The Biogeography of the Resplendent Quetzal (Pharomachrus mocinno)

by Paul Pribor, student in Geography 316
 

Species Name: Pharomachrus mocinno

Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Trogoniformes
Family: Trogonidae
Genus: Pharomachrus
Species: Mocinno
 

Description of Species:

The Resplendent Quetzal (Pharomachrus mocinno) has been called "the most spectacular bird in the New World" (Peterson and Chalif, 1973). The Quetzal was the most sacred symbol of the Aztecs and Mayas. Quetzalcoatl, the Feathered Serpent, is seen wearing the long tail plumes of the male Quetzal, which only the royalty of these societies were allowed to wear. The name quetzal is an ancient Indian term for tail feather and the bird itself represents liberty. An ancient and cherished belief held that a Quetzal would not survive in captivity, it would rather die than be held prisoner. So rather than killing these birds for their precious feathers the Maya would pluck them and set the birds free to grow new feathers. Unfortunately this has since proved false and Quetzals can be viewed in zoos throughout the world.

The adult Quetzal is about 14 inches in length and the male has tail feathers that can grow to 30 inches or longer. "The head and upper plumage are an intense and glittering green, the lower breast, belly, and under tail coverts are of the richest crimson. The bill is bright yellow …. the glittering eye is black and the two median and longest of the covert tail feathers are golden-green with blue and violet iridescence" (Skutch, 1944). The female Quetzal, as other birds, has a more subdued plumage than the male and lacks the long tail plume that gives rise to notion that male Quetzals in flight look like green lighting.

The Quetzal is listed as an Appendix 1 species in the Convention on International Trade in Endangered Species (CITES). This means that it is threatened with extinction that may be accelerated by illegal trade of the species. The primary threats to its existence are habitat destruction, clear cutting forests eliminates seed trees and accelerates erosion, and poaching (Bowes and Allen, 1969). The Quetzal is also the national symbol of Guatemala, appearing on its flag and being the name of its monetary unit. Although a national law has existed since 1875 prohibiting killing, trapping, or exporting Quetzals, poaching and trapping continue (Bowes and Allen, 1969).
 

Habitat:
Although the New World trogons range from Arizona to Argentina, the Resplendent Quetzal is found only in the cloud-forests in the highlands of Central America including southern Mexico, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, and Panama (Skutch, 1944). The other members of the genus are South American (Sibley and Ahlquist, 1990). The Quetzal is a frugivorous species that feeds primarily on Lauraceae fruit (Skutch 1944, Bowles et al, 1969) and is found in disjunct populations throughout its range. There are two subspecies; P. mocinno mocinno, which is found between Mexico and Nicaragua, and P. mocinno costaricensis in Costa Rica and Panama (Powell and Bjork, 1994)(fig.2). These subspecies are located in highland areas separated by a lowland belt that crosses the isthmus along the Rio San Juan and Lake Nicaragua (Skutch, 1944). The Quetzal shows geographic variation along the two sides of the gap, P. mocinno mocinno tends to have tail coverts of greater length (Skutch, 1944) along with other slight morphological and behavioral differences (Sibley and Ahlquist, 1990).

The Quetzal is found on both igneous and limestone terrain where mature or virgin cloud forests occur (LaBastille, et al, 1972). They are generally found between the altitudes of 4000 feet up to 10,500 feet and the forests they inhabit have a canopy of oak trees 100 to 150 feet tall (Skutch, 1944). Interspersed with the oaks are numerous members of the laurel family (Lauraceae) including wild relatives of the avocado (Persea spp.) and species of Nectandra and Ocotea whose fruits are an important source of food for the birds (Wheelright, 1983). The Quetzals are considered specialized frugivores, that is they feed mainly on the nutritious fruits of a few plant species and for which they serve as major seed dispersers and are believed to have coevolved (Avila et al, 1996).
 

Natural History:
Quetzals are known to eat up to 41 species of fruit however much of their biology seems tied not to any one species but to the fruiting patterns of a single family, the Lauraceae (Wheelright, 1983). Quetzals are altitudinal migrants. They breed and nest in montane forests and migrate to lower altitudes where they remain for the non-breeding season (Powell and Bjork, 1994). Breeding occurs during the peak of fruiting in the Lauraceae and emigration occurs when there is a relative paucity of lauraceous fruits even though other species of fruits are available (Wheelright, 1983). Quetzals’ morphology and geographical distribution also reflect their dependence on the Lauraceae. The Trogonidae and Lauraceae have possibly been in association since the late Cretaceous or early Tertiary, both families are pantropical with present centers of diversity in the Neotropics and Southeast Asia (Sibley and Ahlquist, 1990). It has been theorized that the quetzals and Lauraceae (whose fruits they depend on and whose seeds they disperse) colonized the Central American Isthmus in tandem during the Pliocene Epoch (Raven and Axelrod, 1974). Subsequent events have since separated the two subspecies but not long enough for any significant speciation to occur.

