Raso lark
Raso lark | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Passeriformes |
Family: | Alaudidae |
Genus: | Alauda |
Species: | A. razae
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Binomial name | |
Alauda razae (Alexander, 1898)
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Synonyms | |
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The Raso lark (Alauda razae) is a small
Taxonomy and systematics
Originally, the Raso lark was classified as belonging to the genus Spizocorys. Formerly or presently, some authorities considered the Raso lark to belong to the genus Calandrella.[2] Alternate names for the Raso lark include Cape Verde Islands lark, Raso Island lark, Raso short-toed lark and Razo skylark.
Description
Raso larks are relatively small in size. The Raso larks can range from sizes between 14 and 18 cm. The adult population is mostly made up of males who are larger than the females. The body has black and brown short streaks and paler around the chest with an erectile crest. The bill is thick-based and robust, longer for the males. The Raso lark is considered an adult when it has developed a reddish-brown tone between the ears and tail, with a pattern on the crown and back. While in flight they display a short tail with short broad wings. The tail and edge of the wings are white.
Distribution and habitat
The Raso lark is restricted in range to only Raso islet in the Cape Verde archipelago, although historically it is believed to have ranged over two other islands,
The island consists mostly of rocky desert with sandy parts in the west. Most Raso larks are found on level plains with volcanic soil and are associated with small vegetated patches along dry stream beds in which it feeds and breeds. Suitable breeding grounds on the island of Raso cover less than half of the island. The barren island suffers from frequent droughts which create dry plains that force the Raso larks to move across the island in search for food. Their most common areas of habitation are near dry river beds, but due to the scarcity of water, only patches of vegetation remain for Raso larks to reside in. Their nesting and feeding grounds consist of those same areas where vegetation is available. The Raso lark's sensitivity to drought has kept it endangered for several years due to the dry climate on the Cape Verde islands.
Behaviour and ecology
A number of desert-dwelling larks have evolved long bills to aid in digging for food in the sandy environment but the enlarged bill of the Raso lark has evolved for dominance displays among males.[3] Flocks have also been observed feeding among rocks close to the sea, and the birds excavate holes in sandy soil to extract the small bulbs of nutsedges, which are perennial weeds in the sedge family that superficially resemble grasses.
Breeding
Breeding is very unpredictable, as it is dependent on the occurrence of rain. Courtship behaviour is similar to that of the Eurasian skylark. The male courts the female by singing softly, raising its chest, and hopping up and down while the wings are spread open. Once done mating, both the male and female collect dried grass in order to build a nest. The male defends the nesting site while the female finds a safe location to build a nest.
The female Raso lark lays one to three eggs per clutch, usually a day apart. The incubation time is thought to be 15 days. During incubation the female sits on the eggs for ten-minute intervals and then goes off to find food. The Raso lark population changes rapidly in response to rain, and has fallen to extremely low levels during droughts (Ratcliffe et al. 1999, Donald et al. 2003, Donald and Brooke 2006). The females, even though smaller in size, still provide by gathering bulbs while the males stay in the burrows and vigorously watch over the nest, protecting it from outside intruders. The Raso lark is not considered very fit for reproductive success and their reproductive success is very low. The adult sex ratio is unbalanced, with a high proportion of the population being male.
Food and feeding
The Raso lark feeds by digging in the ground for insect larvae, and bulbs of the
Threats
The Raso lark is threatened by predators such as the Cape Verde giant gecko and birds such as the
Status
The tiny population size, which fluctuates from ~200-1,000 birds, coupled with the highly skewed sex ratio (around two males to each female) make this species
Gallery
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Raso lark eggs
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Raso lark chicks
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Raso Island with location of Raso lark nest in centre of view
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View from Raso
References
- . Retrieved 19 November 2021.
- ^ "Alauda razae - Avibase". avibase.bsc-eoc.org. Retrieved 2016-12-05.
- ISBN 0-691-08560-9.
- Donald, P. F.; de Ponte, M.; Pitta Groz, M. J.; Taylor, R. (2003). "Status, ecology, behaviour and conservation of Raso Lark Alauda razae". Bird Conservation International. 13: 13–28. .
- Donald, P. F.; Brooke (2006). "An unlikely survivor: the peculiar natural history of the Raso Lark". British Birds. 99: 420–430.
- Brooke, M. de L.; Flower, T. P.; Mainwaring, M. C. (2010). "A scarcity of females may constrain population growth of threatened bird species: Case notes from the Critically Endangered Raso Lark Alauda razae". Bird Conservation International. 20 (4): 382–384. .
- Ratcliffe, Norman; Monteiro, Luis R.; Hazevoet, Cornelis J. (1999). "Status of Raso Lark Alauda razae with notes on threats and foraging behaviour". Bird Conservation International. 9: 43–46. .
- Donald, P.F. (1999) The ecology and conservation of skylarks Alauda arvensis on lowland farmland. Unpublished DPhil thesis, University of Oxford.
- Donald, P.F., Hille, S., Brooke, M. de L., Taylor, R., Wells, C.E., Bolton, M. and Marlow, T. (2007) Sexual dimorphism, niche partitioning and social dominance in the feeding ecology of the Critically Endangered Raso lark Alauda razae. Ibis, 149: 848–852.
- https://web.archive.org/web/20121027233935/http://www.arkive.org/raso-lark/alauda-razae/#biology
- Brooke, M. de L.; Welbergen, J. A.; Mainwaring, M. C.; van der Velde, M.; Harts, A. M. F.; Komdeur, J.; Amos, B. (2010). "Widespread Translocation from Autosomes to Sex Chromosomes Preserves Genetic Variability in an Endangered Lark". Journal of Molecular Evolution. 70 (3): 242–246. PMID 20300932.
External links
- Species factsheet - BirdLife International