of birds, chiefly by conducting population and breeding surveys, and by bird ringing, all through the activities of a large...
has shown that fluctuations in the Sedge Warbler population stem from the adult survival rate, due to changes in rainfall on the birds' wintering grounds. Global changes in population have not been measured, but the Sedge Warbler's status is designated 'of Least Concern' by
BirdLife InternationalBirdLife International is the international conservation organization working to protect the world’s birds and their habitats...
.
It breeds across
EuropeEurope 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 water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
and western and central
AsiaAsia is the world's largest and most populous continent, located in the eastern and northern hemispheres. It covers 8.6% of the earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population.Asia is traditionally defined as part of the...
and is
migratoryBird 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. These however are usually irregular or in only one direction and are termed variously as nomadism, invasions,...
. After feeding up post-breeding, they migrate quickly across southern Europe and the Sahara from August to September. Studies in
NigeriaNigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising thirty-six states and one Federal Capital Territory. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger...
and
UgandaThe Republic of Uganda is a landlocked country in East Africa. It is bordered on the east by Kenya, on the north by Sudan, on the west by the Democratic Republic of the Congo, on the southwest by Rwanda, and on the south by Tanzania...
suggest that Sedge Warblers return to spend winter at the same sites, year after year.
All Sedge Warblers spend winter in sub-
SaharaThe Sahara , , "The Greatest Desert") is the world's largest hot desert. At over 9,000,000 square kilometres , it covers most of Northern Africa, making it almost as large as the United States or the continent of Europe. The desert stretches from the Red Sea, including parts of the Mediterranean...
n Africa, from
SenegalSenegal , officially the Republic of Senegal, is a country south of the Sénégal River in western Africa. Senegal is bounded by the Atlantic Ocean to the west, Mauritania to the north, Mali to the east, and Guinea and Guinea-Bissau to the south, and it also encircles The Gambia on its three sides,...
in the west to
EthiopiaEthiopia , officially the Federal Democratic Republic of Ethiopia, is a landlocked country situated in the Horn of Africa. Ethiopia is bordered by Eritrea to the north, Sudan to the west, Kenya to the south, Somalia to the east and Djibouti to the northeast. Its size is 1,100,000 km² with an...
in the east, and as far south as the eastern
Cape ProvinceThe Cape of Good Hope Province was a province in the Union of South Africa and subsequently the Republic of South Africa...
of
South AfricaThe Republic of South Africa is a country located at the southern tip of Africa, with a coastline on the Atlantic and Indian Oceans. To the north lie Namibia, Botswana and Zimbabwe, to the east are Mozambique and Swaziland, while Lesotho is an independent country surrounded by South Africa.Modern...
and northern
NamibiaNamibia, officially the Republic of Namibia , is a country in Southern Africa whose western border is the Atlantic Ocean. It shares borders with Angola and Zambia to the north, Botswana and Zimbabwe to the east, and South Africa to the south and east...
. The route taken on the southward migration, and eventual wintering grounds, correspond to the birds' breeding grounds. Birds ringed in the
United KingdomThe United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of Ireland, and many small islands...
and
NetherlandsThe Netherlands is a country in Northwestern Europe, constituting the major portion of the Kingdom of the Netherlands. It is a parliamentary democratic constitutional monarchy. The Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east...
are later found from south-west
IberiaThe name Iberia refers to three historical regions of the old world:* Iberian Peninsula, in Southwest Europe, location of modern-day Portugal and Spain** Prehistoric Iberia...
to
ItalyItaly , officially the Italian Republic , is a country located on the Italian Peninsula in Southern Europe and on the two largest islands in the Mediterranean Sea, Sicily and Sardinia. Italy shares its northern, Alpine boundary with France, Switzerland, Austria and Slovenia...
; birds from
SwedenSweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe...
are recovered in central Europe and Italy; while
FinnishFinland , officially the Republic of Finland
, is a Nordic country and democracy situated in the Fennoscandian region of northern Europe. It borders Sweden on the west, Russia on the east, and Norway on the north, while Estonia lies to its south across the Gulf of Finland...
birds are found in north-east Italy and
MaltaMalta , officially the Republic of Malta , is a densely populated developed European country in the European Union. The Southern European island nation is an archipelago that includes the inhabited islands of Malta, Gozo and Comino, along with a number of smaller, uninhabited islands...
east to the
AegeanThe Aegean Sea is an elongated embayment of the Mediterranean Sea located between the southern Balkan and Anatolian peninsulas, i.e., between the mainlands of Greece and Turkey respectively. In the north, it is connected to the Marmara Sea and Black Sea by the Dardanelles and Bosporus...
region. Sedge Warblers from the former
Soviet UnionThe Union of Soviet Socialist Republics was a constitutionally socialist state that existed in Eurasia from 1922 to 1991. The name is a translation of the , tr. Soyuz Sovetskikh Sotsialisticheskikh Respublik, abbreviated СССР, SSSR. The common short name is Soviet Union, from , Sovetskiy Soyuz...
take routes via the eastern
Mediterranean SeaThe Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by Africa, and on the east by the Levant. The sea is technically a part of the Atlantic Ocean, although it...
and
Middle EastThe Middle East is a region that spans southwestern Asia, southeastern Europe, and northeastern Africa. It has no clear boundaries, often used as a synonym to Near East, in opposition to Far East...
