Horsfield's bronze cuckoo

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Horsfield's bronze cuckoo
Horsfield's Bronze-Cuckoo Newhaven.jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Cuculiformes
Family: Cuculidae
Genus: Chrysococcyx
Species: C. basalis
Binomial name
Chrysococcyx basalis
(Horsfield, 1821)

The Horsfield’s bronze cuckoo (Chrysococcyx basalis) is a small cuckoo in the family Cuculidae. Its size averages 22g[2] and is distinguished by its green and bronze iridescent colouring on its back and incomplete brown barring from neck to tail. What distinguishes the Horsfield’s bronze cuckoo from other bronze cuckoos is its white eyebrow and brown eye stripe.[3] The Horsfield’s bronze cuckoo is common throughout Australia preferring the drier open woodlands away from forested areas.[4]

Taxonomy[edit]

The Horsfield’s bronze cuckoo is one of five Australian species in the genus Chrysococcyx (formally Chalcites) a type of parasitic bird,[3] that parasitises fairy-wrens primarily to raise their young.[2][5]

The five species of cuckoo in the genus Chrysococcyx:

Diet and behaviour[edit]

Photographed at Capertee Valley, NSW, Australia

The main diet of the Horsfield’s bronze cuckoo is insects and they are nomadic, travelling to different regions of Australia to breed and find food.[5] Small insects are taken from leaves, branches, caught on the wing and in breeding season, Horsfield’s bronze cuckoos feed each other in a courtship ritual.[6]

The Horsfield’s bronze cuckoo is known as a brood parasite, this means that they lay their eggs in a host species nest.[7] They mainly parasitise the fairy-wrens in the genus Malurus. It has been well documented that the superb fairy-wren (Malurus cyaneus) and the splendid fairy-wren (Malurus splendens) are the two main species to bare host to the Horsfield’s bronze cuckoo, although they may also parasitise other small Passeriformes including thornbills, warblers and scrub-wrens that can be utilised as a secondary host in certain locations.[2][5][8][9] Although the behavioural attributes of a host species may play a role in parasitism, it is thought that the female selects its host through imprinting, remembering the species that it was raised by and ultimately using that species to raise its brood.[10][11]

Breeding[edit]

The Horsfield’s bronze cuckoos are known to form monogamous pairs in the breeding season and occupy the same breeding territories as their host species, however partnerships are short lived as a female will only occupy the breeding territory for a few weeks, as another female takes her place, she may form a pairing with the same male.[5] Females that leave a breeding site after several weeks may move to another site and continue to breed with another male, forming another bond in a new breeding territory. Breeding territories of the Horsfield’s bronze cuckoo generally do not overlap giving rise to the possibility that a pair will defend an area through the season.[9]

Parasitism[edit]

As a brood parasite the Horsfield’s bronze cuckoo does not build its own nest but will utilise a host species nest to lay its eggs. The breeding season for the Horsfield’s bronze cuckoo relies on their host and they will lay one to mimic that of the fairy wren or thornbill's egg,[2][12] an elongated pinkish-white egg, that is speckled with red-brown spots. The breeding season for the superb fairy-wren is between September and February and a female may have three consecutive broods in this time, allowing the cuckoo multiple attempts to parasitise this species.[13][14] The female cuckoo may choose a breeding site with a high density of hosts, which allows extra opportunity for her success in parasitising a nest successfully. Studies have shown at one site a female did not parasitise a territory with less than 23 breeding pairs of their primary host (Malurus cyaneus).[5]

The egg of a Horsfield’s bronze cuckoo is small for its size, evolving overtime to mimic those of their host in what can be described as an evolutionary arms race between parasite and host, also the smaller the host for the cuckoo, the likelihood of successfully raising multiple broods thus the energy and nutrients needed to produce more smaller eggs than few larger eggs can be utilised more efficiently.[15][16] Egg laying is very fast for the Horsfield’s bronze cuckoo, being able to lay an egg in under 6 seconds typically in the morning shortly after the host has laid,[17] the adult cuckoo removes one egg each time she lays, only laying one egg per nest and replacing one host egg with one of her own.[14]

