Depleted cultural richness of an avian vocal mimic in fragmented habitat

Aim: Conservation has recently shifted to include behavioural or cultural
diversity, adding substantial value to conservation efforts. Habitat loss
and fragmentation can deplete diversity in learnt behaviours such as bird
song by reducing the availability of song tutors, yet these impacts are
poorly understood. Vocal mimicry may be particularly sensitive to habitat
loss and fragmentation through the resulting reduction in both
heterospecific models and conspecific tutors. Here we examine the
relationship between habitat availability and mimetic repertoire size and
composition in male Albert’s lyrebirds (Menura alberti), a near-threatened
species renowned for its remarkable mimetic abilities. Location: Eastern
Australia Methods: We calculated repertoire size and composition from
recordings of male Albert’s lyrebirds from throughout the species’ range.
We estimated patch size and local habitat availability using a species
distribution model and remotely sensed vegetation types. We assessed the
local model species assemblage through species distribution models and
automated acoustic detectors. Results: Individual males in smaller habitat
patches, or in areas with a lower proportion of suitable habitat, mimicked
fewer model species and fewer vocalisation types, though they mimicked
comparatively more vocalisations from each model species than individuals
in larger patches or with more intact habitat. All model species were
likely to occur in most study sites, suggesting that repertoires are not
driven by the availability of model species. Main conclusions: Our results
suggest that mimetic repertoire sizes are influenced by habitat
availability through the number of lyrebird tutors. Further, individuals
in disturbed habitat may partially compensate for mimicking fewer species
by mimicking more vocalisations from each species. This study supports the
hypothesis that cultural diversity may be impoverished by habitat loss and
fragmentation in a similar way to genetic diversity. Variation in song
diversity may therefore signal population health and highlight populations
in particular need of conservation action.