The Cattle Egret Undergoes a Taxonomy Split in 2023
How "Cattle Egret" Became "Western Cattle Egret" in eBird
The Cattle Egret is a long-time breeding resident of Anguilla. It is easily seen across the island throughout the year and is particularly fond of The Valley agricultural areas.
This species has always been listed in eBird as “Cattle Egret.” Since October, however, “Western Cattle Egret” is the only option to record this species. I set out to find out why the change happened.
Each year, the list of bird species is updated. Those changes are recorded in the Clements List. Spearheaded by James Clements, PhD, and now managed by the Cornell Lab of Ornithology, the list is described as follows:
“In today’s arena of continuous taxonomic change, The Clements Checklist presents the most up-to-date and most widely endorsed compendium of the more than 9,930 species of birds recognized by the scientific and birding communities. In taxonomic sequence, this checklist provides the scientific and English name of each species and a description of the worldwide range of each species and subspecies.”
Enter the Cattle Egret. After careful study, the population has been split into two different species.
The 2023 eBird Taxonomy Update explains the Cattle Egret split as follows:
“Cattle Egret Bubulcus ibis is split into Eastern Cattle Egret Bubulcus coromandus and Western Cattle Egret Bubulcus ibis. Eastern Cattle Egret looks strikingly different from Western Cattle Egret in breeding plumage, when it looks like its entire upperparts were dipped in butterscotch sauce. Western Cattle Egret by comparison, looks like it just ended up with a small amount of the same sauce on its crest and breast feathers. The overall look is strikingly different and makes these instantly recognizable. In non-breeding plumage, however, structure may be the only hope of correct identification: Western Cattle Egret is short-necked and short-legged, recalling a night-heron or a Butorides heron (Green or Striated Heron), while Eastern Cattle Egret looks comparatively long-necked and long-legged and more like a slightly short-billed version of an “Intermediate” Egret (i.e., Medium, Plumed, or Yellow-billed Egret). In fact, one vagrant Eastern Cattle Egret was misidentified and originally published as Hawaii’s first Ardea intermedia.
Western Cattle Egret occurs widely in Africa and Europe, and is the bird that has colonized the New World. Eastern Cattle Egret is common from South Asia through East Asia, Southeast Asia, and Australia. Either taxon could occur at islands in the central Pacific (although Western Cattle Egret has populated Hawaii and the Galapagos) or Indian Ocean; vagrant Eastern Cattle Egrets are known from the Aleutian Islands, Midway and the Northwestern Hawaiian Islands, and the Seychelles, while either Western or Eastern Cattle Egrets can occur in parts of Arabia, Iran, and the “stans”. Any records in those regions should be identified with care.
Western Cattle Egret Bubulcus ibis [map] [media] [my records]
RANGE: the Americas, Europe, Africa, the Middle East
Eastern Cattle Egret Bubulcus coromandus [map] [media] [my records]
RANGE: South and Southeast Asia and Australasia
These two species are very difficult to identify in non-breeding plumage, especially without excellent and close looks, so this slash option will remain important for many individuals. Be sure to check your own data, since some records may remain in eBird as a slash (but you should update them to the species level if you are certain of the species involved).
Western/Eastern Cattle Egret Bubulcus ibis/coromandus [map] [media] [my records]
Regional Record Change Logic: These two taxa segregate surprisingly well by range. From Pakistan and Afghanistan east are Eastern, while all records from Arabia, Europe, Africa, and the Americas have been converted to Western. The one exception pertains to records from Midway and the Northwestern Hawaiian Islands; Western predominates there but Eastern is known as a vagrant so records are being checked first.”
David Sibley and his renowned Sibley Guides put the split in much simpler terms with the following graphic:
The mystery has been solved! The stark contrast is readily apparent when they are in breeding plumage.
This was not the only species impacted by this year’s revisions.
“Our 2023 update includes 3 newly-described species, 124 species gained because of splits and 16 species lost through lumps, resulting in a net gain of 111 species and a new total of 11,017 species worldwide.”
To learn all about the changes, please visit the following link: eBird 2023 Taxonomy Update.
For those who say birds are “boring” - think again! There is always something new to learn about our feathered friends.
Interesting!