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The Common Loon population in Yellowstone National Park continues to fluctuate from year to year. There were 14 nest attempts in 1999, yet only two young managed to reach fledgling age. A total of 42 adults were found in the park in 1999 (numbers have ranged between 34 and 51 individuals). Yearly fluctuations in adult numbers and in the production of young are the result of variable weather conditions. Flooding during the month of June was primarily responsible for the poor loonlet production.
Source:
1999 Yellowstone Bird Report by Terry McEneaney
Harlequin Duck
Histrionicus histrionicus
The Harlequin Duck population in Yellowstone continues to maintain itself and is only mildly variable from year to year, with generally 16–20 pairs residing in the park. Monitoring adults is the most effective method of keeping track of population vigor and trends. Monitoring annual productivity is not cost effective, as data collection is extremely time-consuming and difficult due to the remoteness of many of the areas in which harlequins are found. Productivity is extremely variable from year to year and is highly influenced by weather, such as flooding.
Source:
-1999 Yellowstone Bird Report by Terry McEneaney.
Osprey
Pandion haliaetus
The Yellowstone Osprey population fared better than expected in 1999. Egg laying was later than normal due to the late spring weather, resulting in 62 nesting pairs fledging 88 young. Tree nest-site instability and weather continued to play a role in influencing Osprey productivity in the park. The incidence of Bald Eagles taking over Osprey nest sites was noticeable this year and was documented at two sites. Monitoring the population dynamics of Ospreys and other piscivorous bird species is especially important as we chart lake trout numbers over time.
The Yellowstone National Park resident Trumpeter Swan population continues to show signs of a population at risk. Traditionally, the Centennial Valley of Montana has been a hot spot for cygnet production in the greater Yellowstone area. However, events over the last several years have led to a reduction of breeding swans and fledged cygnets. The number of adult swans in Yellowstone National Park has declined over the years and currently stands at 20 individuals. In recent years, trumpeter swan nest attempts have ranged from 4 to 10 per year. There were only six nest attempts in 1999, compared with nine in 1998
As mentioned earlier, the Peregrine Falcon has been removed from the list of endangered species and is now managed as a species of special concern. Yellowstone continues to be a stronghold for peregrines in the Northern Rockies. A new eyrie was found in 1999, bringing the total number of eyries to 14. In spite of unusually cold and wet weather conditions in the spring and early summer, which typically result in the loss of young, 19 young fledged. Monitoring peregrine eyries is a time consuming task, involving; a minimum of three visits to each eyrie per year. Beginning in 2000, a minimum of one-third of all known eyries in the park are expected to be checked each year, thus completing a full parkwide production survey every three years. This will allow the park ornithologist time to check additional cliff faces for new eyries as well.
Did You Know?
Prior to the establishment of the National Park Service, the U.S. Army protected Yellowstone between 1886 and 1918. Fort Yellowstone was established at Mammoth Hot Springs for that purpose.
