Marsh Warbler
Encyclopedia
The Marsh Warbler, Acrocephalus palustris, is an Old World warbler
currently classified in the family Acrocephalidae
. It breeds in temperate Europe and western Asia and winters mainly in south east Africa. It is notable for incorporating striking imitations of a wide variety of other birds into its song.
The Marsh Warbler breeds in a variety of mostly damp habitats, but in Africa winters mainly in dry, well-vegetated areas. It is common over much of its breeding range and expanding its distribution in some areas. However in Britain it is now virtually extinct as a breeding bird. This insectivorous warbler can be easily confused with several close relatives, but the imitative song of the male is highly distinctive.
warblers, such as the Reed Warbler
which also occurs in wetlands and has a similar breeding range. The male's distinctive song is useful for identification, as no other member of the genus mimics other birds to any significant extent. The Marsh Warbler also tends to avoid the stands of pure reed
which are the Reed Warblers' favoured habitat.
The species is monotypic
, and there is no significant geographical variation. The sexes are alike in appearance. Hybridisation with both Reed Warbler and Blyth's Reed Warbler
has been occasionally recorded.
, but breeds, or has bred, in Britain and northern France as well. it is principally a bird of the lowlands, but occurs at altitudes of up to 3000m in Georgia. In recent decades it has expanded its range to the north, with increasing numbers of birds breeding in Scandinavia and north-west Russia.
In western Europe the Marsh Warbler breeds mainly in rank vegetation on damp or seasonally flooded soils, and is particularly attracted to tall herbaceous vegetation such as nettles
, meadowsweet, willowherbs
and to young osiers
and other low woody plants. It may breed in urban brownfield sites with suitable vegetation, for instance in Berlin, and also occasionally in arable crops. In the eastern part of its range, it breeds on dry hillsides with shrubs and in open woodland, as well as the kind of damper habitats it frequents in the west.
The Marsh Warbler winters mainly in south-east Africa, from Cape Province north to Zambia and Malawi. It makes use of a range of well-vegetated habitats, from moist scrub to dense thickets and woodland edge, at altitudes of up to 2400m.
Marsh Warblers tend to migrate
from Europe to Africa via the Middle East, with many crossing Arabia and arriving in Africa on Sudan's Red Sea
coast. Adults usually leave their breeding grounds soon after their young are independent, with their offspring following about two weeks later. On the Red Sea coast most birds arrive from mid-August to mid-September, with numbers of adults peaking in August and of young birds in September. Birds tend to spend much of the autumn somewhere in north-east or east Africa, before continuing south to arrive on their wintering grounds in December or January.
In spring, Marsh Warblers leave their wintering grounds in March or April. They are thought to follow broadly similar routes to their autumn migration. Birds breeding in south-east Europe, for instance on the Black Sea coast, may arrive there by late April. In other parts of their range, the majority of birds do not arrive until mid-May. On the western and northern edge of their range, for instance in England, birds do not tend to arrive until the end of May or early June.
As a vagrant
, the species has been recorded as far away as Iceland and Madeira.
The species is usually monogamous. Marsh Warblers tend to choose new mates each year and do not necessarily return to breed in the same area as previous years. On their breeding grounds they are territorial
, with territories often grouped into loose colonies. In Africa, they are essentially solitary, and may defend territories to some extent.
The nest is a cup, made mostly from leaves and plant stems, and is usually in dense vegetation, at varying heights. Three to six eggs are laid. Both sexes bring food to the nestlings. In continental Europe at least, the species has a short breeding season, of 52-55 days. In some areas, such as Bulgaria, Marsh Warblers suffer significant levels of parasitism by Common Cuckoos
.
s, hornbill
s and pigeons have been noted too. On average, each male bird incorporates imitations of 75 other species into its song, with rather more African than northern species mimicked. All learning seems to take place in the summer the bird is hatched in Europe or Asia, and in its first winter in Africa. The calls of birds heard in subsequent years are not added to the warbler's repertoire. Females may utter a simple, non-imitative song, and a range of other calls are also known.
categorises the species as of least concern
. It is estimated to have a total population of 10 to 27 million individuals.
The reasons for the population decline in Britain are not completely understood, and there appears to be much suitable habitat. The Biodiversity Action Plan
for the species further comments that it is not clear what can be done to conserve the species apart from protecting habitat at known breeding sites and protecting birds from egg collectors and from disturbance.
