Red-breasted Mergansers breed in the boreal forest on fresh, brackish, and saltwater wetlands, typically close to the coast. During migration and on the wintering grounds, they use oceans, lakes, and rivers. They tend to use saltwater, including estuaries and bays, more often than Common Merganser.Back to top
Red-breasted Mergansers primarily eat small fish (4–6 inches long), but also crustaceans, insects, and tadpoles on occasion. In the summer, they forage in shallow waters with submerged vegetation and plentiful fish. In the winter they forage in shallow marine waters. Red-breasted Mergansers dive underwater or swim with their eyes just below the surface as if they were snorkeling to look for prey. Lines of mergansers also herd minnows into restricted areas, allowing easy capture. The serrations on the bill help them keep hold of slippery fish.Back to top
Red-breasted Mergansers nest along forested riverbanks, marsh edges, lakeshores, coastal islands, and sandy shores with vegetation. They are never far from water. Female Red-breasted Mergansers select a spot on the ground under dense cover from low tree branches, fallen logs, or boulders. They nest alone or in colonies often with gulls and terns.
The female creates a depression on the ground that she covers with dead grasses, forming a shallow bowl. She plucks down feathers from her breast to help insulate the nest.
|Clutch Size:||3-24 eggs|
|Number of Broods:||1 brood|
|Egg Length:||2.3-2.7 in (5.8-6.8 cm)|
|Egg Width:||1.7-1.9 in (4.3-4.7 cm)|
|Incubation Period:||28-35 days|
|Condition at Hatching:|
Covered with down, eyes open. Leaves the nest within 24 hours.
Red-breasted Mergansers are among the fastest flying ducks, clocking speeds of up to 81 miles per hour. To get airborne though, they need a running start. Their legs are positioned near their rear making it difficult to walk on land, but are an asset when diving. Red-breasted Mergansers do not defend territories and are social birds year-round. Courting males salute a female with head held high and then curtsy to the female by tipping up and putting their rear in the air with bill held high. In response to the male's gesture, the female often jabs him with her bill. Courting males also shake their head side to side to get the attention of a female. Once the female accepts the male she stretches her neck out while holding her bill down and then lowers her neck again in a bobbing motion. They form a monogamous bond for the breeding season, but the male takes off at the beginning of incubation, leaving the female to tend the young alone. Males head to secluded waters to molt their feathers before migrating south while females tend to molt near the breeding site.Back to top
Red-breasted Mergansers are common and their populations were stable between 1966 and 2015, according to the best estimates of the North American Breeding Bird Survey (although the species’ northern breeding grounds are partially outside of the survey’s coverage area). Aerial surveys on the breeding grounds estimated the total merganser population (Red-breasted and Common) at half a million in 2017, 15% higher than the long-term average from 1990–2016. Partners in Flight estimates the global breeding population of Red-breasted Mergansers at 370,000. The species rates an 11 out of 20 on the Continental Concern Score, which means it is not on the Partners in Flight Watch List and is a species of low conservation concern.Back to top
Craik, Shawn, John Pearce and Rodger D. Titman. 2015. Red-breasted Merganser (Mergus serrator), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.
Dunne, P. (2006). Pete Dunne's essential field guide companion. Houghton Mifflin Harcourt, New York, USA.
Lutmerding, J. A. and A. S. Love (2017). Longevity records of North American birds. Version 2017.1. Patuxent Wildlife Research Center, Bird Banding Laboratory, Laurel, MD, USA.
Partners in Flight (2017). Avian Conservation Assessment Database. 2017.
Sauer, J. R., D. K. Niven, J. E. Hines, D. J. Ziolkowski, Jr., K. L. Pardieck, J. E. Fallon, and W. A. Link (2017). The North American Breeding Bird Survey, Results and Analysis 1966–2015. Version 2.07.2017. USGS Patuxent Wildlife Research Center, Laurel, MD, USA.
Sibley, D. A. (2014). The Sibley guide to birds, second edition. Alfred A. Knopf, New York, USA.
U.S. Fish and Wildlife Service. (2017). Waterfowl Population Status, 2017. U.S. Department of Interior, Washington, D.C. USA.