 One
of most prized birds in South America is Toucan-Barbet (left). James
Ownby took this gorgeous photo as the bird foraged in a fruiting tree
in the western Andes of Ecuador. Toucan-Barbet, found only in the Andes
of Colombia and Ecuador, is one of two species in the genus Semnornis;
the other is Prong-billed Barbet of Central America. Both of aberrant Piciformes
of uncertain affinities that have limited ranges in montane cloud forests,
and together they are known as (small case) toucan-barbets.
Recent molecular evidence has proven that New World barbets, toucans, and these two birds in Semnornis (e.g., the toucan-barbets) are more closely related to each other than they are to Old World barbets (Burton 1984, Prum 1988, Sibley and Ahlquist 1990, Lanyon & Hall 1994, Barker & Lanyon 2000, Johansson et al. 2001, Johansson & Ericson 2003, Moyle 2004). These studies have differed as to whether Semnornis is more closely related to New World barbets or to toucans. The most recent and comprehensive analysis (Moyle 2004) could not place them with certainty, but they seem to be a separate group that evolved early in the New World radiation. Given the evidence that toucans are actually 'big-billed New World barbets' when compared to barbets in the Old World, there are several different taxonomic approaches. The Handbook of the Birds of the World (Short & Horne 2002) sticks with the traditional approach of two families: all the barbets (including these Toucan-Barbets) in a barbet family and the toucans in a toucan family. They argue that it is easy to tell whether any bird in the group is a barbet or a toucan, and that the barbets are ecological counterparts on each of the three major tropical continents. This is true enough, but it is a bit like sticking your head in the ground to avoid the new evidence of relationships. I prefer a more modern approach, discussed below. |
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 My
poor backlit photo is how one more typically sees the Toucan-Barbet, high
in the canopy of a Cecropia canopy, where one glimpse just a touch
of the brilliant reds & yellows, offset by soft grays, that characterize
its plumage. They love fruiting trees — indeed, Remsen et al. (1993) found
that 100% of the stomach contents of both toucan-barbets was fruit.
Old Word barbets are here treated as two separate families, Asian Barbets [Megalaimidae] and African Barbets [Lybiidae]. Recent genetic data (Moyle 2004) support the monophyly of the barbet radiations within each region. To emphasize the close relationships among New World taxa, the three groups — New World barbets, toucan-barbets, and toucans — were treated as subfamilies of a single family, Ramphastidae, by AOU (1998). This approach means that the Toucans are lost as family and they become just "big-billed barbets." I know that from the perspective of world birder, Toucans are a distinctive group, easily recognized as Toucans and nothing else, and that they are exciting birds to see. I like the idea of Toucans as their own family. The only logical way to accommodate this desire, and still be consistent
with evolutionary relationships as we now know them, is to treat all three
New World groups. This is perfectly consistent in ornithology and is the
approach now taken by the South American Checklist Committee. They state
that: "Semnornis is treated as separate family until affinities
resolved," noting that an "analysis of characters of the hindlimb musculature
supported the traditional inclusion of Semnornis in the barbets,
but Prum's (1988) analysis of morphological data indicated that Semnornis
is the sister taxon to the Ramphastidae, not the Capitonidae. Genetic data
indicate that Semnornis may be basal to both families (Barker and
Lanyon 2000)."
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Toucan-barbets do appear transitional between barbets and toucans.
In their 100% fruit-eating behavior they are more similar to toucans than
to New World Barbets. Both toucan-barbets are also unique among all barbet
relatives in having the bill tip extending forward and fitting into a notch
in the tip below. Young birds use these scissor-like tips to easily "bite"
their way out of nesting cavities (Short & Horne 2001). This holds
true for Prong-billed Barbet in the mountains of Costa Rica and western
Panama. It is not nearly as colorful as Toucan-Barbet but it does have
the unique bill, as shown in this nice shot (below) by Marc Fenner:
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In summary: to accurate represent the relationships of what used to
the Barbets and the Toucans, we now have five separate lineages and five
separate families, including the Toucan-Barbets [Semnornithidae]. I'm happy
with that arrangements. They are a special, unique, and highly sought group.
Use the links below to see the other other four families:
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Photos: Both photos of Toucan Barbet Semnornis ramphastrinus were taken along the Nono-Mindo Rd., Ecuador. James Ownby photographed his on 8 Apr 2002 at Septimo Paraiso Resort; my distant shot was higher on the ridge and farther south along the road on 17 Apr 1992. Marc Fenner photographed Prong-billed Barbet S. frantzii at Monteverde, Costa Rica, in March 1991. Photos are © 2004 James Ownby and Don Roberson and Marc Fenner, respectively; used with permission, all rights reserved. More evocative shots from James Ownby's South Americas trip are on his web site [see his Ecuador travel diary]. Marc Fenner hosts a fine web site on birding Costa Rica. Family Book: Rating: I must confess that I don't actually own this book, nor have I done more that quickly glance through it in a bookstore. But every one of the Oxford Univ. Press series on bird families has been excellent, and this looks equally solid. I presume that the "meat" of this book has been summarized by the same authors in their Handbook of the Birds of the World series (Short & Horne 2002) which I do own and have studied.Literature cited: American Ornithologists' Union. 1998. Check-List of North American Birds. 7th ed. A.O.U., Washington, D.C. |
