Eocene bird stomach contents show origins of fruit eating and seed dispersal + allometry in avian cranial evolution + flush-pursue foraging in birds (free pdfs)
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Ben Creisler
Jul 6, 2026, 2:03:03 PM (11 days ago) Jul 6
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Ben Creisler
J W Oyston, J T Thorson, A Knapp, R D Marek & R N Felice (2026)
Structural Equation Modelling Reveals How Allometry Shapes Integration in Avian Cranial Evolution
Integrative and Comparative Biology, icag106
doi: https://doi.org/10.1093/icb/icag106
https://academic.oup.com/icb/advance-article/doi/10.1093/icb/icag106/8723922
Testing hypotheses of phenotypic modularity involves assessing whether groups of traits covary more strongly with each other than with parts outside the group. Structural Equation Modelling (SEM) is a flexible statistical framework for interrogating complex relationships between sets of variables, making it ideally suited to studies of hierarchical modularity and integration. However, quantifying the modular organization of high-dimensional traits using SEM in a phylogenic context has only recently become possible through new methodological advances. Here, we applied SEM to investigate patterns and correlates of phenotypic modularity in the skull and brain of birds. Birds independently evolved relatively large brains multiple times, as well as a wide range of different skull and brain morphologies. While some have proposed the bird skull is composed of several functional or developmental modules, others have suggested the skull is highly integrated, with share allometric scaling structuring trait correlations. The data best supported a model in which brain shape is influenced by changes in shape of the neurocranium as well as a ‘jaw’ module consisting of the rostrum shape and jaw musculature. Rostrum shape itself does not strongly covary with other aspects of the skull and brain, suggesting decoupling of beak morphology from the rest of the avian cranium. All variables, with the exception of rostrum shape, are strongly influenced by size, supporting the idea that allometry is a major influence on craniofacial integration in birds. These results provide new insights into likely drivers shaping the evolution of the skull in birds and highlight the usefulness of phyloSEM testing hypotheses of evolutionary modularity and integration.
Free pdf:
Jinseok Park, Sang-im Lee & Piotr G Jablonski (2026)
Convergent acquisition of a specialized feeding strategy: flush-pursue foraging in birds
Biological Journal of the Linnean Society 148(3): blag032
doi: https://doi.org/10.1093/biolinnean/blag032
https://academic.oup.com/biolinnean/article/148/3/blag032/8722652
Birds exhibit diverse foraging strategies shaped jointly by the morphology and behaviour of predators and prey, as well as by habitat conditions. Some foraging tactics may result from convergent evolution when similar patterns among these factors are found across different lineages. Flush-pursue foraging, where birds use conspicuous wing and tail displays to startle hidden prey and pursue it, is known to drive plumage evolution among birds. However, the diversity and evolutionary relationship of the species using this strategy and associated traits remain poorly documented. For the first time, we compiled a global list of flush-pursuing species and conducted a family-level phylogenetic analysis. We found that flush-pursue foraging has independently evolved in four avian orders, and at least 17 families within Passeriformes, illustrating convergent adaptations to a specialized foraging niche. Flush-pursuers were more likely to be found in families with traits related to pursuit ability, such as smaller body size and longer tarsus length relative to body mass. This foraging strategy was also associated with denser habitats, likely providing various substrates and hiding spots for prey, and thus flushing prey makes foraging more efficient. Similarly, families with broader latitudinal ranges that cover more diverse habitats and prey types were also associated with a higher likelihood of flush-pursue behaviour. Family-level invertivorous diet predicted the presence of flush-pursuers, as expected from the susceptibility of arthropod sensory systems to startle displays. These findings illustrate how convergent acquisition of this unique foraging strategy of birds is shaped by the combination of morphology and ecology.
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Recent avian papers:
Free pdf:
Gerald Mayr & Margaret E. Collinson (2026)
A survey of Eocene stomach contents illuminates the origins of frugivory and seed dispersal in neornithine (crown group) birds
The Science of Nature 113: 81
doi: https://doi.org/10.1007/s00114-026-02130-2
https://link.springer.com/article/10.1007/s00114-026-02130-2
Stomach contents with seeds in avian fossils from the latest early/earliest middle Eocene Messel oil shale (Germany) are surveyed. 20 bird specimens belonging to 10 species with seeds produced by at least 13 different plant species are reported. The fossils provide the earliest direct evidence for avian frugivory and suggest that seed dispersal by neornithine (crown group) birds occurred earlier and was more extensive than currently thought. For the first time, we report seeds in the stomach content of stem group Trogoniformes, which today are important seed dispersers in the New World tropics. Other birds belong to the Galliformes, Gruiformes (Messelornithidae), Coliiformes, Coraciiformes, and the extinct taxa Halcyornithidae and Zygodactylidae. Extant Coraciiformes are predominantly carnivorous, whereas some Galliformes and Gruiformes as well as the Coliiformes today also consume fruits. All reasonably well-preserved seeds appear to be from angiosperms, including specimens identified as Rutaceae, Mastixiaceae, and Vitaceae. Unidentified seeds represent various other plant groups. Several of the arboreal birds ingested seeds of the Vitaceae. This plant family already evolved in the Late Cretaceous, whereas arboreal Neornithes did not radiate before the early Cenozoic. As such, and at least concerning arboreal birds, these fossils provide evidence for the “recruitment hypothesis”, which suggests that early Cenozoic seed dispersers exploited an existing diversity of edible fruits.
