Japanese Tit

Japanese tits produce alarm calls with syntax—combining call elements in rule-governed ways that create novel meanings. The 'ABC' call element means 'scan for danger.' The 'D' element means 'approach the caller.' Combined as 'ABC-D,' the meaning becomes 'scan for danger, then approach'—a snake-mobbing recruitment call. This compositional semantics was thought unique to human language.

The syntax is productive. Artificial combinations follow the rules: 'ABC-D' (novel combination following syntax) triggers appropriate compound behavior, while 'D-ABC' (rule-violating reversal) triggers no coherent response. Birds aren't just learning fixed call meanings but extracting compositional rules.

Call order matters for meaning. The same elements in different orders produce different behaviors—a key property of syntactic systems. 'ABC-D' triggers scanning followed by approach. A hypothetical 'D-ABC' would predict approach followed by scanning, but birds treat it as meaningless, suggesting they've learned order-dependent meaning rather than just element associations.

Cross-species syntax understanding exists. Willow tits and marsh tits, closely related species with similar alarm systems, respond appropriately to Japanese tit syntactic combinations they've never heard before. This suggests syntax comprehension transfers across species boundaries.

For organizations, Japanese tits demonstrate that communication systems can be compositional—combining simple elements into complex meanings. Rather than creating new signals for every situation, compositional systems build unlimited meanings from limited elements.