Polyborinae

 Crested caracara Caracara cheriway, photographed by David M. Jensen.

Belongs within: Falconidae.

The Polyborinae includes the caracaras of South and southern North America. Caracaras are relatively long-legged falcons that often feed as scavengers. They have more or less extensive areas of bare reddish skin on the face around the base of the bill.

The concerns of caracaras
Published 20 May 2024

Falcons are typically thought of as among the most aerial of the birds of prey, their name evoking images of fast, acrobatic flight as they snatch rapidly fleeing prey. But not all members of the family Falconidae are so inclined, and some have adopted a more stately way of living. These are the caracaras of the subfamily Polyborinae.

Northern crested caracaras Caracara plancus cheriway performing a courtship display, copyright Andy Morffew.

The Polyborinae* include about a dozen species of mostly medium-sized to large falcons found in South and Central America (White et al. 1994; Fuchs et al. 2015). One species, the crested caracara Caracara plancus, is found as far north as the southernmost parts of the United States. Caracaras are relatively long-legged birds with less strongly curved talons than other falcons. The profile of the head is longer, and they lack the tomial ‘teeth’ found on the upper mandible in members of the sister subfamily Falconinae. Many of the caracaras have prominent red or yellow patches of bare skin on the face. More recent studies have also resulted in the inclusion in Polyborinae of the spot-winged falconet Spiziapteryx circumcinctus, a small greyish falcon with a more typical round-headed appearance. Some authors have also included the laughing falcon Herpetotheres cachinnans and the forest falcons of the genus Micrastur that are now treated as the distinct subfamily Herpetotherinae.

*The correct name for this subfamily is not entirely clear. The most commonly used name is ‘Polyborinae’, based on the genus Polyborus that has been used for the crested caracara. However, questions have hung over the correct identity of this genus, leading Smith (2017) to suggest that it be struck from the record. Unfortunately, though usage of Caracara rather than Polyborus for the crested caracara has been widely accepted, usage of ‘Caracarinae’ rather than ‘Polyborinae’ has not. At present, the dilemma has not yet been formally resolved.

Striated caracara Phalcoboenus australis, copyright Simon Pierce.

Caracaras are typically less active aerial hunters than other members of the Falconidae, often spending more time foraging on the ground. The diet of most species is a mixture of small vertebrates, invertebrates, carrion, and even vegetable matter such as fruits. The crested caracara is able to dominate turkey vultures and black vultures for access to carcasses, and will harass other birds to steal their prey. The striated caracara Phalcoboenus australis of the Falkland Islands and Tierra del Fuego can take relatively large prey, up to size of a lamb (as does the crested caracara), and will enter seabird colonies in search of chicks. Various species are known to pull ticks from livestock and other large mammals, though they may also pick at the wounds on the mammals themselves. One Argentinian observer said of the chimango Milvago chimango that “all methods of subsistence are known to this bird; it pries into, understands, and takes advantage of everything” (White et al. 1994).

Red-throated caracara Ibycter americanus, copyright Tomaz Nascimento de Melo.

In contrast, the red-throated caracara Ibycter americanus is a specialist on Hymenoptera, making up about three-quarters of its diet with eggs and larvae from wasp and bee nests. Red-throated caracaras often engage in allofeeding, with birds pulling out the contents of nests and feeding them to other adult birds nearby. The apparent ability of red-throated caracaras to avoid getting stung by the wasps they attack, despite the large patches of bare skin on their faces, has led to the suggestion they possess some kind of chemical defence. However, McCann et al. (2013) concluded that instead the birds relied on ‘shock and awe’ tactics, the sheer force of their attack driving the wasps to abandon the nest.

Spot-winged falconet Spiziapteryx circumcinctus, copyright dannyzelener.

The spot-winged falconet is a more typical predator for the family, feeding on insects, lizards and birds. It seems to have a particular relationship with the monk parakeet Myiopsitta monachus. As well as taking both adult and young parakeets for food, the falconets roost and nest in the parakeet’s large communal nests.

Yellow-headed caracara Milvago chimachima, copyright Anthony Batista.

