- Minnesota Breeding Bird Distribution
- Breeding Habitat
- Population Abundance
- Literature Cited
Regular breeding resident and migrant; the Prothonotary Warbler was a rare species during the Minnesota Breeding Bird Atlas (MNBBA).
Primarily restricted to the southeastern United States with local populations extending north along major river valleys, including the Mississippi River. The Prothonotary Warbler is sparsely distributed throughout most of its breeding range; densities are highest along the lower Mississippi River valley in Louisiana and in coastal wetlands in Virginia and North Carolina (Figure 1).
Assigned a Continental Concern Score of 14/20 and designated a Yellow Watch List species by Partners in Flight; designated a Species in Greatest Conservation Need by the Minnesota Department of Natural Resources.
A medium- to long-distance migrant that winters in Central America and northern South America.
A bark and foliage gleaner that feeds primarily on insects.
Unique among eastern wood warblers as a secondary cavity nester, using former cavities excavated by Downy Woodpeckers, natural tree cavities, or nest boxes.
Roberts (1932) provided a detailed account of the first reports of this stunning floodplain-forest species in Minnesota. It was found on the Wisconsin side of the Mississippi River, east of the mouth of the Root River, in 1874 by Dr. Hvoslef of Lanesboro, Minnesota. Another 16 years passed before the first documentation of its presence on the Minnesota side of the river, in 1890, when a local birder in Houston County reported it was breeding near the town of La Crescent in “limited numbers” (Harrison 1890). A few years later, in 1898, a journal article detailed additional breeding records from islands along the Mississippi River in an area that stretched from the town of Red Wing south to Lake Pepin (Johnson 1898). These records led Roberts to conclude that the species first appeared in Minnesota sometime between 1870 and 1890.
The same year that Johnson published his account, 1898, Roberts and a colleague, Dr. L. O. Dart, traveled along the Mississippi River from Hastings to the Iowa border. The Prothonotary Warbler was common along the entire stretch of the river, “increasing in numbers as we went southward. It was confined strictly to the bottom-lands and almost entirely to the wooded and periodically flooded islands.” Although records of single birds gradually accumulated from other Minnesota localities, including Fillmore, Olmsted, Hennepin, and even Crow Wing Counties, the stretch of floodplain forest south of Hastings was considered the species’ primary breeding range.
There was one notable exception. In 1915, “a small colony” of Prothonotary Warblers was found in a floodplain channel along the Rum River, a tributary to the Mississippi River, in Isanti County, and was present for many years. How the birds found a locality so far from their primary breeding range was an enigma to Roberts: “Conditions there are ideal though limited in extent. The valleys of the St. Croix and Minnesota rivers, farther south, offer equally satisfactory and much more extensive nesting-grounds, but thus far they have been passed by.” At the time of his writing, Roberts (1932) had confirmed nesting reports from three counties: Goodhue, Houston, and Isanti.
In the following years, additional reports of the birds outside of their primary range were documented. In 1941 there was a report of nesting at another location along the Rum River, in Anoka (Breckenridge 1945), and during the summer of 1945 a well-established breeding population was documented along the St. Croix River, from Stillwater north to Taylors Falls (Hubert 1945). Other reports included documented nesting along the Mississippi River north of downtown Minneapolis in 1951 (Eastman and Eastman 1952) and observations of several males in Stearns County in 1961 (Russell and Hibbard 1964).
When Green and Janssen provided an updated account in 1975, they described the Prothonotary Warbler as a summer resident in southeastern Minnesota and along the Mississippi, Rum, and St. Croix Rivers in central Minnesota. Breeding had been confirmed in 8 counties: Anoka, Goodhue, Hennepin, Houston, Isanti, Ramsey, Wabasha, and Washington.
A few years later, Janssen (1987) described it as a regular summer resident as far north as central Chisago County and as far west as Scott County. There was even 1 nesting report farther up the Minnesota River valley in Brown County in 1984. Since 1970 nesting had been confirmed in 6 counties: Brown, Hennepin, Houston, Ramsey, Wabasha, and Washington. Hertzel and Janssen (1998) later eliminated the Washington County record and added 6 more counties to Janssen’s list: Anoka, Dakota, Nicollet, Scott, Sherburne, and Winona.
The Minnesota Biological Survey reported 56 breeding season locations for the Prothonotary Warbler during the course of their work in southern and central Minnesota (Minnesota Department of Natural Resources 2016). Every record was located along one of the three major river valleys: the Mississippi, St. Croix, and Minnesota. Their distribution map closely paralleled that of Janssen (1987).
During the MNBBA, observers reported 40 Prothonotary Warbler records in 28 of the surveyed atlas blocks and in 13 of the priority blocks. Breeding was confirmed in 9 blocks (Figures 2 and 3; Table 1). The birds were detected in 19 of Minnesota’s 87 counties (several blocks along the Minnesota River straddled 2 counties) and were confirmed breeding in 9 counties: Carver, Goodhue, Nicollet, Le Sueur, Rice, Scott, Sherburne, Wabasha, and Washington. Four counties were included because of blocks that straddled 2 counties (Nicollet/Le Sueur and Carver/Scott). Five of the counties were additions to the list published by Hertzel and Janssen (1998): Carver, Goodhue, Le Sueur, Rice, and Washington. In addition to the long-established distribution of summer residents along the lower Mississippi, St. Croix, and Minnesota Rivers, breeding evidence was gathered in Rice and Sherburne Counties, both from sites located in the floodplains of smaller rivers. Possible records in Lac qui Parle, Freeborn, Fillmore, and northern Hennepin Counties were all located outside of the floodplains of major rivers, but all blocks had some riparian habitat along small streams or rivers.
In the nearly 140 years since the Prothonotary Warbler first appeared in Minnesota, its breeding distribution has slowly expanded along the state’s major river valleys as well as along some smaller tributaries. Roberts (1932) considered it the first among several southern species to “settle in numbers in a region so far removed from its normal southern habitat.” Others included the Northern Cardinal, Red-bellied Woodpecker, Blue-gray Gnatcatcher, Tufted Titmouse, Blue-winged Warbler, and Louisiana Waterthrush. Today, four of the seven species now have breeding ranges that extend considerably beyond southeastern Minnesota (Northern Cardinal, Red-bellied Woodpecker, Blue-gray Gnatcatcher, and Blue-winged Warbler). The Prothonotary’s strong association with the floodplain forests of slow-moving, large rivers has probably limited its breeding opportunities elsewhere in the state.
Beyond the northward range extensions observed in the late 19th and early 20th centuries, there have been few changes to the species’ distribution in recent decades (Petit 1999).
*Note that the definition of confirmed nesting of a species is different for Breeding Bird Atlas projects, including the definition used by the Minnesota Breeding Bird Atlas, compared with a more restrictive definition used by the Minnesota Ornithologists’ Union. For details see the Data Methods Section.