Research
The major goal of my research is understanding the evolution of sexual signals in birds. I use integrative methods, including genomics, spectrophotometry, high-resolution imaging, and field observations to fully describe sexual phenotypes and investigate how they arise, proliferate, and change. A central component of this work is studying how gene flow among species contributes to the evolution of plumage coloration. Because understanding relationships among species is critical for understanding trait evolution and gene flow, phylogenetic analysis is an important element of my work.
At every step, my research relies on museum collections. See the Museums tab above for more.
The physical and genetic basis of structural colors in bird feathers
The genetic basis of carotenoid-based plumage signals in birds has been an area of intense interest in ornithology. Structural colors, where the physical structure of the feather tissue controls light reflectance and scattering to produce different colors, are in some ways much more complicated, which probably explains why fewer studies have investigated their evolution.
I am now working to address this topic, starting in a group of warblers in the genus Cardellina that show an intriguing geographic pattern of structural and carotenoid-based color elaboration from north to south in North and Central America.
I am currently investigating physical contributors to "structural white" cheek feathers through light and scanning electron microscopy.
Phylogenomics, plumage color, and gene flow among species and genera of New World warblers
Hybridization among species is a key mechanism for adaptive evolution and speciation, and its full impacts are becoming better understood as modern genomics leads to larger and more complete datasets.
We sequenced whole genomes of multiple individuals from nearly every species of warbler to generate a new phylogenetic hypothesis for the family and investigate plumage color evolution. We found that carotenoid metabolism gene BCO2 has undergone at least eight instances of introgression between species and two between genera. These findings suggest that "borrowing" color-related genes from related species may be quite common and more feasible than acquiring advantageous color changes through new mutations.
Publications:
*Shared first authorship
2026 Cespedes Arias LN*, Bennett KFP*, Campagna L, Wood AWW, Bonaccorso E, Cuervo AM, Cadena CD, Lovette IJ, Toews DPL. Diversification and divergence in Myioborus warblers: insights into evolutionary relationships and plumage genetics. Evolution, early view. http://doi.org/10.1093/evolut/qpag085.
2025 Bennett KFP, Wood AWW, Baiz MD, Phung L-N, Lovette IJ, Toews DPL. A colorful legacy of hybridization in wood-warblers includes frequent sharing of carotenoid genes among species and genera. PLOS Biology, 23(12): e3003501. https://doi.org/10.1371/journal.pbio.3003501.
2025 Bennett KFP, Gielow KH, Toews DPL. Genetic confirmation of an “Uncommon Mourningthroat” (Geothlypis philadelphia x G. trichas): a rare but persistent hybrid warbler. Wilson Journal of Ornithology, 138(2): 303–314. https://doi.org/10.1080/15594491.2025.2584827.
Evolutionary implications of sexual trait introgression in a hybrid zone
In western Panama, male golden-collared and white-collared manakins perform acrobatic courtship displays for choosy females. The two species interbreed in a narrow hybrid zone, and the golden collar trait has introgressed into white-collared populations under positive sexual selection via female choice.
Together with a large team of collaborators, I study the genetic, molecular, and chemical basis of traits under selection in this system, including plumage color, behavior, and feather structure. I am also studying the adaptive consequences of sexual selection on these traits and tracing their evolutionary history.
To explore these topics, I have observed manakins in the field, studied museum specimens, and sequenced archival genetic samples.
Publications:
*Shared first authorship
2025 Bennett KFP, Bolton PE, Brumfield RT, Wilkinson GS, Braun MJ. Impact of a putative riverine barrier on genomic population structure and gene flow in the presence of sexual selection. Evolution, 79(10): 2181–2192.
https://doi.org/10.1093/evolut/qpaf146
2024 Lim HC*, Bennett KFP*, Justyn NM, Powers MJ, Long KM, Kingston SE, Lindsay WR, Pease JB, Fuxjager MJ, Bolton PE, Balakrishnan CN, Day LB, Parsons TJ, Brawn JD, Hill GE, Braun MJ. Sequential introgression of a carotenoid processing gene underlies sexual ornament diversity in a genus of manakins. Science Advances, 10:eadn8339.
https://www.science.org/doi/10.1126/sciadv.adn8339
2024 Long KM, Rivera-Colon AG, Bennett KFP, Catchen JM, Braun MJ, Brawn JD. Ongoing introgression of a secondary sexual plumage trait in a stable avian hybrid zone. Evolution, 78: 1539–1553.
https://academic.oup.com/evolut/article/78/9/1539/7675325
2021 Bennett KFP, Lim HC, Braun MJ. Sexual selection and introgression in avian hybrid zones: spotlight on Manacus. Integrative and Comparative Biology, 61: 1291-1309.
Genomic consequences of intense sexual selection in birds
In species like manakins where males compete for choosy females, mating success is highly skewed among males, so only a small fraction of males will pass on their genes. As a result, we expect there to be genomic consequences, like reduced genetic diversity on chromosomes overrepresented in males (i.e., the Z chromosome in birds).
In fact, little hard evidence for this phenomenon exists, and one study found exactly the opposite: species predicted to be under stronger sexual selection had increased Z diversity (Huang and Rabosky 2015).
I am working with collaborators in the Manakin Research Coordination Network and at Cornell University to address genomic consequences of strong sexual selection across the manakin clade, which exhibits great variation in sexual selection intensity.
Publications:
2026 Balakrishnan CN, Toda Y, Ko M-C, Wirthlin ME, Driver RJ, Bolton PE, Miller ET, Mendez-Aranda D, Dikow RB, Frandsen PB, Shogren EH, Bennett KFP, …46 authors…, Baldwin MW. Genomic and physiological changes in a sexually selected and frugivorous bird radiation. Current Biology, 36(12): 3061-3076. https://doi.org/10.1016/j.cub.2026.05.021
2021 Bennett KFP, Lim HC, Braun MJ. Sexual selection and introgression in avian hybrid zones: spotlight on Manacus. Integrative and Comparative Biology, 61: 1291-1309. https://doi.org/10.1093/icb/icab135.
Abundance and activity patterns of free-ranging domestic cats
My Master's research advised by Alan Clark at Fordham University and Peter Marra at the Smithsonian Migratory Bird Center focused on domestic cats in residential areas across an urban-rural land-use gradient.
I used motion-sensor cameras and conducted transect counts at sites across the Washington-Baltimore metro area to estimate cat abundance and how abundance co-varies with urban intensity. I also measured activity timing of cats across the land-use gradient using the camera data.
I determined that cat abundance was greatest at intermediate urban intensity, and that cats at urban sites were more strictly nocturnal, while cats at rural sites were more crepuscular. The implication of these results is that more urban does not always mean more cats--especially when suburban residents leave out cat food--and cat surveys need to plan for differences in cat activity across land-use gradients to avoid bias.
This work relied on the generosity of over 50 community science participants who allowed me access to their yards for camera-trapping. Community science is key for to access human-dominated areas, a necessary component of ecological research in an increasingly human-dominated world.
Publications:
2021 Bennett KFP,* Evans BS,* Clark JA, Marra PP. Domestic cat abundance and activity across a residential land-use gradient. Frontiers in Ecology and Evolution, 9: 643845. https://doi.org/10.3389/fevo.2021.643845.
*Shared first authorship