TY - JOUR
T1 - Resolving the heading-direction ambiguity in vertical-beam radar observations of migrating insects
AU - Hao, Zhenhua
AU - Drake, Vincent Alistair
AU - Taylor, John R.
N1 - Funding Information:
We thank Leesa Sidhu for advice during preliminary investigations and with statistics. Zhenhua Hao is employed through European Research Council Advanced Grant (GAP-741298), and previously held short-term appointments funded by UNSW.
Funding Information:
European Research Council Advanced Grant, Grant/Award Number: GAP-741298
Publisher Copyright:
© 2019 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.
PY - 2019/5
Y1 - 2019/5
N2 - Each year, massive numbers of insects fly across the continents at heights of hundreds of meters, carried by the wind, bringing both environmental benefits and serious economic and social costs. To investigate the insects' flight behavior and their response to winds, entomological radar has proved to be a particularly valuable tool; however, its observations of insect orientation are ambiguous with regard to the head/tail direction, and this greatly hinders interpretation of the migrants' flight behavior. We have developed two related methods of using wind data to resolve the head/tail ambiguity, and we have compared their outputs with those from simply assigning the heading direction to be that which is closer to the track direction. We applied all three methods to observations of Australian plague locust migrations made with an insect monitoring radar. For the study dataset, some of the headings selected by the simpler method are shown to be clearly incorrect. The two new methods generally agree and reveal a significantly different, and presumably more accurate, relationship of heading direction to track direction. However, use of these methods leads to quite a large proportion of the sample being lost because the wind values, which derive from a regional-scale numerical model, are shown to be incompatible with the radar observations. This exploratory study has moreover demonstrated that locusts are frequently oriented at a large angle to their track and that quite often their movement is at least slightly tailfirst. Both new methods appear to be a significant improvement on the simpler method. As well as providing an accurate representation of migratory flight behavior, they allow occasions when the model wind values are unreliable to be eliminated from the data sample.
AB - Each year, massive numbers of insects fly across the continents at heights of hundreds of meters, carried by the wind, bringing both environmental benefits and serious economic and social costs. To investigate the insects' flight behavior and their response to winds, entomological radar has proved to be a particularly valuable tool; however, its observations of insect orientation are ambiguous with regard to the head/tail direction, and this greatly hinders interpretation of the migrants' flight behavior. We have developed two related methods of using wind data to resolve the head/tail ambiguity, and we have compared their outputs with those from simply assigning the heading direction to be that which is closer to the track direction. We applied all three methods to observations of Australian plague locust migrations made with an insect monitoring radar. For the study dataset, some of the headings selected by the simpler method are shown to be clearly incorrect. The two new methods generally agree and reveal a significantly different, and presumably more accurate, relationship of heading direction to track direction. However, use of these methods leads to quite a large proportion of the sample being lost because the wind values, which derive from a regional-scale numerical model, are shown to be incompatible with the radar observations. This exploratory study has moreover demonstrated that locusts are frequently oriented at a large angle to their track and that quite often their movement is at least slightly tailfirst. Both new methods appear to be a significant improvement on the simpler method. As well as providing an accurate representation of migratory flight behavior, they allow occasions when the model wind values are unreliable to be eliminated from the data sample.
KW - Australian plague locust
KW - heading direction
KW - insect migration
KW - orientation
KW - radar entomology
KW - selection method
UR - http://www.scopus.com/inward/record.url?scp=85066264383&partnerID=8YFLogxK
UR - http://www.mendeley.com/research/resolving-headingdirection-ambiguity-verticalbeam-radar-observations-migrating-insects
U2 - 10.1002/ece3.5184
DO - 10.1002/ece3.5184
M3 - Article
AN - SCOPUS:85066264383
SN - 2045-7758
VL - 9
SP - 6003
EP - 6013
JO - Ecology and Evolution
JF - Ecology and Evolution
IS - 10
ER -