The plumage of the Quetzals seems to be a protective camouflage suited to rainy conditions. The bright green feathers show little iridescence and do not glint so that the bird blends remarkably with wet and shiny green vegetation (LaBastille et al, 1972). A Quetzal shows up as brilliant green under sunlight and is far more noticeable in bright light than under overcast conditions, however the general weather pattern is cloudy and rainy so the protective coloration has probably been adapted accordingly (Bowes and Allen, 1969). It is believed that Quetzals never touch ground during their natural life but spend most of their time in or near the canopy between 75 and 200 feet (LaBastille et al, 1972).

Quetzals nest in a hole in decaying trees (Skutch, 1944) usually broken-off, rotting tree stumps. Often these trees are in the last stages of decay before toppling, this makes them much more vulnerable to stochastic events such as windstorms or other trees falling and knocking over the nest tree. The Quetzals actively carve out their nests in these rotting trees and it is surmised that the act of digging may actually play an important role in the reproductive cycle (Bowes and Allen, 1969). Digging may be a necessary release mechanism in the bird’s ovulation stimulating endocrine function (ibid). The average Quetzal territory (defined as a defended area) includes a 1000-foot radius around the nest tree and ranges from around 12 feet above ground to the canopy (Bowes and Allen, 1969).

The prime limiting factor associated with Quetzals is probably the availability of nest-trees. In order for a tree to be a suitable nest it must be sufficiently decayed and soft enough to dig in, the process of decomposition can take a long time, and once the tree is sufficiently decayed it is much more susceptible to the elements (Powell and Bjork, 1994). The Quetzal has a few predators including the Grey Squirrel (Sciurus griseoflavus), the Kinkajou (Potus flavus), the Ornate Hawk-eagle (Spitaetus ornatus), along with a few other hawks and owls (Bowes and Allen, 1969). But the chief threat to its existence comes from human modification of the environment and poaching.

Any population that is highly restricted geographically is much more likely to be eliminated by any force that acts in a certain place (Simberloff, 1994). Since the Quetzals reside in a very specific environment that is slowly being eroded by human encroachment, they run the very real risk of imminent extinction. There are currently reserves specifically designated for the preservation of Quetzal populations but because the Quetzal is an altitudinal migrant existing reserves are not sufficiently large to contain both the highland breeding areas and its lowland offseason haunts. In order to ensure the long-term viability of a species a minimum viable population (MVP) must be determined. An MVP is one that meets "the minimum conditions for the long term persistence of a species or population in a given place" (Soule, 1986). To date there have been no studies detailing the MVP of Resplendent Quetzals and given the complexity of forces affecting population viability and migration, it may be some time before there is an answer. There is however an initiative by both governmental and nongovernmental organizations to preserve and manage biological diversity on a multinational level from Mexico to Panama, called Paseo Pantera (the path of the jaguar) (Rabinowitz, 1996). This project focuses on the biological corridor utilized by the jaguar and other species since the Pleistocene Era, although it does not focus exclusively on Quetzal territory some is included.

Evolution:
The present day distribution of the family Trogonidae suggests they shared a primitive cosmopolitan distribution (Sibley and Ahlquist, 1990) and the presently disjunct distributions resulted from vicariance, perhaps as early as the Cretaceous period. This primitive cosmopolitan distribution corresponds with Gondwanaland whose breakup in the early Cretaceous led to a separation of the Old and New World trogons. The New World trogons diverged from the African trogons about 35 million years ago and from the Asian trogons about 31 million years ago (Sibley and Ahlquist, 1990). These branches probably occurred in the Cenozoic long after the Atlantic rift separated the two continents so it is unlikely that a Trans-Atlantic crossing between South America and Africa can explain these relationships.

