Migration, Orientation,
Movements
What is migration?
Migration:
An annual two-way
movement, usually based
on seasonality
Wintering Area
Breeding Area
We have learned about migration from many efforts
An example of a “watched” migration:
the Broad-winged Hawk
A medium-sized hawk from
Eastern No. America
Tracking Migrating Songbirds
One of first successful attempts
to track the migration of a songbird
(Swainson’s Thrush) With a radio
transmitter
From Cochran et al. 1967. Living Bird
How they tracked the migrating
thrushes.
Now use satellite transmitters
Photo-sensitive micro data loggers
Isotopes
From Cochran et al. 1967. Living Bird
Radar Also Provides Much
Information
Use of radar
Radar detection of birds arriving near Houston, TX
(images from S.A. Gauthreaux, 1999)
Trans Gulf migrants arriving
Apr 25, 0031 GMT
Trans Gulf migrants leaving
Apr 25, 0159 GMT
A. Nocturnal exodus of
birds from stop-over locations
in South Carolina
B. Same data superimposed
on habitat types from
Landsat satellite imagery.
Highest bird densities were in
hardwood forests, not the
predominant pine woodlands.
From Gauthreaux &
Belser 2003: Auk 120:
266-277.
Basic Types of Migration
1. Obligate annual migration
Latitudinal migration (neotrops)
Elevational
2. Irruptive migration (food highly variable)
Rough-legged Hawks
Snowy Owls
Crossbills
Redpolls
3. Partial migration
Some individuals of a species migrate while
others do not. Adapts to local conditions
Resident
vs
migratory
species
Generally, birds that migrate to the tropics survive the winter
better than do those that stay in the temperate zone.
Life history traits
Trait
Temperate
Resident
Migrant
Tropical
Resident
Productivity
High
Moderate
Low
Adult
Survival
Low (2058%
Moderate
(50%)
High (8090 %)
Juvenile
Survival
Low
Moderate
Mod High
Differential Migration
• Sex and age classes may have different
migration characteristics
• Example: Dark-eyed Junco (Slate-colored race)
• Migrate south to eastern US to Gulf Coast, but
migration distances of individual juncos shows
different average wintering distributions of
males, females, and young.
1. Adult females migrate farthest south
2 young males stay farthest north in Indiana &
Ohio.
3. Adult females, young females settle at
intermediate latitudes.
Fat as fuel for migration
Fuels for migration
Fuel
Energy Yield
Fat
Carbohyd.
Protein
38.9
17.6
17.2
Metabolic
Water (g)
1.07
0.55
0.41
Fat as fuel for migration
• Necessary for long-distance migration
• Fat yields 2x as much energy & water as
carbohydrates & protein
• Migrants fatten rapidly before migration and can
add it quickly while feeding at resting points
along the way (called stop-over sites)
• Stop-over sites are very important for birds
crossing vast areas of inhospitable areas (e.g.
ocean, large lakes, deserts)
Timing of migration
• Photoperiod
• Local conditions (food, vegtation changes)
• Weather patterns (cold, warm fronts)
Weather That Prompts Migration
• In fall, largest flights occur in the southward flow
of dry polar air immediately following the
passage of a cold front.
• In spring, major movements occur in warm
southerly air flow on the west side of high
pressure centers.
• Once airborne, passerines usually fly downwind
regardless of wind direction.
From Able, K. (ed.) 1999. Gatherings of Angels
• When migrating over land, songbirds progress in
a series of relatively short flights, up to 200 miles
or so, interrupted by 3-5 days of rest.
• Length of stop-over depends on local weather,
how much fat the bird has, and refueling
conditions
• In one October flight, 500,000 ducks flew from
eastern Saskatchewan & Manitoba to Lousiana
in a little over 1 day! (=1512 miles; mean ground
speed 41-50 mph)
• A flock of Snow Geese flew from James Bay
Canada to Louisiana in 60 hours!
How Fast Do Migrants Fly?
• Most songbirds migrate at about 20-30 mph in
still air
• Waterfowl & shorebirds: 30-50 mph
• Tail winds or head winds can drastically
impact bird speed and (potentially) survival.
Movements are Remarkable
Homing behavior
– Homing pigeons that return to their lofts from
– Distances of 100’s of miles
– Other documented displacements
• Migration
– Latitudinal
– Altitudinal
Displacement of Selected Seabirds
Illustrates Homing Ability
Migratory feats
A. Arctic shorebirds
White-rumped Sandpiper
Baird’s Sandpiper
Migratory Feats
• Arctic shorebirds:
• Stop-over locations
Migratory Feats
Blackpoll Warbler
Long-distance migration in Catharus thrushes
From Outlaw et al. 2003.