.
Loss of wetland areas for feeding on migration, and the expansion of the Sahara desert, pose threats to the Sedge Warbler's breeding population. Birds begin leaving Africa in late February, fatten up at wetlands before and probably after crossing the Sahara, and arrive in
EuropeEurope 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 water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus Mountains , and the Black Sea to the southeast...
from March onwards.
Unlike other members of the
AcrocephalusThe Acrocephalus warblers are small, insectivorous passerine birds belonging to the genus Acrocephalus. Formerly in the paraphyletic Old World warbler assemblage, they are now separated as the namesake of the marsh- and tree-warbler family Acrocephalidae...
genus, the Sedge Warbler's range stretches from the Arctic to mid-latitudes. It is adapted to cool, cloudy and moist conditions. Though it is often found in wetlands, it can breed 500 metres or more away from water. During the breeding season, this is a species found in reedbeds, often with scrub, ditches and habitats away from water including hedgerows, patches of
Stinging NettleStinging nettle or common nettle, Urtica dioica, is a herbaceous perennial flowering plant, native to Europe, Asia, northern Africa, and North America, and is the best-known member of the nettle genus Urtica.-Description:...
s
Urtica dioica, and arable crops. On the African wintering grounds, habitats such as reeds at wetlands, papyrus, grass, sedge and reedmace and tall elephant grass are used. It can be found at altitudes of 1800-2400 metres above sea level in Ethiopia.
Breeding
The song is varied, rushed and chattering, with sweeter phrases and some mimicry, typical of the
Acrocephalus warblers. It is composed of phrases in random order, so that it is never the same. Male Sedge Warblers which have the widest repertoire mate with the largest number of females.
Male Sedge Warblers commence singing only a few hours after arriving on their breeding territory. The song is given from a bare perch such as a reed stem or bush, or from cover and during routine flights within their territory. Song-flights are also performed: while singing, the bird takes off, rises to a height of around 2-5 metres and then after a short circling flight, makes a slow, 'parachuting' descent, often with the wings held up in a 'v' shape. The song has the function of attracting a mate, rather than keeping other males away, and is stopped as soon as a mate is found. Contact calls are described as 'chirr' or 'kerr'; these calls are repeated quickly to form a rattling alarm call.
Studies have found that male Sedge Warblers are often faithful to their breeding sites, but females are less so. A study in
NottinghamshireNottinghamshire is an English county in the East Midlands, which borders South Yorkshire, Lincolnshire, Leicestershire and Derbyshire...
,
EnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...
, showed that a third of males which returned bred within 50 m or less of their previous breeding site, and only 14% bred further than 400 m away. Pairs are usually monogamous, but not strictly so. Males occasionally practice bigamy and promiscuity. If eggs or chicks are predated, the female will often leave the male, who then resumes singing and pairs with another female. Hybridisation with Eurasian Reed Warbler has been recorded.
The male defends a territory of around 0.1 to 0.2 hectares; in a study at
ZaanstadZaanstad is a municipality in the Netherlands, in the province of North Holland. Its main town is Zaandam. It is part of the metropolitan area of Amsterdam.-Population centres :...
,
NetherlandsThe Netherlands is a country in Northwestern Europe, constituting the major portion of the Kingdom of the Netherlands. It is a parliamentary democratic constitutional monarchy. The Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east...
, 68 territories were studied, with an average size of 1064 metres square one year, and 904 m sq the next.
The nest, built by the female, is in vegetation on the ground or up to a height of 50 cm. The cup-shaped structure has an outer layer of grass, stems and leaves, plus spiders' webs, with a thick, finer layer inside including reed flowers, animal hair and plant down. It is woven around vertical plant stems.
Between 3-5 greenish-yellow and brown-mottled
eggIn most birds and reptiles, an egg is the zygote, resulting from fertilization of the ovum. To enable incubation the egg is usually kept within a favourable temperature range as it nourishes and protects the growing embryo. When the embryo is adequately developed it breaks out of the egg in the...
s are laid, measuring 18 x 13 mm and weighing 1.6 g each. They are incubated by the female for 14 days; the chicks are
altricialAltricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
and naked. Both male and female care for the chicks, which fledge after 13–14 days. After leaving the nest, young Sedge Warblers continue begging for food from their parents for between 1–2 weeks after learning to fly.
