Journal archives for February 2022

February 28, 2022

The "Mangrove" Black Hawk

This is one of the most erroneously used avian taxon in all of iNaturalist, the Mangrove Black Hawk (Buteogallus [anthracinus] subtilis). Out of the 60 observations on iNat, most of them are likely not this subspecies.

The problem is, we don't really know what the Mangrove Black Hawk is. It was originally described as a species in 1905, with its distribution being the Pacific coastline of South America. Though many authors have voiced their opinions on the taxonomic status of the Mangrove Black Hawk, for simplicity reasons, I will gloss over those fine details. The real problem started in 1931 when Peters supported the speciation of the Mangrove Black Hawk but extended their range well northward on the Pacific slope, all the way to Chiapas, Mexico. That is a huge range expansion! Ever since, authors argued on the id marks of Mangrove and Common Black Hawk, and whether or not the two species bred sympatrically.

Bill Clark (2007) provided an excellent summary of the complex by saying in places like Costa Rica or Panama, the black hawks looked and sounded identical on both the Pacific and Atlantic slopes. His paper was later cited as the primary source for lumping the Mangrove Black Hawk with the Common Black Hawk in a SACC and NACC proposals. Both committees passed the lumping but kept the current erroneous ranges of the two subspecies.

My take on the issue is, reduce the range of the Mangrove Black Hawk back to what it was in 1905. The Mangrove Black Hawk, and I mean the real ones, are readily and reliable identifiable. There are 5 currently recognized subspecies of the Common Black Hawk, I say there's only two; nominate which resides from Arizona to Trinidad, and subtilis from Panama (possibly) to Peru. Here's some photos to compare to:

Arizona Common Black Hawk:

Ecuadorian Mangrove Black Hawk:

Costa Rican "Mangrove" Black Hawk (Pacific Slope):

Costa Rican Common Black Hawk (Atlantic Slope):

Now that you've taken a good look at hawks from both endpoints of their distributions, and a number of individuals in countries where both of supposedly present, what do you see? The Costa Rican "Mangrove" Black Hawks look nothing like the hawks in Ecuador. Those Costa Rican hawks look no different to those seen on the Atlantic slope, who look identical to hawks seen in Arizona. If we look into what Mangrove BH look like, and by that, I mean those with rufous secondaries, there seems to be a narrow contact zone. See here:

Southeastern Panama:

Pacific Slope of Colombia:

Note the distinct differences again? It seems as soon as you head into South America, suddenly, the hawks become a spitting image of what Mangrove BH are supposed to look like. Regardless of what you think, subspecies or species, that's your opinion. But for identification purposes on iNat, look for these 3 features in identifying:

  1. Rufous secondaries; both readily visible in flight and perched.
  2. Barred emarginated primaries, not dark.
  3. Mangrove BH probably does not occur north of Panama.
Posted on February 28, 2022 05:57 AM by birdwhisperer birdwhisperer | 0 comments | Leave a comment