WHY DID THE SUNBIRD FEED A CUCKOO?

One morning, as I was at my desk, I happened to catch sight of two sunbirds taking turns feeding a larger sized bird, perched on the branches of a semi evergreen forest outside my window. The sunbirds looked exhausted feeding insects to the big one.  I got intrigued by what I saw, for I had little knowledge of the mystery that’s unfolding before my eyes. Why would sunbirds as small as 10 cm in length feed a bird that is heterospecific and larger about a length of 15-16 cm? I sensed that this moment shall pass away in no time; I grabbed a white paper and started sketching outline of what I was seeing. Their interaction as I anticipated didn’t last for long, the trio had translocated.

   I was hell bent on finding the reason behind this subjugation. I went ahead recording in my nature journal the details such as

  • date of observation: 10/02/2013
  • temperature outside: cool at 25 degrees
  • in Middle Andaman islands
  • Name of the sunbirds: Olive backed sunbird (Cinnyris jugularis Andamanicus)(Linnaeus,1766,Syst. Nat.ed), identified with the help of the book. The underparts of both male and female are bright yellow; the backs are olive green in colour. The forehead, throat and upper breast of the adult male is a dark, metallic blue-black. They have slender decurved bills and feeds on nectar as well as small insects
  • Name of the larger bird: juvenile of Violet cuckoo (Chrysococcyx xanthorhyncus,Horsefield,1821), Violet Cuckoo is distributed throughout south east Asia and Indian subcontinent (Ali and Ripley 1981; Rasmussen and Anderton2012). The violet cuckoo species are partially migratory birds.The breeding cuckoo populations in northeast India (Assam, Meghalaya, Nagaland, Manipur, Mizoram and Andaman and Nicobar Islands), Bhutan and Bangladesh are migratory and they move southwards for wintering. Juveniles have barred rufous and greenish bronze feathers on the upper parts of the body, a bright rufous crown, rufous and mottled green or brown wings, a barred brown and rufous tail and brown-barred white under parts.( “Chrysococcyx xanthorhynchus”. BirdForum. Retrieved 4 February 2014.)

     When I searched for the details on why is a sunbird feeding a cuckoo baby? ,there were lots of literature and research done on cuckoo as harbinger of spring and as “brood parasite”, the behaviour of relegating incubation and rearing of offspring to other “foster parent” birds and that Olive backed sunbird is known to be parasitized by cuckoos(Cheke and Mann 2008).

In the book The Avian Brood Parasites: Deception at the nest by Paul A Johngard, the author has referred to the adaptations of obligate brood parasites like common cuckoo  to ensure continuity of their species.In obligate brood parasitism the female cuckoos regularly deposit eggs in other species’nests, but do not perform any nest building, incubation or parental behaviour. Parasite benefits but host suffers from their breeding interactions.

Friedmann(1968) hypothesized that brood parasitism is more common in the cuckoos because they may have been able to “let go”their rather weak nest- building tendencies more easily than passerine groups which have strong nest building instincts and complex nests such as weavers and icterines.

Some of the publications elucidate the various tactics and circumstances that make a cuckoo species successful in parasitizing their host’s nests. I noted down some of them as follows:-

  • The breeding season of violet cuckoo  coincides with the breeding season of the host species. The sunbirds (Aethopyga spp.) and spiderhunters (Arachnothera spp.) are their host birds in India. (https://indianbirds.thedynamicnature.com/2017/05/violet-cuckoo-chrysococcyx-xanthorhynchus.html#Breeding). The breeding season of olive backed sunbird is January-February and May –July(Ali and Ripley,1974).
  • Female cuckoos have secretive and fast laying behaviours, but in some cases, males have been shown to lure host adults away from their nests so that the female can lay her egg in the nest.(Davies, N.B.(18 April 2011)”Cuckoo adaptations: trickery and tuning.”Journal of Zoology .284 1-14 (doi:10.1111/j.1469-798.2011.00810)
  • The parasite’s eggs are somewhat larger and rounded and harder for host species to pick up(Hoy and Ottow,1964)
  • Incubation period among cuckoos are unusually short compared to other families of bird(Lack, 1968), so the chances of predation of their eggs get reduced.
  • Cuckoo lays eggs with thick shells that provides resistance to cracking when the eggs are dropped in the host nest.(Antonov, Anton;Stokke,Bard G;Moksnes,Arne;Roeskaft,Eivin(2008)”Does the cuckoo benefit from laying unusually strong egg?”Animal Behaviour.76(6):1893-900. doi:10.1016/j.anbehav.2008.08.016.)
  • The cuckoo egg hatches earlier than the host’s, and the cuckoo chick grows faster.
  • The cuckoo’s chick evicts the eggs or young of the host.It has been suggested that ejection behaviour probably occurs in Asian and African emerald cuckoos and violet cuckoo, but observations are lacking(Friedmann, 1968). Disposal of potential competitors in the nest via nest ejection by common cuckoo was first described by Edward Jenner(1788). The chick has no time to learn this behaviour, so it must be an instinct passed on genetically. The chick encourages the host to keep pace with its high growth rate with its rapid begging call.(Adams, Stephen(2009-01-04). “Cuckoo chicks dupe foster parents from the moment they hatch”.(The Daily Telegraph, London. Retrieved 2010-04-30.”Cuckoo chicks start to mimic the cries that their foster parents’ young make from the moment they hatch, a scientist has proved.” The chick’s open mouth which serves as a sign stimulus.(Biology(4th edition)NA Campbell, ‘Fixed Action Patterns’(Benjamin Cummings NY, 1996) ISBNO-8053-1957-3
  • Wyllie(1981) described ejection as follows “From about 8-36 hours after hatching, the young cuckoo wriggles about in the bottom of the nest until it manoeuvres one of the host’s eggs against the side of the nest. Its back has a slight hollow between the scapulars which traps an egg against the nest wall. The cuckoo’s head is held down, almost touching its belly. Then with its feet apart and with muscular thighs the youngster slowly works the egg up the side of the nest, holding its tiny wings backward to prevent the eggs from rolling off. When it nears the nest rim the wings clasp the top as the legs push up from the side of the nest. Balancing the egg on its back to the top of the nest, the young cuckoo quivers and jerks for a few seconds and hangs there feeling with its wings to make sure the egg has gone over. Then it drops back into the nest cup. “This process is repeated until the nest is empty of other eggs or chicks.
  • It was disturbing to see this video but it says it all:-

