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 hemisphere’s 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 bird’s 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