Neotropical Migratory Birds

1
Neotropical Migratory Birds

• Neotropical New Tropics
• New World vs old world
• Western Hemisphere
• Neotropical birds breed in Canada and the United
  States during the northern hemispheres summer
  and spends the rest of the year in the tropics.
• Defined as a species in which the majority of
  individuals breed north of the Tropic of Cancer
  (latitude 23 degrees north)
• About 200 species

2
Migration Distance

• Varies across species and within species
• Shortest (a few hundred miles) are those birds
  that breed in the southern US and overwinter in
  Mexico.
• Some of the longest are birds that breed in the
  arctic tundra in northernmost Canada and winter
  as far south as the southermost tip of South
  America
• One way mileage 10,000
• Arctic Tern
• Nests as far north as land extends
• Overwinters near the south pole
• Sees more daylight than any other species
• Round trip covers about 22,000 miles.

3
Why Migrate?

• They can take advantage of seasonally abundant
  food supply and avoid times and places that food
  supply is low.
• Flying insects, caterpillars, fruits and nectar
  are abundant during our spring and summer, but
  not winter.
• Ultimate reason is breeding success.
• Can raise more young if they migrate than if they
  stayed in the tropics.
• Abundant protein-rich food, longer daylight
  hours, more room, possibly fewer predators.

4
When To Migrate?

• Internal clock controls the onset of migration
  and the premigration preparations.
• Environmental factors control this clock
• Certain changes in a birds environment stimulate
  the production of certain hormones, which leads
  to changes in behavior and physiology.
• Change in day length for example

5
How To Get There?

• Short migraters and waterfowl generally learn
  breeding and wintering locations from older more
  experienced birds
• Often family members
• Most long distance migraters are genetically
  programmed to make the trip.
• First migration is completely under genetic
  control
• Subsequent trips may incorporate previous
  experiences (return each year to good
  reproductive grounds)

6
Migration Routes

• Follow land through Mexico into the United States
• Cross the Gulf of Mexico
• First/last encountered land important to survival
• Rest and refueling

7
Seasonal Habitats

• Wintering Grounds
• Sufficient food for premigration preparations
• Migratory Habitat
• Fat reserves, nutrients, vulnerability to
  predation
• Breeding Grounds
• Reproductive success

8
Habitat Variety Important

• With the diversity of migratory birds, a
  diversity of habitats is needed in the migratory
  habitats.
• Reduces competition