Biology Reference
In-Depth Information
herons are otherwise strictly illegal to kill). While this number is by no means sufficient to harm the
heron population, scientists are keeping a wary eye on the upward trend in depredation permits in case
it becomes a problem.
The third concern—and by far the most worrisome in the long run—is increasing human intrusion
near and in heron rookeries. Suburban sprawl, timber cutting, wetland drainage, development, and other
human disturbances are slowly but surely nibbling away at this critical nesting habitat, which rarely has
any legal protection.
Still, there is one encouraging sign in this regard: On Bloodsworth Island, an active U.S. Navy bomb-
ing range in Chesapeake Bay, great blues are happily nesting on wooden towers studded with nesting
platforms. If great blues elsewhere display this sort of adaptability, it bodes well for the species.
Herons have been around for a long time—at least 14 million years, according to the fossil re-
cord—and the great blue heron, or a remarkably similar counterpart, existed nearly 2 million years ago.
Despite the concerns already noted, the great blue seems destined to remain abundant.
Although the whooping crane's prospects grow brighter year by year, this magnificent bird is by no
means out of danger. As a race, cranes are very ancient, and the earliest crane fossils date back roughly
50 million years to the Eocene epoch. By way of comparison, that's only about 15 million years after
the extinction of the dinosaurs. Clearly, cranes have evolved in a way that's made them survivors over
an immense span of time, but humans have recently added a level of stress never before experienced by
these great birds.
Now, after nearly sixty years of painstaking work by dedicated biologists, the restoration of the
whooping crane to its rightful place seems likely. Still, until at least another two flocks of successfully
reproducing whoopers are established, it's too early to declare victory in the struggle to save this splen-
did crane.
Northern raven
;
American (common) crow
