Pūkeko (Porphyrio melanotus)
Ph.D. Student, School of Biological Sciences, The University of Auckland, New Zealand
The Australasian swamp hen is known by its native Maori name “Pūkeko” in New Zealand. This brightly coloured rail (Fig. 1) is found throughout Oceania, having first arrived in Australia around 600,000 years ago (Garcia-R & Trewick, 2015). New Zealand, however, is one of its more recent conquests, with estimates of self-colonisation (from Australia) between 500-1000 years ago (Trewick & Worthy, 2001; Worthy & Holdaway, 1996). Pūkeko are found throughout New Zealand in a range of habitats, however they favour open grass areas near vegetated water systems (Dey & Jamieson, 2013). The endemic and endangered Takahē (Porphyrio hochstetteri) is closely related to the Pūkeko and, interestingly, this flightless bird is believed to have evolved from a previous colonisation of New Zealand by a Porphyrio species ~2.5 million years ago (Garcia-R & Trewick, 2015).
Pūkeko are one of the few native New Zealand species which haven’t experienced significant population declines since the introduction of two major contributors to ecosystem change: agriculture and invasive species. Indeed not only have Pūkeko been unaffected by these changes, they have proliferated in response to them, to the point that they are often regarded as a pest (Dey & Jamieson, 2013). Unlike endemic New Zealand species, Pūkeko evolved in the presence of a variety of terrestrial marsupial predators in Australia and therefore exhibit appropriate anti-predator behaviours (Jamieson, 1994). For this reason, they generally thrive in habitats where introduced predators such as brushtail possum (Trichosurus vulpecula), stoat (Mustela ermine) and rats (Rattus spp.) are present (Bunin & Jamieson, 1995).
Pūkeko have complex social structures. Generally, they live in polygynandrous groups (both, males and females have multiple mating partners), which defend a shared territory (Craig, 1980). They do, however, show considerable inter-population variability in their mating systems and may also be monogamous, polyandrous or polygynous (Jamieson, 1997, 1999). Both sexes can be highly philopatric, which is unusual in avian species (Craig & Jamieson, 1988). Within these social groups, adults form mixed-sex dominance hierarchies which influence access to reproductive opportunities (Craig, 1980; Jamieson & Craig, 1987) as well as non-sexual resources (Craig, 1977). Males and females are morphologically very similar (low sexual dimorphism) and both sexes have a bright red fleshy frontal shield (figure 1 & figure 2). This ornament acts as a “badge of status” and its color is correlated with dominance (Dey, Dale, & Quinn, 2014; Dey, Quinn, King, Hiscox, & Dale, 2017). It is likely that the color is carotenoid-based, given that carotenoids are common components in red, orange and yellow ornaments in other animals (Goodwin, 1984). Similarly, as it is found for the frontal shields of the closely related moorhen (Gallinula chloropus), it is likely to be testosterone-mediated (Dey et al., 2017; Eens, Van Duyse, Berghman, & Pinxten, 2000).
One of the most intriguing facts about Pūkeko is that they are cooperative breeders, meaning that the entire group contributes to raising chicks regardless of parentage (Craig, 1980). Cooperative breeding is rare in avian species; only 8.9% of non-marine bird species are known to engage in this breeding system (Jetz & Rubenstein, 2011). When there is more than one reproductive male and reproductive female in a Pūkeko group, chicks are always of mixed parentage (Lambert, Millar, Jack, Anderson, & Craig, 1994). Furthermore, if there are multiple breeding females present in a group they all lay in a single nest, a phenomenon known as joint-laying (Craig, 1980; Vehrencamp & Quinn, 2004). Females typically lay 4-6 eggs each, meaning that clutch sizes of up to 18 eggs in a single nest can be observed when multiple females lay together (Dey & Jamieson, 2013) (figure 3). Interestingly, conspecifics in Australia have not been reported to exhibit joint-laying, which suggests that this behaviour has evolved relatively recently in New Zealand populations (Dey & O’Connor, 2010).
Joint-laying is a puzzling behaviour as it can lead to intragroup conflict due to the fact that hatching success decreases with increasing total clutch size (Dey, O’Connor, & Quinn, 2014; Quinn, Haselmayer, Dey, & Jamieson, 2012). However, no such conflict appears present in Pūkeko despite the fact that dominant females experience a reproductive cost when a subordinate breeding female is present (Dey, O’Connor, Balshine, & Quinn, 2014; Quinn et al., 2012). There are two possible reasons for this: first, there is an apparent lack of egg recognition in individuals, despite the fact that eggs have distinctive colouring/patterning that is unique to each female (making it relatively easy for researchers to identify separate clutches within a single nest) (Craig, 1974; Quinn et al., 2012). If females are unable to distinguish between eggs then the risk of accidentally ejecting or destroying their own egg is high. Secondly, males have been shown to decrease their incubation investment, occasionally to the point of complete nest abandonment, in response to female-female competition, and so it can be assumed that the threat of this may influence females to tolerate co-breeders (Dey, O’Connor, Balshine, et al., 2014). It is interesting to note that territory size, and therefore quality, is correlated with the number of males present in a group (Craig & Jamieson, 1990). A breeding female benefits from having access to a higher quality territory, which therefore means having more than one breeding males present. However, breeding males benefit from having more than one breeding female present as it increases their potential reproductive output. As such, this may also explain the presence of joint-laying in Pūkeko (Vehrencamp & Quinn, 2004).