Common Cuckoo chick ejects eggs of Reed Warbler out of the …

     After examining  the above reliable sources dual feelings crept into my mind as to whether I must feel happy seeing the parenting instincts of olive backed sunbirds towards caring for a much larger bird, or to empathize with the couple who were forced to grow up a species who may have been responsible for making them loose their own progeny.    

     What might have happened to their actual offspring?

They may have met with the same fate as in the above video. I had begun to understand the reason why those sunbirds were compelled to feed the cuckoo offspring. That was disheartening to know that the two smaller birds were deceived and victimized, having said that , I think they have enabled us to   gain knowledge of a kind of co evolutionary interaction named brood parasitism and made us ponder about the cost of parental care among birds.

The above painting was done using poster colours and set aside as one of my treasured encounters with bird behaviours.

Sources:-

  1. http://eresources.nlb.gov.sg/infopedia/articles/SIP_1512_2009-04-27.html (length of sunbird)
  2. Hails, C. J. (2018). Birds of Singapore. Singapore: Marshall Cavendish Editions, p. 148. (Call no.: RSING 598.295957 HAI); Madoc, G. C. (1947). An introduction to Malayan birds. Kuala Lumpur: Malayan Nature, p. 207. (Call no.: RCLOS 598.29595 MAD-[GBH]); Guy, G. (2002, October–December). Sunbirds of Singapore – from old world jungle jewels to modern national symbols. Nature watch: Official magazine of the Nature Society (Singapore), 10(4), 2–9. Singapore: Nature Society (Singapore), p. 6. Retrieved 2019, August 1 from Nature Society (Singapore) website: https://www.nss.org.sg/articles/3d0e9135-2Sunbirds.pdf; Briffett, C. (1993). The birds of Singapore. Kuala Lumpur; New York: Oxford University Press, p. 69. (Call no.: RSING 598.295757 BRI)
  3. 29. Madoc, G. C. (1947). An introduction to Malayan birds. Kuala Lumpur: Malayan Nature, p. 207. (Call no.: RCLOS 598.29595 MAD-[GBH]); Yong, D. L., & Lim, K. C. (2016). A naturalist’s guide to the birds of Singapore. England: John Beaufoy Publishing, p. 150. (Call no.: RSING 598.095957 YON); Gan, J. (2002). Some interesting notes on the Sunbirds. Wetlands, 9(3), 10–11. Singapore: Sungei Buloh, p. 10. (Call no.: RSING 508.5957 SBNP)
  4. Birds of the Indian Subcontinent by Richard Grimmett, Carol Inskipp and Tim Inskipp
  5. Linnaeus, Carl (1766). Systema naturae : per regna tria natura, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis (in Latin). Volume 1, Part 1 (12th ed.). Holmiae (Stockholm): Laurentii Salvii. p. 245.
  6. OLIVE-BACKED SUNBIRD CINNYRIS JUGULARIS NESTING FROM ELECTRIC WIRES IN GREAT NICOBAR ISLAND, S Pande, N Sant – indianbirds.in
  7. http://ls1.and.nic.in/doef/WebPages/Forest.html
  8. http://indianbirds.in/pdfs/IB_13_2_SridharanETAL_VioletCuckoo.pdf
  9. Bada, Ferdinand. “Cuckoo Birds – Animals of the World.” WorldAtlas, May. 15, 2018, worldatlas.com/articles/cuckoo-birds-animals-of-the-world.html.
  10. HOST LIST OF AVIAN BROOD PARASITES – 2 – CUCULIFORMES – Old World cuckoos Peter E. Lowther, Field Museum version 26 Apr 2013
  11. https://www.birdforum.net/opus/Chrysococcyx_xanthorhynchus
  12. THE AVIAN BROOD PARASITES: DECEPTION AT THE NEST, By Paul A. Johnsgard

Balcony views-Brown Backed needletail

I cherish the memories watching from my balcony a flock of elegant brown backed needle tail birds hovering over grassy vegetation backdropped by Panchwati Hills, Middle Andaman. The weather had been cool from November to February and that’s when these birds are sighted the most. They are brown backed except for the white under tail seen flying swiftly and constantly for hours with their sickle shaped wings and spiny tail ends . I have not seen them settle down anywhere within my field of vision , they would have probably got back to their nests by dusk.

I miss the alluring beauty of nature and the tranquility of the moment that embodied them. Fortunately I captured them in my illustration using poster colors.