Stopover behavior of Red‑eyed Vireos (Vireo olivaceus) during fall migration on the coast of the Yucatan Peninsula

Authors: Richard Evan Feldman, Antonio Celis‑Murillo, Jill L. Deppe and Michael P. Ward

Year: 2021

Publication: Avian Research

Publication Link: https://avianres.biomedcentral.com/articles/10.1186/s40657-021-00299-w

Keywords: Coastal dune, Fruit, Geographic barrier, Gulf of Mexico, Phenology, Stopover, Time-minimization

Abstract:

Background: For migrating birds, stopover requires spending time and energy that otherwise could be allocated to
flying. Thus, birds optimally refuel their subsequent migratory flight by reducing stopover duration or foraging activity
in food-rich environments. In coastal habitats, birds may forego refueling and take short stopovers irrespective of
local food availability. Given the paucity of studies exploring how migrants adjust stopover behavior in response to
temporal variation in food availability, especially in the Neotropics, we fixed radio tags to 51 Red-eyed Vireos (Vireo
olivaceous) over two years at two sites on the coast of Mexico’s Yucatan Peninsula.

Methods: We applied VHF radio tags during the fall of 2016 and 2017, and tracked birds using automatic and manual
receiving units. We estimated stopover duration and activity levels (one site only) for between six and fifteen birds,
depending on site and year. We measured fruit availability weekly along the net lanes where we captured birds. We
used a generalized linear model to estimate the relationships between stopover duration/activity level and fruit density,
bird body mass and year. We interpreted relationships for the model with the lowest AICc value.

Results: We found that approximately half of the birds departed on the same day they were captured. For the birds
that stayed longer, we could not discern whether they did so because they were light, or fruit density was high. On
the other hand, lighter birds were more active than heavier birds but only in one of the two years.

Conclusions: Given our results, it is unlikely that Red-eyed Vireos refuel along the Yucatan coast. However, they still
likely need to recuperate from crossing the Gulf of Mexico, which may necessitate foraging more often if in poor body
condition. If the birds then move inland then stopover should be thought of as a large-scale phenomenon, where
habitats with different functions may be spread out over a broad landscape.

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