Great reed warbler

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Great reed warbler
Adult at a
bird banding
station

Least Concern  (IUCN 3.1)[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Acrocephalidae
Genus: Acrocephalus
Species:
A. arundinaceus
Binomial name
Acrocephalus arundinaceus
Range of A. arundinaceus
  Breeding
  Passage
  Non-breeding
Synonyms

Turdus arundinaceus Linnaeus, 1758
Acrocephalus turdoïdes[2]

The great reed warbler (Acrocephalus arundinaceus) is a

Eurasian bird in the passerine genus Acrocephalus
.

The genus name Acrocephalus is from Ancient Greek akros, "highest", and kephale, "head". It is possible that Naumann and Naumann thought akros meant "sharp-pointed". The specific arundinaceus is from Latin and means "like a reed", from arundo, arundinis, "reed".[3]

It used to be placed in the

Palearctic and migrate to sub-Saharan Africa
in the winter. [4] Great reed warblers favour reed beds as their habitat during breeding months, while living in reed beds, bush thickets, rice fields, and forest clearings during the winter. Great reed warblers exhibit relatively low sexual dimorphism, and both genders of the species are similar in appearance. This species mates both polygynously and monogamously.

Description

The

Eurasian reed warbler (A. scirpaceus), but with a stronger supercilium
.

The sexes are identical, as with most old world warblers, but young birds are richer buff below.

The warbler's song is very loud and far-carrying. The song's main phrase is a chattering and creaking carr-carr-cree-cree-cree-jet-jet, to which the whistles and vocal mimicry typical of marsh warblers are added.

Distribution and ecology

Nest with clutch of eggs

The great reed warbler breeds in

tropical Africa. This bird migrates north at a rather late date, and some birds remain in their winter quarters until the end of April.[1][8][9]

While there are no

Würm ice sheets and the surrounding barren lands. Though the data are insufficient to robustly infer a date for this separation, it suggests the populations became separated around 80,000 years ago – coincident with the first major advance of the ice sheets. The populations must have expanded their range again at the start of the Holocene about 13,000 years ago, but even today the western birds winter in the west and the eastern birds in the east of tropical Africa.[9]

During 2017–2019, miniature data loggers were used to track migratory flights of great reed warblers, over the Mediterranean Sea and Sahara Desert, between their breeding grounds at Lake Kvismaren, Sweden, and their winter quarters in sub-Saharan Africa.[4] When over the Sahara Desert, some birds would ascend to altitudes exceeding 5 km. As of 2023, these are the highest recorded avian ascents. [10] For comparison, such altitudes are comparable to those of the summits of the highest mountains in Africa and Europe. Possible explanations for such high--altitude ascents include avoidance of predation, reduction of risk of hyperthermia and dehydration, and extension of the visual horizon.[4][10]


This

insectivorous, but it will take other prey items of small size, including vertebrates such as tadpoles
.

The great reed warbler undergoes marked long-term population fluctuations, and it is able to expand its range quickly when new

IUCN.[1][9] Population size can be calculated with a suitability model, but direct counts of territorial males in suitable habitat and sampling the population sex-ratio can be a proper alternative to inference-rich predictive modeling based on imperfect habitat-extrapolation of densities of reed warblers at large spatial scales.[11]

Population densities of Great reed warblers (mean±SD) in European countries
Country Method Pairs/ha Birds/ha Nests/ha Ref.
Spain Transect - 1.4 - [11]
Slovakia Nest 6.5±6.2 - - [12]
Poland Nest - - 2.5±1.8 [13]

Behaviour

Diet

A. arundinaceus has a primarily

diptera and arachnids, though this may not be their preferred food.[16]

Communication and courtship

Song, recorded at Diaccia Botrona marsh (Italy)
Song, recorded at Macta marsh (Algeria)
Sonogram of Great reed warbler's song, recorded at Macta marsh (Algeria)
Great reed warbler (Kyiv, Ukraine)

Male great reed warblers have been observed to communicate via two basic song types: short songs about one second in length with few syllables, and long songs of about four seconds that have more syllables and are louder than the short variety. It has been observed that long songs are primarily used by males to attract females; long songs are only given spontaneously by unpaired males, and cease with the arrival of a female. Short songs, however, are primarily used in territorial encounters with rival males.[17]

During experimental observation, male great reed warblers showed reluctance to approach recordings of short songs, and when lured in by long songs, would retreat when playback was switched to short songs.[17]

