Modernization, diversification, and domination: Macroevolutionary origins of living bird diversity

Modern birds comprise over 10,000 living species, occupying a dizzying range of niche space and inhabiting virtually every corner of the modern world. In order to study the origins of this spectacular diversity, as well as the stepwise sequence by which biologically modern birds came to be, insights from the Mesozoic fossil record of feathered dinosaurs are critical, as are early Cenozoic fossils documenting the rise of modern birds. Here, I outline an ambitious research programme composed of distinct, yet broadly overlapping lines of inquiry aimed at illuminating the early evolutionary history of birds. This work will bring us closer than ever before to a more complete understanding of the origins of one of Earth's most dominant living groups of organisms.
The proposed programme builds on my high-profile research in multiple areas of avian evolutionary biology and will deliver fundamental insights into some of the most important and longest-standing questions in avian macroevolution. Work will be divided into projects aimed at clarifying How, Where, and When the spectacular diversity of living birds, their specialised features, and their extraordinary phenotypic disparity have arisen. These studies will draw on abundant new three-dimensional data from pivotally important undescribed fossils, cutting edge visualisation techniques, and a wealth of novel phenotypic and genomic data from ongoing international collaborations.
i) How: Tracing the origin of the modern avian skull, and sophisticated avian flight. Three dimensionally preserved fossils are extremely rare among the closest relatives of modern birds from the Age of Dinosaurs. Exquisite new fossils from this interval, uniquely, exhibit both three-dimensionally preserved skulls and skeletons. High-resolution CT scanning combined with three-dimensional mathematical analyses will elucidate the origin of the modern avian brain, and cutting-edge range-of-motion analyses will illuminate how the modern avian flight stroke evolved.
ii) Where: The origin of modern avian geographic patterns, and the role of historical climate fluctuations in structuring avian distributions. We have previously shown that the geographic distributions of many groups of modern birds have fluctuated dramatically through their evolutionary history, but the causes of these inter-continental range shifts are unclear. By combining the latest palaeoclimate models with cutting-edge 'niche modelling' approaches, we will test-for the first time-the extent to which climatic change over the last 66 million years may have contributed to these patterns and predict future climate-driven geographic changes.
iii) When: Refining the timing of the modern avian radiation. By taking a three-pronged approach (developing new divergence time models, generating new sequence data from understudied species, and evaluating new fossil calibrations) we are poised to generate the first comprehensive and accurately time-scaled picture of the modern bird tree of life, a fundamental step toward discerning the patterns and processes that have generated Earth's modern bird biodiversity. This will also shed light on how major events in Earth history, like the mass extinction event that killed the giant dinosaurs, have shaped avian evolution.
This interdisciplinary project will have impacts on teaching, museum exhibition, digital collections building, and media, and will involve many early career scientists. New data from this project (e.g. CT scans of key modern birds and new fossils) will provide a digital legacy to be made freely available to all. These data will facilitate myriad future studies on avian evolution, and combined with media exposure accompanying publications, will educate both young and old about evolution and palaeontology. To this end, visual data from this project will be incorporated into an exhibit at the Sedgwick Museum of Earth Sciences, allowing the public to manipulate both digital and physical specimens.

This project focusses on the origin of modern birds, among the most charismatic and broadly appreciated groups of organisms. Results from this work will have broad impact across numerous user groups, including the general public, students, and researchers (see Academic Beneficiaries). A key priority in all aspects of this project will be openness: results will be regularly communicated to the general public as described below. Further, all data will be archived in perpetuity and made freely available upon publication.

The general public:

Birdwatching is an enormously popular activity worldwide. In 2011 alone, birdwatching generated well over £80 billion in economic activity; this figure has undoubtedly grown since, especially in the UK, where the Royal Society for the Protection of Birds boasts over one million members. As such, the results of this project, which will shed light on how, where, and when modern birds arose, will be of intrinsic interest to the populace at large.

Moreover, the palaeontological nature of this project is also certain to extend its appeal among the general public. Palaeontology is a hugely popular scientific discipline; indeed, palaeontology is the lens through which many young people first experience the thrill of scientific discovery. The fact that birds represent the only living lineage of dinosaurs will enhance the broad appeal of this work, which will enumerate how and when some of the most characteristic features of birds arose among Mesozoic feathered dinosaurs.

PI Field is committed to bringing results of this work directly to the general public. He will continue to be a regular speaker at local geology and ornithology interest groups around the country, as he already has over his 21 months in the UK, with presentations for the Open University Geological Society, Reading; RSPB Bath; Friends of the Sedgwick Museum, Cambridge; Lapworth Museum of Geology, Birmingham; Bath Geological Society; Oxford Geology Group, etc. He has also been a regular presenter at the Bath Festival of Nature, engaging with the public about palaeontology and evolution. Now that he has relocated to Cambridge, he will do the same at the annual Cambridge Science Festival.

Outreach through online articles, radio, podcasts, and television represents an ideal way to educate the general public about bird evolution specifically, and the excitement of science more generally. PI Field is committed to these forms of public outreach; for example, his 2018 publications have resulted in hundreds of press articles, reaching tens of millions of readers and garnering an advertising equivalent of well over £2 million, according to University of Bath media reports. This includes articles from high profile sources such as the BBC, CNN, National Geographic, Science, Nature, and The New York Times. This attention is likely to continue, as the high-profile publications set to emerge from this project will likely be of considerable media interest.

PI Field and PDRAs Navalón and Chiarenza:

The project will provide PI Field, and PDRAs Navalón and Chiarenza, with ideal opportunities for honing transferable skills in project management, networking, team-working, and written and verbal communication. PI Field and PDRA Navalón will further develop skills in high-dimensional geometric morphometrics, retrodeformation, and palaeoneurology. PI Field and PDRA Chiarenza will hone skills in macroecology, GIS, bioinformatics and palaeoclimatology.

Undergraduate student researchers:

The Department of Earth Sciences at Cambridge offers extensive research opportunities to undergraduates. Research in this proposal is amenable to student participation, including data acquisition and analysis, as well as devising new research from outlined deliverables. Student participation in research will facilitate outlined objectives and will allow the PI and PDRAs to develop mentoring skills.