Dipper population stable in Northern Hills
SPEARFISH CANYON — A recent study has shown that American dipper populations in the Spearfish and Whitewood creek watersheds are stable, but not expanding.
A survey of Black Hills streams was conducted in 2018 by Nancy Drilling, a biologist with the Bird Conservancy of the Rockies. She said she surveyed Bear Butte, Elk, Box Elder, French, and Rapid creeks.
“There is a pair (of dippers) at Thunderhead Falls on Rapid Creek. That is the only birds we found outside of Whitewood and Spearfish creeks,” Drilling said. “That is basically what we found in the early 2000s. They haven’t moved or expanded, which is one thing I was looking at.”
Although there are dipper populations throughout the West, the dipper population in the Black Hills is the farthest east the species is located, and it is also genetically different from other populations, Drilling said.
In 1996, the dippers were listed as a state threatened species.
The South Dakota Game, Fish, and Parks species status review, approved in April 2018, listed several requirements for the species to be removed from the threatened species list.
The first requirement of maintaining a self-sustaining population on Spearfish and Whitewood creeks has been met; however, the state wants a self-sustaining population in a third watershed.
“A single pair in Rapid Creek does not meet that criteria,” Drilling said.
Dippers were once widespread on French and Rapid creeks. The loss of dippers, save the lone pair, is likely due to the creation of Pactola Dam, which has caused erratic and lower stream flows. The loss of breeding birds on French Creek is likely due to pollution, sedimentation, and the construction of Stockade Lake Dam, according to the GF&P species status review report.
The report shows that dippers feed on aquatic insects and rely on clear, cold, fast moving streams. Any changes in water quality are a threat to the species. The population sees a 1% growth annually, but high bird mortality occurs during the winter, likely related to ice freezing over streams preventing them from foraging.
She also resurveyed nearly entire lengths of Spearfish and Whitewood creeks last year following a study that wrapped up in 2010.
In 2017, Drilling said, 27 adults were captured and banded. Ten juveniles were also banded after they left the nest.
Last year, 80 percent of the adults returned and two of the younger birds had been spotted.
“Almost all were back on their same territories and with their same mate,” Drilling said.
One female adult moved downstream about a half mile, and one juvenile moved a couple miles from its nesting area, she said. In all, Drilling found 25 active territories in the Black Hills.
She found that nesting boxes were very popular with the birds.
In the early 2000s boxes were placed around the streams, but have since fallen into disrepair. However, a man in Hanna built 60 replacement boxes which have all been placed.
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