2021 Survey Makes the News
The August eNewsletter of Nestwatch, a project of the Cornell Lab of Ornithology, features an article on the American Dipper Project. You can read the article,Troubled Waters: A Homegrown Effort To Track American Dipper Success, which features photos by Chris Roebuck, here. https://nestwatch.org/connect/blog/
American Dipper Project
By Stephen Monroe and Shelley Silbert
The American Dipper Project began in 2016, due to the concerns of a group of birdwatchers in Durango about the potential impacts of the 2015 Gold King Mine spill in the Animas River on the American Dipper population. The project’s objective is to study the breeding success of American Dippers (Cinclus mexicanus) on the Animas River and other streams in southwestern Colorado. Each year from 2016 through 2020, citizen science volunteers have surveyed Dippers learning about nesting behavior and success, nest site fidelity, and the bird’s unique personalities. In June 2018, a catastrophic wildfire burned portions of the Animas watershed, and subsequent flooding introduced large volumes of sediment to the river, adding another negative impact to American Dipper’s habitat and food sources.
Surveys to date have included sites in disturbed reaches of the Animas River as well as tributary streams that have not been affected by mining or by the 416 Fire. In 2021, we plan to expand the project to the upper San Juan River near Pagosa Springs. Data collected by this project are entered into the Cornell Lab’s NestWatch database (http://nestwatch.org) following each field season and will be included in a report to be completed in the Fall of 2021.
It is noteworthy that no Dipper nesting study had been completed on the Animas River prior to the Gold King Mine spill in August 2015. American Dippers have been documented on the river in Durango during annual Christmas and Spring bird counts, however no baseline data existed for the species. Additionally, the Animas River has been negatively impacted by heavy metal contamination due to historic mining activities for over a century.
The first year of the project consisted of launching a monitoring effort to identify appropriate and accessible reaches for surveys along the Animas River from Silverton south to Durango. We also selected reaches from reference rivers not subject to long-term mining activities. Volunteers identified occupied breeding territories, found and monitored nests, and observed timing of nestling and fledgling activity.
Dipper Nests and Food
For American Dippers to thrive, they need availability of suitable nesting habitat and food. Their diet consists of aquatic macroinvertebrates, like larvae of caddis flies, mayflies, and stoneflies, as well as small fish, fish eggs, and worms. In their natural habitat, Dippers build nests of moss, grass, algae or twigs. Preferred nest sites are close to water, safe from predators, and often on cliffs from one to ten meters above a flowing river. Dippers also build nests on bridges and other human-made structures. We have observed Dippers nesting from mid-March to mid-July, depending primarily on elevation.
Threats to the American Dipper
The following threats put American Dippers at risk in southwest Colorado:
Mining. Mining mobilizes heavy metals, and of particular risk to Dippers are lead, copper, zinc, selenium, and cadmium. High concentrations of these metals can limit reproductive success and cause death. The US Environmental Protection Agency recently released an Aquatic Baseline Risk Assessment for the Bonita Peak Mining District
SuperFund Site1 in the Animas River headwaters, clearly pointing out the high concentrations of metals present in the river pose a significant health threat to the Dipper population.
Climate change. In recent years the size and severity of wildfires in the western United States has increased mostly due rising temperatures resulting from climate change. The devastating effects of wildfire and the resultant runoff creates heavy sediment loads that can negatively impact Dippers’ food supply by limiting macroinvertebrate populations. Surveys of macroinvertebrates in the Animas River by Mountain Studies Institute before and after the 416 Fire showed decreased numbers in the species of insects Dippers rely on for food.2 As time has passed the macroinvertebrate population has begun to recover, but by 2020 it was not back to pre-fire levels. Colorado Parks and Wildlife reported approximately 80% of the fish in the Animas River were killed due to high levels of ash and debris in the river after the 416 Fire.3 When streamside vegetation burns, Dippers lose important streamside habitat, resulting in both the loss of shade that protects them from the sun and the loss of shelter that protects them from predators. Variability in precipitation, temperature, and the timing of snowmelt, can shift when macroinvertebrates hatch, altering food supply during critical nesting periods.4 Extended periods of drought can result in extremely low flows or sometimes complete drying up of perennial streams. Temperature rises in late spring and early summer due to climate change can coincide with the nesting season. Dippers are altitudinal migrants and typically spend winters at lower elevations. They do not tolerate high air temperatures, and when temperatures rise above 91.4° F, Dippers can’t prevent their body temperature from rising to dangerous levels, which can lead to nest failure and death.5
Plastics. There’s been increasing recognition of the presence of microplastics in the environment. In 2020 a study in national parks and wilderness in the western U.S. found that microfibers from clothing and carpeting made up most of the synthetic materials found in air samples from atmospheric deposition.6 A report also published in 2020 studied the European Dipper on upland rivers in South Wales and discovered that they consume high levels of microplastics that have moved their way up through the food chain.7 Most prevalent in fecal matter and regurgitate samples from Dippers were fibers of polyester and polymer mixtures. Studies of microplastics in American Dippers have not yet been done.
