Scientists want to know why so many animals are dying, and if pesticide usage is a major cause of this. In order to figure this out, they have been doing a "Hawk Watch" to track the number and variety of species of hawks flying through the Rio Grande Valley where two major flyways converge. These hawks are coming to make their spring appearance in the Rio Grande Valley. Scientists are interested in the number because the numbers indicate environmental changes and possible hazards. Hawks are raptors, and raptors have been the indicators of environmental hazards such as pesticide abuse because toxins are found in their systems. They are an indicator species because many of the toxic chemicals seem to be biologically amplified as they go up the food chain. These raptors are considered to be at the top of the food chain. They get larger amounts of chemicals because they are receiving the chemicals that all other little animals had. A few years ago, the number of Swainson’s hawks dropped dramatically because of the pesticides applied to the crops in South America where the hawks spend their winter. Several thousand of this species died as a result of this. The number is beginning to increase now because of a cut use of pesticides in South America. Scientists hope that this will be the same for the rest of the species.
Swanson, Gillian. "Migrating hawks spotted in Rio Grande Valley." Dallas Morning
News. Sunday, April 5, 1998. 45A.