Know your fauna: Birds – Yellow Orioles (Icterus nigrogularis curasoensis)

This post is also available in: Dutch, Papiamentu.

Icterus nigrogularis curasoensis

Icterus nigrogularis curasoensis

The bird sits in the tree, like a ripe yellow mango, its bright yellow feathers in shrill contrast to the grayish background of the dry forest. Besides the brightly coloured feathers, it is also the sound the bird produces which is striking, it’s like a sharp coughing bark. In Papiamentu, de local language on Curaçao and Bonaire the bird is called Trupial Kachó (the Dog Trupial), based on the barking sounds it makes. In Papiamento, the local language on the island of Aruba, the bird is called Gonzalito. Few people realize that the yellow oriole, or Trupial Kachó, is a highly skilled singer, and that these animals can produce the most wonderful tunes.If people are not looking, that is!

In Curacao, we know two species of birds which are classified as troupials, the Venezuelan Troupial or orange troupiaal (Icterus icterus) and the Yellow Oriole (Icterus nigrogularis curasoensis).
A species that has a scientific name consisting of three Latin words, is called a subspecies, a type which differs from the ‘original’ species to such a extent that it is known as being different; as a new species in development. The Yellow Oriole also occurs on Bonaire and Aruba. The book ‘Birds of the Netherlands Antilles’ written by Voous in 1983 mentions that the scientific name Icterus nigrogularis curasoensis was used on all three islands, Aruba, Bonaire and Curaçao, although the birds on Aruba look slightly different than the birds on Bonaire and Curacao. The endemic species list by A. Debrot from the year 2006 shows that the animals belonging to the subspecies Icterus nigrogularis curasoensis only occur on Curaçao. In the latest bird publication by De Boer, Newton and Restall from the year 2012 this subspecies of the Yellow Oriole is on record yet again as occurring on all three of the Leeward Islands.

A traditional Yellow Oriole nest made with natural fibres.

A traditional Yellow Oriole nest made with natural fibres.

Artful nestbuilders

Yellow orioles make complex nests, looking like elongated grass-bags often attached to a very  thin twig in which the eggs and young are rocked by the wind. The nests are at least as complex as the wicker baskets woven by man, but the birds have only the use of their beak and legs to build the nests.
These hanging nests are perfect to safely ‘store’ the chicks. The narrow entrance at the top of the nest makes it a virtually impregnable fortress for crafty crooks, such as the Venezuelan Oriole (Icterus icterus), which is always lusting after a fresh egg or a young chick. Usually the birds will use the same nest site time and time again but the nest itself will be completely rebuilt. To breed in a musty, second hand nest is clearly not an option. The nest location is carefully chosen, and will preferably be a location above a substrate which is poorly inviting. These are all strategies to make the life of robbers as difficult as possible. And seeing as to where many nests can be found, it is clear that the best modern place to build a nest is right above an asphalt road.

Not all thieves are fooled by the ingenious nests however. Invasive non-native Shiny Cowbirds (Molothrus bonariensis) will not eat the eggs or chicks of the Yellow Oriole, but act as a parasitic ‘breeder’. The glossy black birds search for a nest of a Yellow Oriole which has already produced eggs. The cowbird will lay its own egg in between the Orioles eggs.

A young Yellow Oriole with a parent.

A young Yellow Oriole with a parent.

When hatched, the Cowbird chick will always be larger than the offspring of the Yellow Oriole, and it will do its utmost to make the young Orioles life as miserable as possible. The bill of the Cowbird chick is larger and the colors on the inside of the beak are brighter, which provides the incentive for the mother to push food trough its throat everytime she comes back to the nest, and by doing this the invasive chick will draw all the food to itself. The Oriole chicks will starve to death, the mother flying off and on to keep the invasive chick alive. European cuckoos also have this same behaviour as they also lay their eggs in nests of other species of birds. The Yellow Orioles have no defense against this behaviour yet, and their numbers suffer severely because of this invasion. Many citizens on Curacao, watching the Orioles very closely, have reported seeing less and less of the yellow birds in urban environments. Reliable numbers about the population of Yellow Orioles are not available though, as no research is being done to establish these numbers.

