Museum Skins Reveal Hidden Family Tree of the World’s Most Divided Bird

The Eurasian Jay is one of the most familiar birds across the woodlands of Europe and Asia, yet it may be far more than a single species. A new study published in the Annals of the Natural History Museum Vienna has produced the most comprehensive genetic map to date of the jay genus Garrulus, revealing that the seemingly ubiquitous Eurasian Jay hides at least eight deeply divergent mitochondrial lineages that broadly match the subspecies groups long recognised by ornithologists based on plumage alone. The findings provide a molecular framework for one of the most taxonomically contested bird complexes in the Palearctic realm.

The genus Garrulus currently comprises three forest-dwelling corvids. The Eurasian Jay Garrulus glandarius sprawls across an enormous range, from the Atlas Mountains of North Africa across northern Eurasia to Japan, and south into the Himalayas and continental Southeast Asia. Its two relatives are far more restricted: the Lanceolated Jay Garrulus lanceolatus lives in the western Himalayas, while Lidth’s Jay Garrulus lidthi is confined to three islands of Japan’s Ryukyu Arc. Across its vast distribution, the Eurasian Jay displays a bewildering array of plumage variation, and the world’s major bird checklists recognise between 34 and 40 subspecies, traditionally arranged into eight groups.

That traditional arrangement, first formalised by Erwin Stresemann in 1940, divides the species into the European glandarius group, the North African cervicalis group, the Middle Eastern and Caucasian atricapillus group, the Caspian hyrcanus group, the largely Siberian brandtii group, the Japanese japonicus group, the Himalayan and southern Chinese bispecularis group, and the Southeast Asian leucotis group. Some of these groups have repeatedly been proposed as full species, and the checklist authority del Hoyo and Collar recently elevated the two Southeast Asian groups to species rank, a move not adopted by other major checklists. The resulting taxonomic confusion prompted the research team to treat the aggregate as the Garrulus glandarius complex and to test whether plumage-based groupings correspond to real evolutionary lineages.

To do so, the researchers analysed sequences of two mitochondrial markers: the protein-coding cytochrome b gene and the mitochondrial control region, the latter generally more variable and well suited to resolving differences among populations. The study relied heavily on museum specimens, with DNA extracted from small foot pad samples, two to three millimetres in diameter, taken from 54 bird skins held in the Natural History Museum Vienna, alongside tissue samples from 38 additional individuals. In total, 92 jays were sampled, including 87 individuals of the glandarius complex covering nine of the ten subspecies groups the authors now recognise, plus specimens of the two other Garrulus species. Even specimens collected between 1831 and 1836 yielded usable DNA fragments of 343 base pairs, a testament to the value of historical collections for modern genomics.

Working with such old material required careful technique. Foot pad samples were digested for up to 71 hours, extractions were performed in a clean room with regular UV irradiation, and blank controls were run at a ratio of at least one per ten samples. Because a C-stretch near the start of the control region hampered sequencing, the team designed new primers and assembled complete sequences from overlapping fragments of roughly 300 base pairs each. The final analyses combined 2483 aligned positions and employed Bayesian inference with millions of Markov chain Monte Carlo generations, complemented by median-joining haplotype networks to visualise relationships among individual birds.

The results confirm that Garrulus is monophyletic and split into two major mitochondrial lineages: one containing the Lanceolated Jay and Lidth’s Jay, which differ from the glandarius complex by uncorrected genetic distances of roughly 10.5 to 12.2 percent, and one containing all Eurasian Jay populations. Within the complex, at least eight major clades emerged, generally matching the established subspecies groups. The most basal split separates the Japanese japonicus group from all remaining jays, a result consistent with earlier, more limited studies. A Southeast Asian clade unites the bispecularis and leucotis groups, while the brandtii and hyrcanus groups each form distinct lineages. The Western Palearctic taxa, comprising the glandarius, cervicalis, atricapillus and glaszneri groups, cluster together in a well-supported western clade, though the relationships among these four remain less certain.

Several findings stand out. The insular subspecies Garrulus g. taivanus from Taiwan proved to be, alongside the japonicus group, the most genetically distinct member of the entire complex, with distances of up to 3.4 percent from its closest relatives, a striking contrast to the morphological uniformity of the bispecularis group to which it belongs. The Cyprus Jay, Garrulus g. glaszneri, emerged as the most distinct lineage within the western clade, supporting its recognition as a separate subspecies group rather than a member of the nominate European group, and suggesting it is a relict of a formerly more widespread form. On Crete, the subspecies Garrulus g. cretorum showed a control-region haplotype separated by at least 15 substitutions from all other European jays, indicating long isolation. In Siberia, jays from Hokkaido were clearly differentiated from mainland and Sakhalin birds in the control-region data, hinting at an independent glacial refugium on the northern Japanese island.