Unsurprisingly, phylogenetic analyses place the spot-winged falconet as the sister taxon to the remainder of the subfamily (Fuchs et al. 2015). However, these analyses have not supported division between the arboreal forest caracaras (the red-throated caracara and the black caracara Daptrius ater) and the more terrestrial species of the genera Caracara, Milvago and Phalcoboenus. Instead, the crested caracara (whether treated as a single species or divided into the northern Caracara cheriway and southern C. plancus) is the sister lineage of the other caracaras. The four species of Phalcoboenus, which are found in tropical uplands along the Andes and temperate lowlands, are supported as a clade, but the two smaller, paler species included in Milvago are not. Instead, Fuchs et al. (2012, 2015) placed the yellow-headed caracara M. chimachima as sister to the black caracara whereas the chimango was more closely related to the Phalcoboenus species. As a result, Fuchs et al. (2015) suggested treated all caracaras except the crested caracara as a single genus Daptrius, but this proposal has not gained widespread acceptance. Fuchs et al. (2012) suggested that the diversification of both the caracaras and the New World vultures of the Cathartidae was related to the aridification of the climate in the Miocene and the resulting expansion of open ground habitats.

Black caracaras Daptrius ater, copyright Ronaldo Garcia.

Most caracaras are not currently regarded as threatened; indeed, some of the more generalist species have absolutely thrived in association with human activity. The red-throated caracara has declined in some areas due to deforestation. The striated caracara has been extirpated from part of its range in the Falkland Islands as a result of human persecution but remains secure elsewhere. Less fortunate, however, was the Guadelupe caracara Caracara lutosus. This species (or possibly subspecies of the crested caracara) was found on the island of Guadelupe off the west coast of Mexico until human settlement led to its identification as a threat to livestock. By 1885, the population was almost extirpated, and the last ever record was on the 1st of December 1900. That record was by ornithologist R. Beck, who was there to collect specimens and himself shot nine individuals of a flock of eleven. He explained that he presumed, based on how little care the caracaras paid to his presence, that they must be abundant on the island. Instead, no-one would ever encounter the Guadelupe caracara again.

Systematics of Polyborinae
<==Polyborinae [Daptriinae]
    |  i. s.: Polyborus Vieillot 1816B94
    |           |--P. brasiliensisF43
    |           |--P. latebrosusSWK87
    |           |--P. lutosusFS01
    |           |--P. plancusEA06
    |           `--P. vulgarisK08
    |--Caracara Merrem 1826JT12, B94
    |    |--C. cheriwayJT12
    |    |--C. lutosaFP64
    |    |--C. plancusJT12
    |    |    |--C. p. plancusFS55
    |    |    `--C. p. auduboniiFS55
    |    `--C. prelutosaFP64
    `--+--Ibycter Vieillot 1816JT12, B94 [Ibycterinae]
       |    `--I. americanusJT12
       `--+--PhalcoboenusJT12
          |    |--P. albogularisJT12
          |    |--P. australis (Gmelin 1788) [=Falco australis]CC10
          |    |--P. carunculatusJT12
          |    |--P. megalopterusJT12
          |    `--P. montanusF43
          `--+--Daptrius Vieillot 1816JT12, B94
             |    |--D. americanusE52
             |    |    |--D. a. americanusE52
             |    |    `--D. a. guatemalensisE52
             |    `--D. aterJT12 [=Ibycter aterSS66]
             `--MilvagoJT12
                  |--M. chimachimaJT12
                  |--M. chimangoJT12
                  `--M. pezoporosF43

*Type species of generic name indicated

References

[B94] Bock, W. J. 1994. History and nomenclature of avian family-group names. Bulletin of the American Museum of Natural History 222: 1–281.

[CC10] Checklist Committee (OSNZ). 2010. Checklist of the Birds of New Zealand, Norfolk and Macquarie Islands, and the Ross Dependency, Antarctica 4th ed. Ornithological Society of New Zealand and Te Papa Press: Wellington.

[E52] Eisenmann, E. 1952. Annotated list of birds of Barro Colorado Island, Panama Canal Zone. Smithsonian Miscellaneous Collections 117 (5): 1–62.

