- Surveys of several sites, including Nepal’s Chitwan National Park, show that the lesser necklaced laughingthrush may be physically mimicking a larger species, the greater necklaced laughingthrush, for benefit.
- Findings suggest the benefits for the smaller bird include no longer needing to be vigilant for predators when foraging for food, as the bigger bird does this job.
- Previous reports show the lesser necklaced laughingthrush is already known for vocal mimicry, where it produces the call of another bird.
- Mimicry among various species potentially serves as an evolutionary strategy for protection and foraging benefits.
KATHMANDU — On an early spring morning in the western forests of Chitwan National Park in Nepal, a cacophony of birdsongs resonates through the air, mingling with the rustling of dried leaves and cries of other animals in the distance.
As the sun’s rays penetrate the thick canopy, a feathered creature adorned with a dark arc looping across its breast and a striped white patch on its cheek serenades with a sequence of whistles that sound like laughter. A short distance away, a smaller bird, mostly brown with hints of rust on its neck and sides, and a conspicuous black pattern on its white chest, composes a tuneful and melodious call.
In the shade of the bushes, the two birds appear similar. But they’re anything but. The two birds — the greater necklaced laughingthrush Pterorhinus pectoralis) and the lesser necklaced laughingthrush (Garrulax monileger) — don’t even belong to the same genus, despite their names and their strikingly similar visual features.
A new study looking at the interactions between the two species, which are found across South and East Asia, suggests that the smaller of the laughingthrushes may have adopted mimicry of the bigger bird as an evolutionary strategy to potentially placate the greater laughingthrush when it’s around, gain some level of protection against predators, and get better access to food by foraging near the larger bird.
“The lesser laughingthrush appears to be mimicking the greater by adjusting the colors of its feathers to match that of the bigger bird when the species live together in mixed flocks in the same geographic area,” researcher Kamal Raj Gosai, who recently completed his Ph.D. looking into the interactions between the two birds, told Mongabay.
“This mimicry is particularly evident in the similarity of the brightness of the necklaces of the two birds when they are in close proximity,” he added. “But the lesser’s feather colors are different when they are not living with the greater.”
As part of the new study, Gosai and his colleagues looked at both museum specimens and live birds in the field. For the former, they took photos and measurements of the specimens, focusing in particular on the color and size of the necklace pattern on the breast, and determined whether the specimens came from areas where both species occurred together or separately depending on where they’d been collected from. For the live birds, they looked at flocks where birds from both species were present, or mixed-species flocks. Three of these surveys were carried out in China, and one in Nepal’s Chitwan.
The surveys also included observations of the behavior and foraging of the two species, Gosai said.
From their findings, they were able to conclude that, where the two species occurred together, the lesser necklaced laughingthrush could be trying to look and behave like the greater necklaced laughingthrush to get along with the bigger bird and the reap benefits of its presence.
“There could be numerous benefits of mimicry for the lesser necklaced laughingthrush,” Gosai said. “For example, when the two species are foraging together the lesser necklaced laughingthrush could concentrate on the food rather than exercise vigilance against potential predators.”
The researchers also noted that the greater laughingthrush could be more aggressive toward predators and raise an alarm when they’re around — a vigilance measure that the smaller laughingthrush could take advantage of.
In areas where the greater laughingthrush was absent, the lesser one had a less prominent necklace, as judged by the lighter coloration of the breast feathers. There was no such change noted among the greater laughingthrush, suggesting there’s no evolutionary benefit for the species to mimic the lesser bird.
The authors of the study note that due to the limited scope of the study, they couldn’t compare other characteristics of the two birds, which could make the mimicry hypothesis either stronger or weaker.
“Future research could delve deeper into the plumage similarities and differences between the two birds beyond the necklace feature,” Gosai said. It could also investigate the behavioral interactions between the two in more detail to elucidate how mimicry influences social dynamics, foraging behavior, and overall fitness within mixed-species flocks.
Conducting field experiments to simulate the presence or absence of mimicry between the two could provide valuable insights into the functional significance of mimicry in their interactions, the authors of the study note.
Various laughingthrush species are already known for vocal mimicry, where they produce the calls of other birds. The lesser necklaced laughingthrush was previously reported to have done just that in Chitwan, according to ornithologist Hem Sagar Baral. Baral, who wasn’t involved with the recent paper but has studied vocal mimicry among gray-sided laughingthrushes (Pterorhinus caerulatus), said the findings make a strong case for convergent evolution — where one species will evolve a trait shared by another that confers it some degree of benefit.
“This is crucial as we tend to think of evolution as being divergent, with different species developing characteristics different from other species,” he said.
Neither the greater nor lesser necklaced laughingthrush is considered a threatened species, so at first glance there doesn’t seem to be a conservation implication from the study. But Gosai noted that birds such as laughingthrushes are indicator species for the wider forest ecosystem: when there’s a healthy population of the birds in a forest, they help in different processes such as pollination and control of insect population, for instance.
“That’s why research into least concern species is also important,” he said.
Abhaya Raj Joshi is a staff writer for Nepal at Mongabay. Find him on 𝕏 @arj272.
Banner image: A lesser necklaced laughingthrush (left) and the greater necklaced laughingthrush (right) photographed in Nepal’s Chitwan National Park. Image courtesy of Kamal Raj Gosai
Citations:
Gosai, K. R., Zhou, L., Liu, Y., Braun, E. L., Kimball, R. T., Robinson, S. K., … Goodale, E. (2024). Investigating flock-associated mimicry: Examining the evidence for, and drivers of, plumage mimicry in the greater and lesser necklaced laughingthrush. Royal Society Open Science, 11(4). doi:10.1098/rsos.230976
Baral, H. S. (2019). Voice mimicry exhibited by grey-sided laughingthrush Garrulax caerulatus (Hodgson, 1836) in Phulchoki Mountain, an important bird area, central Nepal. Our Nature, 17(1), 41-44. doi:10.3126/on.v17i1.34004
