In 2023, eBird released a taxonomic update, and as with previous revisions, birders on the Arabian Peninsula have found themselves grappling with the distinction between two formerly conspecific but now nearly identical species. Think Mediterranean and Turkestan Short-toed Larks, the status of which in Saudi remains largely unaddressed, or Graceful and Delicate Prinia, whose subtle differences nearly broke my brain during my 2021 - 22 deep dive. However, this year's taxonomic update presents an even more perplexing identification challenge.
eBird's new taxonomic update splits the widespread Intermediate Egret (Ardea intermedia) species complex. This group of taxa formerly spanned subsaharan Africa as well as from South Asia to East Asia, extending southwards through Australasia. On the Arabian Peninsula, the status of Intermediate Egret had generally been that of a rare winter visitor, primarily observed in southern Oman, with occasional vagrants reported in northern Oman and the UAE. Although the first record in Saudi dates back to April 2014, sightings of intermediate-type egrets in Jazan Province, in extreme southwest of the Kingdom, have become increasingly frequent since early 2022, with recent reports of four to five individuals. The paucity of sightings between 2014 and 2022 can likely be attributed to a lack of observers and awareness of the possibility of this vagrant, which can easily be mistaken for Great Egret, smaller subspecies of which (A. a. modesta from South Asia and A. a. melanorhynchos from Africa) likely also occur in Arabia.
With the 2023 three-way split of "Intermediate Egret" into Yellow-billed Egret (Ardea brachyrhyncha), Medium Egret (Ardea intermedia), and Plumed Egret (Ardea plumifera), the status of liminal records, particularly from the Arabian Peninsula, situated as it is between South Asia and the East Africa, has been largely resolved based on relative proximity. Consequently, all records of "Intermediate Egret" in eBird from the UAE and Oman were reclassified as Medium Egret (A. intermedia) due to the proximity of southeast Arabia to South Asia. The Asian influence of vagrant avifauna in this region is well documented, with regular sightings of Cotton Pygmy-Goose, Indian Pond-Heron, White-breasted Waterhen, Pheasant-tailed Jacana, Small Pratincole, etc. Similarly, the sixteen records from Jazan Province, fifteen of which were reported in the past two plus years, were reclassified as Yellow-Billed Egret (A. brachyrhyncha) due to the proximity of this species' nearest records, less than 400 kilometers away in Eritrea.
Prior to the split, I was aware that there were Asian and African subspecies of "Intermediate Egret" and was under the impression Asian birds could be distinguished by dark tips to their beaks. For this reason, I identified my Intermediate Egret from March 2022 as an Asian bird on account of the obvious black tip on its yellowish orange beak. Subsequent sightings around Al Sadd Lake from 2022 through early 2024 have predominantly been of birds with dark-tipped beaks as well. For this reason, the reclassification of these eBird records as Yellow-billed (i.e. African) seemed premature. While, yes, southwest Arabia receives vagrants from Africa, as does southern Oman, especially wader species responding to dry conditions in East Africa (e.g. African Openbill, Black-headed Heron and Black Heron), southwest Saudi similarly reports vagrants from South Asia as well (e.g. Cotton Pygmy-Goose, Indian Pond-Heron, Oriental Honey-Buzzard, and Pheasant-tailed Jacana). Furthermore, considering the growing sightings of Medium Egrets in southern Oman since the early 2000s and the lack of avian research in Yemen due to the Arab Spring and ensuing civil war, can we confidently dismiss the idea that Medium Egrets might have extended their range into southwest Arabia?
I have since had a chance to read up on the two species, hoping to uncover features, however subtle, by which they can be separated in the field. Based on the collection of images in Macaulay Library and the scant literature I found online, I suspect separation may only be possible when birds are in full breeding plumage, particularly during courtship, when the morphological differences are most pronounced. The differences between non-breeding and immature birds are so subtle and apparently so variable that they might not be of much use in the field. Let's go over the differences between the two species in breeding plumage.
The splitting of "Intermediate Egret" was based on striking differences in breeding morphology between the three taxa. Yellow-billed Egret have bright red-orange beaks with paler yellow-orange tips and yellowish-green to bright green lores. As Walsh and Chafer (2022) note, the color of the tibias (upper legs) progressively reddens from "yellowish to pink crimson" to "deep pink to red crimson" in full courtship.
Medium Egret, on the other hand, have all-black beaks with yellow lores and dark tibias throughout the year that become blacker as they progress into peak condition.
With these features in mind, the least ambiguous records from the Arabian Peninsula are the two of a Medium Egret in full breeding plumage from the UAE. These individuals were photographed from the blind at the Ras Al Khor Wildlife Sanctuary in Dubai in April 2019 and January 2020. Note the black beak, bright yellow lores, and black legs on the individual below that indicate A. intermedia. Other shots of this same bird show it displaying its breeding plumes.
