小谷村山案内人組合の恒例行事、登山道整備と雷鳥調査を兼ねた白馬岳一泊山行に出かけてきました。

この時期にしては珍しく両日とも晴れ予報。安心して山へ向かったのですが、なぜか稜線上だけは終始雲が流れ続け、意外にもガスに包まれた二日間となりました。とはいえ、そのおかげで暑さに悩まされることもなく、快適に歩くことができました。

そして何より印象的だったのは、いつにも増して雷鳥がたくさん姿を見せてくれたこと。しかも比較的近くで、その行動をじっくり観察することができました。

じっくり観察していると、当然ながらいろいろな疑問も湧いてきます。

ひとつは、砂浴びをしながら結構な量の砂をついばんでいるように見えたこと。「あれは何をしているんだろう？」

もうひとつは名前の話。そういえば雷鳥は英語で「Thunderbird」ではなく「Japanese Ptarmigan」。しかも国の特別天然記念物として保護されている鳥です。一方で、蝦夷雷鳥はたしか狩猟鳥だったはず。同じ「雷鳥」なのに何が違うのだろう？

というわけで、さっそく調べてみました。その詳細は今回のYouTube動画の説明欄にまとめてありますので、興味のある方はぜひご覧ください。

なるほど、鳥が飲み込む小石は「砂嚢（さのう）」の働きを助けるためで、私たちが食材として呼ぶ「砂肝」はその部位のことなのか――などと、ひとつ賢くなりました。

また、調べているうちに思い出したのが、ウイスキーの「The Famous Grouse」。ラベルに描かれているのは雷鳥でしたね。なるほど、「Grouse」と「Ptarmigan」は同じキジ科でも別のグループの鳥なのか、とこちらも納得。

ちなみに「Thunderbird」と聞くと、私などはまず特急列車や、あの人形劇を連想してしまいます。しかし本来の英語では、北米先住民の神話に登場する伝説の巨鳥のこと。カナダ北西海岸のトーテムポールの頂部に刻まれている鳥が、まさにサンダーバードです。

若い頃、カナダ北西海岸をあちこち旅していたこともあって、私にとってはなじみ深い存在でもあります。

そんなわけで、今回は雷鳥をたっぷり観察できただけでなく、鳥の生態や言葉の由来、さらには北米先住民文化にまで話が広がる、なかなか勉強にもなった山行でした。

最後に、小谷村山案内人組合のFacebookページや関連記事へのリンクを貼っておきます。興味のある方はぜひご覧ください。

I recently joined the annual overnight hike to Mt. Shirouma organized by the Otari Mountain Guides Association, combining trail maintenance work with a survey of Japanese ptarmigans.

For this time of year, the forecast looked unusually promising, with sunshine expected on both days. We set off with confidence, only to find that the ridgeline itself remained shrouded in drifting clouds for most of the trip. Still, that turned out to be a blessing in disguise: the cool, misty conditions made for very comfortable walking.

What made the strongest impression, however, was the ptarmigans. There seemed to be more of them than usual, and we had numerous opportunities to observe their behavior at close range and in considerable detail.

And, of course, the more closely you observe something, the more questions arise.

One question came from watching them take dust baths. While doing so, they appeared to peck up and swallow quite a bit of grit and sand. What exactly were they doing?

Another question concerned their name. It suddenly occurred to me that the bird is called the Japanese Ptarmigan, not “Thunderbird.” In Japan it is a protected species and a Special Natural Monument. Yet the Hazel Grouse of Hokkaido is classified as a game bird. How are these birds related, and what makes them different?

Naturally, I started digging into the subject. The answers can be found in the description of my YouTube video for anyone who is interested.

One thing I learned is that the small stones birds swallow help the function of the gizzardーthe muscular digestive organ known in Japanese anatomy as sano, and familiar to many people as the edible “gizzard” served in yakitori restaurants. It was satisfying to finally connect those terms.

The research also reminded me of the whisky The Famous Grouse, whose label features a grouse. That led me down another rabbit hole: grouse and ptarmigan are related birds within the same family, but they are not the same thing.

And speaking of names, the word Thunderbird brought back other associations. Many Japanese people think first of the limited express train, or perhaps the classic puppet television series. In English, however, a Thunderbird is a legendary giant bird from the mythology of Indigenous peoples of the Pacific Northwest Coast of North America.

Anyone who has seen the great totem poles of coastal British Columbia or Alaska will recognize it immediatelyーthe bird often carved at the very top is the Thunderbird itself.

That image is a familiar one for me. When I was younger, I spent quite a bit of time traveling around the Pacific Northwest Coast of Canada, so I have always felt a certain connection to that culture and its stories.

All in all, this turned out to be far more than a trail-maintenance trip. It was an opportunity to spend time with ptarmigans, learn more about their behavior and ecology, explore the origins of their names, and even revisit memories of Indigenous cultures on the other side of the Pacific.

At the end of this post, I have included links to the Otari Mountain Guides Association’s Facebook page and a few related articles for anyone who would like to learn more.