Creature Feature: Pin-tailed whydah

Moving to the big city to follow your dreams is a common trope in pop culture, made famous by movies like La La Land. While one can imagine star-struck and scrappy young people struggling in the competitive industry, what animal might also do this?  The pin-tailed whydah (Vidua macroura), is currently living this plotline. This African bird has recently moved to Los Angeles, in hopes of making it big – in other birds’ nests, that is!

The long tail feathers and elaborate displays of the pin-tailed whydah made it a favorite of the pet trade. [Source]

In its homelands of sub-Saharan Africa, this finch species is a beautiful black and white bird with stunning feather ornaments [1]. Pin-tailed whydahs employ an odd breeding strategy, called brood parasitism.  Brood parasites – unlike other birds who build nests, lay eggs, and raise their chicks – deposit their eggs in other birds’ nests. They leave their babies’ survival up to the host parents’ charity – or rather, their inability or unwillingness to recognize and reject the intruders.  In this way, brood parasites never have actively parent themselves, giving them the flexibility to forage, travel, and mate more than they could if they were caring for a nest.  

In order to ensure their chicks are not abandoned by the unwitting foster parents, Vidua finches, including the pin-tailed whydah, have evolved complex mouth patterns to match those of their hosts’ young. These complex markings can make their babies look like aliens from another world (see picture below). Scientists hypothesize that the strange shapes and other-worldly hues evolved through an evolutionary arms-race [2], a phenomenon that occurs throughout the natural world. This means the host species may have evolved more complex mouthparts over time in hopes of differentiating its young from those of the brood parasite, but this only led to selection for similar changes in the parasite itself to match more closely. However, the selection may go in the opposite direction, with host young also mimicking the parasites to compete for food [3]. Regardless of its origins, these long evolutionary dynamics mean that the whydah tends to have a specialized, short list of species (23, to be exact) that will reliably raise its young [4].

A view of the mouthparts of the brood parasitic pin-tailed whydah ( left ) and common waxbills ( right ) from the same brood. Photo by Justin G. Schuetz, published in Hauber and Kilner (2007). [Source]

However, some pin-tailed whydahs in their native range in sub-Saharan Africa have laid eggs in nests of species where those bizarre mouth patterns don’t match their own [2, 4]. They’ve not only gotten away with it, but they have survived and begun to add those hosts to their list of options. This point, that there is some flexibility in finding novel hosts, may be key to whydahs’ recent emergence in North America.

Part 2: Move to LA

So how did this bird make its way to Hollywood? The whydah began its journey to the United States the same way many invasive species do: through humans.

A popular bird in the pet trade in the 20th century, the whydah’s fancy tails and feathers were in high fashion with California elite. As pets are liable to do, some birds inevitably escaped their garden cages. However, rather than failing to reproduce, as one might expect for such a specialized brood parasite, populations of whydahs began to take up residence. In the late 1990s, birders began to regularly observe these exotic birds flying around the neighborhoods and valleys of Los Angeles and Orange counties [5]. Rather than just being one-off, repeated events of jail-broken pets, the flocks have appeared to be growing. Recently, flocks of up to 100 individuals have been sighted [5]. Despite being miles away from their traditional host species, the whydahs have managed to breed.

A range map of pin-tailed whydah sightings in Los Angeles and Orange Counties from 2010 – 2020, based on data from eBird [7]. Map created by the author in R.

Part 3: Making it in the big city

For any recent transplant to Los Angeles scene, it helps to know someone who’s already been living in Hollywood, who can connect you with their network.

The same is true for the whydah. The secret to their establishment in LA must mean they have connections, i.e. a host they can use. While some of the possible original host species, such as African members of the Estrildid finch group, like waxbills, are sighted on occasion in the Los Angeles area, they have likely been unable to breed in Southern California [4, 5]. No host breeding means there are no nests for the whydahs to recognize and parasitize. Yet, whydah numbers are increasing in the area.

