Cameroon indigobird

Cameroon indigobird
Conservation status
Least Concern  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Passeriformes
Family:	Viduidae
Genus:	Vidua
Species:	V. camerunensis
Binomial name
Vidua camerunensis Grote, 1922

The Cameroon indigobird (Vidua camerunensis) is a species of bird in the family Viduidae. It is considered by some authors to be a subspecies of the variable indigobird (Vidua funerea). Range Sierra Leone to east Cameroon, north east Zaire and South Sudan.

Summary

There are less than 10,000 Vidua camerunensis in the entire which range over 20,000 km2 in the savannah and grasslands of South Africa (2). The birds have a very distinct blue color with underlying brown feathers and small white beak to crack nuts and seeds. There are many Indigobird species in the world, and they are mainly known for their song mimicry. The different species of indigobirds are not morphologically different, but they do differ in the song they choose to mimic (1).

Ecology and Behavior -

Cameroon Indigobirds are known for several different behaviors: song determination and song mimicry. These indigobirds mimic the songs of other bird species (1). The males pick and choose which song they want to mimic; however, when one male chooses a song from a host bird, the other males mimic other songs from a different host species (1). This is an effective way to discriminate each male from another when mimicking the songs. There are also several distinct host species that the Indigobirds mimic from and the most common host species are Black-bellied Firefinch (Lagonosticta rara) and African Firefinch (L. rubricata) (1).

The difference in how the different Indigobirds mimic the different songs is based on the host species (3). Researchers have thought that because different indigobird species sing different songs, they must be reproductively isolated. However, when a paternity test was done between the different indigobird species, it was found that the birds were not reproductively isolated (3). They concluded that Indigobirds switch their song between several different hosts, but, the switching does not conclude that the species are biologically different but in fact, they are very much related to one another in which they are not isolated from other species (3). Reproductive isolation cannot be determined just by the shifts of song mimicry from different hosts (3).

The indigobirds also use the song mimicry for sexual and natural selection. It can be used for aggression in that male indigobirds were most territorial and aggressive when they heard their own song or the host song that the bird mimicked (4). These birds know and recognize which song is the one they mimic, compared to what other species mimic. For natural selection, it is in the bird’s favor to mimic another song compared to other species. They save resources because they do not have to fight with others to mark their territory thus decreasing their aggressiveness. As for the sexual selection, the females are attracted to males that master the art of mimicry (5). The female decides to mate with the male who sings the song that is most known to the females. When the eggs are actually laid, they will be in another host’s nests instead of their own (5).

Song discrimination is also very important in the young. They learn to sing and mimic songs in their sensitive period (6). It is very important in establishing their mimicry for the best fit in natural selection and reproduction with sexual selection.

Brood Parasites

These birds are obligate brooding parasites in which they lay eggs in other nests (7). The learning of the songs and imprinting is also obligate for them because this is how they increase their fitness. The male have impressive vocal repertoires that can be used to mimic, calling, or mating. According to DaCosta et al, they found evidence that host mimicry is important cue for species recognition among the territorial male birds. He predicts that this could have arose due to when juveniles transform into adults and they tend to be dispersed. These calls helps them recognize where the other birds in the same species are, so they could be located. They also did a study on how different mimicry can elicit different responses in these birds. In the experimental group, the scientists recorded these calls and played them to the captive birds. In the control group, they had natural calls that were sounded for the captive birds. They found that birds tended to respond differently to the audio recording compared to natural singing (7).

Scientists has tested whether female indigobirds have a preference on what type of songs the male indigobird sings. They supported that females choose males that have the closest song that matched the foster parent’s songs (10). For example, if the female was going to lay an egg in the Bengalese finches, she would want a mate that would mimic the song of these Bengalese finches (10). This is also not due to innate bias for songs as they prefer songs that improve their fitness and survival (10).