Old World warbler
The "Old World Warblers" is the name used to describe a large group of birds formerly grouped together in the bird family Sylviidae. The family held over 400 species in over 70 genera, and were the source of much taxonomic confusion. Two families were split out initially, the cisticolas into...
currently classified in the family Acrocephalidae
Acrocephalidae
Acrocephalidae is a family of oscine passerine birds, in the superfamily Sylvioidea....
. It breeds in temperate Europe and western Asia and winters mainly in south east Africa. It is notable for incorporating striking imitations of a wide variety of other birds into its song.
The Marsh Warbler breeds in a variety of mostly damp habitats, but in Africa winters mainly in dry, well-vegetated areas. It is common over much of its breeding range and expanding its distribution in some areas. However in Britain it is now virtually extinct as a breeding bird. This insectivorous warbler can be easily confused with several close relatives, but the imitative song of the male is highly distinctive.
Description and taxonomy
This is a medium-sized warbler. It is very similar in appearance to several other acrocephalineAcrocephalus
The 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...
warblers, such as the Reed Warbler
Reed Warbler
The Eurasian Reed Warbler, or just Reed Warbler, Acrocephalus scirpaceus, is an Old World warbler in the genus Acrocephalus. It breeds across Europe into temperate western Asia. It is migratory, wintering in sub-Saharan Africa....
which also occurs in wetlands and has a similar breeding range. The male's distinctive song is useful for identification, as no other member of the genus mimics other birds to any significant extent. The Marsh Warbler also tends to avoid the stands of pure reed
Phragmites
Phragmites, the Common reed, is a large perennial grass found in wetlands throughout temperate and tropical regions of the world. Phragmites australis is sometimes regarded as the sole species of the genus Phragmites, though some botanists divide Phragmites australis into three or four species...
which are the Reed Warblers' favoured habitat.
The species is monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...
, and there is no significant geographical variation. The sexes are alike in appearance. Hybridisation with both Reed Warbler and Blyth's Reed Warbler
Blyth's Reed Warbler
The Blyth's Reed Warbler is an Old World warbler in the genus Acrocephalus. It breeds in temperate Asia and easternmost Europe. It is migratory, wintering in India and Sri Lanka. It is one of the most common winter warblers in those countries...
has been occasionally recorded.
Distribution and habitat
The Marsh Warbler breeds in the middle latitudes of Europe and western Asia, from the English Channel to about 70 degrees east. It mainly occupies areas with a continental climateContinental climate
Continental climate is a climate characterized by important annual variation in temperature due to the lack of significant bodies of water nearby...
, but breeds, or has bred, in Britain and northern France as well. it is principally a bird of the lowlands, but occurs at altitudes of up to 3000m in Georgia. In recent decades it has expanded its range to the north, with increasing numbers of birds breeding in Scandinavia and north-west Russia.
In western Europe the Marsh Warbler breeds mainly in rank vegetation on damp or seasonally flooded soils, and is particularly attracted to tall herbaceous vegetation such as nettles
Stinging nettle
Stinging 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...
, meadowsweet, willowherbs
Epilobium
Epilobium is a genus in the family Onagraceae, containing about 160-200 species of flowering plants with a worldwide distribution. They are generally abundant in the subarctic, temperate and subantarctic regions, whereas in the subtropics and tropics they are restricted to the cool montane biomes,...
and to young osiers
Willow
Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...
and other low woody plants. It may breed in urban brownfield sites with suitable vegetation, for instance in Berlin, and also occasionally in arable crops. In the eastern part of its range, it breeds on dry hillsides with shrubs and in open woodland, as well as the kind of damper habitats it frequents in the west.
The Marsh Warbler winters mainly in south-east Africa, from Cape Province north to Zambia and Malawi. It makes use of a range of well-vegetated habitats, from moist scrub to dense thickets and woodland edge, at altitudes of up to 2400m.
