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