COMMON MERGANSER

Mergus merganser americanus

Status:  Common, locally abundant, regular spring and fall migrant statewide. Rare casual summer visitor statewide. Rare casual breeder west and central. Fairly common, locally abundant, regular winter visitor statewide.

Documentation: Specimen: WSC 522, fall 1975 Madison Co.

Taxonomy:  Some authors, for example Johnsgard (1975) and Gill and Donsker (2017), recognize three subspecies, two in Eurasia, and one in North America, M. m. americanus.  Nebraska birds are americanus.

Changes since 2000:  Reports continue to clarify the presence of apparent molt migrants at a few locations; this phenomenon was first noticed in the 1970s.

Spring:  winter <<<>>> Jun 3, 4, 4

It is difficult to separate winter visitors from early migrants, although there is a discernible increase in numbers in late Feb, peaking in mid-Mar. Few linger into May. A later report was of one in Cuming Co 8 Jun 2018. As many as 24 were at Lake Ogallala 19-31 May 1997.

Later reports are from Lake Ogallala, Keith Co: a male and two females 9 Jun 2007, 3-5 on 7-12 Jun 2003, three on 13 Jun 2011, 6-7 on 13 Jun-8 Jul 2016, up to six from 14 Jun-15 Jul 2017, and males only 17 Jun 2008. As many as 24 were at Lake Ogallala 19-31 May 1997. These early and mid-Jun dates are probably too early to be of molt migrants (see Fall); they are more likely immature non-breeders.

  • High counts: 200,000 at Harlan Co Reservoir, Harlan Co 14 Mar 2003, 4000-5000 at Branched Oak Lake, Lancaster Co 14 Mar 2010, 4000 at Lake McConaughy 24 Mar 1989 (Rosche 1994), and 3400 at Harlan Co Reservoir 3 Mar 2006.

SummerThere are four reports of breeding, only two with published evidence. The first was at Victoria Springs SRA, Custer Co in 1968; a male and female were present during the spring, and on 27 Jul the female was seen by several observers with six ducklings (Bennett 1969). The second documented record was of two broods in the Niobrara Valley Preserve at the Norden Bridge, Brown and Keya Paha Cos 2 Jul 2007; one brood had four half-grown untended young, the other eight downy young with an adult female (Mollhoff 2008). This location has regularly hosted Common Mergansers during the breeding season in subsequent years; 2-3 females were there each year 13-22 Jun 2012-2015. The six in the same location 22 Sep 2009 may have been a locally-raised brood. An adult female with a brood was photographed here on 7 May 2017 and six nearly-fledged young were photographed at a nearby location on 7 Jul 2017. Again, in 2018, a female with three ¾ grown young were present 14 Jun.

Two other reports of possible breeding are of a “recent nesting record for the North Platte Valley to the west of Lake McConaughy” (Rosche 1994), and a pair at Lake McConaughy 31 May 1996 that was “suspected as nesting” (Grzybowski 1996). Neither report was accompanied by details, however.

There are scattered reports statewide during the breeding season; some may be molt migrants (see Fall), but most are probably non-breeding immatures. Lake Ogallala attracts this species in summer; earlier, Jun-Jul, most are likely non-breeding immatures, but later, beginning in Jul, molt migrants add to the numbers there (see Fall). Reports from Lake Ogallala include a male and two females 9 Jun 2007, 3-5 on 7-12 Jun 2003, three on 13 Jun 2011, 6-7 on 13 Jun-8 Jul 2016, up to six from 14 Jun-15 Jul 2017, males only 17 Jun 2008, and six on 24 Jun 2018.

Away from Lake Ogallala there are a few reports, including five reports from Lancaster Co, a male 1 Jun-14 Jul 2002, 14 Jun 1985, 18 Jun-4 Jul 2000, 1 Aug 1999, and 11 Aug 2002, and five from Lincoln Co, 26 Jun 1991, 10 Jul 2003 female or immature, 19 Jul 1997, 1 Aug 1991 (Williams 1987) and a female/immature 25 Aug 2015. Elsewhere, a single bird was in Dakota Co 22 Jun 2009, and one was in Garden Co 17 Jul 1978. Single males are less common; reports are from Saunders Co 11 Jun 2017, Harlan Co Reservoir 14 Jun 2017, Washington Co 21 Jun 2014, and Smith Lake WMA, Sheridan Co 1 Jul 2017.

