Ospreys, swans struggling to keep numbers up in park
Declining population of cutthroat hitting ospreys hard
By MIKE STARK Of The Gazette Staff
Fish-eating ospreys are becoming rarer on Yellowstone Lake in Yellowstone National Park, mostly because of a drastic decline in native cutthroat trout.
Terry McEneaney, Yellow-stone's ornithologist, said only nine nesting pairs of ospreys were observed on the lake last year and that the population in that area appears to be declining "at a staggering rate."
"I go out there and I see very few osprey anymore," McEneaney said. "I used to see 20 or 30 in a day, and now I'm lucky to see a couple."
Trumpeter swans, one of Yellowstone's signature birds, also continue to decline, reaching some of their lowest numbers since the 1930s, according to a 2006 report on the park's birds.
The number of swans in Yellowstone has dropped steadily since 1961 and now stands at 14, McEneaney said. Although the bird is surviving elsewhere in North America, Yellowstone's small, long-running population continues its struggle.
"It's an imperiled species in Yellowstone Park, there's no question about that," McEneaney said.
One of the biggest problems for the osprey is that Yellowstone cutthroat trout, a key food, has been hit hard by non-native lake trout in recent years. At one spot on the lake where more than 70,000 cutthroat were counted in the 1970s, just 471 were tallied last year, the lowest number since record keeping began in 1945.
There are other factors, too, including a 2003 wildfire on Frank Island, in the middle of the lake, that burned 570 of the island's 600 acres, wiping out nearly all the old-growth trees that were a popular spot for nesting ospreys.
In 1994, there were 25 pairs nesting on the island that produced 28 young. The nine pairs counted last year produced just three young, according to the park's annual report.
That's not to say ospreys around Yellowstone Lake are dying out, McEneaney said. It's likely that they flew off and settled somewhere else, perhaps outside the park.
Overall, the population in Yellowstone in 2006 - 41 pairs producing 23 young - is the fourth-lowest production in the last 20 years of collecting detailed data, McEneaney said.
Ospreys, like other wildlife species, run through boom-and-bust cycles and the latest developments at Yellowstone Lake are simply the latest fluctuations, McEneaney said.
"The picture doesn't look good right now, but I think it's not going to be like this forever," he said.
McEneaney said the same about the trumpeter swans. Though the population is low, it could bounce back in the coming decades if human interference is kept at a minimum.
The park's trumpeter swans have struggled as populations outside Yellowstone, which traditionally have provided fresh recruits, have declined also. Predators are also an issue. Wolves killed five swans over a 12-month period in 2005 and 2006. Bald eagles and grizzly bears also limit the population.
"It continues to be a bird on the edge," McEneaney said.
Bald eagle productivity took a slight dip in 2006, including those around Yellowstone Lake, but overall has been climbing for years. Last year, there were 33 active bald eagle nests in Yellowstone.
Published on Wednesday, June 27, 2007. Last modified on 6/27/2007 at 1:20 am
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Last year it appeared all but a handful of swans had disappeared due to predators. I guess wolves like swans. Thank goodness for the Seedskadee and places like that. There were three additional swans on the Firehole this spring. Not sure where the others are. I hope they can avoid the wolves until they are old enough to mate and raise babies.
Then there's those darn bald eagles and grizzly bears. In fact I was watching a trumpeter nest in the park a couple of weeks ago and saw a fox come down and try to snatch a cygnet. Momma managed to get everybody into the water just in time, but that fox sure looked like he had done that before! It's called the "food chain". That's how Nature works. Of course I know that we're all vegetarians!
In the early 1900s, the trumpeter was hunted nearly to extinction for its skin, feathers (for fancy hats), meat, and eggs (by people). By the 1930's it was thought that they were extinct. Just like wolves, grizzlies and many other species, this bird once flourished over much of the continent before the arrival of white men. The trials and tribulations of this bird cannot be blamed on natural predators such as wolves or eagles. While such predation may temporarily reduce a local population, only women's fashion can bring an entire species to the brink of oblivion.
Frank, I haven't heard of any trumpeters being used for hats recently. 5 documented deaths in 1 year by wolves is pretty significant. Last year the story was that they did not expect the swans to return to Yellowstone. Is the nest in the back country?
Marion, honestly, it´s a little bit tiring that you blame wolves for everything that happens in the Greater Yellowstone Ecosystem. I´m sure we all know in the meantime that you absolutely dislike wolves (and bears of course). Why did you visit YNP recently (I read your posting on another blog) and admired it so much ? Two faces?
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