Individual nature lovers have done their utmost best to minimize the numbers of Shiny Cowbirds on the island, and most often focus on urban areas such has inhabited areas in Bandariba and the centre of the island. The real impact of the Cowbirds on native birds and the most effective methods to control this invasive species has never been researched.
The Shiny Cowbird still occurs on the island and we often get notification of invasions of the nests of native Orioles. Some biologists however, expect the Orioles to evolve in their behaviour in such a way that they will learn to recognize the eggs and young of the invaders in their nests, and start removing them themselves, or just start ignoring the invasive young. This would be a natural development in behaviour making sure Shiny Cowbirds do not have the 100 percent success rate they have now as parasites on the motherly care of someone else. Only time will tell what will happen.

A nest made with 'modern' nylon fish lines.

A nest made with ‘modern’ nylon fish lines.

Modern influences

If you ever drive on the small road between Willibrordus and Fontein, at a certain point you will drive under a high tree with several twigs hanging over the road, in which there are always at least 2 nests of Orioles. If you have a little bit of time it is really worth it to start observing these nests. It’s not only the location which is modern, the animals figured out that humans can make some superior nesting materials. Using pieces of fishing nylon and pieces from synthetic rope they construct their nests which are more sustainable in terms of endurance, instead of using natural materials. On this part of the island, in Bandabou, the nests are made from deconstructed blue ropes. At Sint Jorisbay you will find ‘modern’ nests made from white or green fishing lines, depending on the types of nylon left behind by fishermen in the area.
If you happen to encounter an Oriole’s nest, take a little time to observe it. The engineering skills of the ‘modern’ Orioles are distinctively different from the ones using natural materials.

Insect eaters with a taste for fruit

The menu of the Yellow Oriole consists mainly of insects like beetles, flies and grasshoppers. But if there is some ripe fruit hanging around they will not hesitate to eat it. Just put some overripe bananas on a plate in the garden and chances are a Yellow Oriole will arrive shortly to enjoy the sweet treat. They love other sweet fruits like cactus fruits, mango’s, West Indian Cherries and others as well if available, but will not hesitate to eat seeds as well. If there are cactus seeds in the wild or bird seed in the garden, they will enjoy this as well, and even eat bread sometimes.
Especially in the dry season times can get difficult for the animals. The ascending development and urbanization and the destruction of habitat as a consequence eliminates local trees and plants. These produce fruits and seeds in the dry season and provide these animals with necessary nourishment in these difficult times. The destruction of habitat makes life more and more difficult for many birds including the Yellow Oriole. A little bit of help in your garden can go a long way. Just place some overripe fruit which attracts small insects, seeds and a bit of water and you will be giving a helping hand as destruction is going on and on. And by inviting these gorgeous animals into your garden you have the privilege of a free nature documentary seen from your own window.

Michelle da Costa Gomez

About Michelle da Costa Gomez

2 Responses to “Know your fauna: Birds – Yellow Orioles (Icterus nigrogularis curasoensis)”

Read below or add a comment...

  1. Sam says:

    Hi there,
    Your website is greatly appreciated! How can we attract more birds in our yard? Do you have tips on birdhouses, type of food or types of flowers/plants to plant? I would love to have more birds in our yard to observe and photograph. Thank you!

  2. DEar Miss da Costa Gomez— Thank you for the excellent article! It did not describe the immatures of the Yellow Oriole, however. And right now at Coral Estate, we have some interesting visitors which — at first sight — appear to be the immatures of the Orchard Oriole!!!! But we are wondering whether they could be immatures of the Yellow Oriole.

    My only 2 bird-books here are the 1983 “Birds of the Netherlands Antilles” (Voous) and an old Peterson guide to the US birds east of the Rockies. Voous has no description or pictures of the young. Peterson doesn’t cover the Yellow Oriole/Troupial at all, but has pictures of the female and immature male of the Orchard Oriole which look exactly like what we’re seeing at our feeders..

    I’d really appreciate your help with this I.D. Sincerely, Diana