=====
Gerald Mayr & Margaret E. Collinson (2026)
A survey of Eocene stomach contents illuminates the origins of frugivory and seed dispersal in neornithine (crown group) birds
The Science of Nature 113: 81
doi: https://doi.org/10.1007/s00114-026-02130-2
https://link.springer.com/article/10.1007/s00114-026-02130-2
Stomach contents with seeds in avian fossils from the latest early/earliest middle Eocene Messel oil shale (Germany) are surveyed. 20 bird specimens belonging to 10 species with seeds produced by at least 13 different plant species are reported. The fossils provide the earliest direct evidence for avian frugivory and suggest that seed dispersal by neornithine (crown group) birds occurred earlier and was more extensive than currently thought. For the first time, we report seeds in the stomach content of stem group Trogoniformes, which today are important seed dispersers in the New World tropics. Other birds belong to the Galliformes, Gruiformes (Messelornithidae), Coliiformes, Coraciiformes, and the extinct taxa Halcyornithidae and Zygodactylidae. Extant Coraciiformes are predominantly carnivorous, whereas some Galliformes and Gruiformes as well as the Coliiformes today also consume fruits. All reasonably well-preserved seeds appear to be from angiosperms, including specimens identified as Rutaceae, Mastixiaceae, and Vitaceae. Unidentified seeds represent various other plant groups. Several of the arboreal birds ingested seeds of the Vitaceae. This plant family already evolved in the Late Cretaceous, whereas arboreal Neornithes did not radiate before the early Cenozoic. As such, and at least concerning arboreal birds, these fossils provide evidence for the “recruitment hypothesis”, which suggests that early Cenozoic seed dispersers exploited an existing diversity of edible fruits.
=====
Free pdf:
J W Oyston, J T Thorson, A Knapp, R D Marek & R N Felice (2026)
Structural Equation Modelling Reveals How Allometry Shapes Integration in Avian Cranial Evolution
Integrative and Comparative Biology, icag106
doi: https://doi.org/10.1093/icb/icag106
https://academic.oup.com/icb/advance-article/doi/10.1093/icb/icag106/8723922
Testing hypotheses of phenotypic modularity involves assessing whether groups of traits covary more strongly with each other than with parts outside the group. Structural Equation Modelling (SEM) is a flexible statistical framework for interrogating complex relationships between sets of variables, making it ideally suited to studies of hierarchical modularity and integration. However, quantifying the modular organization of high-dimensional traits using SEM in a phylogenic context has only recently become possible through new methodological advances. Here, we applied SEM to investigate patterns and correlates of phenotypic modularity in the skull and brain of birds. Birds independently evolved relatively large brains multiple times, as well as a wide range of different skull and brain morphologies. While some have proposed the bird skull is composed of several functional or developmental modules, others have suggested the skull is highly integrated, with share allometric scaling structuring trait correlations. The data best supported a model in which brain shape is influenced by changes in shape of the neurocranium as well as a ‘jaw’ module consisting of the rostrum shape and jaw musculature. Rostrum shape itself does not strongly covary with other aspects of the skull and brain, suggesting decoupling of beak morphology from the rest of the avian cranium. All variables, with the exception of rostrum shape, are strongly influenced by size, supporting the idea that allometry is a major influence on craniofacial integration in birds. These results provide new insights into likely drivers shaping the evolution of the skull in birds and highlight the usefulness of phyloSEM testing hypotheses of evolutionary modularity and integration.
=====
Free pdf:
Jinseok Park, Sang-im Lee & Piotr G Jablonski (2026)
Convergent acquisition of a specialized feeding strategy: flush-pursue foraging in birds
Biological Journal of the Linnean Society 148(3): blag032
doi: https://doi.org/10.1093/biolinnean/blag032
https://academic.oup.com/biolinnean/article/148/3/blag032/8722652
Birds exhibit diverse foraging strategies shaped jointly by the morphology and behaviour of predators and prey, as well as by habitat conditions. Some foraging tactics may result from convergent evolution when similar patterns among these factors are found across different lineages. Flush-pursue foraging, where birds use conspicuous wing and tail displays to startle hidden prey and pursue it, is known to drive plumage evolution among birds. However, the diversity and evolutionary relationship of the species using this strategy and associated traits remain poorly documented. For the first time, we compiled a global list of flush-pursuing species and conducted a family-level phylogenetic analysis. We found that flush-pursue foraging has independently evolved in four avian orders, and at least 17 families within Passeriformes, illustrating convergent adaptations to a specialized foraging niche. Flush-pursuers were more likely to be found in families with traits related to pursuit ability, such as smaller body size and longer tarsus length relative to body mass. This foraging strategy was also associated with denser habitats, likely providing various substrates and hiding spots for prey, and thus flushing prey makes foraging more efficient. Similarly, families with broader latitudinal ranges that cover more diverse habitats and prey types were also associated with a higher likelihood of flush-pursue behaviour. Family-level invertivorous diet predicted the presence of flush-pursuers, as expected from the susceptibility of arthropod sensory systems to startle displays. These findings illustrate how convergent acquisition of this unique foraging strategy of birds is shaped by the combination of morphology and ecology.
====
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