The Double-Crested Cormorant: Symbol of Ecological Conflict

8. Ashmole’s Halo: A Righteous Model of What Should Have Happened [Image Plates]

8  Ashmole’s Halo A Righteous Model of What Should Have Happened the spring sun warmed Little Galloo Island’s ‹fty or so rocky acres and the waters of Lake Ontario surrounding it. The ‹rst cormorants to arrive that season settled on the water and the island’s stony beaches at the ‹nish of their thousand-mile migration from the Gulf Coast states and the Carolinas. The more mature and the well-traveled adults had left their southern wintering grounds in late April, while the very small number of young birds hatched the previous spring waited a few weeks and then headed north in early May. Fewer birds gathered on Little Galloo Island this season than had appeared the previous year. This year’s numbers could easily be counted in scores or perhaps mere dozens. For years now, males had acted out their display rituals to attract females, they paired off, males collected nesting materials, and females built and cemented the nest together. The pairs mated, and females laid their clutches of blue eggs in the ›at stick nests. Every encounter and every action constituted a measured stage in an unchanged ritual. The ritual remained the same, but in these same years far too many of the fragile, membranous, thin-shelled eggs were crushed under the weight of a parent attempting to warm and protect the embryos. And among the hatchlings, many suffered debilitating birth defects that severely lessened their chances for survival. 93 Many perished of starvation within the span of only a few days because their deformities would not allow them to take food from the parents. Thirty years earlier, when the colony thrived, the chicks in two or three of the four or ‹ve eggs in each brood lived through their ›edgling stage and migration to return the next year. In recent years, mating pairs sometimes produced only one successful offspring. And many nests failed completely. The youngsters that did survive the grueling roundtrip migration would not reach sexual maturity for at least another two years, keeping them out of the current breeding pool. This year fewer breeding adults would form fewer pairs because they would age out and die as their natural mortality rate far exceeded their current birth rate. The double-crested cormorant was about to pass out of existence. Despite their grimly shrinking numbers, there was a slim glimmer of hope for the birds. The year was 1973, and this spring was the ‹rst breeding season in three decades in which cormorants and other wildlife would not face the burden of additional tons of DDT entering the Great Lakes. In the seasons to come the forage ‹sh and smaller game ‹sh that sustained the Little Galloo Island colony would become less and less toxic. Every ‹sh the cormorants consumed would no longer bring them closer to extinction. Each season every new generation of ‹sh would be spawned in cleaner, purer water. These cormorants would ingest fewer of the DDT-derived DDE molecules that mimicked their own hormones and in›icted such massive damage on their reproductive cycle. It would again be possible for the cormorants’ births to exceed their mortality rate. They may have edged that very short, fateful distance back from the brink of extinction—the distance that would make a difference. Cormorants had been more susceptible to the toxic effects of DDT than many other animals on the Great Lakes, but they also recovered from the insecticide more quickly than many other species. Avian predators such as bald eagles, vultures, and various gull species, which fed on cormorant eggs and chicks, were slower to recover. So, at least for the immediate future, cormorants had a slight numbers advantage over these predators, letting more of the newly emerged cormorants survive the season on Little Galloo and elsewhere on the Great Lakes. Cormorants were facing a reprieve and, feasibly, better times, but once again their own success was about to drag them into ecological con›ict. Controversies and con›icts between double-crested cormorants and 94 • the double-crested cormorant humans always involve trade and industry issues, and trade and industry issues always mean money. It’s known that the everyday activities of cormorants sometimes get in the way of people making a living. The largest dispute takes place when cormorants feed, creating the perception that they are consuming the same ‹sh as humans. Angry commercial and sport‹shermen witness double-cresteds...