White-necked Jacobin. Credit: Lukas Hummel. CC BY.
A Panamanian hummingbird uses mimicry of a dangerous hairy caterpillar to disguise its young chicks, according to a new study.
Some science discoveries take years. Other just take one curious observation, and as Jay Falk, a US National Science Foundation (NSF) Postdoctoral Fellow working at the University of Colorado – Boulder, and at the Smithsonian Tropical Research Institute (STRI) in Panama said, having the right people in the right place.
Falk has been studying white-necked jacobins (Florisuga mellivora), a neotropical hummingbird species, for more than ten years. However, he always focused on the adults.
When Michael Castaño-Díaz and Sebastián Gallan Giraldo, a PhD student and a research assistant also working at STRI, saw a white-necked jacobin nest with a caring female and one egg inside on Plantation Road, a trail within the Soberanía National Park in Panama, they didn’t hesitate to tell Falk.
They all decided to monitor the nest by doing regular visits, since it was the first white-necked jacobin nest they have ever seen.
Newly hatched white-necked jacobin chick. Notice its dorsal fluffy down feathers. Credit: Michael Castaño-Díaz. CC BY.
New discovery
Falk previously discovered that approximately 20% of the females in this species look like males, probably to increase access to food, and this chick’s mother was one of them.
Around 18-20 days later, they went to do their regular visit to observe the nest, but this time they were accompanied by Scott Taylor, Falk’s advisor at University of Colorado.
Finally, the egg had hatched and a tiny baby hummingbird came to this world.
Taylor noticed something he had never seen before in a baby hummingbird: it had long, fluffy down feathers on its back that made it look just like a dangerous caterpillar.
They immediately realised this could be a new discovery.
Some caterpillars cover themselves with urticating hairs that cause painful skin reactions, inflammation and even headaches, nausea and fever in humans.
One example of this type of mimicry is the Cinereous Mourner (Laniocera hypopyrra), a bird native to South America known for their caterpillar-like baby chicks.
With this in mind, they searched online for photos of newly hatched related hummingbird species and even some non-related hummingbirds to check whether the presence of these fluffy feathers was unusual.
Most of the species they found lacked these particular feathers, showing that what they were looking at was special.
They also noticed the nest was covered with what appeared to be seeds of local Balsa trees (Ochroma pyramidale) which are also hairy-looking, making the chick very camouflaged.
Therefore, another possibility is that the chick is camouflaging.
Caterpillar of the family Megalopygidae, known for its hurticating hairs that can cause painful reactions when touched. Credit: Herschel Raney, iNaturalist. CC BY.
Predation
Nonetheless, the team was lucky enough to observe a carnivorous wasp nearby the chick, while the chick appeared to shake its head upwards, moving just like some caterpillars do in the presence of a potential predator.
They explain that because predation rates are very high in hummingbird chicks, and because white-necked jacobins build open cup-like nests in exposed branches near the ground, strategies like mimicry or camouflage – or maybe both – might have evolved in this species.
However, more long-term observations and finding more individuals, are needed to support these hypotheses.
Tropical forests are full of mysteries and discoveries waiting to be made.
This finding shows that every observation, especially when in collaboration with other curious observers, might reveal something extraordinary
The study is published in Ecology.
