Overview

The taxonomy here follows the eBird/Clements taxonomy and the AOS taxonomy. The western or northern taxa is always named first.

Little-to-no hybridization

Several species come into contact in Nebraska that possess little-to-no hybridization within this region. More research is needed to understand the dynamics of these species when and where they come into contact.

This section also includes species whose primary hybrid zones appear to be outside Nebraska.

Myiarchus flycatchers

Contopus pewees

Overview

The Western Wood-Pewee Contopus sordidulus and the Eastern Wood-Pewee Contopus virens are geographic replacements of each other across the North American continent, coming into contact from central Canada southwards across the central plains as far south as Nebraska. South of Nebraska, they are largely separated by untreed areas in the Great Plains.

No hybrids between these two species had ever been confirmed before the 2010s, when genomic research uncovered multiple hybrid individuals from the Nebraska contact zone.¹ Research seems to indicate that there has been some level of gene flow between populations, though the species themselves are remaining rather separate overall.

Identification

Western and Eastern wood-pewees are best distinguised by song. Western Wood-Pewees give a slightly mournful, burry “BEE-eer” in repetition.

Eastern Wood-Pewees give a starkly different, clear “Pee-wee-rheeEEE!”

Sayornis phoebes

Overview

There are three species of Sayornis that occur within North America - two of these breed in Nebraska, acting largely as latitudinal replacements of one another. In the west, Say’s Phoebe Sayornis sayae frequents farms, old buildings, rocky outcrops, and some other open areas. Eastern Phoebe Sayornis phoebe is found predominately in the east, but in the western regions of its range frequents arid canyons, bridges, and outcrops near water. Work in adjacent Kansas has shown that Eastern Phoebes appear to be displacing Say’s as afforestation occurs, with many sites formerly occupied by Say’s Phoebes now occupied by Eastern, and a noticeable uptick of Say’s x Black S. nigricans hybrids in the southwestern portion of the range.² The increased levels of hybridization between Eastern & Black Phoebes as compared to Eastern & Say’s Phoebe is unsurprising given that Say’s Phoebe represents the outgroup within this genus.³

Work in Nebraska should focus on the dynamics of these species with respect to modern and historical distributions, as well as focusing on the habitats these species utilize. As Nebraska continues to become afforested, especially along watercourses, we predict that we will continue to see a westwards shift of Eastern Phoebe, with the species potentially replacing Say’s Phoebe in many areas.²

Identification

Eastern Phoebes are overall grayish (with an occasional greenish tone to the gray), being white on the belly and variably dingy on the chest. There is no eye ring, birds may appear slightly crested, and when perched Eastern Phoebes often wag their tails. Eastern Phoebes are often found near water, frequently nesting in culverts, under bridges, and in shelters.

Say’s Phoebes are very similar in shape, but are overall browner-gray, sometimes darkest towards the head and cap, with a distinctive salmon belly. They are less tied to water than Eastern Phoebes, and are frequently found around farmsteads, especially in areas where there are sheds or farm equipment providing multiple perches. Away from human habitation, they are often found near rock faces or steep banks that provide habitat for perching and nesting.

Sialis bluebirds

Overview

Two sister species of bluebird, Mountain Sialis currucoides and Eastern S. sialis, come into contact in western Nebraska. These species hybridize occassionally hybridizing across the Great Plains.

Identification

Blue-gray Gnatcatcher Polioptila caerulea

Overview

The Blue-gray Gnatcatcher Polioptila caerulea is the only member of Polioptilidae found in the state of Nebraska. In the pine forests and cedar breaks of the western part of the state, western Blue-gray Gnatcatchers P. c. amoenissima (part of the P. c. obscura group) have been increasing in frequency, abundance, and regularity over the past several decades. These birds are primarily restricted to the far west of the state, such as in the Pine Ridge, but they have been expanding eastwards along the Niobrara and there there has been a single record of this taxon found in Custer County, central Nebraska, in cedar breaks as well by UNK researchers.⁴ Eastern Blue-gray Gnatcatchers P. c. caerulea have also been increasing in frequency in the state, but are found predominately in deciduous forests, especially in areas with some large trees (near edge and occassionally more in the forest).

Identification

Cistothorus Marsh-Wrens

Overview

We here deviate from established checklists in considering the Western Marsh-Wren as separate from the Eastern Marsh-Wren. These species are vocally distinct, show clear distributional differences, and apparently show limited evidence of interbreeding in the Nebraska contact zone.

Identification

White-breasted Nuthatch Sitta carolinensis

Overview

Sturnella meadowlarks

Overview

Identification

Warbling-Vireos

Overview

We here deviate from established checklists based on data from Canada indicating extremely high levels of reproductive isolation between Western swainsoni and Eastern gilvus.⁵

Identification

Localized hybrid zones

Tympanuchus grouse

Pheucticus grosbeaks

Overview

Identification

Passerina buntings

Overview

Identification

Icterus orioles

Overview

Identification

Extensive hybridization

Northern Flicker Colaptes auratus

Overview

Identification

Pipilo towhees

Overview

Identification

Other transition zones

Downy Woodpecker Dryobates pubescens

Hairy Woodpecker Leuconotopicus villosus

Horned Lark Eremophila alpestris

Northern House Wren Troglodytes aedon

Ovenbird Seiurus aurocapilla