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Migration:

Migration: Overview Case Histories Mechanisms 7 March 2014 Definition The movement of animals from one place to another occurs regularly usual seasonal round-trip example: Pacific Brandt migratory route Migration known from all classes of vertebrates and some insects

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Migration:

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  1. Migration: Overview Case Histories Mechanisms 7 March 2014

  2. Definition • The movement of animals from one place to another • occurs regularly • usual seasonal • round-trip • example: Pacific Brandt migratory route

  3. Migration known from all classes of vertebrates and some insects • Fish: salmon, eels • Reptiles: sea turtles • Mammals: gray whale, African hoofed animals • Birds: widespread • Amphibians: California newt • Insects: butterflies, bees, beetles

  4. Non-migratory geographical movements • Emigration, immigration • Irregular movements: irruptions • Wandering: nomadism • Dispersal

  5. Techniques for Studying Migration • Direct Observation • Visual • Sound • Preserved Specimens • Marking • Bands • Radio Tracking • Satellite Tracking • Radar Observation • Laboratory • Orientation and Navigation • Physiology of Migration

  6. Migratory Patterns: Birds • Flyways and Corridors • Patterns of Migration • Latitudinal migration: breed at one latitude, winter in latitude with milder climate • Long-distance migration • Arctic terns breed in Arctic, winter in Antarctic.  Can feed during migration. • Many shorebirds (e.g. bristle-thighed curlew) breed in Arctic, winter in Polynesia. 10-15 thousand km over water where can not stop to rest, feed • Northern Wheatears (a thrush relative) breed in Greenland, migrate 2-3 thousand km over water to winter in Europe • eastern US: many birds migrate over the Atlantic & Gulf of Mexico.  Use favorable winds. • altitudinal migration • some finches: breed at higher elevation, migrate to lower elevation in winter • blue grouse breed at medium elevation, migrate to higher elevation in winter • partial migration: some individuals migrate, others do not (ex: some raptors, goldfinches) • differential migration: all individuals migrate, but some age &/or sex classes migrate farther than others (ex: dark-eyed juncos, American kestrels)

  7. Latitudinal migration USGS NPWRC: Arctic tern • Arctic tern (Sterna • breed in Arctic • winter in Antarctic • 11,000 m. 1-way.  • Can feed during migration.

  8. Other latitudinal migrants • Many shorebirds (e.g. bristle-thighed curlew) • breed in western Alaska • Fall migration over Pacific to Polynesia. • 10-15 thousand km over water • can not stop to rest, feed • Lifespan to 23 years • Short-tailed shearwater • Neotropical migrants, e.g. tanagers, thrushes, warblers • migrate over the Atlantic & Gulf of Mexico.  Fly at night, use favorable winds, do not feed

  9. some finches: breed at higher elevation, migrate to lower elevation in winter, e.g. gray-crowned rosy finch blue grouse breed at medium elevation, migrate to higher elevation in winter Elevational migrants

  10. Other classifications • partial migration: some individuals migrate, others do not • Fox sparrow • some raptors • goldfinches • differential migration: all individuals migrate, but some age &/or sex classes migrate farther than others • dark-eyed juncos • American kestrels

  11. Migratory Patterns: Green turtle (Chelonia mydas) • Physical separation of feeding and breeding areas • Feed in marine pastures in quiet, low-energy areas • Nest on high energy beaches

  12. Migratory Pattern: Gray Whale(Eschrichtius robustus) 14,000 miles round trip

  13. Why migrate? • A way to use habitats or resources that are only available seasonally • Food • Breeding areas • Retreats from high predation

  14. Cost Benefit Migrating Energetics of migration movement to areas with favorable food types Exposure to hazards en route Movement to areas with favorable breeding conditions Not migrating energetic costs to thermoregulation in temperate regions Reduce risks (energetic, hazards) low food abundance in seasonal climate

  15. How did migration evolve? • Benefits must outweigh costs. • Three-step process, starting with nonmigratory population • Environmental or ecological pressure • change in local climate creates more pronounced seasons, thereby affecting food supply). • Forces part of population to move to adjacent regions for part of year • these adjacent regions must have better food supply • Population moves back into ancestral region for breeding or wintering • This creates a partially migratory population, and those with higher reproductive success will make it over those with lower reproductive success.

  16. Resources: • Weidensaul, Scott. 2000. Living on the Wind: Across the hemisphere with migratory birds. North Point Press • U.S. Fish and Wildlife Service

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