Hawk Migration

1. Hawk Migration Why do they Migrate?

2. Hawk Migration • Every fall hawks migrate south in spectacular migrations “rivers” of hawks • 1000s passing particular locations at a time • Spring migration is also observable but more spread out

3. Hawk Migration • Migration is related to food availability • Hawks that feed on cold blooded prey (insects) must winter in the tropics • Hawks that feed on small birds (who feed on insects) must follow the birds when they migrate • Hawks that feed on fish must follow the fish back down south and/or avoid frozen areas

4. Why don’t they stay down South? • If they stayed in the southern areas they would deplete their food resources over time.

5. Hawks as Indicator Species • An indicator species gives scientists information on the health of an ecosystem. • Hawks/Eagles/Falcons/Vultures are excellent indicator species because they are at the top of the food chain • Therefore; if there numbers are low, scientists can assume that something is going wrong in the ecosystem (affecting the raptors as well as lower animals on the food chain because they are the raptors food source)

6. Example of Raptors as Indicators • In the 1960’s the number of many raptors went down due to DDT • What Happened? Their food source had been contaminated by the DDT which then entered the birds body. In some instances this would kill the bird, but in others it would weaken their egg shells affecting the population.

7. By seeing the number of raptors go down, scientists knew that something was wrong in the Ecosystem. • Often times you can see the effect on the larger predators before the smaller organisms due to their relatively smaller population size • And due to the fact that the pollutant will bioaccumulate through the food chain causing the greatest effect on the organisms at the TOP of the food chain