RED-BREASTED MERGANSER – Birds of Nebraska

Mergus serrator

Status: Uncommon regular spring migrant east and central, rare west. Uncommon regular fall migrant statewide. Rare casual summer visitor central and east. Uncommon regular winter visitor west, south, east.

Documentation: Specimen: HMM 2492, Apr 1900 Funk WPA, Phelps Co.

Taxonomy: No subspecies are recognized (Gill et al 2022).

Spring: Jan 28, 29, 30 <<<>>> May 20, 21, 22

Early dates above are away from Keith Co and of non-wintering birds.

Later dates away from Keith Co are 24 May 2014 Dawes Co, 26 May 2020 Buffalo Co, and 2 Jun 2022 female type Lancaster Co.

It is a later migrant than the Common Merganser, typically arriving in mid-to late Mar. About one-third of spring records are for the last week of Mar, but the species may be seen regularly into mid-Apr. Most reports are from the east, although it occurs with some regularity at Lake Ogallala, Keith Co, and Lake Minatare, Scotts Bluff Co. It is rare in the Rainwater Basin; the first spring record there was of two in Clay Co 7 May 2011.

High counts: 300 at Lake Yankton, Cedar Co 29 Mar 2008, “hundreds” there 27 Mar 2011, 138 at Youngman Lake, Douglas Co 1 Apr 2023, 133 at Pawnee Lake, Lancaster Co 24 Mar 2019, and 103 at Lake Ogallala on 18 Apr 1998.

Summer: There are eight records (Jun through mid-Oct): a female was at Lake Ogallala, Keith Co 7-22 Aug 2000, another or the same summered there in 2001, a female/immature, likely injured, was at Offutt Base Lake, Sarpy Co 9 Jun-17 Jul and 14 Aug 2023, three were at Fontenelle Forest, Sarpy Co 14 Jun 2024, one was at Harlan County Reservoir, Harlan Co 20 Jun 2004, three, including a “non-breeding” male, were about 10 miles west of Norden Bridge on the Niobrara River 3 Jul 2013, singles were at Sutherland Reservoir, Lincoln Co 9 Jul 2024, and an injured female was at Lake McConaughy, Keith Co 26 Jul-27 Sep 2024.

Fall: Oct 26, 26, 27 <<<>>> Dec 19, 20, 21

An earlier date was of two at Lake Minatare, Scotts Bluff Co 23 Oct 2023.

The fall migration is more leisurely than in spring, without large concentrations or a significant peak. This species is less cold-tolerant than the other merganser species, and generally leaves before Dec. There are far fewer fall reports than spring reports, but a greater proportion are from the west. A few records from North Platte NWR, Scotts Bluff Co suggest early Oct arrivals there might be molt migrants along with the larger numbers of Common Mergansers; seven were at Lake Alice 10 Oct 2020 and one at Lake Minatare 19 Oct 2020. These early dates in Scotts Bluff Co may also be of molt migrants: 22 Sep 1978, 23 Sep 1981, 3 Oct 1984, and 11 Oct 1977.

There are early dates away from Lake Ogallala of two on 16 Sep 2017 at Sutherland Reservoir, Lincoln Co, 12 on 20 Sep 2012 in Cherry Co, 12 Oct 2003 Lancaster Co, and 23 Oct 2010 Lancaster Co, and a later date 29 Dec 2015 Branched Oak Lake, Lancaster Co.

High counts: 120 at Lake McConaughy, Keith Co 10 Nov 2024, 58 in Lancaster Co 8 Nov 2009, 47 at Summit Reservoir SRA, Burt Co 9 Nov 1997, and 47 at Pawnee Lake, Lancaster Co 12 Nov 2019.

A total of 137 were reported in fall 1996, most at eastern reservoirs (Grzybowski 1997).

Winter: There are several reports of overwintering, mostly of small numbers mixed with large wintering flocks of Common Mergansers. Most such records are on major Platte River Valley reservoirs, Harlan County Reservoir, and below Gavin’s Point Dam, Knox and Cedar Cos. At Lake McConaughy, Keith Co, best counts were 44 on 2 Jan 2024 and 27 that wintered 1999-2000, and 38 on the CBC there 2 Jan 2021. At Harlan County Reservoir, 1-2 wintered beginning 1999-2000. The spillway of Gavin’s Point Dam, Cedar Co hosted nine in Jan 2007, with fewer most other years.

Elsewhere there are about 60 records from 22 Dec-27 Jan, none in the north; best count among these is only six, at Johnson Lake, Gosper Co 7 Jan 2024.

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