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Chasing the High Fliers:
Radar Studies of Insect Migration
Jason W. Chapman
Centre for Ecology and Conservation,
University of Exeter,
Cornwall Campus
• Annual summer migrant to N Europe from winter-breeding areas in N Africa
• Periodically a pest in UK (brassicas & sugar beet) in invasion years
• 1996, 2000, 2003, 2006…
• Immigrations occur in May–June, disappears Aug–Sep
• Migrates at night at high altitudes
• Can it influence its movement direction?
• Is there is a significant return
to winter-breeding areas?
Silver Y Moth Autographa gamma
Vertical-looking
Insect Radar (VLR)
Tracking bird-radar
Lund
Falsterbo
Radar Locations
Alertsam, Chapman et al (2011) PRSB
Pied Flycatcher
0 10 20 30 40 50 60
Insect Abundance (Number / 5 minutes / Height Band)
12:00 16:00 20:00 24:00 04:00 08:00
200 m
1000 m
600 m
Time (GMT)
• Silver Y moths typically migrate in “layers” between 400–800 m agl
• Layers correspond with altitude of warmest air and max wind-speed: mean ~15 m/s (50 km/hr)
Chapman et al (2008) Current Biology
Flight Altitude
Flight Altitude
Flight altitude (m)
Pro
po
rtio
n a
t e
ach
altitu
de
(%
)
Moths:
Mean Flight Altitude ~ 200 – 600 m
Songbirds:
Mean Flight Altitude ~ 600 – 1200 m
Alerstam, Chapman et al (2011) PRSB
Migration Directions
Songbirds: outer circle
Moths: inner circle
Willow Warbler
Chapman et al (2015) J Animal Ecology
Movement Speed
13.5 m/s 16.6 m/s 12.1 m/s 13.8 m/s
Chapman et al (2015) J Animal Ecology
Songbirds
Airspeed ~10-15 m s-1
Willow Warbler
4 m/s = 14 km/hr
10 m/s = 36 km/h
15 m/s = 54 km/hr
20 m/s = 72 km/hr
25 m/s = 90 km/hr
Moths
Airspeed ~4 m s-1
Silver Y moth
Modelling Migration Trajectories
Inert Particles ‘Virtual’ Moths
Chapman et al (2010) Science 327: 682–5
Reproductive Benefits of Seasonal Migration
Spring Immigrationof A. gamma
Autumn Returnof A. gamma
Invasion Years 233 ± 5 Million(34–36 tonnes)
445 ± 130 Million(47–86 tonnes)
Increase N = 3 yrs 1.9 ± 0.6
Non-invasion Years 26 ± 4 Million(3–5 tonnes)
90 ± 16 Million(11–16 tonnes)
Increase N = 7 yrs 3.8 ± 0.7
Mean 88 ± 32 Million(8–18 tonnes)
197 ± 65 Million(20–39 tonnes)
Increase N = 10 yrs 3.2 ± 0.6
Chapman et al (2012) PNAS 109: 14924-29
Quantifying Migration Intensity & BiomassGao Hu (Visiting Scholar from Nanjing Agricultural University)
• 10 years of radar & aerial sampling data
Spring
Summer
Fall• These larger insects migrate in seasonally-beneficial directions: north in spring & south in autumn
• Net flux of 1 – 2 Billion towards N in some years, but towards S in other years
• Huge implications for spread of nutrients, pathogens & genetic material
• ~3.5 Trillion day-flying insects (~3200 tonnes) in the air over S England each year – mostly in the day
• >99% are ‘micro-insects’ <10 mg (e.g. aphids, parasitic wasps, planthoppers etc)
• ~15 Billion day-flying larger insects (e.g. hoverflies, ladybirds; ~600 tonnes) migrate over S England each year
• Andy Reynolds, Jason Lim (RRES)
• Don Reynolds (NRI, University of Greenwich)
• Gao Hu (Nanjing Agricultural University & Exeter)
• Jeremy Thomas, Mike Bonsall (University of Oxford)
• Thomas Alerstam, Cecilia Nilsson (University of Lund)
• Henrik Mouritsen (University of Oldenburg)
• Funding (Rothamsted & BBSRC)
Acknowledgements
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