A team of researchers, John and Kimball Garrett, set out to solve this mystery by carefully observing whydah behavior in Orange County.  Sitting quietly under trees and brush in public parks, the researchers caught the birds red-handed, parasitizing an unexpected species, the scaly-breasted munia (Lonchura punctulata) [5]. Another pet-trade escapee, the scaly-breasted munia originally hails from India and has no range overlap with the African whydah (though it is a cousin of the Estrildid finch family).  Garrett and Garrett saw male whydahs displaying around munia nests, and females entering those same nests, displaying interest. Munias feeding fledgling whydahs in a park – the tell-tale sign of a successful brood parasite – provided strong evidence that at least some whydahs had successfully parasitized the munias.   An invasive species that relies on other invasive species by parasitizing them. An invasion of an invasion.

The unsuspecting scaly-breasted munia, the likely host of breeding whydahs in southern California. [Source]

How then is the African whydah able to parasitize the Indian scaly-breasted munia, a species that normally would never interact beyond the rich mixing pot that is Los Angeles? How did the whydahs even “know” that the munias would be viable options? Garrett and Garrett hypothesize that the domed nests of the munia may resemble the nest types of their original hosts [5]. But beyond these proximate triggers, the question remains: where did this flexibility come from? It is a intriguing question that has yet to be answered.

While the success of whydahs outside of their original hosts in this novel environment brings up many questions, a more practical one has been on many conservationists’ minds:  will this surprisingly flexible brood parasite be a risk to the native species? Researchers do not know if the whydahs will specialize on the munia in their new range, or if they will continue expanding and trying new hosts. Modeling studies predict that if they do parasitize native species, it will likely start with native finches, like house finches and goldfinches [4]. However, other researchers believe this is unlikely as native finches do not build domed nests that may entice the whydahs [5, 6].

Unfortunately, this tale of a California dream will have to end on a cliff-hanger, as scientists are watching this species establish and spread each year.  Overall, the pin-tailed whydah makes for a fascinating study of animal behavior – how it can change with environment and context, which behavioral traits that evolved over long periods can be side-stepped and which are more hard-wired. It presents a natural experiment in motion, and reminds us once again that evolution is occurring now, in real time, before our very eyes under the Hollywood sign.


If you sight a pin-tailed whydah on your next trip to Disneyland or Southern California, report it on eBird! https://ebird.org/about/resources/sharing-your-sightings-on-ebird


References:

[1] R. B. Payne, in Birds of the World, S. M. Billerman, B. K. Keeney, P. G. Rodewald, T. S. Schulenberg, Eds. (Cornell Lab of Ornithology, 2020; https://birdsoftheworld.org/bow/species/pitwhy/1.0/introduction).

[2] N. B. Davies, in Cuckoos, Cowbirds and Other Cheats (T & A D Poyser, London, UK, 2000).

[3] M. E. Hauber, R. M. Kilner, Coevolution, communication, and host chick mimicry in parasitic finches: who mimics whom? Behav. Ecol. Sociobiol. 61, 497–503 (2007).

[4] R. Crystal-Ornelas, J. L. Lockwood, P. Cassey, M. E. Hauber, The establishment threat of the obligate brood-parasitic Pin-tailed Whydah ( Vidua macroura) in North America and the Antilles. The Condor. 119, 449–458 (2017).

[5] J. F. Garrett, K. L. Garrett, The Pin-tailed Whydah as a Brood Parasite of the Scaly-breasted Munia in Southern California. West. Birds. 47, 314–322 (2016).

[6] N. K. Strycker, A Birding interview with Kimball Garrett. Bird. Mag. (2011), pp. 16–19.

[7] eBird. eBird: An online database of bird distribution and abundance [web application]. (2017) eBird, Cornell Lab of Ornithology, Ithaca, New York. Available: http://www.ebird.org.

Main featured image drawn by Victoria Farrar

[Edited by: Meredith Lutz]

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