Recently a misidentified swamphen from Qatar in my eBird review queue brought my attention to the fact the small Gulf nation has both Gray-headed Swamphen (Porphyrio poliocephalus) and African Swamphen (Porphyrio madagascariensis), the latter belonging to a local breeding population of unknown provenance dating back to 2004 and, according to the Qatar Bird Records Committee, the most common of the two. Sure enough, the eBird filter for Qatar reflected a high count of only 10 for Gray-headed compared to 30 for African. I was intrigued, particularly for the fact the species could expand into eastern Saudi Arabia.
The population in question centers around the Abu Nakhla sewage treatment facility and nearby wetlands, but an eBird search for observations of African Swamphen from Qatar turned up checklists from virtually every wetland hotspot in the country, including the Al Karanah sewage lagoons, only 40 kilometers from the Saudi border as the swamphen flies. All but a few of these records lacked supporting media let alone descriptive details. The few images for P. madagascariensis recently uploaded to eBird were difficult to judge. From many of the same locations, more images had been uploaded for Gray-headed. Given how common African was said to be, I was surprised there weren't more media in the Macaulay Library.
Online searches produced images by Neil Morris from 2012 showing three individuals with the typical features for African, including the distinctive olive-green on the lower back, scapulars, tertials, and tail. Besides these, the only others I found online were taken by John Thompson back in 2009, showing possible hybrids in which the olive-green feathering appears much reduced. One of Morris's, which was labeled as African, shows a similar bird with perhaps even less green above and leg features better for Gray-headed.
The situation only got muckier still when I queried some birdwatchers currently living in Qatar. They explained that they distinguished between the two species based on head coloring with blue-headed birds ("purple" swamphens) as P. madagascariensis and gray-headed birds as P. poliocephalus. There was no mention of any other features used in separating them.
The problem here likely stems from the belief, reflected in Jennings' account for Purple Swamphen (Porphyrio porphyrio sensu lato), the species complex in which the two present taxa were once lumped, whereby blue-headed birds and gray-headed birds were thought to represent two distinct subspecies (Jennings 2010). This understanding, I suspect, has been superimposed in the minds of some on the separation criteria for P. madagascariensis and P. poliocephalus in Qatar, hence the talk of "purple" and "gray-headed" swamphens. This is forgivable given the taxonomic debate around species limits in this genus. While eBird, Clements, and the IOC recognize a three-way split for swamphens in the Western Palearctic—Western (Porphyrio porphyrio sensu stricto), African (P. madagascariensis), and Gray-headed (P. poliocephalus), other taxonomic authorities only recognize African Swamphen (P. madagascariensis) and Purple Swamphen (P. porphyrio) with Gray-headed a subspecies of the latter. Qatar eNature, whose website only features species accounts for African and Purple (P. porphyrio), appears to follow the opinion of the latter. Given the striking difference in appearance and the prior assumption different colored heads meant different taxa, it's easy to see how some confused P. madagascariensis as the "purple" ones and P. porphyrio as the "gray-headed" ones.
Head coloring in P. poliocephalus proper, however, is actually quite variable, and blue-headed individuals can be found across the different subspecies, especially among the two most likely to have colonized the Gulf countries. A genetic study on the feral population in Florida suggests this difference may reflect a degree of sexual dimorphism with females more often displaying blue heads (Pranty 2013). This means far more care should be taken with swamphen identification in Qatar and elsewhere around the region than previously appreciated.
Two blue-headed individuals from the caspius subspecies with a gray-headed bird in Azerbaijan
Two more blue-headed individuals from the caspius subspecies, this time from northwestern Iran
Five blue-headed individuals from the caspius subspecies also from northwestern Iran
A very dark individual from the seistanicus subspecies in southwestern Iran
Another very dark individual from the seistanicus subspecies from Pakistan
Lastly, here's a dark individual from Al Askar Marsh in Bahrain, presumably the same subspecies that has colonized northeastern Saudi and Qatar
So, as should be clear by now, the blue-headed = P. madagascariensis and gray-headed = P. poliocephalus formulation is utterly faulty. eBirders in Qatar will now be prompted to provide supporting media or detailed descriptions when reporting African Swamphen. Lament not though, dear birders! Here are the most critical features to pay attention to.
