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42 Cards in this Set
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Migration - Slide 1 Movement away from and then subsequentreturn to the same location on a regular basis(usually annual) Dispersal - movement away from a particulararea |
North America Home To World Last Great Migrations |
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• Primarily a non-tropical phenomenon – (altitudinal migration in the tropics) • 5 billion birds of 200 species migrate each year in North America – Go from north down to Central or South America |
80% of all bird speciesbreeding in the boreal regionof Canada winter farthersouth ~ 50% winter in tropical orsubtropical regions In Mexico in winter, 50% ofbirds are migrants•Panama: 30-40% •Ecuador: 10-25% |
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Many shorebirds fly 80-90hr nonstop – bar-tailed godwit flies 11,000km across Pacific from Arctic to south For many birds, long nonstop flights drain allfat and water reserves – Equivalent to human sprinting for 80hr nonstop Birds try to reduce the energetic costs ofmigration |
Ducks & Geese – Use particular flyways – Narrow & well defined – Hunter band returns • Useful conservation info |
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Songbirds - Less is know about flyways - Appear to use weather front |
Other methods to track migration: stable isotope analysis •Deuterium in feathers reflects rainfall inareas where feathers were grown •Used feathers of overwintering birds insouth to map where they came from(where breeding occurred). |
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Major patterns of migration • Birds that soar (eagles, hawks) – Use updrafts & thermals – Only fly in daytime – Must stay over land |
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Major patterns of migration
• Birds that soar (eagles, hawks) • Birds that flap (songbirds) – Often fly over the ocean • Creates fewer updrafts, less turbulence – Mostly fly at night
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Night flying Avoid predators & can feed during the day Less turbulence caused by thermals andupdrafts Cooler,thus avoid overheating flight musclesgenerate lots of heat Convective & evaporative cooling...no sweatglands but can secrete water through their skin& respiratory tract Night is more humid so less moisture loss |
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The Ultimate Migrant - The Arctic Tern |
Arctic tern - Ultimate sun follower - Fairly small bird (<125 g) - Long-lived ...up to 34 years - Opportunistic feedersmall fish, crustaceanson top surface (50 cm) of ocean - Used archival loggers placed on birds to followthem. |
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Until recently, only able touse loggers on large Wandering albatrosses - 3-m wingspan - Satellite tags |
Light sensitive loggers Geolocators Record ambientlight intensity, reveal informationon sunrise & sunset Combine light data with timerecordings, 2 daily geographicalpositions can be calculated andmigration routes can be mapped Based on sunrise and sunset can determine location |
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Geolocators vs. satellite locators • Smallercan go on small birds • CheaperBUT • Cannot transmit data (must be retrieved) • Accuracy of location is within 185km |
Tagged 50 terns in Greenland and 20 birds inIceland One year later, retrieved 10 from Greenlandand 1 from Iceland. |
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Pause in areas ofhigh productivity Northboundtwice as fast assouthbound |
• Average round trip was 70,900 km (range59,500 - 81,600 km)
– Lifespan > 30 years: total distance flown in alifetime may be >2.4 million km ( ~3 returnjourneys to the Moon) • Northboundcorresponded with windpatterns (averaged 40 days) • Southbound journey always longer & lessdirect than northbound (averaged 93 days) – Some areas where birds stopped for a bit |
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• Hot-spot in mid-Atlantic oceanspent 25 daysat this spot • Using NASA data, identified areas of high marineproductivity (chlorophyll) – coincided with areas of stop-over points |
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How did this behaviour evolve?
Three basic stages 1. Partial migration – Some species migrate over short ranges 2. Splitmigratory & resident populations |
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How did this behaviour evolve? 1. Partial migration 2. Split -> migratory & resident populations 3. Finally -> only migrant population remains – gradual elimination of the resident population |
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2 hypotheses 1. Lived in warm place • Competition for resources & range expansion • During warm months, some members of thespecies began living in more northern warm areas • winter came, food grew scarce -> so theytemporarily relocated to warmer latitudes |
2. Climate change - Species lived in the north all year during periodswhen the climate was warm - The climate gradually changedeventually thewinters grew too cold, forcing the species tohead south each year. -> phylogenetically most migrating species actually tropical in origin |
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Slide 1 Why migrate??(instead of staying put) |
Ultimate vs. Proximate Proximate explanations refer to causalmechanism or developmental questions Ultimate explanations refer to the functionalor evolutionary history questions |
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Fall migration of birds. Why does a bird migrate? Proximate – perception of day length, hormonal triggers Ultimate – what is the purpose, and why now? |
Assume behaviours are produced by naturalselection – the process of differentialsurvival and reproduction of alternativegenetic variants within a population.
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Adaptive Behaviour
Adaptation = inheritable characteristic that givesthe individual an advantage (reproductively)over others with different inherited abilities |
Critical part of the adaptationist programall traits have positive and negative effects onan individual’s reproductive success (but really...is it all???) i.e., costs & benefits.