Fall:  Oct 4, 5, 7 <<<>>> winter

Migration begins in late Sep and early Oct, and numbers peak in Dec. Major Central Nebraska reservoirs, Lake McConaughy, Sutherland Reservoir, and Harlan Co Reservoir, are important staging areas for this species. Earlier dates from sites where molt migrants do not usually occur are: 21 Aug 1999 Oliver Reservoir, Kimball Co, three on 31 Aug 2010 Sutherland Reservoir, 4 Sep 1973 McPherson Co, 7 Sep 2016 Gavin’s Point Dam, Cedar Co, 16 Sep 2017 Sutherland Reservoir, Lincoln Co, 17 Sep 2016 Calamus Reservoir, Loup Co, 18 Sep 1971 Douglas-Sarpy Cos, 26 Sep 1986 Pierce Co, 26 Sep 2010 Hitchcock Co, and 30 Sep 1992 Lincoln Co.

In recent years, it has been recognized (Silcock 1995) that molt migrants use two or three Nebraska locations, notably Lake Alice in the North Platte NWR, Scotts Bluff Co, Lake Ogallala, and possibly Harlan Co Reservoir. Few yearling and mature males remain on breeding grounds after mid-Jul (Palmer 1976); Nebraska molt migrants likely follow the Platte River Valleys from breeding locations in the mountains of Wyoming and western Colorado.

Arrival at Lake Alice has been in mid-Jul most years since 1973, and as early as 25 Jun in 1997. Around 100-200 birds use the lake (Silcock 1995). A second location is Lake Ogallala, where up to 25 have appeared in recent years (see Summer). A possible third location is Harlan Co Reservoir, where there are seven reports, albeit of only 1-2 birds, 4 Jun-25 Jul in the years 1998-2009.

  • High counts:  48,000 at Harlan Co Reservoir 14 Dec 1997, 40,000 at Lake McConaughy 23 Dec 1994, and 36,119 there 21 Dec 2003.

WinterWintering birds may occur on open water anywhere in the state, but largest numbers are at major reservoirs where open water remains through the winter. High winter counts are 15,000 at Sutherland Reservoir 11 Feb 1994 and 12,000 at Lake McConaughy 15 Jan 1998.

Abbreviations

NWR: National Wildlife Refuge
SRA: State Recreation Area
WMA: Waterfowl Management Area (State)
WSC: Wayne State College

Literature Cited

Bennett, E.V. 1969. 1968 Nebraska nesting survey. NBR 37: 39-46.

Gill, F., and D. Donsker (Eds). 2017. IOC World Bird List (v 7.3), accessed 30 January 2018.

Grzybowski, J.A. 1996. Southern Great Plains Region. Field Notes 50: 296-300.

Johnsgard, P.A. 1975. Waterfowl of North America. Don Mills, Ontario: Fitzhenry & Whiteside.

Mollhoff, W.J. 2008. The 2007 Nebraska nest report. NBR 76: 155-165.

Palmer, R.S., ed. 1976. Handbook of North American birds. Vol. 2. Waterfowl (Parts 1 and 2). New Haven, CT, and London: Yale University Press.

Rosche, R.C. 1994. Birds of the Lake McConaughy area and the North Platte River valley, Nebraska.  Published by the author, Chadron, NE.

Silcock, W.R. 1995. Summer Field Report, June-July 1995. NBR 63: 70-82.

Williams, F. 1987. Southern Great Plains Region. American Birds 41: 297-300.

Recommended Citation:

Silcock, W.R., and J.G. Jorgensen.  2017.  Common Merganser (Mergus merganser), Version 1.0. In Birds of Nebraska — Online. www.BirdsofNebraska.org


Birds of Nebraska – Online