Refuge Notebook

Article

July 14, 2006

Skilak Lake Birds Trying on New Colored Leg Bands
By: Todd Eskelin

The Double-crested Cormorants at Skilak Lake have come a long way in the last 70 years. That’s right; they have been nesting on little islets on the east end of Skilak for at least 70 years!

The earliest published record I have seen describing the cormorants of Skilak Lake was an article in The Alaska Sportsman July 1936. While the activities described by H.A. Anderson were quite creative, it should be noted that this would be highly illegal under current regulations. Back in 1936, Mr. Anderson boated from his Caribou Island cabin up the lake to the bird colony and placed his White Leghorn chicken eggs in the cormorant nests. Three weeks later he went back and retrieved the eggs as they were beginning to hatch. Since his chickens were unwilling to incubate the eggs, Mr. Anderson found a way to use wild birds to facilitate the process. Unfortunately, there was no mention of the number of nesting birds in the article. He did describe heavy flea infestations in the nest and did not reproduce his experiment in subsequent years.

The earliest record I can find of the population status of the cormorants at Skilak was a survey done in 1951 and 1952 by David Klein. In 1952 he counted 30 nests, with and average of 3 eggs per nest for an estimated production of 90 eggs. The next recorded survey effort was conducted by the U.S. Fish and Wildlife Service from 1982 to 1985. That group of surveyors only had an average of 6.5 nests per year with an average of 20 eggs produced. That is a fairly significant reduction in productivity from 1952 to 1982. We must use caution in interpreting this data and not extrapolate too much from it. It is just a snapshot from 20 and 50 years ago and for all we know, 1952 was just an aberrant high year.

Since those earlier surveys, the Kenai National Wildlife Refuge has been tracking the cormorant colony on a more consistent basis and has documented a steady increase in productivity since the 1980’s surveys. The most recent survey in June 2006 recorded 62 nests with a total of 199 eggs produced. With this steady increase we felt it was important to get a more detailed picture of what may be driving the changes we are seeing in the population.

Starting in 2005, we fitted 100 cormorant chicks with colored metal leg bands on the right leg. Each year, for the next 3 years, we will fit the cormorants with different colors for each year. In 2005, the cormorants were all fitted with 3 anodized metal bands. The color for 2006 will be green. With these color-marked birds we will be able to track the incorporation of young birds into the breeding population at approximately age 3 years.

If we continue to see increases in the number of nests, but don’t see color marked birds in the breeding population, then we can assume that birds are immigrating into the colony from other areas. Another possibility is that the birds are simply producing more eggs per nest. All of these questions will be answered over the next 3 years and as with all good mysteries, many more puzzling questions will be spawned from the answered questions.

So, if you see any cormorants in the area check the right leg for bright colored jewelry and report your findings to the Refuge. It is interesting to think the cormorants have changed with the times. Seventy years ago they were being used as chicken egg incubators and now they are out sporting the latest in fashion statements.

Todd Eskelin is a Biological Technician at the Kenai National Wildlife Refuge. He specializes in birds and has conducted research on songbirds in many areas of the state. You can check on new bird arrivals or report your bird sighting on the Kenai National Wildlife Refuge Birding Hotline (907) 262-2300.