The image above shows Crow-billed Drongo (left) and Black Drongo. The former was noted in Shanghai on 11 Oct., a first for the city. The latter is a common passage migrant in Shanghai. In this post, I show you how to separate the two species.
by Craig Brelsford
On 11 Oct. at Cape Nanhui, Shanghai’s major birding spot on the East China Sea, Shanghai Birding member kaca found a first-winter Crow-billed Drongo Dicrurus annectens. kaca’s record was the first for Crow-billed Drongo in Shanghai.
Is kaca’s historic discovery a one-off, or is it the result of more birders with greater skills more thoroughly covering Shanghai’s hot spots and communicating more readily with one another? If the answer is the latter, then there may be a Crow-billed Drongo in your future! To sift out Crow-billed from the many Black Drongo in our area, note the following:
• All drongos have a strong, black bill. Crow-billed (Panel 2a, above) may have the stoutest, as deep at its base as it is wide.
The swollen look of its bill may be Crow-billed’s most striking feature. The bill of Black Drongo Dicrurus macrocercus cathoecus is broad and short but noticeably less thick-based than that of Crow-billed. Compare bills of the two species in the image at the top of this post. (Race cathoecus is the form of Black Drongo birders are most likely to see in Shanghai.)
• The iris in kaca’s first-winter Crow-billed is reddish-brown (2a). Adult Crow-billed has a blood-red iris.
Compare brown iris of adult Black at top of post.
• Black Drongo often shows white spot at gape, never present in Crow-billed.
Note again the photo leading off this post.
• First-winter Crow-billed shows white spotting from breast to undertail coverts (2b, 3).
First-winter Black, by contrast, shows more patchily white underparts (panels 1a, 1b in photo below).
• The tail of Crow-billed shows a less shallow fork than the tail of Black. On average, the tail of Black is forked about twice as deeply as that of Crow-billed.
Compare Panel 4 in photo above to Panel 2 in photo below. Adult Crow-billed and Black have deeper forks, but the proportions are the same as in the sub-adults. In addition, the outer rectrices of Crow-billed’s tail are more likely to curl upward.
BACKGROUND ON THE SPECIES
A monotypic species, Crow-billed Drongo Dicrurus annectens breeds from the Himalayan foothills in India east to Hainan. In winter some birds go as far south as Sumatra and Java. Shenzhen-based French birder Jonathan Martinez, an expert on southeast China birds, reports breeding populations of Crow-billed in northern Guangdong and southwest Hunan. There are coastal records, most likely of migrants, from Hong Kong and Guangxi. Shanghai Birding member Paul Holt writes that Crow-billed is “undoubtedly overlooked” in southern China and “is probably quite rare or at least very localized.” Martinez agrees, calling Crow-billed “scarce” even at the Guangdong and Hunan sites.
I’m trying to get over missing the Crow-billed Drongo. I tell myself, “That’s birding,” but those words can’t fully dispel the empty feeling.
I am however happy for kaca, and I am encouraged, because the growing fluidity in reporting is leading to ever more astounding new bird records for Shanghai.
Brelsford, Craig, moderator. Shanghai Birding, a WeChat chat group. Quotations in post from Paul Holt and Jonathan Martinez taken from this chat group. News about kaca’s discovery of Crow-billed Drongo was first disseminated in this chat group.
del Hoyo, Josep, et al., eds. The Handbook of the Birds of the World. Lynx Edicions. Vol. 14, “Bush-shrikes to Old World Sparrows.” Highly detailed species accounts for Crow-billed Drongo (p. 212) and Black Drongo (p. 222) written by G.J. Rocamora and D. Yeatman-Berthelot.
MacKinnon, John & Karen Phillipps. A Field Guide to the Birds of China. Oxford University Press. Entry on Crow-billed Drongo, p. 282.
Message, Stephen & Don Taylor. Waders of Europe, Asia and North America.
Robson, Craig. Birds of Southeast Asia. Princeton University Press. Crow-billed Drongo and Black Drongo, p. 176.