Plans for 2021
We are welcoming volunteer birders to help continue the American Dipper Project, monitoring nesting success on the Animas River and its tributaries, and in 2021, expanding the project to the upper San Juan River near Pagosa Springs. Surveys will be conducted beginning in March 2021 and continuing into the summer months of July or August when Dipper nesting season ends in Colorado. During field surveys, we will look for signs of courtship and nesting activity including copulation, nest building, incubation, feeding of nestlings, and presence of fledglings.
Volunteers may sign up to monitor dipper nesting activity along the rivers and reaches of their choice. We encourage volunteers to form teams for each nest site to share the workload. We seek to recruit volunteers to serve as Team Leaders for one or more nest sites. A Team Leader will organize the schedule of visits across the season and amongst their team of volunteers.
The general schedule for field visits will consist of one visit per active nest per week beginning in mid-March at lower elevations, or as late as mid- to late May for nests at higher elevations. This frequency of site visits should be maintained throughout the duration of the nesting cycle, increasing to two or three visits each week as nestlings mature and approach fledging. Observation of fledglings is essential for being able to determine nest success.
Birding experience is not required but helpful. Access to binoculars and GPS is useful.
Following the field season all data are entered to the NestWatch database. This is a big job, and we are also seeking volunteers to assist with this.
We are grateful for the support provided to The American Dipper Project by Audubon’s Western Water Network.
For additional information about the American Dipper Project and to be included in the volunteer participant list contact: Stephen Monroe at sm3662@gmail.com
References
1 US Environmental Protection Agency. 2019. Aquatic Baseline Risk Assessment for the Bonita Peak Mining District SuperFund Site, San Juan County, Colorado. Prepared by: TechLaw, Inc., ESAT Region 8, 1 Denver Federal Center Bldg. 25, PO Box 25227, Denver, CO 80225. Prepared for: US Environmental Protection Agency, Region 8, 1595 Wynkoop Street, Denver, CO 80202. DCN: 03072-6-06-R012-RA-0590
2 Mountain Studies Institute. 2021. The 416 Fire: Post-fire Impacts and Recovery of Watersheds & Forests. Available at: https://storymaps.arcgis.com/stories/ba65b6213d774e5ab4d57635fdb54061
3 Colorado Parks and Wildlife. 2020. Animas River, Durango: Fish Survey and Management Information. Available at: https://cpw.state.co.us/thingstodo/Fishery Survey Summaries/AnimasRiverDurango.pdf
4 Nilsson, A.L.K., E. Knudsen, K. Jerstad, O.W. Røstad, B. Walseng, T. Slagsvold and N.C. Stenseth. 2011. Climate effects on population fluctuations of the white-throated dipper Cinclus Cinclus. Journal of Animal Ecology, Vol. 80, No. 1, pp. 235-243.
5 Murrish, D. E. 1970. Responses to temperature in the dipper, Cinclus mexicanus. Comparative Biochemistry and Physiology. Vol. 34, pp. 859-869.
6 Brahney, J., M. Hallerud, E. Heim, M. Hahnenberger, and S. Sukumaran. 2020. Plastic rain in protected areas of the United States. Science. Vol. 368, Issue 6496, pp. 1257-1260.
7 D’Souza, J.M., F.M. Windsor, D. Santillo, and S.J. Ormerod. 2020. Food web transfer of plastics to an apex riverine predator. Global Change Biology. 2020;00:1–12.
Sidebar:
In Spring of 2020, we discovered a nesting pair of Dippers under a highway bridge over Hermosa Creek north of Durango. Hermosa Creek is a tributary of the Animas River and drains the watershed burned by the 416 Fire in 2018, and presence of nesting Dippers was an encouraging sign of watershed recovery. We learned the Colorado Department of Transportation (CDOT) was planning a maintenance project on the bridge during the nesting period. We informed CDOT about the nesting Dippers and consequently CDOT postponed the project. The American Dipper is protected by the federal Migratory Bird Treaty Act, which prohibits disturbance of active nests. In early June that year, we observed two fledglings dipping and dancing on top of the nest, two nestlings watching from inside, and both parents singing on a nearby beach. A day later, all four fledglings had left the nest and headed upstream. The bridge construction project was delayed, but CDOT completed the project later in June.
Migratory Bird Treaty Act: The American Dipper is protected by the federal Migratory Bird Treaty Act, which has been one of the most effective American laws to protect birds and prohibits disturbance of active nests. In January 2021, the Interior Department of the Trump Administration finalized a new version of the MBTA, which stripped away some of its key protections. On the first day of the Biden Administration, an Executive Order called for a review of the Trump Administration’s rule gutting the Migratory Bird Treaty Act.
On February 4, 2021, the Trump administration rule was delayed by the Biden administration, and will be reopened for public comment.
Take action through Audubon: https://act.audubon.org/a/reinstate-mbta