It has been alternatively hypothesized that birds underwent massive extinctions during the late Mesozoic and then had an explosive evolution that paralleled mammals in the early Tertiary (Feduccia, 1995). Under this model modern bird families were not established until the late Eocene, by which time the continents were more or less in their present configuration. This hypothesis lends credence to the punctuated equilibrium theory of evolution that has been gaining momentum in recent years but it is vehemently disputed by many other scientists who favor a more gradualistic approach to avian evolution (Chiappe, 1995). Chiappe speculates that by calibrating the phylogeny of Mesozoic groups, whose sister taxa must have common origins, that the Cretaceous lineages were present very early in this period (Chiappe, 1995) and were therefore vicariantly distributed. The debate is bound to rage on with mudslinging on both sides however at this point the vicariance model of distribution lends itself to a more easily apprehended explanation.

Distribution
The family Trogonidae has a pantropical distribution except for Australia. It consists of 6 genera (Pharomachrus, Apaloderma, Euptilotis, Priotelus, Harpactes,. and Trogon) and 39 species. There are five species of Pharomachrus: P. antisianus – crested quetzal, P. fulgidus – white-tipped quetzal, P.auriceps – golden-headed quetzal, P. pavoninus – pavonine quetzal, and two subspecies of P. mocinno –resplendent quetzal – P. mocinno mocinno and P. mocinno costaricensis.

The family Trogonidae consists of three subfamilies: Apaloderminae, which is distributed in the forested areas of Africa from the tropics to Cape region of South Africa, Harpactes, which is found throughout India and Sri Lanka, southeast Asia, Indonesia, Borneo, and the Phillipines, and Trogonidae, the New World trogons, which range from southern Arizona to northern Argentina including Cuba, Hispaniola, and Trinidad (fig. 1).

Other interesting issues:
Quetzals provide a huge draw for tourists in Central America and the money tourists bring with them can provide an incredible bonus to local economies, to this end there are plans afoot to preserve even more critical habitat for Quetzal migration including corridors between existing forest patches (Powell and Bjork, 1994).

It has been recently claimed by an acoustics expert that the ancient Maya knowingly planned the temple Kukulkan to cast forth an echo sounding like the chirp of a Quetzal when someone claps their hands in front of the entrance (Weiss, 1999). Although this may seem farfetched it cannot be argued that the ancient Maya did not hold the Quetzal in great esteem, something we would do well to emulate soon before this "messenger of the gods" is heard no more.
 

Bibliography
Avila, Lourdes, V. Hugo Hernandez, and Enriqueta Velarde. 1996. "The Diet of Resplendent Quetzal (Pharomachrus mocinno mocinno: Trogonidae) in a Mexican Cloud Forest." Biotropica 28(4b): 720-727.

Bowes, Anne LaBastille and David G. Allen 1969. "Biology and Conservation of the Quetzal." Biological Conservation 1(4): 297-306

Chiappe, Luis M. 1995. "The First 85 Million Years of Avian Evolution." Nature 378(23): 349-355.

Feduccia, Alan. 1995. "Explosive Evolution in Tertiary Birds and Mammals." Science 267: 637-638.

LaBastille, A., D.G. Allen, and L.W. Durrell. 1972. "Behavior and Feather Structure of the Quetzal." The Auk 89:339-348.

Peterson, R.T. and E.L. Chalif. 1973. A Field Guide to Mexican Birds. Boston, Mass, Houghton Mifflin Co.

Powell, V.N. George and Robin Bjork. 1994. "Implications of Altitudinal Migration for Conservation Strategies to Protect Tropical Biodiversity: a Case Study of the Resplendent Quetzal Pharomachrus mocinno at Monteverde, Costa Rica." Bird Conservation International 4:161-174.

Powell,V.N. George and Robin Bjork. 1995. "Implications of Intratropical Migration on Reserve Design: a Case Study using Pharomachrus mocinno." Conservation Biology 9(2): 354-362.

Raven, P.H. and D.L. Axelrod. 1974. Angiosperm Biogeography and Past Continental Movements. Ann. Missouri Botanical Gardens 61:539-673.

Sibley, Charles G. and Jon E. Ahlquist. 1990. Phylogeny and Classification of Birds. New Haven and London. Yale University Press.

Simberloff, Daniel. 1994. "Habitat Fragmentation and Population Extinction of Birds." Ibis 137:s105-s111.

Skutch, Alexander F. 1944. "Life History of the Quetzal." The Condor 46(5) 213-235.

Soule, Michael E. and David Simberloff. 1986. "What do Genetics and Ecology Tell Us About the Design of Nature Preserves?" Biological Conservation 35: 19-40.

Weiss, Peter. 1999. "Singing Stairs." Science News 44(1):155-158.

Wheelright, Nathaniel T. 1983. "Fruits and the Ecology of Resplendent Quetzals." The Auk 100: 286-301.
 
 
 
 
 
 
 
 

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