Tuesday, 29 December 2015

Honduras 2: a second look

Male Velasquez's Woodpecker: depending on your taxonomic outlook, it's a Central American endemic (IOC) or a form of Golden-fronted Woodpecker, which occurs north to the southernmost USA (Clements).  This individual, photographed at Pico Bonito in Honduras, is of the subspecies pauper, which is narrowly barred above; santacruzi, which occurs in south-west Honduras, has buff or brown tones in the mantle barring. 

Male Golden-fronted Woodpecker, photographed in Texas in March 2008. Note the differences in crown pattern and upperparts barring; together with genetic and vocal differences, there are valid reasons for separating these two woodpeckers at species level, and surely it is only a matter of time before Clements catches up with the IOC.
I mentioned in the first post on my recent trip to Honduras that the country boasted either 779 or 772 bird species, depending upon which world taxonomic authority the national checklist is based. Such are the differing views on avian taxonomy these days that perhaps most, maybe all, of the world’s countries are affected in similar ways – there are enough disparities between different taxonomic perspectives to affect national lists around the globe, and wherever you go it’s worth getting to grips with the detail of what’s involved.

In the case of Honduras, at seven species the headline difference between the International Ornithological Congress view (779 spp) and that of Clements (772 spp) amounts to just 1 per cent of the total avifauna. But actually it’s much more complex than that, as the distinctions between these two authorities also involve differences in subspecies and both English and scientific names. Using the excellent tool that is Avibase, I managed to generate a tabulated summary of these differences:

While in the field in Honduras with a group of birders mainly from the US, the North American preference for following Clements was both expected and obvious (Clements also being the taxonomy adopted by Cornell’s eBird program, which our group used to submit sightings in the field). However, as welcome as it might be to set eyes on the likes ‘Golden-fronted Woodpecker’, this is not the same bird as my compadres and I know from Texas. Clements currently considers the differences significant only at subspecies level, but the more progressive IOC treats it as the specifically distinct Velasquez’s Woodpecker, including all former Golden-fronted subspecies bar nominate aurifrons in the newly split species on the basis of Garcia-Trejo et al 2009. I suspect Clements will eventually play catch-up on this, as the American Ornithologists’ Union already has a proposal on the table setting out the reasoning to accept this split.

In general, the example of Golden-fronted and Velasquez’s Woodpeckers can be used to characterise the differences between the IOC and Clements perspectives. Broadly, the IOC view is based on an international consensus and is relatively fast moving and proactive; in contrast, Clements is somewhat more conservative – at least it has been since it was taken over by Cornell after the death of Jim Clements in 2005 – and in the Americas it now, unlike previously, rigidly follows the line of the American Ornithologists’ Union.

Which species? This is a Middle American Screech Owl if you follow the IOC, or a Vermiculated Screech Owl in Clements's world order - a species which in the IOC's view occurs no further north than Costa Rica. Either way,
this Megascops species is one beautiful owl.
Back to the case in point with Honduras, where the species-level differences between the two taxonomies can be identified in the following which are recognised by IOC but not Clements:
  • White-breasted Hawk Accipiter chionogaster split from Sharp-shinned Hawk A striatus.
  • Spot-bellied Bobwhite C leucopogon split from Crested Bobwhite C cristatus.
  • Azuero Dove Leptotila battyi split from Grey-headed Dove L plumbeiceps.
  • Guatemalan Pygmy Owl G cobanense split from Northern Pygmy-Owl G gnoma.
  • Velasquez’s Woodpecker Melanerpes santacruzi split from Golden-fronted WoodpeckerM aurifrons.
  • Mistletoe Tyrannulet Zimmerius parvus split from Paltry Tyrannulet Z vilissimus.
  • Mayan Antthrush Formicarius moniliger split from Black-faced Antthrush F analis.
  • Yellow Warbler Setophaga petechia being split into Mangrove Warbler S petechia and American Yellow Warbler S aestiva.
  • Yellow-rumped Warbler S coronata being split into Myrtle Warbler S coronata and Audubon’s Warbler S auduboni.
That’s nine species-level differences, not seven, one of the other two being explained by the Clements list recognising Tricoloured Munia Lonchura malacca, an introduced species which is established in Honduras, and which should therefore also appear on the IOC’s version (in which case the IOC Honduras list total becomes 780). The other ‘missing’ species-level difference is not immediately identifiable, so presumably may have resulted from a similar glitch.

Significant diversity in a species doesn't always equate to a 'split', whatever taxonomy you follow.  The range of American Kestrel extends from southern Brazil and Chile north to Alaska, and there are 17 subspecies, including three in Honduras alone, two of which breed. These birds are probably tropicalis, the distribution of which extends from northern Honduras to southern Mexico - but they are still considered by all authorities as American Kestrels.
All of which goes to show that perhaps no checklist or taxonomy is ideal, and that it pays to check the minutiae of your chosen world order and keep on top of any changes. There is no perfect solution!

In the next post: mammals and more in Honduras.

I visited Honduras courtesy of Leica Sports Optics to attend the world launch of its new Trinovid binocular range. Many thanks to Jeff Bouton of Leica, and to fellow participants Nina Cheney (Eagle Optics), Ed Hutchings, Laura Kammermeier (Nature Travel Network), David La Puma (Cape May Bird Observatory), Jonathan Meyrav (Champions of the Flyway/IOC Tourism), Rob Ripma (Sabrewing Nature Tours), Nate Swick (American Birding Association) and Drew Weber (Nemesis Bird). Thanks also to all at The Lodge at Pico Bonito, especially James Adams and our guide Elmer Escoto, for supporting this visit.

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