SWAINSON’S THRUSH

Catharus ustulatus swainsoni, C. u. almae

Status:  Common regular spring migrant statewide. Fairly common fall migrant statewide. Rare casual breeder Pine Ridge. Accidental in winter.

Documentation:  Specimens: almae: UNSM ZM6673, 23 May 1900 Monroe Canyon, Sioux Co; swainsoni: UNSM 11684, 8 May 1917 Lancaster Co.

Taxonomy:  There are six subspecies recognized, often separated into groups, “Russet-backed” and “Olive-backed”. Western subspecies ustulatus, phillipsi, and oedicus comprise the Russet-backed Group, and incanus, swainsoni and appalachiensis comprise the Olive-backed Group (Mack and Yong 2000). Among the latter group, incanus breeds in central and eastern Alaska and western Canada, swainsoni breeds in central and eastern Canada and northern USA, and appalachiensis in the eastern USA (Mack and Yong 2000).

Virtually all of Nebraska’s migrant Swainson’s Thrushes are likely to be swainsoni, which is the most widespread of the Olive-backed Group (Phillips 1991). However, we retain subspecies almae, the Rocky Mountains breeder (Obersolser 1898), based on the recommendation by Oberholser that birds reported in summer on the Pine Ridge (Cary 1902) be assigned to almae (Bruner et al 1904). Mack and Yong (2000) and Gill and Donsker (2017) merged almae into swainsoni. The Alaskan subspecies incanus may occur in Nebraska; it has been reported in northeast Illinois (AOU 1957).

It is possible that individuals of the Russet-backed Group of Pacific coast subspecies ustulatus may occur in Nebraska; it has been collected as far east as southeast Iowa (AOU 1957). There are several recent reports with photographs from extreme northeastern Colorado of Swainson’s Thrushes referable to the Russet-backed Group; essentially these are birds that have uniformly more rusty than buffy upperparts and buffy flanks (eBird.org, accessed October 2017).

Spring: Apr 16,17,18 <<<>>> Jun 6,7,7 (east, south), Apr 23,24,24 <<<>>> Jun 17,18,19 (north, west)

Most pass through in May. Departure in the south and east is complete by early Jun, but not until mid-Jun in the north and west. There are later reports in the south and east 10 Jun 1989 Lincoln Co, 13 Jun 1983 Adams Co, 17 Jun 1981 Douglas Co, 19 Jun 1939 Lincoln Co (Tout 1947), and 19 Jun 2008 Hamilton Co.

The earliest specimen date for Kansas is 24 Apr (Thompson et al 2011); Tallman et al (2002) noted that they are “not confident” of reports earlier than the last week of Apr. Most such reports are probably of Hermit Thrushes.

  • High counts:  499 in Sarpy Co 11 May 1996 (including 272 at Fontenelle Forest, Sarpy Co), 150 in Kimball Co 28 May 2011, and 148 in the Panhandle 15 May 2002.

A late fallout yielded 37 in the Panhandle 4 Jun 2005.

Summer: The only documented breeding record is of a nest in West Ash Creek Canyon, Dawes Co 12 Aug 1973 (Rosche 1974).  This nest was located in deciduous riparian growth adjacent to ponderosa pines, and contained two eggs and an “advanced fledging” nestling on 12 Aug, but the nestling was gone and the two remaining eggs were cold on 15 Aug. The eggs are now specimen UNSM ZM17073.  As stated by Rosche (1974), there was no prior evidence for breeding, although it had been assumed based on Hudson’s collecting a female with enlarged ovaries 17 Jun 1938 in Squaw Canyon, Sioux Co (Hudson 1939).

Mollhoff (2001) found “several territorial males” in West Ash Canyon, Dawes Co, May, Jun, and Jul 1999, but no breeding evidence was found; no birds were there in 2000. In 2004 at least five singing males and two pairs were present 5 Jun, and a complete but empty nest was being guarded by a singing bird 8 Jun (Mollhoff 2005). In 2005 in the same area, singing birds were again present mid-Jun, but no nest was found (Mollhoff 2005). There are Jun and Jul reports from Sioux Co 1976-79, although no evidence of breeding was reported, as well as late Jun (but not Jul) reports for the years 1967, 1972, 1974, and 1986, and for Jul (but not Jun) in 1975. Cary (1902) and Bruner et al (1904) considered breeding to be probable in West Warbonnet Canyon based on several summer observations.

Migrants are not uncommon, however, as late as the second week of Jun in the northwest (Rosche 1982); Jun reports may also be the basis for purported nesting in the central Niobrara Valley (Bates 1900; Youngworth 1955). That these reports are likely non-breeding birds is indicated by summer reports from unlikely breeding locations 18 Jun and 27 Jul 1981 Garden Co, 22 Jun 1995 Garden Co, 23 Jun 1969 McPherson Co, 30 Jun 1967 Greeley Co, and 1-10 Jul 1989 Lincoln Co. A remarkable report was of a singing bird near Orleans, Harlan Co 6 Jul 2000 by observers familiar with the species from residence in the state of Washington; another was in the same place 23 Jun 2002.

