The Great Blue Heron
Mortality and conservation
The Great Blue Heron lives as long as 17 years. The adult birds
have few natural enemies. Birds of prey occasionally attack them, but
these predators are not an important limiting factor on the heron
population. Draining of marshes and destruction of other favourite
haunts is the most serious threat. The number of herons breeding in a
local area is directly related to the amount of feeding habitat.
Mortality of the young is high—both the eggs and young are preyed
upon by crows, ravens, gulls, birds of prey, and raccoons. Heavy rains
and cold weather at the time of hatching also take a heavy toll.
Sickness is not normally a major cause of mortality; however, when
food is scarce the weakest young birds often do without and waste
away. Pesticides are suspected of causing reproductive failures and
deaths, although data obtained up to this time suggest that toxic
chemicals have not caused any decline in overall population levels.
Herons are particularly sensitive to disturbance while nesting.
Scientists suggest as a general rule that there should be no
development within 300m of the edge of a heron colony and no
disturbance in or near colonies from March to August.
Source: Hinterland's Wildlife
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