Skip to content

Coal Tits Responded More Strongly to Strangers; Green-backed Tits Showed No Clear Neighbour–Stranger Difference

Coal tit perched on a spruce branch with cones at Steinodden, Lista, Norway
Research · Behaviour

A playback study at Liupanshan National Nature Reserve in Ningxia, northwestern China, compared neighbour–stranger discrimination in two closely related species with very different song systems. Coal tits (Periparus ater) have relatively complex repertoires, while green-backed tits (Parus monticolus) produce much simpler, more stereotyped songs.

During the 2024 breeding season, researchers recorded territorial songs and then played familiar-neighbour and unfamiliar-stranger songs to males at active nests. The experiment included 20 male coal tits and 23 male green-backed tits and asked whether differences in vocal complexity were accompanied by differences in territorial recognition.

Coal tit songs were more varied and individually distinctive

The researchers identified 19 song types in the coal tit population but only five in green-backed tits. Individual coal tits also used larger syllable repertoires, averaging 4.45 types per male compared with 1.95 in green-backed tits.

Coal tit males also differed more from one another acoustically, whereas green-backed tit songs were more similar among individuals. The authors argue that this greater vocal distinctiveness may provide more information that birds can use to recognize familiar neighbours.

Coal tits responded more strongly to strangers

Nineteen of 20 coal tits responded to stranger playback, compared with 16 of 20 during familiar-neighbour playback. Males also approached strangers more closely and made more flights near the nest. Together, the responses were consistent with the “dear enemy” effect, in which established neighbours are treated as less threatening than unfamiliar intruders.

Green-backed tits showed a very different pattern. Only six of 23 males responded to stranger playback and none responded to familiar-neighbour songs. Despite that numerical contrast, responses were too sparse to provide clear support for neighbour–stranger discrimination in this species.

Song complexity may help recognition, but it is not the whole explanation

The authors interpret the parallel differences in song structure and territorial behaviour as evidence that a larger, more individually distinctive vocal repertoire can facilitate neighbour recognition. They do not argue that repertoire size alone determines this ability: other birds with simple songs can distinguish individuals, and subtle acoustic differences within a song type may also carry identity information.

The very low responsiveness of green-backed tits remains an important uncertainty. The experiment lacked a separate positive-control stimulus that could confirm that all males were territorially motivated when tested. The authors therefore cannot rule out that temporary motivation contributed to the weak responses as well as limited vocal discrimination.

Within those limits, the study found a clear dear-enemy response in coal tits but not in green-backed tits. The main biological result is that the species with more individually distinctive songs also showed clearer neighbour–stranger discrimination.

Sources and image credit

  1. Zhao, L., Zhang, F., Liu, J., & Liang, W. (2026). Vocal Complexity Constrains the Dear Enemy Effect: A Comparative Study of Coal Tits and Green-Backed Tits. Ecology and Evolution, 16, e72918. https://doi.org/10.1002/ece3.72918Primary open-access peer-reviewed study, published 9 January 2026. Full text was checked. Playback trials involved 20 male coal tits and 23 male green-backed tits at Liupanshan National Nature Reserve in Ningxia; coal tits showed statistically supported neighbour–stranger discrimination, whereas green-backed tits showed low responses with no significant stimulus effect. The authors note the lack of a positive control for territorial motivation as an important limitation.

Image: Marton Berntsen / Wikimedia Commons — coal tit photographed at Steinodden, Lista, Norway, 27 February 2015. Representative image for this story; not presented as an animal or scene from the reported study or event. · CC BY-SA 4.0 · Source

About this content: This story was produced with AI assistance within an editorial workflow developed by Wildlife Vagabond. Editorial responsibility remains with Wildlife Vagabond.How AI is used

Behaviour

SPECIES IN THIS STORY

Species in this story

Coal Tit Periparus ater Explore species

Independent research and conservation news archive

Did you find this information useful?

Wildlife Vagabond is independently built and maintained. Voluntary support helps cover source verification, hosting and continued work on research and conservation news.

Support Wildlife Vagabond

The news archive will remain freely available.