Auk 120: 299-310.
Migratory Feats
Migratory Feats
• Short-tailed
Shearwater
Importance of Stopover Sites
To Migrate (and move about
beyond the range of local cues),
Birds:
• Use a two step process
– Consult a map to determine the compass
course to their goal
– Use a compass to navigate to the goal
(Wiltschko and Wiltschko 2009)
Use of Map and Compass
• Compass mechanisms are relatively well known
–
–
–
–
Magnetic
Sun
Stars
Combinations
• Maps less so
– Geophysical gradients
– Landmarks
• Learned and innate components
• Recent Review in Wiltschko and Wiltschko
(2009)
How Do Birds Navigate?
• Geomagnetism
Solar storms that disrupt the earth’s
magnetic field, also disrupted
the orientation of Ring-billed Gulls.
A bar magnet interferes with a pigeon’s
ability to return to its loft on overcast days.
Birds “see” the inclination of the
magnetic field, not its polarity
Direction of arrow in He (natural)
or H (experimental) does not
matter, it is the angle e relative
to p that is sensed
Birds “see” this by photopigments in the eye. “Radical-pair” model suggests
photon absorption leads to formation of a pair of radicals (singlet and triplet) with
unpaired electrons. Light triggers this and the ratio of single to triplet states
depends on magnetic field. Birds compare singlets to triplets using pigments in
eye, which form patterns on the retina.
Sun-compass orientation
-Not constant
moves across
sky—requires a
clock
-Not always
available
Sun rises and sets rapidly,
but is slow to change
position around noon
--birds use this information
--because rate of change
varies with location on
earth, birds also learn to
use this mechanism
Polarized Light
• At sunrise and sunset polarization forms a
band at 90° relative to the sun. So,
position of sun (and E or W) is noticeable
even with clouds.
Star compass
Integration of Cues
• Magnetic field provides a
reference system for
linking sun position and
internal clock with
geographic direction
• Young birds rely on sun
compass more than
magnetic, older birds
adjust misinformation from
sun compass (in
experiments) by consulting
magnetic field
More Integration
• Night migrants set
compass with polarized
light before star compass is
visible
• Magnetic compass may
also be used at this time
• The magnetic, sun, and
star compasses are
integrated components of a
single complex system that
provides directional
information
Landmarks are a Start to the Map
• Navigating around the home
range, can be expanded to
navigate back to a familiar area
(homing)
– Can be done by route reversal,
or better yet by keeping track
of direction to home and using
compasses to navigate in that
direction, then local cues
• Seems to only be done by
very young birds
– Different from migration to a
new location (first time
migrants)
– Older birds use a real map,
coordinate based, system
What about the Map?
• Gradients used are not
known
• Geomagnetic field
• Olfaction
• Gravity
• Sound (ocean roar)
Compass and Map
Innate
(direction to
migrate) and
learned
components
are involved
Why do birds migrate ?
• Temperate Origin: birds escape from the
inhospitable climates in the north which
negatively impact a bird’s life history.
• Tropical Origin: migrants aggressively exploit
favorable opportunities. Neotropical migrants are
essentially tropical species that temporarily
exploit the long days & abundant insects of high
latitude summers. (rather than as temperate
birds that tolerate the tropics to escape the
northern winter)
Intraspecific, genetic Approach
Population founded from South,
Likely then developed migration
Tropical origin of migration behavior suggested
Time of divergence suggests southern populations
were original and northern expansion followed retreat
of glaciers about 18000 years ago
(Mila et al 2006)
Migration May Constrain Brain Size
•Large brains are metabolically
expensive
•Weight counts when you migrate
•Sedentary birds typically have larger
brains than migrants
•Which came first?
•Big brain > behavioral flexibility >
no need to migrate?
•Put another way, Small brain > not
flexible > need to migrate
•OR
Compare timing of evolution of
migration and brain size within
1 species, the White-crowned
sparrow
•Sedentary behavior > big brains >
to enable behaviorally flexible
strategies that promote survival
(Pravosudov et al. 2007)
Big brains came after shift to sedentary habit, not
as a precursor
Older,
migratory
subspecies
Recently
evolved,
sedentary
subspecies
(Z. i. nuttalli)
Side bar: Migratory
subspecies has larger
hippocampus and
reduced size of
remainder of
telencephalon
--selection works to
fashion different parts
of the brain
Hazards of Migration
Birds killed by television transmitter at Madison, Wisconsin
Sept. 7-8 and 13-14, 2005. Tower is 1,000 ft tall.
