Tracking Steller’s Sea-eagles
Posted at 4:20 pm March 24, 2008 by Mike McGrady
Well, here I am, blogging about Steller’s sea-eagles. First, a bit of background to the current work and the maps on this Web site: the San Diego Zoo, Natural Research Limited, and Magadan State Reserve in Russia (state reserves are called zapovedniks in Russia) teamed back in 2006 to track young Steller’s sea-eagles via satellite. Our aims were twofold. First, we wanted to track eagles in the years prior to becoming breeders (large eagles like the Steller’s sea-eagle take four years or more to come into adult plumage). Surprisingly, very little is known about this period of time for any eagle species, and this undermines conservation. This is particularly true for the Steller’s sea-eagle, because its population is relatively small (probably naturally so), and it breeds in remote areas, so its breeding numbers are not closely monitored. We also wanted to weave the movements of Steller’s sea-eagles, this Web site, and the birds in the San Diego Zoo’s collection together as a tool for public conservation awareness.
In 2006, we fitted five nestling Steller’s sea-eagles with satellite-received transmitters. The birds fledged in August from their nests and started to live their life outside of their nests. Four of these birds started on their migration, one most probably died at the hands of humans near its nest, roughly one month after fledging. We found the transmitter (PTT 65629) near the nest site in 2007. Its harness had been cut.
As we tracked the others, two also seemed to be victims of human activity. One tag (65633) stopped transmitting near a village on the Russian coast south of Vladivostok. We later found out that it was probably shot at the border of the Botchanskiy Strict Nature Reserve, in an area clear cut in the 1990s. Botchanskiy and Magadan reserves were planned in 1984; Botchanskiy was established in 1995 after the clearing up of logging operations, and it is the northern-most realm of the Siberian tiger. The other tag (PTT 65631) is, even now, transmitting from the edge of a fishing village of Chumikan near the mouth of the Amur River in Russia. The eagle was apparently shot at a fishery near the mouth of a small river some 12 miles (20 kilometers) northeast from the Chumikan village (not far from the Antykan river). A third bird that did start its migration was also “lost” near Shantar Island (probably on ice floe near a small island called Sivuchi Kamni (Sea Lion’s Rocks).
So, we were left with a single active transmitter on a live bird by the end of 2006. This was disappointing but gave us pause because of so many of the tags being “lost” due to human persecution in this remote part of the world! However, this remaining bird (ID 65362) was to provide us with some joy as we tracked it through its first summer and into its second winter, but let’s not get ahead of the story!
Later that year, 65362 migrated south along the Russian mainland and jumped across to Sakhalin Island (directly north of Hokkaido, Japan) in late November 2006. So, while Americans were sitting down to large bird dinners on Thanksgiving, this large bird had thankfully made it to Sakhalin. From there it continued south, crossing the La Perouse Strait to Hokkaido around Christmas time. It then fly across a short and maybe frozen stretch of sea to two islands off the northwest coast of Hokkaido, Rishiri-to and Rabun-to, where it spent its first winter.
In early April 2007, 65632 headed north across the La Perouse Strait again for its first summer as an independent eagle! It spent most of the spring in southern Sakhalin, and then in early June 2007 it pushed farther north and about half way up the eastern seaboard. We were a bit concerned about this because this is in the heart of the oil and gas development area of Sakhalin. It seemed to us that this place was potentially dangerous.
In early October 2007, the young eagle headed north to the northern tip of Sakhalin for about two weeks before returning to the eastern seaboard. In early November 2007, it headed south again and crossed onto Hokkaido around November 11. Rather than returning to where it wintered in 2006-2007, in this winter it headed along the northeast coast of Hokkaido and then jumped back into Russian territory on southernmost of the Kuril Islands, Kunashir on November 18. In early December, it made another hop, this time to the next island to the north, Iturup, and there it was at the turn of the New Year.
Well, where does that leave us as we enter 2008? Somewhat of a surprise and of no small concern now is that a large proportion of the birds we tagged in the last years have apparently died, and in most cases, the culprits in those deaths are humans! Steller’s sea-eagles face many threats. There was the lead poisoning threat of the 1990s, and there is the constant pressure (as yet unmeasured) of purported overfishing. The fossil fuel energy developments of Sakhalin and the wind farms of Hokkaido have been a worry. We always knew that there would be some direct human persecution. Although few people live in these areas, most have guns and many are very bored. Despite this and because not everyone out there shoots eagles, if our sample is representative, we should be worried!
Stay tuned for part II for details on a group we tagged in the summer of 2007. Please send a comment if you have any questions about Steller’s sea-eagles or this project or just want to discuss things. In due course we will be publishing these data, but a great benefit can be had from raising public consciousness in Steller’s sea-eagles and the environment on the western Pacific Rim.
Dr. Mike McGrady is a researcher with Natural Research Limited, partnered with the San Diego Zoo.
Here’s more information about the Steller’s sea-eagle project…
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March 25th, 2008 at 7:12 am
What amazes me are things like these and people like those involved…Besto! I am eagerly awaiting the next story in this series.
March 26th, 2008 at 8:05 am
What a gorgeous bird. I’m sorry that so many of your 2006 birds met such a sad fate but look forward to hearing about the 2007 group and the continuing adventures of 65632. Thanks!!
December 4th, 2008 at 2:07 pm
Well, the birds seem to be doing better than last year. Four of the five birds Eugene and Irina tagged this year are living. Three of them have pushed south of Shantar Island, and I hope they will be making the jump to Sakhalin and south to Hokkaido. Right now, one (82161) is near the mouth of a remote river that empties into the Southwest Okhotsk Sea. Another (82165) is inland on a river that flows north and empties into the Tugursky Gulf of the Sea of Okhotsk. A third (62629) is not very far from there and has been heading south (up river) recently. Unfortunately, one bird (82164) that is transmitting is still on the Okhota River, not far from where it was reared. We had a bird behave similarly in 1997. It settled in a place where the river did not freeze over until later in the year and eeked out a living. While it waited, winter closed in. As the open river water was closed by ice, it found itself trapped. Food was not available and the rivers and sea had frozen, meaning it was hundreds of miles away from open water and available food. It perished in January near the Okhota River. Let’s hope this one does not suffer the same fate. I’ll be watching the movement of the birds over the next few weeks…hopefully months and years, and will try to provide details here on the blog.