Identifying subspecies of Little Ringed Plovers

Little Ringed Plover (Charadrius dubius) is one of the most common and widespread waders in Thailand, so as in many places throughout Asia. Two subspecies are recognised in Thailand; the resident C. d. jerdoni and the migratory C. d. curonicus. I’m lucky to be in northern Thailand where both subspecies can often be seen side by side. This post will summarise my observation about the identification of these 2 subspecies.

Adult non-breeding curonicus (20 September 2014)
Adult non-breeding curonicus with some retained breeding plumage (8 September 2021)

Let’s start with the more abundant taxon, the migratory C. d. curonicus. This subspecies breeds across the northern parts of Europe and Asia and winters in Africa and south-east Asia. It is the default subspecies of Little Ringed Plover in Thailand, particularly during winter. It can be found throughout the country in wetlands and open habitats. Since it’s a winter visitor, the non-breeding plumage is the most frequently seen plumage type in Thailand. The non-breeding plumage of this subspecies consists of drab brownish face and a broad brown breast band. The yellow eye-ring is often thin and broken. The bill is largely blackish with a slight orange/yellowish spot at the base of lower mandible. The legs are quite consistently yellowish.

Adult breeding curonicus; note thin yellow eye-ring and small pale spot at bill base (24 March 2021)
Adult breeding curonicus (17 April 2021)

The subspecies curonicus usually moults into breeding plumage shortly before it migrates back to the breeding ground in spring. In the breeding plumage, the facial mask becomes black (or blackish-brown in female) with a large black band across the forecrown. The breast band also becomes black and is usually equally large across the breast. The yellow eye-ring becomes more prominent, although still relatively thin. The bill is still largely black as in the non-breeding plumage with a very small yellowish or flesh-coloured spot at the base of lower mandible. The legs can turn slightly more pinkish when in the breeding plumage.

Juvenile curonicus (18 September 2019)
Juvenile curonicus (10 September 2021)

The juvenile plumage of curonicus is not as often seen as the non-breeding plumage, as most birds already attain some adult-type feathers when they reach the wintering ground. In general, the juvenile plumage is similar to the non-breeding plumage but with thin scaling on wing coverts, mantle, scapulars and crown.

Adult breeding jerdoni; note bold yellow eye-ring, smaller breast band and extensive pinkish area at bill base (20 April 2021)

Now on to the less common subspecies, the resident C. d. jerdoni. This subspecies is known to breed in northern, western and north-eastern Thailand. The known southernmost limit of this subspecies is in Phetchaburi province, above the Isthmus of Kra. During the breeding season, it is mostly found along large rivers or vast dry area, but disperse into other types of habitat along with curonicus during the non-breeding season.

Adult breeding jerdoni (front) with adult non-breeding curonicus (back); note the size difference, jerdoni being smaller (10 November 2018)
Another photo showing the size difference between the larger curonicus (back) and the smaller jerdoni (front) (10 September 2021)

Unlike curonicus, the most frequently seen plumage type of jerdoni is the breeding plumage, which it retains nearly throughout the year except a small gap of just few months in late summer/early autumn. It’s quite easy to pick out jerdoni among the flock of curonicus in winter, as jerdoni would already be in the breeding plumage, while curonicus only attains the breeding plumage in spring.

When seen together, one of the first things that I usually notice is the size difference between the 2 subspecies with jerdoni being noticeably smaller than curonicus. It also seems that jerdoni has proportionately larger eyes than curonicus, which gives it a cuter look.

Adult breeding jerdoni; this individual has a particularly thin black breast band (10 November 2018)
Adult breeding jerdoni; during courtship, the eye ring can become much larger and swollen (4 February 2016)

Adult jerdoni in breeding plumage is quite an attractive bird. Comparing to curonicus, it has a bolder yellow eye-ring in the breeding plumage, which can become even larger and swollen during courtship, making it look more cartoonish. The black breast band, although quite variable, is usually narrower than in curonicus. The most distinguishable feature is probably the bill colouration. In jerdoni, the bill base is largely pinkish or flesh-coloured unlike in curonicus where the bill is largely black with very small pale spot at the base. The legs of jerdoni are also usually flesh-coloured, pinkish-orange or even greyish, rather than yellow as in curonicus.

Non-breeding jerdoni (10 September 2021)

The non-breeding plumage of jerdoni is rarely seen and documented. It seems to retain this plumage type only for few months between July to early September. By late September, most of them would already be in the breeding plumage that will remain through to summer. Even in the non-breeding plumage, jerdoni still show more prominent yellow eye-ring and larger pinkish area at bill base than in curonicus.

By later September, most jerdoni would already be in the breeding plumage (23 September 2014) while all curonicus would be in the non-breeding plumage
Juvenile jerdoni (29 April 2021)

The juvenile plumage of jerdoni is also rather poorly documented. It looks quite similar to juvenile curonicus but the pinkish spot at bill base appears to be larger and more prominent, as well as the eye ring. I haven’t seen that many juvenile jerdoni, so I’m not sure about the variability, but you would definitely not see a juvenile jerdoni at the same time of the year as juvenile curonicus.

Left column: C. d. curonicus VS right column: C. d. jerdoni
Top row: adult breeding; middle row: adult non-breeding; bottom row: juvenile

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