Microsat allele calls for D. robustus

Microsat allele calls for the extinct South Island giant moa (Dinornis robustus), genotyped in six microsatellite loci

Juvenile Osprey Navigation during Trans-Oceanic Migration

<div><p>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 (<i>Pandion haliaetus</i>) 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.</p></div

Track segment straightness in transformed magnetic coordinates.

<p>Track segment straightness in transformed magnetic coordinates.</p

The Constantly Changing Seven Magnetic Field Elements.

<p>The magnetic field experienced at or near the Earth's surface is constantly changing in both space and time due to secular variation in the Main Field (>90% of the total field intensity), interactions with the unpredictable and temporally dynamic interplanetary magnetic field (largely of solar origin and as large as 10% of the total field intensity) and the crustal anomaly field (<1% of the total field intensity). The seven elements include: F, the total field intensity measured in nanotesla (SI) or gauss (CGS); D, the declination angle measured positive to the east of true north; I, the inclination angle measured positive in the downward direction relative to horizontal; H, the horizontal component of the total field intensity; X, the north-south component of H measured positive to the north; Y, the east-west component of H measured positive to the east; Z, the vertical component of the total field intensity measured positive in the downward direction. X, Y, and Z define a three-dimensional Cartesian coordinate space, whereas F, I, and D define a three-dimensional spherical coordinate space. The bicoordinate F-I space is polar by definition and is equivalent to the two-dimensional H-Z Cartesian coordinate space (see also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114557#pone-0114557-g007" target="_blank">Figure 7</a>).</p

Vector representations of various movement behaviors in response to wind.

<p>Animals moving through air and water exhibit a variety of orientational responses to flow <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114557#pone.0114557-Chapman1" target="_blank">[31]</a>, including full drift (A), no drift (B), partial drift (C), and full compensation of both the perpendicular and parallel wind drift vectors (D). In these diagrams, the groundtrack direction and speed (g) determined from sequential PTT tag locations represents the vector sum of the wind vector (w) and the bird's heading vector (h). These three vectors represent the classic ‘wind triangle’. Wind drift analysis requires further determination of components of these vectors relative to a fixed direction, here defined as the mean track segment direction. The direction of the forward movement (f_m) vector equals the mean track segment direction and the forward movement velocity equals the groundspeed times the cosine of the drift angle (δ), where, δ =  groundtrack direction - mean track segment direction. The forward movement vector must also equal the tailwind vector (t_w) plus the active forward movement vector (a). The perpendicular wind (p_w) and perpendicular movement (p_m) vectors are the vector components of the wind vector and groundtrack vector, respectively, that are perpendicular to the mean track segment direction. In order to maintain a constant course movement in dynamic flows a migrating animal must be able to monitor and adjust the magnitude and direction of its heading vector at regular intervals that are smaller than the duration of the constant course movement.</p

Trans-oceanic juvenile osprey migration track maps (Mercator Projection).

<p>Colors correspond with individual ospreys (pink  =  Belle; red  =  Felix; yellow  =  Moffet; light green  =  Henrietta; green  =  Bea; dark green  =  Luke; light blue  =  Caley; royal blue  =  Mittark; dark blue  =  Isabel; purple/gray  =  Chip). Symbols correspond with different constant course track segments identified by piecewise linear regression breakpoint analysis (circles  =  first track segment following departure; triangles  =  second track segment; addition symbols  =  third track segment; diamonds  =  fourth track segment). Only the trans-oceanic portion of each bird's migration is shown. Gray addition symbols correspond with Chip's movements following his first night aloft, presumably when he was resting on or in contact with one or more vessels (see text). Northing and Easting values are shown in kilometers.</p

Hourly-scale juvenile osprey navigational responses to wind during trans-oceanic migration.

<p>Symbols and colors as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114557#pone-0114557-g001" target="_blank">Figure 1</a>. Symbol size is proportional to wind velocity (A) and forward movement velocity (B) as shown in the velocity legend. Blue vectors (B) correspond with the wind direction and wind speed (scale bar shown) experienced by the juvenile osprey ‘Felix’ during his>1500 km constant course movement between Martha's Vineyard and the Bahamas between the morning of September 16 and evening of September 17, 2007.</p

Relationship between osprey airspeed and tailwind velocity.

<p>Symbols correspond with one-hourly osprey GPS-enabled PTT tag locations. Linear least-squares regression equation is represented as the solid black line.</p

Transformed magnetic coordinate osprey locations.

<p>Colours and symbols as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114557#pone-0114557-g001" target="_blank">Figure 1</a>. Gray shaded area corresponds with the area encompassed between 20° and 42° north latitude and −67° and −78° west longitude. The origin of the transformed magnetic coordinate space shown here corresponds with each bird's hatching site (see text).</p

Wind vector analysis.

<p>Relationship between wind velocity and juvenile osprey movement velocity perpendicular to (A, B) and parallel to (C, D) the mean ground track direction of migration track segments. Wind velocities were determined for one-hourly GPS locations (A, C) using a dynamic regional mesoscale meteorological model. Track segment mean velocities (B, D) ±1σ error bars are also shown. Track segment colors and symbols as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0114557#pone-0114557-g001" target="_blank">Figure 1</a>. Dashed lines represent 1:1 relationship.</p