Originally posted January 4, 2022
A Taxonomic Tangle
The Graceful Prinia (Prinia gracilis) is a small, brownish, long-tailed warbler of damp habits in otherwise arid environments, including in and around anthropogenic sites. Where it occurs, it's often quite abundant—nigh ubiquitous. Owing to this, birders have often paid little mind to this tiny brown #birb beyond simply noting its presence.
However, the announcement in 2021 that Graceful Prinia was now considered to comprise two distinct species—Graceful (P. gracilis) and Delicate Prinia (P. lepida)—means that birders in the Middle East have more reason to pay closer attention to the prinias they're encountering. This is particularly true in eastern Arabia, where both species are now known to occur.
The authors of the paper on which the split was based—Alstrom et al—made this recommendation on the basis of genetic, morphological, and vocal differences. According to the paper, Graceful Prinia now occupies roughly the southwestern half of its former range, including the central and Al Ahsa (eastern) regions of Saudi Arabia, while Delicate Prinia occupies roughly the northeastern half, including Kuwait, the UAE, and northern Oman. The close proximity of Delicate Prinia to eastern Saudi, a region, like the rest of the country, that has been significantly under-birded, held out the promise that both species actually just might occur here. Indeed, a figure from the paper presenting the distribution of the taxa for both species showed the locally endemic subspecies of Graceful (P. gracilis hufufae) in the east, sandwiched, as it were, between Delicate (P. lepida irakensis) to the north in Kuwait and Delicate (P. lepida carpenteri) to the southeast in the UAE (Alstrom et al 2021). The prinias in Bahrain are also said to be Graceful (P. gracilis hufufae)*, but the status of those in Qatar is not discussed. The authors do, however, acknowledge a lack of data on the status and distribution of the different prinia taxa in eastern Arabia, leaving a golden opportunity for local birders to help fill in the gaps in their study.
Upon reading of the split last summer, the open question on the status of the prinias here in the east fired up my interest in these quintessential little brown jobbies in a way that stood in stark contrast with how much I previously took them for granted. All of sudden, they became a mini birding obsession for me. I gathered images and audio to confirm that the birds found around Al Ahsa are, in fact, Graceful Prinia, based on key features in appearance and voice. Then I directed my energy to whether Delicate Prinia had actually crossed into Saudi from Kuwait and the UAE. Since then we have confirmed that P. lepida irakensis has, in fact, colonized northeastern Saudi, with birds observed from the border town of Al Khafji to as far south as the farms and wetlands of the Al Qatif area.** We've also confirmed that Delicate, presumably P. lepida carpenteri, has colonized eastern and south-central Qatar***, strengthening the possibility the taxon also occurs in Saudi near the border towns of Batha and Salwa. It appears that Graceful Prinia (P. gracilis hufufae) also occurs in the small Gulf country, but despite an abundance of eBird observations, this has not yet been confirmed through adequate documentation.
Since the evidence gathered over the past few months indicates that both prinias are present in the northeastern corner of the Arabian Peninsula, we've pulled all prinia observations in eBird for Bahrain, Qatar, and Saudi for review to help us further untangle this taxonomic knot. We've been asking eBirders to use the default Graceful/Delicate Prinia option in their eBird checklists unless any of the following apply:
Uploaded images clearly show diagnostic field marks for the chosen species
Uploaded audio recordings contain singing males
Descriptions sufficiently detail the key features observed in the field
Any observations of either species submitted for eastern Saudi, Bahrain, or Qatar without supporting documentation will now be marked as unconfirmed and excluded from eBird’s public data. This at least until we have a clearer understanding of which species occurs where and are more confident with the nuances of IDing them.
The proceedings have been made all the more challenging due to the fact that these prinias are quite similar in many ways and thus easily confused. It's taken reading the Alstrom et al paper thrice over, studying probably near a hundred images, and listening to a couple dozen audio recordings for each species, where I feel confident enough to break down the key features we've been looking and listening for in the field. This is still a work-in-progress, but what follows is an identification guide to help birders in the region separate the two species. I hope you find it helpful.
Key Features—Morphological Differences
The Alstrom paper includes the following table, which conveniently distills the key morphological differences between Graceful and Delicate Prinia, the most prominent and reliable of which they show in boldface (Alstrom et al 2021). Key features A - C are more difficult to judge under typical field conditions, with the exception, perhaps, of the length and shape of the tail, which leaves features D and E as the clinchers, at least as far as visual identification goes. When observing prinias in the field, we need clear views of the upper- and undertail as determining which species we have ultimately comes down to scrutinizing bars and bands. I'll focus on each of these key features in turn, starting with the last and most critical for ID.