Exploring Movements of Residents
Nest predators with hypothesized
forest edge dependency
Estimation of the Home Range
Create UD
Utilization distribution
Relate UD
to various
resource
metrics
Quantify Resources
Within UD
Distribution of vegetation
at each pixel in UD
Surface depicting meters
of high contrast edge within
200m of each pixel in UD
Marzluff et al. 2001
Univariate Analysis of Land Cover
Average Use
25
• High Use of
Human
Occupied
Areas is
Confirmed
20
0.05
15
10
5
0
Late Med. Young Clear Human
Seral Seral Seral Cut Activity
N= 24
22
12
20
10
Landscape Pattern is Deduced From Land Cover
Land Cover
Contrast-weighted Edge
Utilizes Rempel’s
“Patch Analyst”
and FRAGSTATS
Landscape Metrics
• We selected 4
variables that were
minimally
correlated
– Number of Patches
– Contrast-weighted
Edge Density
– Juxtaposition
– Mean Shape Index
High
Low
=
+
Use is Related
to Cover and
Pattern
Variables Pixel
by Pixel Using
Multiple
Regression
Multiple Regression Produces a
Resource Utilization Function
• Relative Use = 1.32
Use is a
CONTINUOUS
MEASURE
Use:Availability Can Be
Incorporated to Any
Degree Desired
- 0.14 (Mature Forest)
- 0.29 (Clear cut)
+ 0.09 (Number of Patches)
+ 0.005 (Contrast-weighted Edge)
- 0.002 (Patch Juxtaposition)
+ 0.14 (Patch Shape)
Relative Importance of Resources at
the Population Level (n = 25)
Resource Attribute
Mean
Standardize
d

95%
Confidence
Interval
P
( =
0)
# of jays with use
significantly
associated with
attribute
+
-
Number of Patches
+0.11*
-0.57 – 0.28
0.19
14*
9
Contrast-weighted Edge
+0.06*
-0.13 – 0.26
0.50
10*
9
Mature Forest
-0.05
-0.18 – 0.08
0.45
12
8
Clear cut
-0.04
-0.17 – 0.09
0.51
6
9
Interspersion –
Juxtaposition
-0.01*
-0.14 – 0.16
0.87
11
8*
Patch Shape Index
+0.01*
-0.11 – 0.14
0.84
9*
12
* Use in direction predicted if jays select for edgy, fragmented areas within their home range
Relative Importance of Resources at
the Population Level
(n = 25)
Pattern more
Resource Attribute
Mean
Standardize
d

important
than
95%
P
type
of
Confidence
( =
Interval
0)
vegetation
# of jays with use
significantly
associated with
attribute
+
-
+0.11*
-0.57 – 0.28
+0.06*
-0.13 – 0.26
Mature Forest
-0.05
-0.18 – 0.08
Clear cut
-0.04
-0.17 – 0.09
Interspersion –
Juxtaposition
-0.01*
-0.14 – 0.16
0.87
11
8*
Patch Shape Index
+0.01*
-0.11 – 0.14
0.84
9*
12
Number of Patches
Contrast-weighted Edge
0.19
14*
Greater use of
0.50
10*
areas with
0.45 patches
12
many
and
edge6as
0.51
expected
9
9
8
9
* Use in direction predicted if jays select for edgy, fragmented areas within their home range
Relative Importance of Resources at
the Population Level (n = 25)
Resource Attribute
Mean
Standardize
d

95%
Confidence
Interval
P
( =
0)
# of jays with use
significantly
associated with
attribute
+
-
Number of Patches
+0.11*
-0.57 – 0.28
0.19
14*
9
Contrast-weighted Edge
+0.06*
-0.13 – 0.26
0.50
10*
9
Mature Forest
-0.05
-0.18 – 0.08
0.45
12
8
Clear cut
-0.04
-0.17 – 0.09
0.51
6
9
Interspersion –
Juxtaposition
-0.01*
-0.14 – 0.16
0.87
11
8*
Patch Shape Index
+0.01*
0.84
9*
12
Population Not Consistent in Use of Resources
-0.11 – 0.14
* Use in direction predicted if jays select for edgy, fragmented areas within their home range
Correlates of s Can Indicate
Why Effects Are Not Greater
• Use of edges is
related to proximity
to human activity
(F(1,24) = 5.4;
P=0.04)
Relative Use () of Edge
0.6
0.5
0.4
0.3
0.2
0.1
0.0
N = 10
N = 15
<1 Km
>5 Km
-0.1
-0.2
Proximity to Settled Areas and Campgrounds
– Anthropogenic food
available in these
settings
– Rate of predation on
other birds’ nests is
highest closest to
such edges in our
study area
Learning how
Steller’s Jays forage
Vigallon and Marzluff (2005)
Incidental Predation