Fall:  Aug 24 (Tout 1947),25 (Ludlow 1935),25 <<<>>> Oct 22,23,26

Arrival is in late Aug statewide, although there are earlier reports 12 Aug 1971 and 12 Aug 1973 from Scotts Bluff Co and 12 Aug 2015 Douglas Co. There are later reports 30 Oct 1977 Douglas Co, and 30 Oct 2001, a hatching-year bird banded at Bellevue, Sarpy Co. A specimen collected at Glenvil, Clay Co 3 Nov 1918 and identified as this species is no longer extant; it was likely a Hermit Thrush (Jorgensen 2012). We consider reports after Oct to be of Hermit Thrushes. See Comments.

  • High counts: 24 in Lincoln, Lancaster Co 13 Sep 2012, 13 at Fontenelle Forest 15 Sep 2012, and 10 near Chadron, Dawes Co 12 Sep 2014.

Winter: There is a single winter report, with “excellent details”, for 27 Jan-10 Feb 1980 in Washington Co (Williams 1980, Cortelyou 1980).

Comments: Far fewer Swainson’s Thrushes occur in fall than in spring. Ruegg and Smith (2002), using banding and genetic studies, proposed that the breeding range of “continental” Swainson’s Thrush (subspecies swainsoni ) shrank to a southeastern US refugium during the last glacial maximum. As the ice sheet receded, the breeding range expanded north and west. However, during fall migration, the thrushes continued to migrate southeastward to their ancestral breeding refugium, then south across the Gulf itself, thus setting up an elliptical migration pattern that largely avoids the central USA in fall.  Western “coastal” Swainson’s Thrushes (subspecies ustulatus and incanus), less disrupted by ice sheets, continued to migrate along the Pacific Coast on their ancestral pathway.

Abbreviations

UNSM: University of Nebraska State Museum

Acknowledgement

Photograph (top) of a Swainson’s Thrush at Fontenelle Forest, Sarpy Co 18 Sep 2010 by Phil Swanson.

Literature Cited

American Ornithologists’ Union [AOU]. 1957. The AOU Check-list of North American birds, 5th ed.  Port City Press, Baltimore, Maryland, USA.

Bates, J.M. 1900. Additional notes and observations on the birds of northern Nebraska. Proceedings of Nebraska Ornithologists’ Union 1: 15-18.

Bruner, L., R.H. Wolcott, and M.H. Swenk. 1904. A preliminary review of the birds of Nebraska, with synopses. Klopp and Bartlett, Omaha, Nebraska, USA.

Cary, M. 1902. Some general remarks on the distribution of life in northwest Nebraska. Proceedings of Nebraska Ornithologists’ Union 3: 63-75.

Cortelyou, R.G. 1980. 1980 (Fifty-fifth) Spring Occurrence Report. NBR 48: 70-87.

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

Hudson, G.E. 1939. Some ornithological results of a six-week’s collecting trip along the boundaries of  Nebraska. NBR 7: 4-7.

Jorgensen, J.G. 2012.  Birds of the Rainwater Basin, Nebraska.  Nebraska Game and Parks Commission, Lincoln, Nebraska, USA.

Ludlow, C.S. 1935. A quarter-century of bird migration records at Red Cloud, Nebraska. NBR 3: 3-25.

Mack, D.E. and W. Yong. 2000. Swainson’s Thrush (Catharus ustulatus), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.540

Mollhoff, W.J. 2001. 1999-2000 Nebraska nesting report. NBR 69: 92-101.

Mollhoff, W.J. 2005. The 2003-2004 Nebraska nest report. NBR 73: 15-19.

Oberholser, H.C. 1898. Description of a new North American thrush. Auk 15: 303-306.

Phillips, A.R. 1991. The known birds of North and Middle America. Part 2.  Published by the author, Denver Colorado, USA.

Rosche, R.C. 1974. A Nebraska Swainson’s Thrush nest. NBR 42: 17.

Rosche, R.C. 1982. Birds of northwestern Nebraska and southwestern South Dakota, an annotated checklist. Cottonwood Press, Crawford, Nebraska, USA.

Ruegg, K.C., and T.B. Smith. 2002. Not as the crow flies: A historical explanation for circuitous migration in Swainson’s thrush (Catharus ustulatus). The Proceedings of the Royal Society of London B 269: 1375–1381.

Tallman, D.A., Swanson, D.L., and J.S. Palmer. 2002. Birds of South Dakota. Midstates/Quality Quick Print, Aberdeen, South Dakota, USA.

Thompson, M.C., C.A. Ely, B. Gress, C. Otte, S.T. Patti, D. Seibel, and E.A. Young. 2011. Birds of Kansas.  University Press of Kansas, Lawrence, Kansas, USA.

Tout, W. 1947. Lincoln County birds. Published by the author, North Platte, Nebraska, USA.Williams, F. 1980. Southern Great Plains Region. American Birds 34: 286-288.

Youngworth, W. 1955. Some birds of the Quicourt Valley. NBR 23: 29-34.

Recommended Citation

Silcock, W.R., and J.G. Jorgensen.  2018.  Swainson’s Thrush (Catharus ustulatus), Version 1.0. In Birds of Nebraska — Online. www.BirdsofNebraska.org


Birds of Nebraska – Online