As mentioned, the key morphological feature for separating non-breeding birds was thought to be the dark tip to the beak on Medium Egret compared to the wholly yellowish-orange beak on Yellow-billed. Images in Macaulay Library of Medium from its home range indicate that this is a consistent feature. However, the intensity of the dark tip appears variable, with some birds showing only a faint gray tip, as with the bird below.
Likewise, while most images of Yellow-billed in Macaulay Library show birds lacking dark-tipped beaks, as we can see on the bird from South Africa below, several do show beaks with dark tips, like the individual from Uganda that follows. Walsh and Chafer mention that non-breeding birds in both species often have dark-tipped beaks, and this proves to be the case, as evidenced in Macaulary Library's collection (2022).
Based on Walsh and Chafer's analysis, the feature on non-breeding birds that should then be most useful for identification is tibia coloring. They indicate that non-breeding Medium Egret show variable dark green, brown, or black tibias whereas non-breeding Yellow-billed show a variable yellowish to pale brown. Comparing non-breeding birds of both species, indeed, we see instances where this hold true, as in the four Yellow-billed below.
No images of Medium Egret show birds with such light-colored tibias. However, as with dark-tipped beaks, there are many images of Yellow-billed with dark tibias, virtually concolorous with the tarsi, as we find in nearly all the images of Medium in Macaulay Library. Compare the first two images of Yellow-billed below with the two of Medium that follow.
What, then, can we make of the "Intermediate Egret" records from the Arabian Peninsula? The occurrence in the UAE of potentially two birds in full breeding plumage as well as the consistency in the appearance of non-breeding individuals (i.e. dark-tipped beaks, dark tibias, and pale-yellow to yellow lores) support these as Medium Egret. In Oman, the situation is slightly more complicated by the lack of birds in breeding plumage. As with the UAE, relative proximity and the strong Asian influence in the region would suggest Medium; however, there are currently no images of birds in breeding plumage, so the only features suggestive of Medium are dark-tipped beaks and dark tibias. As for loral coloring, some of the Omani birds have pale yellow to yellow lores like those in the UAE, while others have greenish-yellow lores, such as the one below. Since, as I've shown, some can have dark tips to their beaks and dark tibias, I'm not sure that vagrant Yellow-billed from Africa, perhaps responding to draught conditions, as happened with the long-staying African Openbills, can be fully ruled out.
At this point, as the eBird reviewer for Saudi, I'm not sure how best to handle Yellow-billed Egret observations moving forward. To date, we haven't had observations of any unambiguously plumaged birds. All those reported to eBird have shown dark-tipped beaks, dark tibias, and yellowish lores, with my March 2022 record representative of the features we've documented thus far. Do we rule by proximity, thus precluding all but those of Medium Egret in full breeding plumage? Or do we require folks to use the Medium/Yellow-billed option for any ambiguously marked individuals, which would render all of the current Saudi records as unconfirmed?
One final note on identification: In reviewing images of both species, I encountered several misidentified Great Egret (Ardea alba). It should be noted that both the African (A. a. melanorhynchos) and Asian (A. a. modesta) subspecies are smaller than the nominate (A. a. alba), which is the dominant form on the Arabian Peninsula. However, the possibility of vagrants from these populations cannot be discounted, especially in the locales where Medium/Yellow-billed are known to be occurring. While smaller than A. a. alba, these Great Egret forms are still larger, longer necked (with a more pronounced S-shape in resting birds), and longer beaked than either "intermediate" species. However, non-breeding birds can often have dark-tipped beaks. To avoid potential misidentification, besides the length of beak, try to judge the position of the gape of the beak in relation to the eye. On Medium or Yellow-billed Egrets, the gape, if visible, stops below the eye, while on Great Egret the gape will extend noticeably past the eye, as can be seen in the side-by-side comparison below of a Great Egret and a (putative) Medium Egret in southern Oman.
In breeding plumage, A. a. melanorhynchos in Africa is hardly confusable with Yellow-billed Egret given its black beak and dark tibias.
More caution should be exercised, though, in separating A. a. modesta and Medium Egret when both are in breeding plumage since both sport black beaks and bright lores. While Medium Egret has bright yellow lores, though, A. a. modesta has bright green lores. Likewise, there's a clear difference in the color of the tibias of the two species. Medium Egret's tibias will be dark, concolorous with the rest of the legs, whereas A. a. modesta will have reddish tibias contrasting with dark tarsi.
Here is Walsh and Chafer's paper on separating Medium, Plumed, and Yellow-billed Egrets. I just glossed it for key differences between Medium and Yellow-billed. However, if you're interested in reading it and possibly gleaning more useful ID tips, you can read it here or just click on the displayed PDF and then you should see a download button.