Having previously worked with primates, I enjoy referring to Pūkeko as feathered baboons; they are noisy, aggressive, territorial, and have social ranks within their groups. Due to their complex and variable social structure, Pūkeko are excellent models for examining cognition and social learning in the wild. Cognition can be defined as “the acquisition, processing, storage and use of information”, and cognitive abilities allow animals to adjust their behaviour in response to new situations (Shettleworth, 2010). Traditionally, it has been studied almost exclusively in the lab, however studying cognition in the field has become more common in recent years, providing numerous benefits including reduced stress, ecologically relevant settings and a wider array of species (Pritchard, Hurly, Tello-Ramos, & Healy, 2016). There have been fascinating results emerging from recent cognition studies on wild bird populations (for examples please refer to: Cauchard, Angers, et al., 2017; Cauchard, Doucet, Boogert, Angers, & Doligez, 2017; Preiszner et al., 2017), and therefore there is huge potential for further research in this field. My research interests encompass establishing any potential relationships between cognitive ability, dominance, testosterone and ornamentation. The project is still in its early stages (designing and trialling experiments, as well as banding/PIT tagging individual birds), but I have no doubt that the coming years will uncover new insights into these rails, and indeed - hopefully - into animal cognition in general.
About the Author
Aileen Sweeney is a Ph.D. student in the School of Biological Sciences at The University of Auckland in New Zealand. She is co-supervised by Dr Kristal Cain and Dr Gregory Holwell. Hailing from Ireland, she spent time researching Vervet monkey (Chlorocebus pygerythrus) and Kinda baboon (Papio kindae) behaviour in South Africa and Zambia before emigrating to New Zealand. Her Ph.D. is focused on Pukeko behaviour, specifically their cognition and social learning in relation to dominance, testosterone and ornamentation.
Bunin, J.S. & I.G. Jamieson. 1995. New Approaches Toward a Better Understanding of the Decline of Takahe (Porphyrio mantelli) in New Zealand. Conservation Biology 9: 100–106. https://doi.org/10.1046/j.1523-1739.1995.09010100.x
Cauchard, L., B. Angers, N.J. Boogert, M. Lenarth, P. Bize & B. Doligez. 2017. An Experimental Test of a Causal Link between Problem-Solving Performance and Reproductive Success in Wild Great Tits. Frontiers in Ecology and Evolution 5. https://doi.org/10.3389/fevo.2017.00107
Cauchard, L., S.M. Doucet, N.J. Boogert, B. Angers & B. Doligez. 2017. The relationship between plumage colouration, problem-solving and learning performance in great tits Parus major. Journal of Avian Biology 48: 1246–1253. https://doi.org/10.1111/jav.00953
Craig, J.L. & Jamieson, I.G. 1990. Pukeko: different approaches and some different answers. In P. B. Stacey & W. D. Koenig (Eds.), Cooperative Breeding in Birds: Longterm Studies of Ecology and Behavior (pp. 385–412). Cambridge: Cambridge University Press.
Craig, J.L. 1974. The social organization of the pukeko, Porphyrio porphyrio melanotus, Temminck, 1820 : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Zoology at Massey University. Palmerston North, N.Z. : Manawatu Microfilm Services, Palmerston North, N.Z.
Craig, J.L. 1977. The behaviour of the pukeko, Porphyrio porphyrio melanotus. New Zealand Journal of Zoology 4: 413–433. https://doi.org/10.1080/03014223.1977.9517966
Craig, J.L. 1980. Pair and group breeding behaviour of a communal gallinule, the pukeko, Porphyrio P. melanotus. Animal Behaviour 28: 593–603. https://doi.org/10.1016/S0003-3472(80)80068-6
Craig, J.L. & I.G. Jamieson. 1988. Incestuous Mating in a Communal Bird: A Family Affair. The American Naturalist 131: 58–70. https://doi.org/10.1086/284773
Dey, C.J., J. Dale & J.S. Quinn. 2014. Manipulating the appearance of a badge of status causes changes in true badge expression. Proceedings of the Royal Society B: Biological Sciences 281: 1775. https://doi.org/10.1098/rspb.2013.2680
Dey, C.J. & I.G. Jamieson. 2013. Pukeko | New Zealand Birds Online. Retrieved 8 May 2018, from http://www.nzbirdsonline.org.nz/species/pukeko
Dey, C.J. & C.M. O’Connor. 2010. Evidence for a lack of egg recognition in the pukeko (Porphyrio porphyrio melanotus: Rallidae). Notornis 57: 209–211.
