Inbound arrivals: using weather surveillance radar to quantify the diurnal timing of spring trans-Gulf bird migration

Authors: Annika L. Abbott, Yuting Deng, Katie Badwey, Andrew Farnsworth and Kyle G. Horton

Year: 2023

Publication: Ecogeography

Publication Link:

Keywords: aeroecology, avian migration, flight behavior, Gulf of Mexico, radar, remote sensing

Abstract: More than two billion birds migrate through the Gulf of Mexico each spring en route
to breeding grounds in the USA and Canada. This region has a long history of complex
natural and anthropogenic environments as the northern Gulf coast provides the
first possible stopover habitats for migrants making nonstop trans-Gulf crossings during
spring migration. However, intense anthropogenic activity in the region, which is
expanding rapidly at present, makes migrants vulnerable to a multitude of obstacles and
increasingly fragments and alters these habitats. Understanding the timing of migrants’
overwater arrivals has biological value for expanding our understanding of migration
ecology relative to decision-making for nonstop flights, and is imperative for advancing
conservation of this critical region through the identification of key times in which
to direct conservation actions (e.g. temporary halting of wind turbines, reduction of
light pollution). We explored 10 years of weather surveillance radar data from five sites
along the northern Gulf of Mexico coast to quantify the daily timing and intensity of
arriving trans-Gulf migrants. On a daily scale, we found that migrant intensity peaked
an average of nine hours after local sunrise, occurring earliest at easternmost sites. On
a seasonal level, the greatest number of arrivals occurred between late April and early
May, with peak intensity occurring latest at westernmost sites. Overall intensity of
migration across all 10 years of data was greatest at the westernmost sites and decreased
moving farther to the east. These findings emphasize the differential spatial and temporal
patterns of use of the Gulf of Mexico region by migrating birds, information that is
essential for improving our understanding of the ecology of trans-Gulf migration and
for supporting data-driven approaches to conservation actions for the migratory birds
passing through this critical region.

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