Yeah... All they way through the Everglades and south. It is also known as the Everglades Kite.
http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/Snail_Kite.html#map - It states #map, but it's not just the map, it's an information page
Interesting about the Osprey.... If it was the snails, I would think they would have been More affected by DDT in Florida than elsewhere in the country. Osprey range over Most of the US and they don't eat or even find applesnails over most of their range but were affected by DDT as well... The link above Does state the Snail kite is listed as "Federal and State Endangered" but it doesn't mention if it's because of DDT poisoning... This site (
http://cars.er.usgs.gov/sofla/Snail_Kite/snail_kite.html) however, Does state their decline was in large part due to the draining of the Everglades. If it was the snails, I would have thought it would have been mentioned and they would have been affected more dramatically than the Osprey, and maybe even wiped out completely since it is their main food source.
The Cornell University site states Osprey eat fish Almost Exclusively and makes up 99% of their diet.
http://www.birds.cornell.edu/AllAboutBirds/BirdGuide/osprey.html#map
Another large bird of prey that was seriously affected by DDT was the Bald Eagle, which also eats a lot of fish... I think the documentary may have been incorrect about the snails being the main source of their DDT poisoning... Fish are notorious for concentrating toxins in the environment... The smaller fry get contaminated by the food they eat, the larger fry eat them and add to the amounts they already have, the larger ones eat them and so on until you have a large fish with VERY high levels of contaminants... Same happens with mercury. I thought I remembered learning that's why the Eagle and the Osprey were so affected.
Maybe I'm remembering incorrectly?