Weminuche Audubon meeting on the nesting habits of the American dipper

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    By Jean Zirnhelt
    and Stephen Munroe
    Weminuche Audubon Society

    The regular monthly meeting of the Weminuche Audubon Society will be held via Zoom on Wednesday, Feb. 17, at 6:30 p.m. The focus of our meeting will be a bird that “flies” underwater, the American dipper. 

    Our presenter for the evening will be Stephen Munroe, chapter member from Durango, who leads a study of the nesting success of these amazing birds on the Animas River. Monroe is a hydro-ecologist who lives in Durango and has been studying springs, streams and rivers in the Four Corners region for more than 25 years.

    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 birds’ 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.

    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 during annual Christmas and spring bird counts; however, no baseline data existed. Additionally, the Animas River has been negatively impacted by heavy metal contamination due to historic mining activities for over a century.

    For American dippers to thrive, they need availability of suitable nesting habitat and food (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 1 to 10 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.

    This year, with Munroe’s guidance, we hope to be able to extend these studies to the San Juan River and tributaries in the Pagosa area. Attend the meeting to find out the protocols of the survey and how to become involved. For the Zoom link to the meeting, view the events tab on our website, www.weminucheaudubon.org.