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The Great Blue Heron has an expected life span of as long as 17 years.
They have few natural enemies. Birds
of prey occasionally attack, but they
are not an important factor on the heron
population. The number of herons breeding in a local area is
a direct result of the amount of feeding habitat.
Mortality of the young is high: birds of prey, ravens, crows, gulls, and raccoons prey upon both the Great Blue Heron's eggs and young. Cold weather and heavy rains at the time of hatching take a heavy toll. Sickness isn't a major cause of mortality. When food is scarce the weakest young birds often waste away. Pesticides are suspected of causing reproductive failures and deaths, but this has not been confirmed. Herons are sensitive to disturbance while nesting. Researchers suggest that there shouldn't be any development within the general area of the heron colony from March to August. |