Bird Species Spotlight: Montezuma Oropendola

by Jake Jacoby | April 11, 2021

© Jake Jacoby

In January 2020, I had the opportunity to travel to Costa Rica in Central America. I departed from Tampa, changed planes in Miami and then arrived in San Jose, the capital of Costa Rica. The Costa Rica Colon is the country’s currency and was named after Christopher Columbus. The currency bills depict the wild animals and birds of Costa Rica and are both colorful and beautiful.

Heron - Montezuma Oropendola © Jake Jacoby

Costa Rica is one of the most biodiverse countries in the world and contains about 5-percent of the world’s species. Unlike many other countries, Costa Rica enjoys a stable and friendly political climate suitable for all types of tourism, especially birding and photography. It is also one of the few countries in the world with no Army as its military was successfully abolished in 1948.

Costa Rica is truly a birder’s paradise and home to over 900 species, including 35 of which are on the endangered list, and 8 endemics (found nowhere else). These 900 species of birds are more than all of the species in North America and they are concentrated in an area that is one-half the size of the state of Kentucky – amazing.

Heron - Montezuma Oropendola © Jake Jacoby

The Montezuma Oropendola is a New World tropical “icterid” bird (Icterids make up a family of small-to medium-sized, often colorful, New World passerine birds. Most species have black as a predominant plumage color, often enlivened by yellow, orange or red. The species in the family vary widely in size, shape, behavior and coloration). Both the English and scientific names of this species commemorate the Aztec emperor Moctezuma II.

The sexes are very different in size; the male is 20-inches long and weighs 18-ounces while the smaller female is 15-inches long and weighs 8-ounces. In total body mass, the males are 100% bigger than the females, which is a 2:1 body-to-mass ratio and makes this bird one of the most sexually dimorphic birds in the world.

The size difference in males and females is probably directly related to the differences in foraging habits. The females often forage on thin branches, eating insects out of curled up leaves, while the males often perch on thick branches and forage on plants like bromeliads. Sexual dimorphism seems to be more obvious in the length of the wing and body mass. Male size and body mass is associated with sexual fitness and dominance. Males defend sexually-receptive females. While the females nest, the males fight and fend off one another, and the males are ranked depending on the outcome of each fight. The alpha male eventually pushes out all other males until he is the only one left. When the alpha male leaves the others come back and defend the females until he returns. This type of mating system is unusual in that it is similar to that of polygynous mammals (having more than one wife or mate), not birds.

Heron - Montezuma Oropendola © Jake Jacoby

The “unforgettable” song of the male Montezuma Oropendola is given during the bowing display, and consists of a conversational bubbling followed by loud gurgles. It is also a very common bird in parts of its range in Costa Rica. They are omnivorous and are often seen in small flocks foraging in trees for small vertebrates, large insects, nectar, and fruit including bananas.

The Montezuma Oropendola is a colonial breeder and only the females build hanging woven nests of fibers and vines 24-to-70 inches long in trees that are usually at least 90-feet tall. The birds favor trees that bear large nests of wasps, whose stinging attacks deter both potential nasty predators and parasitic insects. Each colony has a dominant male that mates with most of the females following an elaborate bowing display. The female lays two dark-spotted white or buff eggs and she incubates them without help from the male until they hatch in 2-weeks. The young then fledge 30-days later. While the young are in the nest, they are mostly fed spiders and other arthropods, frogs, lizards, and fruits. There are about 30 nests in a typical colony.

Heron - Montezuma Oropendola © Jake Jacoby

About the Author

To see more of Jake's work as well as his favorite photographs check out his Flickr page.

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