Juvenile Osprey Navigation during Trans-Oceanic Migration.

Travis W Horton,Paul Sagar,Richard N Holdaway,Peyman Zawar-Reza,Richard O Bierregaard,Joseph Najbauer

doi:10.1371/journal.pone.0114557

Abstract

To compensate for drift, an animal migrating through air or sea must be able to navigate. Although some species of bird, fish, insect, mammal, and reptile are capable of drift compensation, our understanding of the spatial reference frame, and associated coordinate space, in which these navigational behaviors occur remains limited. Using high resolution satellite-monitored GPS track data, we show that juvenile ospreys (Pandion haliaetus) are capable of non-stop constant course movements over open ocean spanning distances in excess of 1500 km despite the perturbing effects of winds and the lack of obvious landmarks. These results are best explained by extreme navigational precision in an exogenous spatio-temporal reference frame, such as positional orientation relative to Earth's magnetic field and pacing relative to an exogenous mechanism of keeping time. Given the age (<1 year-old) of these birds and knowledge of their hatching site locations, we were able to transform Enhanced Magnetic Model coordinate locations such that the origin of the magnetic coordinate space corresponded with each bird's nest. Our analyses show that trans-oceanic juvenile osprey movements are consistent with bicoordinate positional orientation in transformed magnetic coordinate or geographic space. Through integration of movement and meteorological data, we propose a new theoretical framework, chord and clock navigation, capable of explaining the precise spatial orientation and temporal pacing performed by juvenile ospreys during their long-distance migrations over open ocean.

Highlights

How do animals navigate during long-distance migration? Finding an answer to this complex problem requires an integrated research approach involving scientists from a variety of disciplines, and any attempt at an answer must start by documenting what animals do during migratory movement
We present an integrated analysis of geospatial, meteorological, and magnetic coordinate data derived from high resolution, satellite-monitored global positioning system (GPS) track data determined for ten,1 year-old ospreys migrating across the western Atlantic Ocean
How do juvenile ospreys navigate during trans-oceanic migration? a complete answer to this question remains elusive, our research has provided several relevant findings

Summary

Introduction

How do animals navigate during long-distance migration? Finding an answer to this complex problem requires an integrated research approach involving scientists from a variety of disciplines, and any attempt at an answer must start by documenting what animals do during migratory movement. How do animals navigate during long-distance migration? The widespread application of high-resolution satellite-monitored platform transmitter terminal (PTT) technology creates an unprecedented opportunity to explore how animals achieve their remarkable long-distance migrations. Displacement by wind complicates a bird’s ability to successfully navigate between habitats, several studies have demonstrated that many birds, including ospreys [1], European honey buzzards (Pernis apivorus) [1], western marsh harriers (Circus aeruginosus) [2], passerines (e.g. Phylloscopus trochilus)[3, 4], near passerines (e.g. Merops apiaster) [5], and a variety of shorebirds (e.g. Calidris canutus; Limosa lapponica; Pluvialis squatarola; Charadrias hiaticula; Arenaria interpres; Calidris alba) [6], have the ability to compensate for the effects of wind drift. A fundamental question remains largely unanswered despite the widespread nature of these findings: how do they do it?

Methods

Results

Conclusion