Migratory Connectivity:Science and

Technology for Policy and Conservation

Peter P. Marra

Smithsonian Migratory

Bird Center

Migratory Connectivity:

The geographic linking of individuals or populations between different stages of the annual cycle, including between breeding, migration, and winter stages.

Hypothetical Species

species range

Hypothetical Species

species range

breeding

wintering

Weak ConnectivityWeak Connectivity

Birds from one breeding population disperse throughout wintering range, and

vice versa.

Hypothetical SpeciesPopulation

Connections

Hypothetical SpeciesPopulation

Connections

Strong Strong ConnectivityConnectivity

One-to-one connections

between summer and winter

populations

Hypothetical SpeciesPopulation

Connections

Hypothetical SpeciesPopulation

Connections

For most species,For most species, we don’t know the we don’t know the

strength of strength of migratory migratory

connectivityconnectivity

Hypothetical SpeciesHypothetical Species

JF

M

A

M

JJ

A

S

O

N

D

breedingwinteringmigrationmolt

Periods of the annual cycle are

inextricably linked

Why Study Migratory Connectivity?Why Study Migratory Connectivity?

ConservationPopulation Vulnerability

Population VulnerabilityPopulation Vulnerability

Why Study Migratory Connectivity?Why Study Migratory Connectivity?

Population Abundance

Ecology, Behavior, EvolutionDemography, Mating SystemsLife History Strategies

Human HealthSpread of Invasive Disease

(HPAI,WNV)

• Conservation• Population Vulnerability

Why Study Migratory Connectivity?Why Study Migratory Connectivity?

Population Abundance

• Conservation• Population Vulnerability

Seasonal Interactions

• Events in one period of the annual cycle influence events in subsequent periods.

2. Individual-level (carry-over effects)

1. Population-level (density effects)

(Sutherland 1996)

Seasonal Interaction Model: Population-level

Total Population Size

Per

Cap

ita

Rat

e

E

Winter Mortality

Net BreedingOutput

(Sutherland 1996)

Seasonal Interaction Model: Population-level

Total Population Size

Per

Cap

ita

Rat

e

E

Winter Mortality

Net BreedingOutput

E1

(Sutherland 1996)

Seasonal Interaction ModelPopulation-level

• Population change depends on the relative strengths of density dependence between winter and summer.

• The consequences of habitat loss is greatest for the season in which there is the strongest density-dependence.

• For Oystercatchers, winter was the most limiting season.

Total Population Size

Per

Cap

ita

Rat

e

E

Winter Mortality

Net BreedingOutput

E1E2

Few examples of population-level seasonal interactions exist.

• Weak understanding of migratory connectivity

• Few estimates of DD from non-breeding season

• Little research during the non-breeding season

Individual-level:Carry-over effectsIndividual-level:

Carry-over effects

Study Design

• 2002 - 2006 • Font Hill Nature Reserve

• American redstart

• 3 mangrove, 3 scrub sites

• Range in size 1 - 5 ha

Performance is driven by habitat occupancy

Black mangrove Second-growth scrub

Physical condition

Spring departure date

Annual Survival

maintain

early

high

decline

late

low

Hypothesis:Environmental conditions on

wintering grounds influence reproductive success via carry-over effects

Arrival dynamics

Winter habitat(wet / dry)

Breeding territory quality

Fecundity

Hypothesis:Environmental conditions on

wintering grounds influence reproductive success via carry-over effects

Moisture Gradient WETDRY

C3

C4

Enriched 13C Depleted 13C

Wet Lowland Forest

Black Mangrove Forest

Second-growth Forest

13C

(m

ean

+/-

se)

Carbon Isotope Signatures from American Redstart

N = 5

N = 10

N = 34

N = 8

N = 24

-25.0

-24.5

-24.0

-23.5

-23.0

-22.5

-22.0

-21.5

-21.0

Jamaica Honduras

Prediction:

1. have lower levels of 13C relative to redstarts arriving later.

American redstarts arriving early will

2. be in better physical condition than those arriving later.

13C and arrival date in ASY males

R2 = 0.38, p < 0.0001n=35

R2 = 0.34, p = 0.0004n = 32

2001 2002

0

5

10

15

20

25

Arr

ival

dat

e

-24 -23.5 -23 -22.5 -22 -21.5 -21

13C

5

10

15

20

25

Arr

ival

dat

e-24 -23.5 -23 -22.5 -22 -21.5

13C

Arrival Date (May)

Mas

s C

orr

ecte

d f

or

Bo

dy

Siz

e

Physical Condition vs. Arrival Date

P = 0.02 r = -0.52

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

12 14 16 18 20 22 24 26 28 30

5

4

3

wet forest mangrove scrub

Num

ber

of Y

oung

Fle

dged

females

ASY males

Winter Habitat Origin

wet dry

citrus

Predicted changes in number of young fledged

Summary• Winter habitat occupancy drives patterns of

reproductive success on the breeding grounds

• Our other work suggests:1) Winter conditions drive mortality during

migration

2) Winter habitat drives natal dispersal

3) Reproductive costs influence feather color and quality

Where are we in tracking wide-ranging animals?

• Transmitters (radio & satellite )

• Isotopes (individual & population)

1. Intrinsic• Banding (capture-recapture)

2. Extrinsic

• Microbes and Parasites

• Molecular Markers

• Trace elements

Band Recovery Data - Purple Martins

Atlantic Ocean

NJ

DE

PA

NY

MD

Atlantic City

Philadelphia

Trenton

100 km

Delaware Bay

5 13

1

3

1

4(10)

3(10)

34

6

7

9

2

3

6

7 (10)

4

3

4

5

4

12

3

www.IcarusInitiative.org

International Space Station

Birds in Space

Copyright ©2006 by the National Academy of Sciences

Shaffer, Scott A. et al. (2006) PNAS 103, 12799-12802

Sooty Shearwater Migrations

Isotopes

Stable-hydrogen isotopes

• Stable-hydrogen isotopes vary with latitude

• Feathers sampled in the nonbreeding period reflect origins in the previous summer

-45

-95

-75-55

-50

-125-115

-165

-135

-135-165

-165

-125-115

-95

-75

-55

-50

-45

60°

50°

60°

50°

40°

40°

30°

30°

20°

20°

10°

10°

H isotopes and banding data

American redstartSetophaga ruticilla

Summary

• We still have no clear solution for measuring connectivity…..but we are getting there

• The best approach will probably be to integrate multiple markers

Conclusions

• Seasonal interactions and carry- over effects influence the ecology and evolution of species

• Investment in technological research is critical

• Understanding migratory connectivity is critical for conservation

• International cooperation through treaties