The most important visual feature (E) to pay attention to is the size, shape, and strength of the subterminal bands on the undertail feathers. As noted in the table, the subterminal bands on Graceful Prinia are larger and more prominent than those found on Delicate, whose tend to be smaller and weaker (Alstrom et al 2021). In addition to the larger size, it should also be noted that there is often a difference in the shape of the subterminal bands found on each species, with Graceful having something closer to spots—more rounded, sometimes heart-shaped—and Delicate having something closer to proper bands, distinctly narrower than those on Graceful. As for the strength of the bands, I don't believe this is just an effect of the intensity of the color—with Graceful's bands running darker and more contrasting than Delicate's—but possibly also a difference in the overall color on the underside of the tail feathers. The Graceful Prinias I've photographed over the past six months appear to be lighter in color along the underside of the tail feathers than the Delicates, whose bands seem to grade slightly at the edges, making them appear weaker still. Click through the images below to compare the size, shape, and strength of the subterminal bands between the two.
Subterminal bands on Graceful Prinia (P. gracilis hufufae)
Subterminal bands on Delicate Prinia (P. lepida irakensis)
As for the barring on the uppertail, this is a key feature (D) to consider with caution as the Graceful Prinias in Al Ahsa also show varied degrees of barring. Here's where the length and shape of the tail may help. Delicates have slightly longer and narrower tails, which they fan less frequently. Add noticeable barring on the uppertail and you might just be looking at one; however, this wouldn't be enough to confirm the ID in the absence of clear views of the subterminal bands. Depending on light and angle, however, the bands may just show through on upper side of the tail feathers, giving at least some impression of the shape and intensity. Just to sum up this key feature, however, uppertail barring on Graceful is often weak and perhaps barely visible whereas on Delicate it should stand out more obviously. The images below for each species will give you an idea of the variability of this key feature within and between the species; however, taken in conjunction with the other features, such as GISS and coloration, it can be a strong indicator of which species we've found.
Uppertail barring on Graceful Prinia (P. gracilis hufufae)
Uppertail barring on Delicate Prinia (P. lepida irakensis)
Key Features—Vocal Differences
Based on my reading of the Alstrom paper, I expected the differences in song to be the surest way of separating the two species in the field. Just looking at the spectrograms featured in the figure below, the key differences are clearly visible—the space between individual phrases, affecting the tempo of the delivery, and the amount of buzzy filler at the start of each phrase. The overall impression from Graceful's song is a steady, rhythmic, if monotonous, delivery at around 3 - 3.5 phrases per second.
Delicate's song, on the other hand, has very short spaces between phrases—around 4 - 5 phrases per second—and with a lot of buzzy filler, producing a song that sounds like a "continuous grating reel" (Alstrom et al 2021).
The following recordings from the Macaulay Library—one of mine of a Graceful Prinia at Al Asfar Lake in Al Ahsa and one of a Delicate Prinia in the UAE—represent what the typical song for each species sounds like—surely not easily confused, right?
Well, turns out all of the Delicate Prinias I've recorded in northeastern Saudi, all presumably belonging to the subspecies irakensis, which, according to Mike Jennings, began colonizing Kuwait in the 1990s and apparently continued its advance southward into the Kingdom (Jennings 2010), sing a bit slower than all of the other recordings I've heard for the species, even from other irakensis in Iraq and Iran. How this is the case is a mystery to me when there is so little difference in the overall tempo and buzziness of the songs across the other subspecies of Delicate. However, though slower than a typical Delicate's song, they're still faster than that of the local population of Graceful Prinia, 4 - 4.5 phrases per second to the Graceful's typical 3 phrases per second, and generally contain more buzzy filler at the start of each phrase. As for the calls, Alstrom et al don't discuss whether there is a notable difference; however, Graceful's might actually be higher pitched than Delicate's. Compare the songs and calls of the prinias of the Eastern Region below.
Song of Graceful Prinia (P. gracilis hufufae)
Song of Delicate Prinia (P. lepida irakensis)
Call of Graceful Prinia (P. gracilis hufufae)
Call of Delicate Prinia (P. lepida irakensis)
Well, I hope you found this identification guide helpful. Please share your questions or comments below, and watch out for updates as we continue learn about the prinias in eastern Arabia. Good birding, y'all!
* Update (January 9, 2022): To date, all media collected in Macaulay Library from Bahrain, including images and audio I gathered this past weekend, point to Graceful Prinia (hufufae) being the resident prinia on the island. There's no evidence that Delicate Prinia has reached there yet.
** Update (April 7, 2022): On the same day that I was due to fly out of Saudi and return to the US for good, I confirmed Delicate Prinia at a small lake close to the airport and in the nearby village of Abu Ma'an. Again, however, these birds, like all the others I've photographed and recorded in the northeast, show the morphological features of P. l. irakensis but sing at a slightly slower rate than those recorded in Kuwait, Iraq, and Iran.
*** Update (May 8, 2022): Kindra Andrews, an eBirder based in Qatar, uploaded audio and a supporting image to eBird that further confirms that Delicate (P. l. carpenteri) has indeed colonized Qatar. A couple of other birders there now appear poised to confirm Graceful as well, but as of yet no one has been able to provide both audio and visual evidence as Ms. Andrews has done here with her observation of Delicate from April 16, 2022.