A hummingbird chick in Panama mimics a venomous caterpillar to hide from predators – a rare case of birds mimicking insects. When Jay Falk and Scott Taylor first spotted white-necked Jacobin hummingbird chicks in Panama's dense rainforest, the two avian biologists weren't sure what they were seeing.

A white-necked Jacobin hummingbird hatches eggs. Photo credit: Michael Castaño-Díaz

The chick was born a day earlier, was no larger than the little finger, and was covered in brown fluff. As they approached the nest, the chicks began to twitch and shake their heads, a movement that researchers had never observed in birds.

They soon realized that the little bird might be mimicking a poisonous caterpillar that grows in the same area, using this behavior to defend itself against predators. In a paper published in the journal Ecology on 17/0, Taylor, an associate professor of ecology and evolutionary biology at the University of Colorado Boulder, and his team documented this mimetic behavior of hummingbirds for the first time.

"We know very little about the behavior of birds in tropical nests," said Falk, the study's lead author and a postdoctoral researcher at Taylor's lab. "If we had spent more time observing and exploring the natural world, this could have been much more common than we realize."

This hummingbird chick is covered in long brown feathers all over its body. Photo credit: Scott Taylor/University of Colorado Boulder

The white-necked Jacobin hummingbird is commonly found in Central and South America. Males have sparkling blue-green feathers, while females have understated green feathers.

Falk, who is also a researcher at the Smithsonian Tropical Research Institute, said the rainforest is a dangerous place for small birds. Snakes, monkeys, birds, and even insects prey on them. Previous studies have shown that chicks in tropical regions are more likely to be eaten by predators than those in temperate forests.

As the researchers approached the hummingbird's nest, the hummingbird chick began to shake its head like a caterpillar. Photo credit: Jay Falk/University of Colorado Boulder and Smithsonian Tropical Institute

So, how do tiny hummingbird chicks survive? Falk may have stumbled upon the answer during a trip to Panama's Soberania National Park in 2024.

Although the white-necked Jacobin bird often visits Falk's feeder outside the Panama research station, Falk has never seen a white-necked Jacobin chick or its nest.

But last March, Michael Castaño of the Smithsonian Tropical Research Institute and Sebastián Galan-Giraldo of the University of Antioquia in Colombia spotted a female Jacobin hummingbird incubating eggs in a nest not far from a forest trail. This nest is smaller than the palm of Falk's hand and is made of plant fragments that blend perfectly with its surroundings.

白頸雅各賓蜂鳥幼鳥。 圖片來源:Michael Castaño-Díaz

Over the next month, the research team closely monitored the hive and witnessed a chick hatching from an egg. Unlike most hummingbirds, which are born naked, the chicks of the Jacobin hummingbird are covered in long brown feathers that look almost exactly like the hive material. It was then that the research team witnessed the unusual convulsive behavior of the chicks. Scientists have never reported similar behavior in other hummingbird species.

"I started sending videos to people and asking them 'what does this look like?' Taylor said. They always say, 'This looks like a caterpillar.'" It's so exciting. ”

The day after the eggs hatched, the team found that a predatory wasp approached the chicks when the mother bird was not there. As the wasps circled above the nest, the chicks began to jerk their bodies violently, swinging their heads from side to side, as the researchers had seen. A few seconds later, the wasp flew away.

The Jacobin hummingbird chick reminded Falk and Taylor of a paper they had read earlier. Another group of researchers reported that a young songbird native to the Amazon rainforest, the gray-white wailing bird, may be similar to the poisonous orange caterpillars in the region because they have a bright orange coat and shake their heads left and right when disturbed.

Falk and his colleagues studied other caterpillars in this part of Panama and found that many had similar brown hairs that could give predators painful stings and even kill them. Some caterpillars also shake their heads when they feel threatened, just like chicks.

Scientists refer to this survival strategy, which mimics the defense signals of harmful species, as Bayesian mimicry. For example, some non-venomous milk snakes evolve red, yellow, and black patterns that resemble venomous coral snakes to ward off predators.

"Many classic examples of Pei's mimicry include butterflies imitating other butterflies, or snakes imitating other snakes. But here, we have the potential to see birds mimicking insects and vertebrates mimicking invertebrates," Taylor said.

While the study describes only one observation, the researchers hope to test their theories in the future through experiments, such as placing artificial chicks with different appearances and behaviors into hummingbird nests to see which chicks are more susceptible to predator attacks. They also hope to encourage birdwatchers and citizen scientists to document more hummingbird nests.

"Our perception of the natural world is heavily influenced by our own ideas about what could happen," Taylor says. "What we were able to discover was incredible, but we did have to think widely."

編譯自/ScitechDaily