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Psarocolius montezumaMontezuma oropendola

By Reena Gupta

Geographic Range

Psarocolius montezuma are found in southern Mexico to central Panama. Because the land is high and broad on the Pacific coast, they are restricted to the Caribbean side in Guatemala and southern Costa Rica. In northern Costa Rica, they are found on the Pacific slope for the same reason (Skutch 1996).

Habitat

Montezuma Oropendolas live in the rainforest regions near water and clearings, but not too deep in the forest. These birds can be found close to banana plantations and bamboo thickets. Tall, wide dicotyledonous trees are usually chosen, but they have been seen in a variety of trees if there is an absence of dicotyledonous trees (Skutch 1996; Jaramillo and Burke 1999).

Physical Description

A large bird compared to other oropendolas, Psarocolius montezuma are very visible because of their bright colors. Males and females are mostly deep chestnut in color, except for shades of yellow on their outer tail feathers and a black head complete with a pale, blue patch of skin and pink wattle. Their sharp bills are black and orange, and in males, the orange extends over their forehead. Males also have extra skin on either side of their chin and are considereably larger than females, which accounts for the wide ranges of mass. An adult male can grow to 51 cm in length, while females are 38cm in length on average. Juveniles are similar to adults except the colors are duller and they are smaller in size (Skutch 1996; Jaramillo and Burke 1999).

  • Range mass
    230 to 520 g
    8.11 to 18.33 oz

Reproduction

Mating season is from January to May. Females, alone, incubate around 1-2 eggs at a time. After incubation, which can last around 15 days, the eggs hatch. Fledging occurs 15 days after hatching. A juvenile reaches sexual maturity in less than 1 month, but will not mate until the following year. The mortality rate is high in oropendolas because depredation occurs often by toucans, snakes, monkeys, and botfly larvae. Females will mate up to three times during the season, but less than one half percent of the chicks live past hatching (Kraucunas 1996; Jaramillo and Burke 1999).

Behavior

Psarocolius montezuma are known for their strange calls and shrieks, which at some times are not very pleasant. They have a wide range of sounds from whining to clucking.

Males are much larger than females. There is a male hierarchy by size and only a small proportion of the males have a chance to perform copulations -- they are polygynous. As females build nests and make constant sounds in a single tree, a single male struts around on the branches protecting its territory and females. A male will dash after other males and alarm females when danger is near because of its dominant nature.

In one single tree there can be up to 150 nests, although most trees have 30-40 nests. They are talented builders with elaborate nests made from banana fibers and twigs that hang from branches "like overgrown, gourdlike fruits" (Skutch 1996). A female makes her own nest, which takes 9-11 days to complete.

During mating season, the male Montezuma Oropendola will approach females and bow at a forty-five degree angle. Before copulation, he moves around the female and pecks her yellow tail feathers and then more intensely ruffles and spreads her tail feathers. If the female does not leave the male, he will mount and begin to mate. During egg-laying, a cowbird will sometimes lay her eggs with the eggs of the oropendola. To prevent this, a good tree also has hornets present to keep the cowbirds away. This is an example of mutualism since the Oropendolas, in turn, keep bees away from the hornets. After the mating season, they wander in flocks until January and are easy to spot because of their yellow tails (Kraucunas 1996; Skutch 1996; Jaramillo and Burke 1999).

Communication and Perception

Food Habits

Montezuma Oropendolas are primarily fruit eaters. They have also been known to eat flowers from the surface of open grasslands, larger insects, and grass clumps of organic material. Females forage for food away from the colony in groups while males tend to search alone. They will eat throughout the day, but end their searches before dark (Orians 1985; Kraucunas 1996).

Economic Importance for Humans: Positive

The bright yellow and chestnut brown feathers are used in the indigenous cultures of the Amazon rainforests as ornamentation. While they are worn for ceremonial occasions, they do not carry religious significance (American Museum of Natural History, 2000).

Psarocolius montezuma are also popular among bird watchers. They are great for sighting because of their colorful appearance and loud calls (Skutch 1996).

Economic Importance for Humans: Negative

They do not have any negative impacts on humans. Although confident in their own colonies, they tend to shy away in the presence of humans (Skutch 1996).

Conservation Status

Oropendolas are not endangered, therefore, they have no special status. However, the rainforests in which they live have been diminishing. Trees are cut down every day because of human development. It is fortunate that they adapt well to open country where scattered trees still remain to provide food and homes (Skutch 1996; Jaramillo and Burke 1999).

Contributors

Reena Gupta (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

American Museum of Natural History, 2000. "Amazon Featherwork" (On-line). Accessed March 18, 2001 at http://www.amnh.org/exhibitions/expeditions/treasure_fossil/Treasures/Amazon_Featherwork/amazon.html?50.

Jaramillo, A., P. Burke. 1999. New World Blackbirds: The Icterids. Princeton, New Jersey: Princeton University Press.

Kraucunas, N. 1996. "Milwaukee Public Museum: Birds of the Rainforest" (On-line). Accessed March 18, 2001 at http://www.mpm.edu/research/vertzoo/vertzoo_bird05.html.

Orians, G. 1985. Blackbirds of the Americas. Seattle, Washington: University of Washington Press.

Skutch, A. 1996. Orioles, Blackbirds, & Their Kin. Tucson, Arizona: The University of Arizona Press.

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