Younger semi-experienced females were generally selected over new and novice breeding females due to their success and experience. The Horsfield’s bronze cuckoo chose females that would choose similar breeding sites to previous years and were likely to raise several broods in one season.[15] Generally the superb fairy wren will not reject the cuckoo's egg, fairy wrens make oval dome nests that can be dark inside, meaning it is harder for the fairy wren to distinguish between their own egg and the host’s egg, furthermore the mimicry in eggs from the Horsfield’s bronze cuckoo have evolved over time and are hard to distinguish besides their slight elongation and glossier finish.[2][9][12]

The cuckoo chick hatches within 12 days of incubation, 2 days before the host egg, ejecting other eggs in the nests within two days of hatching, leaving the cuckoo the sole chick. As newly hatched cuckoo chicks eject host eggs they do not get to learn the host’s begging call, but can possess begging call polymorphism, where nestlings produce the calls of their primary host.[8][12][18][19] As the nestling grows it will be fed by the host parent and possibly the group growing more rapidly until fledged.

Coevolutionary arms race[edit]

Counter-adaptations have been documented for host species and cuckoos alike, as each adapts to the other in a coevolutionary "arms race".[20] Studies show that coevolutions happens at all stages of the growth cycle, not just the early stages.[21][22]

In the case of the fairy wrens, they have adapted some host defences to reduce parasitism. The high cost of hosting a parasitic species, in energy and genetics, drives the host to improve its defences, which in turn drive the parasite to improve its offences.[23]

Among the host's defensive adaptations:

  • Hosts like to nest in large colonies, to cooperate in spotting cuckoos and chasing them away.[24][25]
  • Helpers in large colonies provision the female so she can spend more time guarding the nest.[26]
  • Hosts learn and recognise their own eggs, and abandon any that are in the nest before they have started their own.[12][15]

Among the cuckoo's adaptations:

Media[edit]

Typical call, SE Queensland, Australia

References[edit]