[EA06] Ericson, P. G. P., C. L. Anderson, T. Britton, A. Elzanowski, U. S. Johansson, M. Källersjö, J. I. Ohlson, T. J. Parsons, D. Zuccon & G. Mayr. 2006. Diversification of Neoaves: integration of molecular sequence data and fossils. Biology Letters 2 (4): 543–547.

[FS55] Felten, H., & J. Steinbacher. 1955. Zur Vogelfauna von El Salvador. Senckenbergiana Biologica 36 (1–2): 9–19.

[FP64] Fisher, J., & R. T. Peterson. 1964. The World of Birds: A comprehensive guide to general ornithology. Macdonald: London.

[FS01] Flannery, T. & P. Schouten. 2001. A Gap in Nature: Discovering the World’s Extinct Animals. Text Publishing: Melbourne.

[F43] Fraser, L. 1843. On the collection of birds brought to England by Mr. Bridges. Proceedings of the Zoological Society of London 11: 108–121.

Fuchs, J., J. A. Johnson & D. P. Mindell. 2012. Molecular systematics of the caracaras and allies (Falconidae: Polyborinae) inferred from mitochondrial and nuclear sequence data. Ibis 154: 520–532.

Fuchs, J., J. A. Johnson & D. P. Mindell. 2015. Rapid diversification of falcons (Aves: Falconidae) due to expansion of open habitats in the Late Miocene. Molecular Phylogenetics and Evolution 82: 166–182.

[JT12] Jetz, W., G. H. Thomas, J. B. Joy, K. Hartmann & A. Ø. Mooers. 2012. The global diversity of birds in space and time. Nature 491: 444–448.

[K08] Kellogg, V. L. 1908. Wissenschaftliche Ergebnisse der Schwedischen Zoologischen Expedition nach dem Kilimandjaro, dem Meru und den Umgebenden Massaisteppen Deutsch-Ostafrikas 1905–1906 vol. 15. Corrodentia pt 4. Mallophaga. Almqvist & Wiksells Boktryckeri-A. B.: Uppsala.

McCann, S., O. Moeri, T. Jones, C. Scott, G. Khaskin, R. Gries, S. O’Donnell & G. Gries. 2013. Strike fast, strike hard: the red-throated caracara exploits absconding behavior of social wasps during nest predation. PLoS One 8 (12): e84114.

[SS66] Sclater, P. L., & O. Salvin. 1866. Catalogue of birds collected by Mr. E. Bartlett on the River Uyacali, Eastern Peru, with notes and descriptions of new species. Proceedings of the Zoological Society of London 1866: 175–201.

Smith, P. 2017. On the correct application of the generic name Polyborus Vieillot, 1816 (Aves: Falconidae). Proceedings of the Biological Society of Washington 130: 108–112.

[SWK87] Snyder, N. F. R., J. W. Wiley & C. B. Kepler. 1987. The Parrots of Luquillo: Natural history and conservation of the Puerto Rican parrot. Western Foundation of Vertebrate Zoology: Los Angeles.

White, C. M., P. D. Olsen & L. F. Kiff. 1994. Family Falconidae (falcons and caracaras). In: Hoyo, J. del, A. Elliott & J. Sargatal (eds) Handbook of the Birds of the World vol. 2. New World Vultures to Guineafowl pp. 216–275. Lynx Edicions: Barcelona.

2 comments

    1. I was on the cusp of including some more detailed comments about this in the post but deleted them because it’s the sort of thing that tends to be tedious to anyone other than me. The practice of ‘correcting’ family-group names when the genus they were based on was recognised as a synonym used to be fairly standard, and affects a lot of bird family names. When there has been disagreement over whether the synonymy should have implied, it gets even more complicated.

      The issues with Polyborinae essentially come down to the issues with identifying the type species of Polyborus. And I’m not entirely sure I follow that mess myself. Vieillot effectively stated that the type was the Caracara of Buffon, which was not a binomial species because Buffon did not use binomial nomenclature. So the question is whether Polyborus‘ type species should be identified as the species represented by Buffon’s ‘Caracara’ (which is probably Milvago chimachima, though this is far from universally agreed), or whether Polyborus should be regarded as a genus name published without an included species. If the latter, then the type species is probably the first properly named species included in it, which is probably Caracara plancus. And yes, that’s a lot of ‘probablies’. That’s the point.

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