Migration Biology

The period of a migratory bird’s annual cycle thought to be the most perilous — its twice-annual journey over oceans and inhospitable landscapes — is also the least understood. We pursue questions about how animals overcome the challenges of migration using advancing technologies and analytical tools that are now making it possible to solve many of the important mysteries about migratory animals. Research in our lab focuses on en route biology, recognizing that migratory phases occur within the context of the full annual cycle and are inclusive of both flight and stopover. We address fundamental questions about stopover ecology and aeroecology including how and why migration is changing and migratory species are declining and inclusion of stopover and airspace habitats into conservation and management efforts for migratory species.

Community Ecology of Bird Migration

Our new NSF-supported migration research tests the hypothesis that a wider view on animal migration is needed – one that considers migrating animals as communities engaged in networks of ecological interactions that influence assembly processes. This work will advance an integrated understanding of animal migration, inclusive of the mechanisms through which interactions affect migratory costs, measured in time, energy, and mortality, that may scale-up to impact migratory success, route, and phenology. See: Cohen & Satterfield (2020)

Stopover-to-Passage Ratio (SPR)

Millions of migrating birds fly through the night each spring and autumn migration. During the day they stop in trees and shrubs to rest and recover from the night’s journey and to build up fuel for the next flight. These are the two components of the migratory journey, passage (flight) and stopover (foraging). Over the past few years we have learned a lot about each of these phases, where and when birds pass through the airspace and the kinds of habitats we find them in on the ground. But until recently we studied them each in isolation. We are not making use of data collected by weather surveillance radars to measure the stopover-to-passage ratio, integrating both phases of migration to understand where birds stop relative to where they are moving through the airspace at night. As declines of most migratory bird species outpace current management interventions, SPR can be applied to identify convergence at ‘migratory hotspots’ where targeted management efforts could uniquely benefit the declining abundance of migratory communities. Now that we can quantify the proportion of passage migrants that select a stopover site and map stopover habitat use within and between seasons across entire regions, we may need to rethink how we prioritize stopover areas for conservation. See: Cohen et al. (2020)


Cohen, E.B., Buler, J.J., Horton, K.G., Loss, S.R., Cabrera-Cruz, S., Smolinsky, J.A., and P.P. Marra. In revision. Exposure of nocturnally migrating birds to current and potential wind development around the Great Lakes. Conservation Letters.

Cohen, E.B., Lafleur, J., and F.R.. Moore. In revision. Density dependent refueling of migratory songbirds during stopover within an urbanizing coastal landscape. Frontiers in Ecology and Evolution.

Clipp, H. L., Buler, J. J., Smolinsky, J. A., Horton, K. G., Farnsworth, A., & Cohen, E. B. (2021). Winds aloft over three water bodies influence spring stopover distributions of migrating birds along the Gulf of Mexico coast. The Auk, 138(4), ukab051.

DeBrock, S., Cohen, E., Balasubramanian, S., Marra, P. P., & Hamer, S. A. (2021). Characterization of the Plasmodium and Haemoproteus parasite community in temperate-tropical birds during spring migration. International Journal for Parasitology: Parasites and Wildlife, 15, 12-21.

Scarpignato, A. L., Stein, K. A., Cohen, E. B., Marra, P. P., Kearns, L. J., Hallager, S., & Tonra, C. M. (2021). Full annual cycle tracking of Black‐crowned Night‐Herons suggests wintering areas do not explain differences in colony population trends. Journal of Field Ornithology.

Cohen, E. B., & Satterfield, D. A. (2020) ‘Chancing on a spectacle:’co‐occurring animal migrations and interspecific interactions. Ecography, 43: 1657-1671.

Cohen, E. B., Horton, K. G., Marra, P. P., Clipp, H. L., Farnsworth, A., Smolinsky, J. A., & Buler, J. J. (2020) A place to land: spatiotemporal drivers of stopover habitat use by migrating birds. Ecology Letters,24:38-49.

Clipp, H. L., Cohen, E. B., Smolinsky, J. A., Horton, K. G., Farnsworth, A., & Buler, J. J. (2020) Broad-scale weather patterns encountered during flight influence landbird stopover distributions. Remote Sensing, 12: 565.

Cabrera-Cruz, S. A., Cohen, E. B., Smolinsky, J. A., & Buler, J. J. (2020) Artificial light at night is related to broad-scale stopover distributions of nocturnally migrating landbirds along the Yucatan Peninsula, Mexico. Remote Sensing, 12: 395.

Horton KG, Van Doren BM, La Sorte FA, Cohen EB, Clipp HL, Buler JJ, Fink D, Kelly JF, and Farnsworth A (2019) Holding steady: little change in intensity or timing of bird migration over the Gulf of Mexico. Global Change Biology 25: 1106-1118

Cohen EB, Barrow Jr. WC, Buler JJ, Deppe JL, Farnsworth A, Marra PP, McWilliams SR, Mehlman DW, Wilson RR, Woodrey MS, and Moore FR (2017) Understanding how en route events around the Gulf of Mexico impact intercontinental migratory landbird populations. The Condor: Ornithological Applications 119: 327-343

Cohen EB, Aukland L, Marra PP and Hamer SA (2015) Avian migrants facilitate invasions of Neotropical ticks and tick-borne pathogens into the United States. Applied Environmental Microbiology 81: 8366-8378

Cohen EB, Németh Z, Zenzal Jr. TJ, Paxton K, Diehl R, Paxton, EH, and Moore FR (2015) Spring resource phenology and timing of songbird migration across the Gulf of Mexico. Chapter in Wood, EM and Kellermann, JL (eds) Phenological synchrony and bird migration: changing climate and seasonal resources in North America. Studies in Avian Biology (no. 47). CRC, New York, USA.

Cohen EB, Moore FR, and Fischer RA (2014) Fuel stores, time of spring, and movement behavior influence red-eyed vireo stopover duration. Journal of Ornithology 155: 785-792

Paxton, KL, Cohen EB, Paxton EH, Németh Z, and Moore FR (2014) Climatic variability at over-winter sites in Caribbean-Central and South America differentially affects intercontinental migrants during spring migration. PLoS One 9: e95383

Cohen EB, Pearson S, and Moore FR (2014) Effects of landscape composition and configuration on migrating songbirds: inference from an individual-based model. Ecological Applications 24:169-180

Cohen EB, FR Moore, Fischer RA (2012) Experimental Evidence for the Interplay of Exogenous and Endogenous Factors on the Movement Ecology of a Migrating Songbird. PloS One 7: e41818


Cover Photo by Claire Nemes