  1. ^ BirdLife International (2012). "Chrysococcyx basalis". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013. 
  2. ^ a b c d e Brooker, M.G; Brooker, L.C (1989a). "Cuckoo Hosts in Australia". Aust Zool Rev. 2: 1–67. 
  3. ^ a b Morcombe, Michael (2003). Field Guide to Australian Birds (second ed.). Australia: Pascal Press. p. 192. ISBN 9781740214179. 
  4. ^ Brooker, M.G; Brooker, L.C (1992). "Evidence for Individual Female Host Specificity in 2 Australian Bronze-Cuckoos (Chrysococcyx Spp).". Australian Journal of Zoology. 40 (5): 485–493. doi:10.1071/zo9920485. 
  5. ^ a b c d e Langmore, N.E; Kilner, R.M (2007). "Breeding site and host selection by Horsfield's bronze-cuckoos Chalcites basalis". Animal Behaviour. 74: 995–1004. doi:10.1016/j.anbehav.2007.02.028. 
  6. ^ Lorenzana, J.C; Sealy, S.G (1998). "Adult Brood Parasites Feeding Nestlings and Fledglings of Their Own Species: A Review". Journal of Field Ornithology: 364–375. 
  7. ^ Davies, N.B (2010). Cuckoos, Cowbirds and Cheats. A&C Black. 
  8. ^ a b Brooker, M.G; Brooker, L.C (1989b). "The comparative breeding behaviour of two sympatric cuckoos, Horsfield's Bronze‐Cuckoo Chrysococcyx basalts and the Shining Bronze‐Cuckoo C. lucidus, in Western Australia: a new model for the evolution of egg morphology and host specificity in avian brood parasites". IBIS. 131 (4): 528–547. doi:10.1111/j.1474-919x.1989.tb04789.x. 
  9. ^ a b c Langmore, N.E; Kilner, R.M (2009a). "Why do Horsfield's bronze-cuckoo Chalcites basalis eggs mimic those of their hosts?.". Behavioral Ecology and Sociobiology. 63 (8): 1127–1131. doi:10.1007/s00265-009-0759-9. 
  10. ^ Lack, D (1963). "Cuckoo hosts in England". Bird Study. 10 (4): 185–203. doi:10.1080/00063656309476050. 
  11. ^ Brooker, L.C; Brooker, M.G (1990). "Why are cuckoos host specific?". Oikos. 57: 301–309. doi:10.2307/3565958. 
  12. ^ a b c d Langmore, N.E; Hunt, S; Kilner, R.M (2003). "Escalation of a co-evolutionary arms race through host rejection of brood parasitic young.". Nature. 422: 157–160. doi:10.1038/nature01460. 
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  15. ^ a b c Brooker, L; Brooker, M (1996). "Acceptance by the splendid fairy-wren of parasitism by Horsfield's bronze-cuckoo: further evidence for evolutionary equilibrium in brood parasitism.". Behavioral Ecology. 7 (4): 395–407. doi:10.1093/beheco/7.4.395. 
  16. ^ Payne, R.B (1974). "The evolution of clutch size and reproductive rates in parasitic cuckoos". Evolution. 28: 169–181. doi:10.2307/2407320. 
  17. ^ Brooker, M.G; Brooker, L.C; Rowley, I (1988). "Egg deposition by the bronze-cuckoos Chrysococcyx basalis and Ch. lucidus". Emu. 88: 107–109. doi:10.1071/mu9880107. 
  18. ^ Langmore, N.E; Maurer, G; Adcock, G.J; Kilner, R.M (2008). "SOCIALLY ACQUIRED HOST‐SPECIFIC MIMICRY AND THE EVOLUTION OF HOST RACES IN HORSFIELD'S BRONZE‐CUCKOO CHALCITES BASALIS". Evolution. 62 (7): 1689–1699. doi:10.1111/j.1558-5646.2008.00405.x. PMID 18419751. 
  19. ^ Payne, R.B; Payne, L.L (1998). "Nestling eviction and vocal begging behaviors in the Australian glossy cuckoos Chrysococcyx basalis and C. lucidus.". Oxford Ornithology Series. 9: 152–172. 
  20. ^ Dawkins, R; Krebs, J.R (1979). "Arms races between and within species.". Proceedings of the Royal Society of London. Series B. Biological Sciences. 205 (1161): 489–511. doi:10.1098/rspb.1979.0081. PMID 42057. 
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  23. ^ Kilner, R.M; Langmore, N.E (2011). "Cuckoos versus hosts in insects and birds: adaptations, counter‐adaptations and outcomes". Biological Reviews. 86 (4): 836–852. doi:10.1111/j.1469-185x.2010.00173.x. PMID 21223481. 
  24. ^ Brown, M; Lawes, M.J (2007). "Colony size and nest density predict the likelihood of parasitism in the colonial southern red bishop Euplectes orix–diderick cuckoo Chrysococcyx caprius system". Ibis. 149 (2): 321–327. doi:10.1111/j.1474-919x.2006.00633.x. 
  25. ^ Welbergen, J.A; Davies, N.B (2009). "Strategic variation in mobbing as a front line of defense against brood parasitism". Current Biology. 19 (3): 235–240. doi:10.1016/j.cub.2008.12.041. 
  26. ^ Canestrari, D; Marcos, J.M; Baglione, V (2009). "Cooperative breeding in carrion crows reduces the rate of brood parasitism by great spotted cuckoos". Animal Behaviour. 77 (5): 1337–1344. doi:10.1016/j.anbehav.2009.02.009. 
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External links[edit]