Galápagos Lava Heron confirmed as distinct species
New research reshapes understanding of Butorides herons, revealing the island population is more closely related to Green Heron than to mainland Striated Herons
A long-standing taxonomic question resolved
A major new genetic study has clarified the evolutionary relationships within the genus Butorides, confirming that the Galápagos Lava Heron should be treated as a distinct species rather than a subspecies of the widespread Striated Heron.
Using thousands of genomic markers alongside morphological data, researchers found that the Lava Heron Butorides sundevalli forms a clearly defined lineage, resolving years of uncertainty over its status. {index=0}
Closer to Green Heron than expected
One of the most striking findings is that the Lava Heron is more closely related to the North and Central American Green Heron Butorides virescens than to the South American Striated Heron Butorides striata, overturning long-held assumptions based largely on appearance.
This relationship was strongly supported by genome-wide data, with alternative evolutionary scenarios statistically rejected. The results suggest that traditional classifications, which grouped these birds together, do not reflect their true evolutionary history.
A global rethink of Butorides herons
The study reveals a deeper split within the genus, separating Old World and New World populations into distinct evolutionary lineages. Within this framework, at least four major groups emerge, including the Green Heron, Lava Heron, South American Striated Heron and the Old World Little Heron.
This challenges the long-standing view of the Striated Heron as a single, globally distributed species, instead pointing to multiple distinct evolutionary lineages that have diverged over time.
Genetics and morphology tell the same story
Alongside genetic evidence, the study highlights consistent physical differences in the Lava Heron, particularly in bill structure. Birds from the Galápagos show significantly larger and more robust bills than mainland populations, even after accounting for body size.
These differences are thought to reflect adaptation to the islands’ rocky shorelines, where Lava Herons feed on hard-shelled prey such as crustaceans rather than the softer prey typically taken by other Butorides species.
Plumage can mislead
The research also demonstrates the limits of relying on plumage to define species. Some Galápagos birds show a more typical ‘Striated Heron’ appearance, yet genetic analysis shows they belong to the Lava Heron lineage.
This suggests that all Butorides herons on the islands form a single, distinct population, despite variation in appearance, and highlights how easily cryptic diversity can be overlooked.
An island origin
The findings support the idea that the Lava Heron evolved following colonisation of the Galápagos by dispersing birds, likely related to the migratory Green Heron. Isolation on the islands then led to divergence, producing a unique endemic species.
This pattern mirrors that seen in several other Galápagos birds, where long-distance dispersal has been followed by rapid evolutionary change.
A complex evolutionary history
Interestingly, the study also found some conflict between nuclear DNA and mitochondrial DNA results, suggesting a more complex history involving past hybridisation or gene flow.
Researchers caution that such patterns are not unusual and emphasise that the broader genomic data provide the clearest picture of relationships within the group.
A clearer picture - but more to learn
Overall, the study provides one of the most detailed insights yet into the evolution of Butorides herons, combining global sampling with modern genomic techniques.
Read the full paper here
March 2026
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