Bird Exam 2: Mig and Nav

history of migration

• people used to think that birds just disappeared

• aristotle

  • knew cranes migrated

  • thought swallows, larks, and doves hibernated 

• barnacle goose

  • high arctic breeding ground

  • mysterious winter arrival

  • do they turn into geese from barnacle?

cost of migration

• dangerous

• time 

• energy 

migration allows for year-round activity

• birds can exploit season feeding opportunities

• hand out in favorable climates year round

migration patterns

• extremely important part of the annual cycle in many birds

• tied to predicable, seasonal opportunities

  • bug reemergence

  • fruit growth 

nomadic wandering

• scatter resources attract species

• fruit eating birds in tropics

  • tend to travel in groups

• pine seeds in crossbills

• need to be nomadic to find the scattered resources

migration is a season cycle of departures and returns

• Cycles of climate or insects generate corresponding cycles of breeding, flocking, migration

traditional migration

• standard north-south migration

• raptors, geese, songbirds

vertical migration

• ocal migration

• seen in the propics

• up and down mountains

• hummingbirds, quetzals 

routes

• as varied as birds themselves

• shorebirds

  • want to get back to breeding grounds in the spring as fast as possible

  • fall migration

    • slower to get to nonbreeding grounds

    • no temporal restrictions

    • a lot of young

• technology has assisted in route ID

  • banding, satellites, weather radar, feather chemistry

Radar ornithology

• Experts can identify warblers, ducks, shorebirds

  • Based on distinctive airspeeds and patterns of flight

• Supplemental information 

  • Acoustical analysis

  • Microphones placed on rooftops

• These two methods mesh well!

• ratio to estimate how many birds

feather chemistry

• When feathers grow they lock-in any local chemical signatures

• These signatures can be mapped to determine where the bird was when the feather was growing

• Recent research has shown the method needs more fine-tunning

geolocators

• track individuals

  • records sunrise and sunset

  • allows for the location to be determined 

• bird needs to be re-trapped to download info

• 14C gold baby

• preprogramed for where they are released at

major migration routes

• north america

  • north south

  • bc of coastlines. major mountains, river trends

• europe and asia

  • east west

    • net southern movement

  • mountains, seas, great deserts

• some routes are circular

  • Sooty Shearwater: circle the Pacific clockwise

  • Shy Albatrosses circumnavigate the Antarctic landmass 

• birds in the southern hemisphere migrate shorter distances

  • SA: austral migrants

  • fewer birds migration over a larger front

time of day

• birds travel at the least costly, safest, and most rapid time

  • hawks: daytime

    • windy out

    • thermals 

  • warblers: nighttime

    • no wind

    • use stars

  • waterfowl: both

feats of migration

• bar-tailed godwit

  • cross the pacific

• blackpoll warbler

  • south america, atlantic, land in cape may

  • impressive for small bird

• arctic tern

  • longest migrant

  • artic to anarctic 

• kansas and nebraska

  • crazy sandhill crane migration

why migrate

• Many birds that migrate to high northern latitudes are tropical birds that temporarily exploit favorable opportunities

  • Food, nest sites, lower predation, day length

sex and age differences

• differential migrants

  • difference in migration based on sex and age

• females migrate farther

  • males want to get back to the breeding ground first

• younger farther than adults

• class of birds that migrate farthest

  • small. subordinate, arrive later on breeding grounds

dark-eyed junco

• Adult females migrate farthest

• Young males stay farthest north

• Adult males and young females stay at intermediate latitudes

• drivers

  • Greater mortality among young of both sexes

    • Migration = stress; don’t go as far

  • Males that get to the breeding ground first win

    • Males should be offset to winter farther north

  • Adult females can handle the migration

    • Have the highest non-breeding survival of the group

Hooded Warbler non-breeding habitat

• Males stay in forested areas

  • Forested habitat = higher survival

• Females stay in successional habitat

fat and fuel

• blackpolls

• importance of stopover sites

  • Regular refueling usually accompanies migration

    • Songbirds travel a few hundred kilometers

    • Then refuel for a couple days

      • and then rest up a bit

    • Some push it… traveling for extended periods

    • They need sufficient remnant energy to find food at stopover sites

    • High-quality stopover sites CRITICAL for successful migration

red knots

• Late May – Fatten-up on horseshoe crab eggs

• Energy CRITICAL to completion of their migration to the Arctic

• At peak numbers in the 1990’s

  • 95,000 knots would consume 226 metric tons of horseshoe crab eggs gaining 5.2 metric tons of fat

• Conservation of stopover sites obviously is important

navigation

• On hemispheric scales individual birds can return to the same tree after wintering in South America

• This goes back to Audubon marking Phoebes in Mill Grove, PA with silver thread

challenges of navigation

• choice of compass direction

• understanding its own position relative to the goal

  • when do I stop

navigation includes

• visual landmarks

• sun compass

• star compass

• geomagnetism

visual landmarks

• step one, a lot of birds use them

• coastlines, ridges, bodies of water

  • corridors are identified based on these characteristics

    • cape may

    • hawk mountain

• you need experience to do this

  • need to know what you’re looking at

sun compass

• Long expected as a navigational tool

• The first study involved starlings in ’50s

  • On sunny days birds oriented themselves towards the northeast corners of their cages

  • On cloudy days they showed no directional preference

star compass

• Stars work great for aiding migration direction

• Research showed that birds tended to hangout in directions toward migration preference

  • What’s COOL! We can control star location…kinda

  • Planetariums were used to reverse the night sky

    • Birds, then, reverse the preferred location in their cage

geomagnetism

• Ornithologists were slow to accept that birds might use the Earth’s magnetic field to navigate

• Researchers started to glue magnets to birds

  • Major disruption in their navigational abilities

  • homing pigeons

•  We now understand that many birds navigate by using the earth’s magnetic field

  • Bobolinks

  • sparrow esq, need big grasslands 

learning and navigation

• Navigational abilities are partially learned and partially innate

  • Young become lost more often than adult birds

  • Rare birds that excite birders are often lost young

  • Cranes and geese undertake their first migrations with parents

• Short distance migrants relying on innate behavior often use geomagnetism 

• Long distance migrants use stars more, allowing time to adjust internal compass for issues associated to declination

• declination

  • the earth’s magnetic field is never pointing true north