As discussed above, many of the African Swamphens in Qatar display a limited amount of 1) olive-green on their lower back, scapulars, tertials, and tail, perhaps representing a hybrid form. Gray-headed Swamphens can even show greenish feathering in their wing coverts. Note, though, 2) the color of the wing proper can also be helpful, with African running a deep blue and Gray-headed a torquoise-green. This means the coloration of the upperparts may prove far less reliable for identification, making the proceedings all the more difficult. If you encounter a blue-headed swamphen, try to get good views of its legs. 3) African Swamphen have bright coral pink legs with concolorous tarsal and carpal joints ("knees and toes"). Gray-headed Swamphen, on the other hand, have light pink legs with contrasting dark joints. This distinguishing characteristic is obvious in virtually all of the images online. If no other field marks for African line up besides a blue head, then most likely it is a Gray-headed Swamphen.
An African Swamphen from Israel showing the typical plumage features and coral pink legs with concolorous "knees and toes"
A Gray-headed Swamphen of the nominate subspecies from northern Thailand showing the contrasting tarsal joints on light pink legs that confirm its identity
A Gray-headed Swamphen of the nominate subspecies from India showing the contrasting joints and turquoise-green wings
An African Swamphen from Egypt showing distinctly green upperparts and almost electric blue wings
Records of Typical-looking African Swamphen from Qatar
The only images I have seen so far of African Swamphens from Qatar displaying the expected plumage and leg features have come from Neil Morris, which he features on his website, and John Thompson, three of whose images can be found in the Macaulay Library's collection. He has subsequently shared more images of African Swamphen from his time in Qatar, another of which shows evidence of a possible hybrid (discussed below).
Three typical African Swamphen from left to right: Sailiyah, November 4, 2012; Abu Nakhla, March 20, 2013; Abu Nakhla, April 29, 2013. © Neil Morris
This juvenile from Abu Nakhla looks good for a typical African owing to the green, almost bronzy upperparts and concolorous joints
Four seemingly "pure" African Swamphens, Abu Nakhla, September 2008 to September 2010. © John Thompson
Possible African x Gray-headed Hybrids from Qatar
The images below were shared by Simon Tull, Uma Pandiyan, and John Thompson. These are blue-headed swamphens lacking one or more key feature of either P. poliocephalus or P. madagascariensis. All were documented near the Abu Nakhla sewage treatment facility, the site from which the population of P. madagascariensis originated. The lack of recent images of swamphens displaying the typical features of P. madagascariensis suggests that the population may now be mostly hybrids.
A P. madagascariensis type from Abu Nakhla with mostly blue upperparts, but this could be an effect of light and angle
A possible P. madagascariensis type from Abu Nakhla based on the blue wrist to the wing
An interesting record from Sila'a, UAE from May 16, 2022 raises the possibility that the Abu Nakhla swamphens could potentially disperse to suitable wetlands in neighboring countries. The bird in question appears to show features of a possible hybrid. This and a recent swamphen sighting in Al Qassim Province in central Saudi Arabia, purported to be Gray-headed, reminds us that the Porphyrio species of Eastern Arabia will very likely continue to expand across the Arabian Peninsula. For these reasons, birdwatchers in Saudi should study up on the differences between African and Gray-headed and look out for swamphens at their local wet patches.
Literature Referenced
Birds of the World: Gray-headed Swamphen (March 2020) https://birdsoftheworld.org/bow/species/purswa3/cur/introduction
Birds of the World: African Swamphen (March 2020)
eBird. 2020. eBird: An online database of bird distribution and abundance. Cornell Lab of Ornithology, Ithaca, N.Y. https://ebird.org/home
Fraker, R. 2020. Frontiers of Taxonomy: Parsing Purple Swamphen
Jennings, MC. 2010. Atlas of the Breeding Birds of Arabia. Fauna of Arabia 25
Pranty, B. (2013). Introducing the Purple Swamphen: Management, taxonomy, and natural history. Birding 45 (3):38-45. https://www.aba.org/birding/birding453pranty.pdf