Volume 45, No. 2

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Overland flight by seabirds at Isla Isabela, Galápagos.


1Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA (
2Department of Geosciences, Boise State University, Boise, ID 83725, USA


ANCHUNDIA, D.J., ANDERSON, J.F. & ANDERSON, D.J. 2017. Overland flight by seabirds at Isla Isabela, Galápagos.. Marine Ornithology 45: 139 - 141

Received 6 February 2017, accepted 3 May 2017

Date Published: 2017/10/15
Date Online: 2017/06/14
Key words: Sulidae, Fregatidae, Suliformes, seabird biogeography, seabird distribution 


Oceanic seabirds are generally thought to avoid overland flight, perhaps limiting larger-scale distribution, but examples exist to the contrary. We asked whether Blue-Footed Boobies Sula nebouxii, Brown Pelicans Pelecanus occidentalis, or frigatebirds Fregata spp. crossed the Perry Isthmus (width 12.25 km, minimum height 23 m), a low point in the wasp-waist shape of Isla Isabela, Galápagos. Except for the Perry Isthmus, Isla Isabela presents an elongated, high-elevation challenge to movement between the central and western waters of Galápagos. Daytime observations over 3.5 d in June 2012 revealed ≥48 crossings by boobies and more than two crossings by frigatebirds. Overland crossing of a terrestrial barrier of this size may be facilitated by the seabirds' ability to see water across the Perry Isthmus from an altitude of 42 m looking west and 43 m looking east, altitudes that both the boobies and frigatebirds attain during foraging.


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