Traditionally, monogamous species of genus Acrocephalus use long, variable, and complex songs to attract mates, whereas polygynous varieties use short, simple, stereotypical songs for territorial defence. There is evidence that long songs have been evolved through intersexual selection, whereas short songs have been evolved through intrasexual selection. The great reed warbler is a notable example of these selective pressures, as it is a partial polygynist and has evolved variable song structure (both long and short) through evolutionary compromise.[17]

In addition to communication, the great reed warbler's song size has been implicated in organism fitness and reproductive success. Though no direct relationship has been found between song size and either territory size or beneficial male qualities, such as wing length, weight, or age, strong correlation has been observed between repertoire size and territory quality. Furthermore, partial correlation analysis has shown that territory quality has significant effect on the number of females obtained, while repertoire length is linked to the number of young produced.[18]

Mating system and sexual behavior

Eggs
Nest containing a slightly larger common cuckoo egg and four warbler eggs (Apaj, Hungary)

Great reed warbler females lay 3–6

eggs in an open cup-nest in reeds. Some pairs of warblers are monogamous, but others are not, and unpaired, so-called "satellite" males still father some young.[19] Great reed warblers defend their nests using graded alarm calls, directed towards a wide range of enemies,[20] although these alarm calls might reveal the whereabouts of the nest to brood parasites.[21]

A long-term study of the factors that contribute to male fitness examined the characteristics of males and territories in relation to annual and lifetime breeding success. It showed that the arrival order of the male was the most significant factor for predicting pairing success, fledgling success, and number of offspring that survive. It also found that arrival order was closely correlated with territory attractiveness rank. Females seem to prefer early arriving males that occupy more attractive territories. These females also tend to gain direct benefits through the increased production of fledglings and offspring that become adults. In addition, male song repertoire length is positively correlated to annual harem size and overall lifetime production of offspring that survive. Song repertoire size alone is able to predict male lifetime number of surviving offspring. Females tend to be attracted to males with longer song repertoires since they tend to sire offspring with improved viability. In doing so, they gain indirect benefits for their own young.[22][23]

Great reed warblers have a short,

female choice. The differences in territory characteristics seemed to be more important. However, there is also a strong correlation between males and their territory characteristics. Models based on the polygyny threshold and sexy son hypotheses predict that females should gain evolutionary advantage in either short-term or long-term in this mating system, yet the study did not support this. The data showed that secondary females had greatly reduced breeding success.[24][25]

References

  1. ^
    doi:10.2305/IUCN.UK.2017-1.RLTS.T104317670A111179363.en
    . Retrieved 12 November 2021.
  2. ^ For instance in Gould, John (1873). The Birds of Great Britain. Vol. II. pp. Plate LXXII (and accompanying text).. See also: Digital Collections, The New York Public Library. "(still image) Acrocephalus turdoïdes. Thrush-Warbler., (1862 - 1873)". The New York Public Library, Astor, Lennox, and Tilden Foundation. Retrieved July 17, 2019.
  3. ISBN 978-1-4081-2501-4
    .
  4. ^
    ISSN 0036-8075
    .
  5. ^ "Acrocephalus arundinaceus (Linnaeus, 1758)".
  6. ISBN 84-87334-20-2
    .
  7. ISBN 978-0856610790
    .
  8. ^ a b Traylor, Marvin; Daniel Parelius (13 November 1967). "A Collection of Birds from the Ivory Coast". Fieldiana Zoology. 51 (7): 91–117.
  9. ^
    doi:10.1111/j.1095-8312.1999.tb01882.x
    .
  10. ^
    ISSN 0960-9822
    .
  11. ^
    PMID 30059562
    .
  12. ^ Prokešová, J.; Kocian, L. (2004). "Habitat selection of two Acrocephalus warblers breeding in reed beds near Malacky (Western Slovakia)" (PDF). Biologia Bratislava. 59: 637–644.
  13. doi:10.1111/j.1439-0310.2006.01308.x
    .
  14. S2CID 22647139
    .
  15. ^ Grzimek, Bernhard (2002). Hutchins, Jackson; Bock, Olendorf (eds.). Grzimek's Animal Life Encyclopedia, Vol. 11.4 (2nd ed.). Farmington Hills, MI: Gale Group. p. 17.
  16. S2CID 35524752
    .
  17. ^
    S2CID 53192983
    .
  18. S2CID 32813295
    .
  19. S2CID 84661011
    .
  20. S2CID 53164964
    .
  21. PMID 31811179
    .
  22. S2CID 21645256
    .
  23. doi:10.1890/0012-9658(1998)079[2376:PIGRWA]2.0.CO;2
    .
  24. JSTOR 5418
    .
  25. doi:10.1093/beheco/6.1.27
    .

External links

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