Orioles are colorful songbirds found in many parts of the world. There are about 30 different species of orioles, including the widespread and well-known Baltimore oriole of North America. Orioles belong to the family Oriolidae, which is in the larger songbird group known as the Passerines. Within the Oriolidae family, orioles are most closely related to figbirds and pihas. Understanding the evolutionary relationships between oriole species and other bird groups can provide insight into their biology and ecology. This article will examine which birds are the closest living relatives of orioles based on DNA and anatomical evidence.
Taxonomy and Phylogeny of Orioles
Orioles belong to the order Passeriformes, which contains over half of all bird species, including perching birds and songbirds. The oriole family Oriolidae is placed within a larger group called the Corvoidea, which also includes crows, jays, and shrikes. According to the Handbook of the Birds of the World, the Oriolidae family contains 33 extant species divided into three genera:
- Oriolus – contains the typical orioles of the Old World
- Sphecotheres – figbirds found in Australasia
- Pitohui – found in New Guinea
DNA hybridization studies in the 1990s established that New World orioles like the Baltimore oriole are not as closely related to Old World orioles as previously thought. Instead, they are more closely related to an assemblage of other New World species including blackbirds, meadowlarks, and grackles. As a result, New World orioles were placed in a separate family called Icteridae.
Modern phylogenies based on DNA analyses consistently group the Oriolidae family together with the birds known as figbirds (Sphecotheres) and the pitohuis of New Guinea. Figbirds are stocky, fruit-eating birds from Australia and surrounding regions that superficially resemble orioles. Pitohuis include several poisonous species from New Guinea. Together, these three groups form a monophyletic clade, meaning they share a common ancestor and contain all of its descendents.
Evidence for Relationship Between Orioles and Figbirds
Several lines of evidence support the close relationship between orioles and figbirds revealed by DNA studies:
Physical characteristics
Orioles and figbirds share similar body plan, skeletal anatomy, and jaw/beak structure optimized for fruit-eating. Both groups have stout, Hooked bills suited to grasping fruit and thickset bodies. They share skeletal features like a highly reduced furcula (wishbone).
Behavioral traits
Orioles and figbirds exhibit similar feeding behaviors focused on eating fruits and some insects. Both build pendulous nests and exhibit nesting behaviors like lining nests with green leaves.
Biogeography
The distribution of orioles and figbirds overlaps significantly in the Australasia region. Figbirds are found from Indonesia to Australia, which is part of the broader region occupied by orioles. Their ranges likely extended further when land connections like Sundaland existed.
Vocalizations
One analysis found the structure of vocalizations used in territorial defense are similar between Eurasian golden orioles and green figbirds. This suggests a shared ancestral vocal repertoire.
Parasite sharing
Orioles and figbirds share some of the same feather lice species (Ischnoceran parasites), providing evidence of a close evolutionary relationship. Parasites often cospeciate with their hosts.
Evidence Type | Example |
---|---|
Physical characteristics | Similar body plan and feeding adaptations |
Behavioral traits | Build hanging nests, line nests with leaves |
Biogeography | Overlap in distribution in Australasia |
Vocalizations | Similar territorial defense vocalizations |
Parasite sharing | Share some feather lice species |
Phylogenetic Relationship of Orioles to Other Passerine Families
Within the perching birds, Oriolidae belongs to the infraorder Corvoidea along with several other families like crows (Corvidae), birds-of-paradise (Paradisaeidae), and Australian mudnesters (Corcoracidae). Corvoidea in turn sits within the larger superfamily Corvoidea.
Recent phylogenetic studies place Oriolidae as most closely related to the bird family Vireonidae within Corvoidea. The vireonids are small insectivorous birds restricted to the New World, including species like the red-eyed vireo. Oriolidae and Vireonidae appear to have diverged from each other around 29 million years ago.
Other close relatives of orioles include the Old World drongos (Dicruridae), monarchs and magpie-larks (Monarchidae), and whistlers (Pachycephalidae). Further out groups in Corvoidea include birds like the crows and shrikes. The exact placement of some families is uncertain, but orioles consistently group with the vireos.
Key Points:
- Within the oriole family Oriolidae, Old World orioles are most closely related to figbirds.
- The Oriolidae family forms a clade with figbirds and pitohuis.
- Orioles share many traits with figbirds indicative of a close relationship.
- DNA studies place orioles as sister group to the vireos within the Corvoidea.
Conclusion
Based on multiple lines of evidence from DNA analyses, anatomy, behavior, and biogeography, the birds most closely related to orioles are figbirds from Australia and surrounding regions. Figbirds and orioles share many similar traits and cluster together in phylogenies of passerine birds. Within the larger perching bird radiation, orioles appear most closely related to the vireo family. Their relationship highlights the complex evolutionary history of songbirds as they diversified around the world. Going forward, scientists can use the close evolutionary ties between orioles and figbirds to better understand aspects of their biology and ecology.