To be selected for, a trait must confer more + than - (benefit > cost). |
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Cost/Benefit Approach B >C Always in terms of reproductive success |
Costs of Migration -- HIGH Energy PredationGetting lost |
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Costs of migrating • Energetics – V formation: reduces drag byup to 65% • Risk of starvation – 2 strategies • Get really fat & then long flight • Not so fat, short flights,stopover & feed Quality of wintering grounds can affectsurvival and breeding success |
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Costs of migrating Risk of predation – Eleonora’s Falcon • preys on migrants • breeds during migration Storms – weather –blown off course, getlost |
Latitudinal trade-off between survival & reproduction in birds Tropical birds lay smaller clutches, less frequently– offset by higher survival |
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Benefits of Breeding North: Greater habitat available for breeding Long periods of daylight for foraging Superabundance of food in spring(higher resources) Fewer competitors Fewer predators |
Latitudinal decrease in predation Do migratory shorebirdsexperience reduced nestpredation the farther norththey travel? |
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Test using artificial nests at 7 breeding sites • At each site, 40 nests were randomlypositioned in shorebird nesting habitat – Twice each breeding season, 2 summers • 1555 artificial nests in total 4 Japanese quail eggsplaced in smalldepression in ground |
Why bother using artificial nests? Why not justlook at natural nests? Artificial nests control for differences in: •nest density •camouflage •incubation patterns (exposure time) •parental care (uniparental/biparental) •nest defense |
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Nest survival increased with latitude Thus, higher egg survival is a benefit of longer migration |
Slide 1 III. MigrationNot just for the birds
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Maximize access to abundant & high quality forage
Minimize interactions with predators and insects |
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Bathurst & Porcupine herds
• Winter in areas in southregions with less snow feed on lichens primarily • Move north to calving areas in spring on tundra, minimize encounters with predators good foraging during lactation winds keep insects away • up to 300ml of blood lost per day per caribou |
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Bowhead Whales Icebreaking skull(bow...) Blubber layer 2-ft thick(floating thermos flask) Eat around 1,800 kg ofplankton / day Weigh up to 60 tons(tongue alone weighs 900 kg) |
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Annual Bowhead Whale migration cycle... |
Gray whale migration 22,000 km annualmigration from coastalArctic Ocean to BajaCalifornia and Mexico Feeding grounds inArctic (summer) Breeding and birthinggrounds in tropicaleastern Pacific (winter) |
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Gray whale migration Fall migration (Oct-Feb) • Pregnant females head south first, soon followed by males and other adult females, then juveniles. Spring migration (Jan-June) Occurs in pulses, or waves. First adults males and juveniles, and newly pregnant females. Mothers and babies stay a month or two longer, so babies can gain blubber and strength |
One population ofHumpback whales hasa similar route Feed AlaskaCalving Hawaii or Baja |
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Humpback Whale |
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• Six bat species in Manitoba:
– Hibernators: Myotis lucifugus, little brown bat Myotis septentrionalis, northern long-eared myotis Eptesicus fuscus, big brown bat – Migrators: Lasionycteris noctivagans, silver-hairedbat Lasiurus cinereus, hoary bat Lasiurus borealis, eastern red bat |
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Conservation Concern Echolocation?Sudden drop in pressure – damages respiratory system |
Conservation concern
• White-nosed syndrome (WNS) • Fungal growth– Geomyces • Cold loving fungus • First documented in Feb. 2006 – New York State • Spread to other caves Little brown bat White nose more of a concern for hibernating bats then migratory bats White noise syndrome effects ability to hibernate |
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Only butterfly that migrates both northand south on a regular basis (like birds) • conserve energy by riding columns ofrising warm air & taking advantage ofstrong winds to speed up their flight. No single individual makes the entireround trip. •Females deposit eggs for the nextgeneration during these migrations. •cycle takes place over four generations Avoid killing freezes •High elevations, remain moist & cool•2 million can die in a single night |
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Pacific Salmon Migration |
Zooplankton Yellow and red show the richest areas for zooplankton |
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Atlantic salmon migration Principal ocean feeding grounds are off Greenland andLabrador, and north of the Faroe Islands. |
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Zooplankton Vertical Migration - Feed at night - Light does not penetrate as well so difficult to see if deep during day |
Depth ranges from 40 m at noon, up tothe surface at dusk and returning again tothe same depth just before dawn. |
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IV. Navigationhow do they “know”where to go? |
Cues to direction • Visual landmarks • Solar compass • Stellar compass • Geomagnetism • Olfaction |
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Solar compass Reset circadianrhythm in captivity Homing pigeons released on sunny day. • Use direction of sun, not height in the sky |
Stellar compass Important for birds that migrate at night:tested in a Planetarium with carbon paper |
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Geomagnetic cues Glue magnets on pigeons’ heads;modifies the magnetic cues. Birds oriented in wrong direction. |
Olfaction |
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2. Trick them – deflect scents Baffles were used to deflect wind by 90o...altered perceptionof direction ---> made pigeons think odors were from thesouth when they were really from the west |
Genetic basis of migration Blackcaps – passerine birds living in Europe & Africa European blackcaps migrate to Africa for winter African black caps do not migrate. Experiment – raised birds from both populations in isolation, noenvironmental cues • used electronic perches to record movements Result – only European birds get restless.Genetic differences! |
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Migratory blackcaps have2 flight paths |
Hybrids between Austrian & Southwest GermanyWhat do you predict for direction? |
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The ultimate reason for birds to migrate is because it is good for the individual in terms of reproductive success not for the species
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