Spatiotemporal organization of songbird migration covering

30,000 km

Institute of Avian Research „Vogelwarte Helgoland“

Heiko Schmaljohann, James W. Fox & Franz Bairlein

Introduction

movement ecology • quantify migration in a high spatiotemporal resolution

Nathan et al. 2008 PNAS

elements of migration • flight route, flight direction, stopover duration, flight speed, fuel deposition rate

optimal migration theory Alerstam & Lindström 1990 Phys & Ecophys

• predicts by assuming time minimization as the overall strategy that the bird’s fuel load is a function of stopover duration, fuel deposition rate, flight routes and flight speed

Lindström & Alerstam 1992 Am Nat, Hedenström & Alerstam 1995 Phil Trans R Soc B,

Alerstam 2001 Science, Hedenström 2008 Phil Trans R Soc B

studies• in large birds by satellite tracking (geese, raptors)

Mandel et al. 2008 PNAS, Klaassen et al. 2010 Proc R Soc B

• but not in small birds: due to weights of tracking devices studies have been focused on single flight legs / stopover sites

Lindström and Alerstam 1992 Am Nat, Wikelski et al. 2003 Nature,Schmaljohann & Naef-Daenzer 2011 J Anim Ecol

light-level geolocator

„Light-level geolocation is the calculation of position fromambient light level readings with reference to time.“ BAS

• development of light-level geolocators has set ecologists in a euphoric mood

Shaffer et al. 2008 PNAS, Robinson et al. 2009 TREE, Stutchbury et al. 2009 Science,Bächler et al. 2010 PLoSONE, Conklin et al. 2010 Nat Comm, Egevang et al. 2010 PNAS

Introduction

Introduction

light-level geolocator• advantage

- small and „cheap“

• disadvantage- sample size depends on recapture probability- equinoxes (is the date when the day length is the same

throughout all latitudes)„2-3 weeks around each equinox the calculation of

latitude is unreliable or impossible!“ BASthis is the main migration period of many bird

species!Stutchbury et al. 2009 Science, Bächler et al. 2010 PLoSONE

Stutchbury et al. 2009 Science

Introduction

Purple Martin (Progne subis)

Wood Thrush(Hylocichlamustelina)

Bächler et al. 2010 PLoSONE

Introduction

Longitude is unaffected by equinox.

Introduction

northern wheatear (Oenanthe oenanthe)

- insectivorous songbird (~ 30 g)

- nearly circumpolar breeding distribution

- prefers open habitats (tundra, savannah)

- all over-winter south of the Sahara

Aim of study

to quantify migration in a high spatiotemporal resolution

allows a detailed description of northern wheatear’s

migration strategy

- flight route

- organization of stopover

- flight speeds

- temporal distribution of life history stages within an annual cycle

Alaska

June 2009: 30 birds with geolocators

June 2010: 5 returned, gained 3 geolocators

Methods

Methods

PrecalibrationHelgoland, Germany (54° 11’ N, 07° 55’ E)20th May - 27th of May 2009

Accuracy of single fixes to the reference site during precalibration was limited to 76 ± 33 km (nnumber of fixes = 39).

longitudinal deviation: 45.6 ± 35.0 kmlatitudinal deviation: 47.1 ± 37.6 km(nnumber of fixes = 39)

Methods

40° E

80° E

120° E

160° E

160° W

1.4.

15.4

.

1.5.

15.5

Spring 2010

6 8

6

Methods

● midnight fix

● noon fix

Defining stopover sites

> 2 noon fixes within 1° of longitudeDierschke & Delingat 2001 Behav Ecol Sociobiol, Schmaljohann & Dierschke 2005 J Anim Ecol

Dierschke, Mendel & Schmaljohann 2005 Behav Ecol Sociobiol, Schmaljohann et al. 2011 J Ornithol, Schmaljohann & Naef-Daenzer 2011 J Anim Ecol

Methods

40° E

80° E

120° E

160° E

160° W

1.4.

15.4

.

1.5.