Not everything fits the neat subspecies map, however. The study detected several cases of possible interbreeding between representatives of different groups. Two birds from Azerbaijan with intermediate plumage between the hyrcanus and atricapillus groups carried mitochondrial DNA of the atricapillus clade, strongly suggesting they are genuine intergrades. A specimen of the Turkish subspecies ferdinandi, normally assigned to the European group, clustered within the Caucasian atricapillus clade, complicating interpretations of intergradation around the Bosporus. Most puzzling, five Crimean jays of the subspecies iphigenia, traditionally placed in the black-capped atricapillus group, instead clustered within the European glandarius clade. The authors caution that a major invasion of migrating jays occurred in Europe during the winter when most of these birds were collected, so the samples might represent migrants from more northern breeding grounds rather than local birds, underscoring how migration can blur phylogeographic patterns.

The Southeast Asian picture is equally intriguing. The two sampled leucotis individuals from Myanmar did not form their own cluster but nested among bispecularis haplotypes, rendering the bispecularis group paraphyletic. The authors propose two main explanations: the sampled birds may be intergrades carrying mitochondrial DNA of the bispecularis group, or mitochondrial capture through large-scale introgression may have replaced the authentic leucotis lineage. Either scenario implies interbreeding in the contact zone of northern Myanmar, where intermediate birds have long been recorded and even described as named subspecies. Notably, the data do not support the recent species-level split of the bispecularis and leucotis groups, because such a move would render the remainder of Garrulus glandarius polyphyletic given the even stronger differentiation of the Japanese japonicus group.

Biogeographically, the results complicate the long-standing assumption that Garrulus originated in the tropical rainforests of Southeast Asia. Although the deepest mitochondrial splits occur in eastern Asia, the genus’s closest relatives appear to be arid-country corvids such as the magpie genus Pica, the Ethiopian Bush-Crow Zavattariornis, the Piapiac Ptilostomus and the ground jays Podoces, an assemblage adapted to open landscapes. The authors suggest that the radiation of this group may have occurred along the mid-latitude belt during the cooling and aridification of Eurasia that began in the early Miocene, and that Garrulus may have emerged in more northern regions of Eurasia, its current distribution reflecting ancient woodland refugia rather than a recent spread out of the tropics.

For now, the authors recommend treating the glandarius complex as a single species while regarding its subspecies groups, and the distinctive island forms of Cyprus and Taiwan, as Evolutionarily Significant Units for conservation purposes. Formal species status for the Cyprus Jay would likely lead to its classification as globally threatened, given forest fragmentation, corvid shooting and illegal trapping on the island. The study deliberately stops short of taxonomic changes, noting that several groups were represented by only one or two individuals and that the minor group of the Atlas Mountains was not sampled at all. Future work with larger sample sizes, nuclear genomic markers such as whole-genome or RAD sequencing, and detailed studies of contact zones and vocalisations will be needed to settle, once and for all, how many jays really share the name Garrulus glandarius.

Subject of Research: Mitochondrial phylogenetics and phylogeography of the jay genus Garrulus and the Eurasian Jay subspecies complex

Article Title: Phylogenetic relationships within the genus Garrulus Brisson, 1760 ( Corvidae , Aves ) with special emphasis on the Garrulus glandarius complex based on mitochondrial marker sequences

Article References: Wolf, P., Töpfer, T., Kryukov, A., Aoki, D., & Haring, E. (2026). Phylogenetic relationships within the genus Garrulus Brisson, 1760 (Corvidae, Aves) with special emphasis on the Garrulus glandarius complex based on mitochondrial marker sequences. Annals of the Natural History Museum Vienna, 127, 13-37. https://doi.org/10.3897/anhmw.168785

Image Credits: AI Generated

DOI: 10.3897/anhmw.168785

Keywords: Garrulus glandarius, Eurasian Jay, mitochondrial DNA, phylogeography, museum specimens, cytochrome b, control region, corvids, subspecies, taxonomy, biogeography, Cyprus Jay