Marsh Warblers tend to migrate
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...
from Europe to Africa via the Middle East, with many crossing Arabia and arriving in Africa on Sudan's Red Sea
Red Sea
The Red Sea is a seawater inlet of the Indian Ocean, lying between Africa and Asia. The connection to the ocean is in the south through the Bab el Mandeb strait and the Gulf of Aden. In the north, there is the Sinai Peninsula, the Gulf of Aqaba, and the Gulf of Suez...
coast. Adults usually leave their breeding grounds soon after their young are independent, with their offspring following about two weeks later. On the Red Sea coast most birds arrive from mid-August to mid-September, with numbers of adults peaking in August and of young birds in September. Birds tend to spend much of the autumn somewhere in north-east or east Africa, before continuing south to arrive on their wintering grounds in December or January.
In spring, Marsh Warblers leave their wintering grounds in March or April. They are thought to follow broadly similar routes to their autumn migration. Birds breeding in south-east Europe, for instance on the Black Sea coast, may arrive there by late April. In other parts of their range, the majority of birds do not arrive until mid-May. On the western and northern edge of their range, for instance in England, birds do not tend to arrive until the end of May or early June.
As a vagrant
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...
, the species has been recorded as far away as Iceland and Madeira.
Status in Britain
In Britain the species was never widespread, and disappeared from many areas from the 1930s onwards. By the 1970s Marsh Warblers bred in significant numbers only in Worcestershire, where 40-70 pairs were recorded each year during that decade. This population was effectively extinct by the end of the 1990s. From the 1970s and 1980s onwards, a very small population slowly developed in south-east England. However this population is also now close to extinction.Social behaviour and breeding
Territory (animal)
In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...
, with territories often grouped into loose colonies. In Africa, they are essentially solitary, and may defend territories to some extent.
The nest is a cup, made mostly from leaves and plant stems, and is usually in dense vegetation, at varying heights. Three to six eggs are laid. Both sexes bring food to the nestlings. In continental Europe at least, the species has a short breeding season, of 52-55 days. In some areas, such as Bulgaria, Marsh Warblers suffer significant levels of parasitism by Common Cuckoos
Common Cuckoo
The Common Cuckoo is a member of the cuckoo order of birds, Cuculiformes, which includes the roadrunners, the anis and the coucals....
.
Song
The Marsh Warbler is best known for the highly imitative song uttered by males, and very occasionally by females. Each male Marsh Warbler incorporates imitations of a wide range of other birds into its song. Other passerines are most commonly imitated, but the calls of other kinds of bird such as waderWader
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, hornbill
Hornbill
Hornbills are a family of bird found in tropical and subtropical Africa, Asia and Melanesia. They are characterized by a long, down-curved bill which is frequently brightly-colored and sometimes has a casque on the upper mandible. Both the common English and the scientific name of the family...
s and pigeons have been noted too. On average, each male bird incorporates imitations of 75 other species into its song, with rather more African than northern species mimicked. All learning seems to take place in the summer the bird is hatched in Europe or Asia, and in its first winter in Africa. The calls of birds heard in subsequent years are not added to the warbler's repertoire. Females may utter a simple, non-imitative song, and a range of other calls are also known.
Diet and feeding behaviour
The Marsh Warbler is mostly insectivorous, also taking some spiders and small numbers of snails. It generally gleans insects from vegetation but sometimes catches them on the ground or in mid-air. In autumn small numbers of berries may be eaten. There have been no detailed studies of the bird's diet in Africa, though foraging techniques during winter are known to be very similar.Conservation
Globally, the population is believed to be increasing, and the IUCNWorld Conservation Union
The International Union for Conservation of Nature and Natural Resources is an international organization dedicated to finding "pragmatic solutions to our most pressing environment and development challenges." The organization publishes the IUCN Red List, compiling information from a network of...
categorises the species as of least concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
. It is estimated to have a total population of 10 to 27 million individuals.
The reasons for the population decline in Britain are not completely understood, and there appears to be much suitable habitat. The Biodiversity Action Plan
Biodiversity Action Plan
A Biodiversity Action Plan is an internationally recognized program addressing threatened species and habitats and is designed to protect and restore biological systems. The original impetus for these plans derives from the 1992 Convention on Biological Diversity...
for the species further comments that it is not clear what can be done to conserve the species apart from protecting habitat at known breeding sites and protecting birds from egg collectors and from disturbance.
Further reading
- Vinicombe, Keith (2005) ID in depth: Marsh Warbler BirdwatchBirdwatch (magazine)Birdwatch is a British monthly magazine for birdwatchers, established in 1992 by Solo Publishing. Distributed by subscription and also through newsagents, it has a cover price of £4.10...
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