Everything about oropendolas is cool and quirky, says Helen Pilcher. Starting with their vocalisations, oropendolas make noises that sound like static or ripping thick fabric. Sometimes, these evolve into complex songs that have been described as ‘liquid synth’ with ‘sci-fi elements.’
The birds hang out in groups, like mods on scooters, but in the canopy of the Central and South American rainforests.
There, males assert their dominance by engaging in the avian equivalent of a rap battle. They perform competitive duets, in which they overlay their songs and strategically tweak the low frequency parts.
These low notes are more difficult to produce, and the males that make them tend to be bigger and fitter. Vocal contests, then, provide a way for males to determine who is top dog, without coming to blows.
- It weighed more than 2 tonnes and holds the record for the largest bird nest in the world
- Weighing a tonne and packed with hundreds of rooms – each home to a family — it can house a staggering 500 households. Is this the ultimate apartment block?
To the victor go the spoils. Oropendola colonies typically contain one dominant male, a handful of subordinate males, and dozens of females. The alpha male gets to mate with most of the females and then guard their nests.
And what nests they are! From a distance, they may look like walnuts in socks but come closer and the influence of Chanel can be seen again. Just as Coco used great technical skill to construct garments that were both comfortable and practical, so too oropendolas carefully engineer their nests to be cozy and functional. These aren’t just any old nests. These are ergonomic egg hammocks, suspended 30 metres or more above the ground, from the boughs of tropical trees.
They are built by females, using vines, grasses, palm leaf fibres and bark strips. This is a technically skilled, but largely innate process. After lassoing an anchor point to a branch, the female then attaches long, vertical strands to form the structure’s backbone.
Fibres are woven through the framework, and the bottom is expanded to form a deep, protective pocket, which is then lined with leaves. The overall effect is a large, tear-shaped structure, which can be a metre or more in length. Females then lay one to three eggs, which they incubate and feed on their own.
Most colonies contain a few dozen nests, but one colony of Montezuma oropendolas in Costa Rica contained 130 nests in a single tree – a vast city in the sky! The nests are difficult for predators, such as snakes and monkeys, to get into, and their clustering provides relative safety in numbers. Sometimes, the birds even build their nests in trees that have wasp nests, because it adds another layer of security.
The birds are a marvel, so it’s devastating to learn that in recent years, some have started to weave plastic into their nests. In a survey of 36 crested oropendola nests, from coastal sites in the Brazilian Amazon, two-thirds contained plastic, including bits of blue fibres and ropes from discarded fishing gear. Much of this plastic contained toxic chemical contaminants, and now researchers fear that these visibly blue nests could affect the health of the chicks that develop inside them.
