Lecture 8 – Migration & Navigation

Migration Timing• Highly precise due to “biological clock”• Phenology of Minnesota Birds

– Winter (November –February)– Early Spring (March-April)– Late Spring (May)– Summer (June – July)– Late Summer (August)– Fall (September – October)

• Specifics (Jim Gilbert) (S. Stensaas)– March 12th – Woodducks - Feb 19th – G.H.Owls– April 2nd – Tree Sparrows - March 13th – Gulls– May 5th – Red-eyed Vireo - April 1st – Tundra Swans– May 16th-23rd – Warblers - May 1st – Winter Wrens

North American Flyways

Fat Deposition

• Completion of fat deposition in small passerines can be accomplished in 4-10 days

• Most species can rapidly restore depleted reserves during migration– stopover habitats

• Amount of fat deposited is related to distances to be covered– fat deposits may constitute 30 - 50 % of

live weight

Stopover Ecology

• Refuel• Examples

– Woodlands in agricultural areas– Riparian areas in the desert– Coastal Areas

• Habitat loss = loss of essential stopovers– Coastal stopovers heavily impacted

Navigation• Topographic – diurnal migrants –

coastlines, river valleys, mountain ridges; “Lead lines”

• Solar orientation – evidence of orientation with the sun

• Stellar orientation – evidence of orientation with different night skies, continuously recalibrated

Navigation continued

• Geomagnetism – use of the Earth’s magnetic field for orientation, continuously recalibrated

• Olfactory – use of smell, evidence in some seabirds

“thrushes set their courseusing a magnetic compass,which they calibrate to thesetting sun before takeoff each evening.”

“use stars, sun, geomagnetic field and polarized light for orientation”

Navigation Continued

• Twilight Cues– Polarized setting sun rays align N-S– Define departure after dark

• Learning– Young birds often get lost– Learn stopovers from experience– Ex: Whopping Cranes

Migration ‘Help’Whooping Crane Recovery Programs

Songbirds Fly Three Times Faster Than ExpectedScienceDaily (Feb. 16, 2009)

The study found that songbirds' overall migration rate was two to six times more rapid in spring than in fall. "We were flabbergasted by the birds' spring return times. To have a bird leave Brazil on April 12 and be home by the end of the month was just astounding. We always assumed they left sometime in March," she said.

Fig. 1. Interpolated geolocation tracks of individual purple martins (A and B) and wood thrushes (C and D) that bred in northern Pennsylvania, USA (42°N, 80°W). Blue, fall migration; yellow, winter range movements; and red, spring migration.

Studying Migration

Why?How:• Observing• Trapping• Tracking• Radar

Migration Trends• Case Study early 1960s• Hawk Mountain migration counts show numbers of

Peregrine Falcons and Bald Eagles in rapid decline• Rachel Carson sites declines due to DDT in Silent Spring• DDT banned in 1972

Observing and Counting

Passerine Banding

Trapping – the Blind

Trapping - Nets

Mist-net trap of a Sharp-shinned Hawk

Tracking

www.hawkwatch.org

Swainson’s Hawks

Radar Ornithology

http://virtual.clemson.edu/groups/birdrad/COMMENT.ht

WSR-88D (NEXRAD) weather surveillance radar

• Near complete coverage of U.S.• Transmits microwave signals into the

atmosphere and measures returning energy– “reflectivity”

• Reflectivity estimates density of targets

• Doppler radar at Duluth airport

Migration on the North Shore

Hawk Ridge, Duluth

• Averages 94,000 raptors

• Over 180,000 non-raptors– Many are Passerines– Corvids

Conservation Issues

• Impacts with structures – towers, guy wires, buildings, houses, windows

• Wind-turbine development• Stopover habitat Loss• Climate change

Birdsafe and Lights Out

•Minnesota Audubon•Migrating birds attracted to lighted structures•Results in exhaustion or collisions

A study of North Shore bird migration in the

context of potential wind turbines

Anna Peterson Jerry Niemi, Heidi Seeland, Annie Bracey,

Hawk Ridge Bird ObservatoryNatural Resources Research Institute

University of Minnesota Duluth

Wind Potential along North Shore

The Conflict…

http://www.ckwag.org/issues.html

http://www.aweo.org/

(320 feet tall)

Diurnal Migration Study

Study Sites

Percent of migratory birds at each flight height category

0102030405060708090

100

Mig

rant

s (P

erce

nt o

f To

tal)

100m to 500m

Canopy to 100m

Below Canopy

North Shore Stopover Study

Important Bird Areas- MN Audubon

• Identify, monitor and conserve important sites for birds

• MN’s first IBA: Hawk Ridge– Stopover habitat