15.5

Spring 2010

6 8

6

Methods

6

● midnight fix

● noon fix

40° E

80° E

120° E

160° E

160° W

15.8

.

1.9.

15.9

.

1.10

.

15.1

0.

1.11

.

15.1

1.

1.12

.

Autumn 2009

5

5

4

54

10 18 98

Methods

● midnight fix

● noon fix

Methods

Methods

raw data, NO outliners

Methods

Local Polynomial Regression Fitting;loess(latitude ~ longitude, data excluding „outliners“)

Methods

raw data, 7 outliners not shown

Methods

Estimating „uncertainty“ of migration route

Methods

●

distance of raw fix to smoothed migration route

smoothed migration route

raw fix

106 ± 107 km, n = 15

220 ± 212 km, n = 37

Methods

A

B

C

D

mean ± SD distance of

fixes from smoothed lines

A: 156 ± 153 km, n = 14

B: 276 ± 155 km, n = 7

C: 719 ± 577 km, n = 18

D: 99 ± 59 km, n = 15

Results – migration strategy

Onset of autumn migration 17 Aug, 20 Aug, 20 Aug 2009

Distance between stopover

prior to Arabian desert ~ 280 ± 115 km

Arrival in eastern Africa 11 Nov, 13 Nov, 14 Nov 2009

Distance of autumn migration 14.800 km, 14.900 km, 15.300 km

Ø migration speed autumn ~160 km·day-1 [370 km·night-1]

Distance between wintering

areas ~ 400 ± 180 km

Onset of spring migration 8 Apr, 30 Mar, 28 Mar 2010

Arrival at breeding area -, 23 May, 24 May 2010

Distance of spring migration -, 14.100 km, 14.250 km

Ø migration speed spring ~260 km·day-1 [400 - 500 km·night-1]

Results – migration strategy

Results – migration strategy

search and settling time/cost

to establish feeding territories and to adapt physiologically to replenish their energy expenditure from the previous flightAlerstam & Lindström 1990 Phys & Ecophys, Alerstam & Hedenström 1998 J Avian Biol, Jenni &

Schaub 2003 Bird Migration

this search and settling time is an important hypothesis influencing the predicted fuel load, stopover duration and number of flights during the entire migration

Alerstam & Lindström 1990 Phys & Ecophys

only little evidence for a natural search and settling time Schwilch & Jenni 2001 Auk, Delingat et al. 2006 Ardea

“stop-and-go” migration strategy for Alaskan northern wheatears

This diminishes the biological importance of a search and settling time at least for northern wheatears.

Results – migration strategy

These nocturnal flight speeds are far higher than formerly

predicted.

overall migratory speed

“two” times higher in spring than in autumn indicating a higher

time pressure to reach the migratory goalHall-Karlsson & Fransson 2008 Ring & Mig, Stutchbury et al. 2009 Science, Bächler et al. 2010

PLoSONE

as northern wheatears migrate only at night, also when crossing

ecological land barriers, the nocturnal flight speed ranged here

between 300 and 500 km·night-1

Schmaljohann et al. 2007 Proc R Soc B, Schmaljohann & Naef-Daenzer 2011 J Anim Ecol

autumnmigration

~ 88 days

spring migration

~ 55 days

wintering area

~ 140 days

breeding area

~ 80 days

breeding

~ 70 days

+ complete moult

~ 50 days

Results – migration strategy

To maximize the flexibility in timing of the life history stages northern wheatears

overlap breeding and moult.McNamara & Houston 2008 Phil Trans R Soc B, Wingfield 2008 Phil Trans R Soc B

spatiotemporal organization

take-home massages

optimal migration theory

search and settling time seems to be low

flight speed of songbirds: up to 500 km per night

overlap of life history stages (breeding and moult) to maximize the flexibility in timing of these

Thank you for your attention!

Thanks to

Robert Gill

Beth Pattinson

Ellen Paul

Susan Sharbaugh

Kevin Winker

Rachel MuheimBeat Neaf-Daenzer

Marc Bulte, Ommo Hüppop, Rolf Nagel, Freimut Schramm