curado wrote:I always thought they were really rare but I've heard them several times. It's kinda neat.
Back in the early 80s I would go with my Scout troop up to Squaw Creek NWR (NW MO) and we might see 2 or 3 bald eagles, and that was through a spotting scope at a mile or so distance. By the mid 90s I could count, without optics other than my contact lenses, around a hundred. And I parked under a tree holding 10 or so. Amazing recovery.
I am pretty sure that DDT was responsible for the decline in that it is fat soluble so it accumulates in the food chain and stays with the animal. So a duck with DDT gets eaten by an eagle and the DDT stays with the eagle. The DDT caused the bird egg shells to be so thin that a nesting bird would crack the eggs.
From:
http://en.wikipedia.org/wiki/DDT
"DDT, DDE, and DDD magnify through the food chain, with apex predators such as raptors having a higher concentration of the chemicals than other animals sharing the same environment. They are very lipophilic and are stored mainly in body fat. DDT and DDE are very resistant to metabolism; in humans their half-lives are 6 and up to 10 years, respectively. In the United States, these chemicals were detected in almost all human blood samples tested by the Centers for Disease Control in 2005, though their levels have sharply declined since most uses were banned in the US.[32] Estimated dietary intake has also declined,[32] despite it still being commonly detected in food samples tested by the FDA.[33]"