Migratory Eurasian reed warblers can use magnetic declination to solve the longitude problem
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In: Current Biology, Vol. 27, No. 17, 11.09.2017, p. 2647-2651.
Research output: Contribution to journal › Article › peer-review
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T1 - Migratory Eurasian reed warblers can use magnetic declination to solve the longitude problem
AU - Chernetsov, Nikita
AU - Pakhomov, Alexander
AU - Kobylkov, Dmitry
AU - Kishkinev, Dmitry
AU - Holland, Richard
AU - Mouritsen, Henrik
PY - 2017/9/11
Y1 - 2017/9/11
N2 - The longitude problem (determining East-West position) is a classical problem in human sea navigation. Prior to the use of GPS satellites, extraordinarily accurate clocks measuring the difference between local time and a fixed reference (e.g., GMT) were needed to determine longitude. Birds do not appear to possess a time-difference clock sense. Nevertheless, experienced night-migratory songbirds can correct for East-West displacements to unknown locations. Consequently, migratory birds must solve the longitude problem in a different way, but how they do so has remained a scientific mystery. Here we suggest that experienced adult Eurasian reed warblers (Acrocephalus scirpaceus) can use magnetic declination (the difference in direction between geographic and magnetic North) to solve the longitude-problem at least under some circumstances under clear skies. Experienced migrants tested during autumn migration in Rybachy, Russia were exposed to an 8.5° change in declination while all other cues remained unchanged. This corresponds to a virtual magnetic displacement to Scotland if and only if magnetic declination is a part of their map. The adult migrants responded by changing their heading by 151° from WSW to ESE, consistent with compensation for the virtual magnetic displacement. Juvenile migrants that had not yet established a navigational map also oriented WSW at the capture site, but became randomly oriented when the magnetic declination was shifted 8.5°. In combination with latitudinal cues, which birds are known to detect and use, magnetic declination could provide the mostly east-west component for a true bi-coordinate navigation system under clear skies for experienced migratory birds in some areas of the globe.
AB - The longitude problem (determining East-West position) is a classical problem in human sea navigation. Prior to the use of GPS satellites, extraordinarily accurate clocks measuring the difference between local time and a fixed reference (e.g., GMT) were needed to determine longitude. Birds do not appear to possess a time-difference clock sense. Nevertheless, experienced night-migratory songbirds can correct for East-West displacements to unknown locations. Consequently, migratory birds must solve the longitude problem in a different way, but how they do so has remained a scientific mystery. Here we suggest that experienced adult Eurasian reed warblers (Acrocephalus scirpaceus) can use magnetic declination (the difference in direction between geographic and magnetic North) to solve the longitude-problem at least under some circumstances under clear skies. Experienced migrants tested during autumn migration in Rybachy, Russia were exposed to an 8.5° change in declination while all other cues remained unchanged. This corresponds to a virtual magnetic displacement to Scotland if and only if magnetic declination is a part of their map. The adult migrants responded by changing their heading by 151° from WSW to ESE, consistent with compensation for the virtual magnetic displacement. Juvenile migrants that had not yet established a navigational map also oriented WSW at the capture site, but became randomly oriented when the magnetic declination was shifted 8.5°. In combination with latitudinal cues, which birds are known to detect and use, magnetic declination could provide the mostly east-west component for a true bi-coordinate navigation system under clear skies for experienced migratory birds in some areas of the globe.
KW - magnetic compass
KW - star compass
KW - magnetic sense
KW - magnetic map
KW - bird migration
KW - bird navigation
U2 - 10.1016/j.cub.2017.07.024
DO - 10.1016/j.cub.2017.07.024
M3 - Article
VL - 27
SP - 2647
EP - 2651
JO - Current Biology
JF - Current Biology
SN - 0960-9822
IS - 17
ER -