Osprey

A bird in flight against a blue sky

Ospreys are monitored by park staff. In 2014, 30 active nests were monitored in Yellowstone.

NPS/Bowersock

 

Like many other birds of prey, osprey (Pandion haliaeetus) populations declined due to pesticide use in the mid-1900s. Populations rebounded during the latter part of the 1900s. The first study of osprey in Yellowstone National Park occurred in 1917 by M. P. Skinner, the park's first naturalist. It was not until 1987 that the Yellowstone National Park bird program began monitoring breeding osprey annually, although an extensive survey on reproduction, diet, and habitat was conducted during the 1970s.

Since monitoring began, Yellowstone's population of osprey has been considered relatively stable. On average, 50% of nests succeed (produce young) each year, with each successful nest producing an average of one to two young. These statistics are slightly lower than expected for a stable and healthy population, and may be explained by the park's harsh environment. In a recent study, scientists found that declining nest success for osprey around Yellowstone Lake is due, in part, to the decline of cutthroat trout.

Ospreys are surveyed via fixed-wing aircraft and by ground-based surveys from May through August. During the survey flights, the majority of nests are monitored for occupancy and breeding activity. In addition, all suitable lakes and rivers are surveyed for potential new territories and nest sites.

Research

A recently completed study conducted by park biologists found a significant relationship between the declines in cutthroat trout and osprey reproduction at Yellowstone Lake. Recent increases in the number of young cutthroat trout caught by the Yellowstone fisheries program during the fall netting assessment are encouraging. An increase in cutthroat trout production may lead to an increase in nesting pairs of ospreys and improved nesting success at Yellowstone Lake.

 

Quick Facts

Number in Yellowstone

  • In 2014, 30 active nests were monitored, with 73% of them successful, greater than the 28-year average (51%).
  • Young produced per breeding pair averaged 1.47 in 2014, while the 28-year average was 0.86.
  • Only one osprey nest at Yellowstone Lake was successful in 2014.
  • Parkwide, osprey reproduction has increased each year since 2003.

Identification

  • Slightly smaller than the bald eagle.
  • Mostly white belly, white head with dark streak through eye.
  • Narrow wings, dark patch at bend.
  • Fledglings have light edges to each dark feather on their backs and upper wing surfaces, which gives them a speckled appearance.

Habitat

  • Usually near lakes (such as Yellowstone Lake), river valleys (such as Hayden, Madison, Firehole, and Lamar valleys), and in river canyons (such as the Gardner Canyon and the Grand Canyon of the Yellowstone River).

Behavior

  • Generally returns to Yellowstone in April and leaves in September.
  • Builds nest of sticks in large trees or on pinnacles close to water.
  • Lays 2–3 eggs in May to June.
  • Eggs hatch in 4–5 weeks
 

More Information

References

The list below includes academic publications, government publications, management documents that inform the decision-making process at parks and protected areas, as well as links to websites that provide additional relevant information. The Yellowstone Resources and Issues Handbook, updated annually, is the book our rangers use to answer many basic park questions.

Annual Bird Program Reports. National Park Service, Yellowstone National Park.

Baril, L.M., D.W. Smith, T. Drummer, and T.M. Koel. 2013. Implications of cutthroat trout declines for breeding opsreys and bald eagles at Yellowstone Lake. Journal of Raptor Research 47(3): 234–245.

Poole, A.F., R.O. Bierregaard, and M.S. Martell. Osprey. The Birds of North America Online.

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