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these magnificent birds standing on the rail of fishing bridges and piers waiting for free hand-outs from fellow human "fisherfolk."  This habit often results in disaster for the Great Blue Heron who easily confuses an edible bit of fish with other entangling debris tossed by humans.  In the heron

family, the differences in leg length

causes differences in the depth of the water

in which the bird can feed.  This keeps

them from competing with each other and

putting too much strain on the food supply

in any one area.

CONSERVATION:Almost all of the Great Blue Herons in the United States were killed during the 1950s and 1960s by farmers using massive amounts of DDT (an insecticide used by the farmers to poison insects that were eating agricultural crops).  In fact, many bird species such as brown pelicans and bald

eagles were also greatly reduced.  

How did DDT harm the general bird population?  The insect poison was obtained through the birds' food chain.  

(1)Insects ate plants that had been sprayed with DDT;

(2)The birds ate the poisoned insects;

(3)The more insects the birds ate, the more concentrated the DDT became in their digestive and reproductive systems;

(4)The DDT in the reproductive systems caused the bird's egg shells to be

thin and fragile;

(5)When the birds laid their eggs or

tried to incubate them, the thin-shells would crack open and the unborn baby birds would die.

The Great Blue Heron (and other marine shorebirds), also got DDT from fish which acquired the poison when it was carried into streams, lakes, and bays by rainwater washing it off the surface of the farms.

Fortunately, the cause (DDT) of the breeding

failures was identified in time and the use

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