By Anne Murray
The local media enthused over the great abundance of Bald Eagles this winter. It seemed like a good news nature story during a time of worldwide bird declines, yet looks can be deceptive. Eagles gathered together do not mean more eagles region-wide, just as flocks of Snow Geese spilling onto Richmond school fields are not necessarily a sign of a healthy population. We need to look closer to see the real story.
For decades Bald Eagles declined across North America due to culls by the fishing industry and the use of DDT in the fields. Once these practices were halted, populations rebounded. In the 1960s, only one or two pairs nested in Greater Vancouver. Now there are almost 200. Superbly adapted for life around the Georgia Strait, Bald Eagles gather from miles around to feed at salmon runs on coastal rivers. In January 1994, a record 3,769 eagles were observed during the annual winter count at Brackendale, in Squamish. Harrison River is another important area. When the salmon feast ends, many head for the abundance of Boundary Bay where 100,000 to 175,000 ducks spend the winter.
In the last two years, the situation has changed. Only 893 eagles were counted at Brackendale in January 2008. This year there were 755. The salmon were in short supply, so local and migrant eagles gathered earlier and in larger numbers in the Fraser delta. Boundary Bay provided ducks as usual, but in the cold snap of midwinter the shallow water in the bay froze, and the eagles sought refuge in warmer forest areas around Burns Bog and the landfill. They hung out around farms and scavenged along roadsides. It seemed like eagles were everywhere, but there were not really more eagles, just a greater concentration.
Wildlife dynamics are difficult to comprehend, and false conclusions can easily be drawn with incomplete knowledge. Changes in distribution have cumulative effects. More Bald Eagles around Boundary Bay puts stress on Great Blue Heron colonies and may cause sea duck flocks to move further offshore. Far too many development decisions are being made by local governments, or in environmental assessments, claiming that harm to birds can be “mitigated”. How can we know this when we know so little about what is happening to their populations and why?
Snow Geese that nest on Wrangel Island in Russia flock in winter to between the Fraser and Skagit estuaries and California. Following many decades of hunting pressure, an increased effort to protect geese through “greenfields” programs have helped them approach a population goal set by the U.S.-Canada management plan. However, environmental factors in their wintering grounds are changing. A higher proportion of Snow Geese that used to migrate to California are now wintering in the Fraser estuary, where heavily grazed marshes, fewer arable fields and more development are minimizing their foraging habitat. The geese then congregate on urban playing fields, and people say they have never seen so many.
Redistribution of bird populations, due to climate change and food source availability are a frequent occurrence. Some birds are quietly disappearing. Sixty percent of North American wintering birds are shifting their range northwards. Waterbird populations are declining in tandem with declines in herring and other fish. Fewer Western Sandpipers migrate through the Fraser delta now than during the early 1990s, and insectivorous birds, like the Nighthawk that once graced our skies on summer evenings, are now rare. Nighthawk numbers have plummeted across southern Canada, even where breeding habitat has not been disturbed.
Birds need to be extensively studied to understand what is happening. Volunteers are a major source of data and two new initiatives are of particular value. The B.C. Breeding Bird Atlas is a seven-year project to record and map breeding evidence. The data collected will be invaluable in assessing bird populations. The B.C. Important Bird Area Program is part of an international attempt to protect critical bird habitats around the world. So far 84 Important Bird Areas have been designated in B.C., with volunteer “caretakers” who conduct bird surveys and monitor threats. Without these habitats, bird diversity would be substantially reduced.
It is imperative that governments and the private sector support such initiatives and that the media keep up with information on wildlife populations. Otherwise we will wake up one morning to find that we truly have a “silent spring”.