Most of how species are names is based on the biological species concept, so it is a critical role to know which species of birds these were breeding. Imprinting and sexual courtships are very important in these type of birds as they need to behave a certain way to lay their eggs. The males of these Indigobirds courted heterospecific females to increase genetic diversity (8). These males know that to increase fitness, they need to mate with females who have the highest genetic diversity to pass onto the offspring (8). Due to this, there has been molecular analysis done on these birds to show the clades of the phylogenetic tree (9). When the scientists did the analysis on all the birds that were similar to multiple host colonizations. They each contribute to interbreeding populations that acquired the singing from these host species (9). They hypothesized that interbreeding is relevant in these birds because they mate with several species, so it hard to distinctly specify species of one clade.

In the creation of the phylogenetic tree, their found that African brood parasitic finches are actually the host specialists that mimic the songs and nestling of their finch hosts (11). These birds also have high rates of cospeciation as many of these birds interbreed with one another (11). Host switches have also been involved in the creation of new hosts with the close or same related genus which would be apparent for congruence of the hosts and the parasitic birds (11).

References

Paper 1 -

Payne, R. B., Barlow, C. R., Balakrishnan, C. N., & Sorenson, M. D. (2004). Song mimicry of Black-bellied Firefinch Lagonosticta rara and other finches by the brood-parasitic Cameroon Indigobird Vidua camerunensis in West Africa. The Ibis, 147(1), 130–143.

Paper 2 -

BirdLife International. 2016. Vidua camerunensis. The IUCN Red List of Threatened Species 2016: e.T22732834A95049885. http://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22732834A95049885.en. Downloaded on 27 February 2017.

Paper 3 -

Balakrishnan, C. N., Sefc, K. M., & Sorenson, M. D. (2009). Incomplete reproductive isolation following host shift in brood parasitic indigobirds. Proceedings. Biological Sciences / The Royal Society, 276(1655), 219–228.

Paper 4 -

Balakrishnan, C. N. (2006). Song discrimination suggests premating isolation among sympatric indigobird species and host races. Behavioral Ecology: Official Journal of the International Society for Behavioral Ecology, 17(3), 473–478.

Paper 5 -

Payne, R. B., Hustler, K., Stjernstedt, R., Sefc, K. M., & Sorenson, M. D. (2002). Behavioural and genetic evidence of a recent population switch to a novel host species in brood-parasitic indigobirds Vidua chalybeata. The Ibis, 144(3), 373–383.

Paper 6 -

Balakrishnan, C. N., & Sorenson, M. D. (2006). Dispersal ecology versus host specialization as determinants of ectoparasite distribution in brood parasitic indigobirds and their estrildid finch hosts. Molecular Ecology, 16(1), 217–229.

Paper 7 -

Dacosta, J. M., & Sorenson, M. D. (2014, 10). An experimental test of host song mimicry as a species recognition cue among male brood parasitic indigobirds ( Vidua spp.). The Auk, 131(4), 549-558. doi:10.1642/auk-14-35.1

Paper 8 -

Sorenson, M. D., Hauber, M. E., & Derrickson, S. R. (2010, 05). Sexual imprinting misguides species recognition in a facultative interspecific brood parasite. Proceedings of the Royal Society B: Biological Sciences, 277(1697), 3079-3085. doi:10.1098/rspb.2010.0592

Paper 9 -

Sefc, K. M., Payne, R. B., & Sorenson, M. D. (2005, 04). Genetic continuity of brood-parasitic indigobird species. Molecular Ecology, 14(5), 1407-1419. doi:10.1111/j.1365-294x.2005.02492.x

Paper 10 -

Payne, R. B., Payne, L. L., Woods, J. L., & Sorenson, M. D. (2000, 01). Imprinting and the origin of parasite–host species associations in brood-parasitic indigobirds, Vidua chalybeata. Animal Behaviour, 59(1), 69-81. doi:10.1006/anbe.1999.1283

Paper 11 -

Sorenson, M., Balakrishnan, C., & Payne, R. (2004, 02). Clade-Limited Colonization in Brood Parasitic Finches (Vidua spp.). Systematic Biology, 53(1), 140-153. doi:10.1080/10635150490265021