Surf Scoter. Photo by Dr. Eric Anderson
There are 3 species of Scoters in the Salish Sea; Surf, White-winged, and Black. Scoters are among many species of sea birds and sea ducks that have seen major population declines in recent years. Birds are sentinels for the health of our ecosystem and their declines are telling us that something is seriously wrong. Since 2000, the SeaDoc Society has been conducting innovative studies to advance our knowledge of the reasons for seabird declines and to craft ways to protect them.
For Scoters, our work has included surgically implanting satellite transmitters so biologists can study migration routes, bringing scientists together to identify knowledge gaps and where science shows us that we need a policy change, and using science to understand how hunting is impacting populations and how changing food availability can support or hinder recovery.
Surgical implantation of satellite transmitters
Satellite transmitters can be used to better understand the movement patterns of many wildlife species. For Scoters, satellite transmitters are implanted in the ceolomic cavity with the antennae exiting from the lower back. SeaDoc helped the Washington Department of Fish and Wildlife surgically implanting satellite transmitters in nearly 100 Scoters to track their winter movements (they tend to stay pretty local when they winter on the Salish Sea) and their summer migrations (after their third year they migrate north into Canada and Alaska to breed).
Hunting rules that needed adjustment
What do you do when a species in decline is still being hunted or fished? Well, you better get some data to see if harvest is high enough to be adding to the problem.
When it came to the decline of Scoters, we knew hunting was not the root of the decline, but hunters and managers were not sure whether hunting was having an added impact. The Washington Department of Fish and Wildlife had collected data on Scoter hunting, but they didn't have the funds to analyze the data.
So SeaDoc stepped in, seeing the opportunity to use good science to help answer a tough management question.
Scoter in rehab tank. Photo by Linda Tanner via Flickr Creative Commons
The analysis showed that there were 3 counties in Washington where hunting was occuring at an unsustainable level. Remember, Scoters stick around in a small area during the winter so focused hunting could really impact species in a small area.
We shared this information with the Fish and Wildlife Commission, which is the body responsible for making hunting rules. They eventually reduced the bag limits on Scoter hunting throughout the state and made a ruling that if the Scoter population dropped below 50,000 animals, all hunting would stop. This is an example of how SeaDoc works to gather good data and makes the science gets off the shelf and into the hands of decision-makers.
We are not an advocacy group and we are not anti-hunting. We just wanted to get the data needed to see if hunting was having an impact, because that type of information is critical to enable managers to make informed decisions.
Scoter and whales
Food webs can be complex. Would you have thought that the feeding behavior of gray whales has an impact on the diets of diving sea ducks? A 2008 paper supported by SeaDoc funding describes how gray whales disturb the bottom when they feed, which creates better feeding opportunities for Surf Scoters (Melanitta perspicillata). Dr. Eric Anderson found that the feeding opportunities presented by gray whales can provide particularly important foraging opportunities for Scoters during spring, when other foods may have declined and requirements to prepare for migration and reproduction are high.
How Scoter migration patterns reflect food availability
Thousands of Scoters can be found eating mussels in Penn Cove, Washington during the fall and early winter. But then they leave. Why?
It turns out—as revealed by a SeaDoc-supported study—that Scoters prefer mussels of a certain size. Once that size class of mussel is hard to find, Scoters will move on to find other food. This makes sense, when you know that Scoters swallow the mussels whole.
When the right size mussels aren't available, it’s more productive for Scoters to move to eelgrass habitats where they can feed on creatures like small crabs and shrimp that live on the eelgrass. The authors of this study hypothesize that declines in eelgrass beds may be part of the reason that Scoter populations have declined so significantly.
This study is another reminder that food webs are complex (something we’ve been saying for years) and that the ecosystem and its varied habitats are highly interconnected.
Science helps us understand these relationships and helps us identify and protect important habitats and species.
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