Dey, C.J., C.M. O’Connor, S. Balshine & J.S. Quinn. 2014. Cooperative males reduce incubation in response to cues of female-female competition. Ibis 156: 446–451. https://doi.org/10.1111/ibi.12111
Dey, C.J., C. O’Connor & J.S. Quinn. 2014. Hatching order affects offspring growth, survival and adult dominance in the joint-laying Pukeko Porphyrio melanotus melanotus. Ibis 156: 658–667. https://doi.org/10.1111/ibi.12158
Dey, C.J., J.S. Quinn, A. King, J. Hiscox & J. Dale. 2017. A bare-part ornament is a stronger predictor of dominance than plumage ornamentation in the cooperatively breeding Australian Swamphen. The Auk 134: 317–329. https://doi.org/10.1642/auk-16-119.1
Eens, M., E. Van Duyse, L. Berghman & R. Pinxten. 2000. Shield characteristics are testosterone-dependent in both male and female moorhens. Horm Behav 37: 126–134. https://doi.org/10.1006/hbeh.1999.1569
Garcia-R, J. C. & Trewick, S. A. 2015. Dispersal and speciation in purple swamphens (Rallidae:Porphyrio). The Auk, 132: 140–155. https://doi.org/10.1642/auk-14-114.1
Goodwin, T.W. 1984. The Biochemistry of the Carotenoids. II. Animals (Vol. 2). London: Chapman & Hall.
Jamieson, I.G. 1994. Pukeko-The indomitable swamphen. New Zealand Geographic 21: 54–70.
Jamieson, I.G. 1997. Testing reproductive skew models in a communally breeding bird, the pukeko, Porphyrio porphyrio. Proceedings of the Royal Society of London B: Biological Sciences 264: 335–340. https://doi.org/10.1098/rspb.1997.0048
Jamieson, I.G. 1999. Reproductive skew models and inter-species variation in adjustment of individual clutch sizes in joint-nesting birds. In N.J. Adams & R.H. Slotow (Eds.). Presented at the International Ornitological Congress. Retrieved from https://www.internationalornithology.org/proceedings/Proc22%20IOC/Symposium/S47/S47.3.htm
Jamieson, I.G. & J.L. Craig. 1987. Dominance and Mating in a Communal Polygynandrous Bird: Cooperation or Indifference towards Mating Competitors? Ethology 75: 317–327. https://doi.org/10.1111/j.1439-0310.1987.tb00663.x
Jetz, W. & D.R. Rubenstein. 2011. Environmental Uncertainty and the Global Biogeography of Cooperative Breeding in Birds. Current Biology 21: 72–78. https://doi.org/10.1016/j.cub.2010.11.075
Lambert, D.M., C.D. Millar, K. Jack, S. Anderson & J.L. Craig. 1994. Single- and multilocus DNA fingerprinting of communally breeding pukeko: do copulations or dominance ensure reproductive success? Proceedings of the National Academy of Sciences 91: 9641–9645.
Preiszner, B., S. Papp, I. Pipoly, G. Seress, E. Vincze, A. Liker & V. Bókony. 2017. Problem-solving performance and reproductive success of great tits in urban and forest habitats. Animal Cognition 20: 53–63. https://doi.org/10.1007/s10071-016-1008-z
Pritchard, D.J., T.A. Hurly, M.C. Tello-Ramos & S.D. Healy. 2016. Why study cognition in the wild (and how to test it)? Journal of the Experimental Analysis of Behavior 105: 41–55. https://doi.org/10.1002/jeab.19
Quinn, J.S., J. Haselmayer, C.J. Dey & I.G. Jamieson. 2012. Tolerance of female co-breeders in joint-laying pukeko: the role of egg recognition and peace incentives. Animal Behaviour 83: 1035–1041. https://doi.org/10.1016/j.anbehav.2012.01.027
Shettleworth, S.J. 2010. Cognition, Evolution, and Behavior (Second Edition). Oxford, New York: Oxford University Press.
Trewick, S.A. & T.H. Worthy. 2001. Origins and prehistoric ecology of Takahe based on morphometric, molecular, and fossil data. In W.G. Lee & I.G. (Ian G. Jamieson (Eds.), The takahē : fifty years of conservation management and research. Dunedin, N.Z.: Dunedin, N.Z. : University of Otago Press 2001.
Vehrencamp, S.L. & J.S. Quinn. 2004. Joint laying systems. In W.D. Koenig & J.L. Dickinson (Eds.), Ecology and Evolution of Cooperative Breeding in Birds (pp. 177–196). Cambridge, UNITED KINGDOM: Cambridge University Press. Retrieved from http://ebookcentral.proquest.com/lib/auckland/detail.action?docID=266552
Worthy, T.H. & R.N. Holdaway. 1996. Quaternary fossil faunas, overlapping taphonomies, and palaeofaunal reconstruction in North Canterbury, South Island, New Zealand. Journal of the Royal Society of New Zealand, 26: 275–361. https://doi.org/10.1080/03014223.1996.9517514