Food and feeding
Prey taken by Sedge Warblers includes mayflies,
dragonflies and damselfliesOdonata is an order of insects, encompassing dragonflies and damselflies . The word dragonfly is also sometimes used to refer to all Odonata...
,
grasshoppersThe Orthoptera are an order of insects with paurometabolous or incomplete metamorphosis, including the grasshoppers, crickets and locusts.Many insects in this order produce sound by rubbing their wings against each other or their legs, the wings or legs containing rows of corrugated bumps...
,
bugsHemiptera is an order of insects, comprising around 80,000 species of cicadas, aphids, planthoppers, leafhoppers, shield bugs, and others. They range in size from 1 mm to around 15 cm, and share a common arrangement of sucking mouthparts ....
,
lacewingsThe insect order Neuroptera, or net-winged insects, includes the lacewings, mantidflies, antlions, and their relatives. The order contains some 4,000 species...
,
mothsLepidoptera is an order of insects that includes moths and butterflies. It is one of the most speciose orders in the class Insecta, encompassing moths and the three superfamilies of butterflies, skipper butterflies, and moth-butterflies...
,
beetlesA coleopter is a type of Vertical Take-Off and Landing aircraft design where the fuselage is surrounded by an annular wing. The aircraft is intended to take off and land on its tail...
and
flies Hymenoptera is one of the largest orders of insects, comprising the sawflies, wasps, bees, and ants. The name refers to the heavy wings of the insects, and is derived from the Ancient Greek ὑμήν : membrane and πτερόν : wing...
. Vegetable material includes elderberries and
blackberriesRubus is a large genus of flowering plants in the rose family, Rosaceae, subfamily Rosoideae. Raspberries, blackberries, and dewberries are common, widely distributed members of the genus. Most of these plants have woody stems with prickles like roses; spines, bristles, and gland-tipped hairs are...
. On their wintering grounds food includes
non-biting midgesChironomidae are a family of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae. Many species superficially resemble mosquitoes but they lack the wing scales and elongate mouthparts of the Culicidae...
and flowers and berries from the
Toothbrush TreeSalvadora persica , is a species of Salvadora....
Salvadora persica.
In late July, prior to migration, it appears that Sedge Warblers seek out sites with large numbers of
Plum-reed AphidsAphididae is a very large insect family in the aphid superfamily , of the order Hemiptera. There are several thousand species in this family, many of which are well-known for being serious plant pests...
Hyalopterus pruni and stay longer there than at other places; ringing studies show that birds may move considerable distances (eg. from southern
EnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...
to northern
FranceFrance , officially the French Republic , is a country located in Western Europe, with several overseas islands and territories located on other continents. Metropolitan France extends from the Mediterranean Sea to the English Channel and the North Sea, and from the Rhine to the Atlantic Ocean...
) in search of food before beginning their actual migration. In
PortugalPortugal , officially the Portuguese Republic , is a country located in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of mainland Europe and is bordered by the Atlantic Ocean to the west and south and by Spain to the north and east...
, the aphid supply dries up too early for Sedge Warblers to utilise it, so many birds do not stop off there and are already heavy with fat when they pass through.
Birds with the heaviest fat reserves built up before migration are capable of non-stop flights from Africa to southern Britain, or from
UgandaThe Republic of Uganda is a landlocked country in East Africa. It is bordered on the east by Kenya, on the north by Sudan, on the west by the Democratic Republic of the Congo, on the southwest by Rwanda, and on the south by Tanzania...
to
IraqIraq , officially the Republic of Iraq , also known as Mesopotamia, is a country in Western Asia spanning most of the northwestern end of the Zagros mountain range, the eastern part of the Syrian Desert and the northern part of the Arabian Desert.Iraq shares borders with Jordan to the west, Syria...
, for example. Some double their normal weight when 'fuelling' for migration. Lighter birds are forced to make the journey in several shorter parts.
Sedge Warblers feed in low, thick vegetation, especially reeds and rushes, but also in arable fields and around bushes. A study at
Attenborough, NottinghamshireAttenborough is a suburb in the Broxtowe borough of Nottinghamshire. It forms part of Greater Nottingham, and is to the southwest of Nottingham, between Long Eaton and Beeston ....
in
EnglandEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...
, found that the habitats used for foraging during the breeding season were 47% marshland, mostly
GlyceriaGlyceria is a genus of grasses known commonly as mannagrass or sweet-grass. These are perennial rhizomatous grasses found in wet areas in temperate regions worldwide. The base of the grass grows along the ground and may root at several places. Then it grows erect and bears leaf blades which may be...
grasses, 26% shrub, 21% field vegetation and 6% woodland. Feeding techniques include 'picking' insects from vegetation while perched or sometimes hovering, and 'leap-catching', when the bird grabs flying insects as it flies between perches. Sedge Warblers tend to hop between plant stems and pick insects from underneath leaves; they take advantage of the low temperatures around dusk and dawn which make their prey less mobile.
Further reading