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Montana Field Guide

Montana Field Guides

Blue-gray Gnatcatcher - Polioptila caerulea

Species of Concern
Native Species

Global Rank: G5
State Rank: S3B

Agency Status

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Copyright by Borror Laboratory of Bioacoustics, Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, OH, all rights reserved.
General Description
The Blue-gray Gnatcatcher is a very small (10.0 to 11.5 cm in length, 5 to 7 grams in weight), bluish-gray, long-tailed songbird; tail length constitutes about 45% of the total length. The bill is fine-tipped and narrow with a slight lateral flattening at the base, which is surrounded by prominent rictal bristles. Upperparts are medium plumbeous mixed with ultramarine, and there is a prominent white eye-ring. Males in alternate plumage show a narrow black line over the bill and extending over and behind the eyes. Underparts are white, and the tail is black with outer retrices edged in white. The tail is frequently fanned and waved, showing the white edging. Females appear slightly paler (grayer) overall (Ellison 1992).

For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.

Diagnostic Characteristics
Only gnatcatcher in Montana.

Species Range
Montana Range Range Descriptions

All Ranges
(Click legend blocks to view individual ranges)

Western Hemisphere Range


Observations in Montana Natural Heritage Program Database
Number of Observations: 177

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density


SUMMER (Feb 16 - Dec 14)
Direct Evidence of Breeding

Indirect Evidence of Breeding

No Evidence of Breeding

WINTER (Dec 15 - Feb 15)
Regularly Observed

Not Regularly Observed


(Observations spanning multiple months or years are excluded from time charts)

Breeding birds in Montana migrate out of state for the winter. Over-wintering locations have not been identified for Montana breeders.

Breeding habitat in Montana is restricted to open stands of Utah Juniper (Juniperus osteosperma) and Limber Pine (Pinus flexilis) with intermixed Big Sagebrush (Artemisia tridentata). All nests found have occurred 0.8 to 1.7 meters above ground in Utah Juniper or Big Sagebrush growing on the lower slopes or bottoms of canyons (P. Hendricks unpublished data).

Throughout their range Blue-gray Gnatcatchers typically inhabit deciduous forest, riparian woodland, open woodland, second-growth, scrub, brushy areas and chaparral in the east, south, and coastal west (Tropical to lower Temperate zones) (American Ornithologists' Union 1983, Ellison 1992). In the Great Basin region of the west they also occupy open pine woodland, where (in Wyoming) they are associated with rosaceous shrubs and rock outcrops (Pavlacky and Anderson 2001).

They nest especially where tracts of brush, scrub, or chaparral are intermixed with taller vegetation (e.g., forest edge, riparian corridors); nesting often occurs near water. Nests are built on branches or forks of trees or shrubs, usually 1 to 25 meters above ground (Harrison 1978) and both sexes participate in nest construction. A broad range of brushy habitats is occupied during winter (Ellison 1992).

Ecological Systems Associated with this Species
  • Details on Creation and Suggested Uses and Limitations
    How Associations Were Made
    We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
    1. Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
    2. Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
    3. Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
    4. Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
    Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.  In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.  However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if point observations were associated with that system.  Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.  The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.  If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.

    Suggested Uses and Limitations
    Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.  These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.  Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.  Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.  Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).  Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.

    Literature Cited
    • Adams, R.A.  2003.  Bats of the Rocky Mountain West; natural history, ecology, and conservation.  Boulder, CO: University Press of Colorado.  289 p.
    • Dobkin, D. S.  1992.  Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34.  Missoula, MT.
    • Foresman, K.R.  2012.  Mammals of Montana.  Second edition.  Mountain Press Publishing, Missoula, Montana.  429 pp.
    • Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998.  Montana atlas of terrestrial vertebrates.  Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT.  1302 p.
    • Hutto, R.L. and J.S. Young.  1999.  Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32.  72 p.
    • Maxell, B.A.  2000.  Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species.  Report to U.S. Forest Service Region 1.  Missoula, MT: Wildlife Biology Program, University of Montana.  161 p.
    • Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath.  2004.  Amphibians and reptiles of Montana.  Missoula, MT: Mountain Press Publishing Company. 262 p.

Food Habits
Blue-gray Gnatcatchers feed on adult insects as well as their larvae and eggs, and also other arthropods (spiders, etc.). They forage by darting out from a perch and catching insects in the air, or by gleaning food from twigs and branches (Ellison 1992).

Breeding pairs establish a territory that the male defends, occasionally assisted by the female. In California, breeding territories averaged 1.8 hectares (n = 9), ranging from 0.9 to 3.0 hectares. In Vermont, mean size was 0.7 hectare (n = 4), ranging from 0.5 to 1.1 hectares (Ellison 1992).

Reproductive Characteristics
Clutch size in Montana (n = 9 nests) is 4 to 5 eggs. Nest construction begins in late May, eggs are laid in early to late June, and nestlings are present from mid-June to mid-July. Both sexes incubate eggs and tend nestlings (P. Hendricks unpublished data). Nestlings are altricial and naked at hatching. Young are brooded and fed by both parents, and leave the nest in 13 (10 to 15) days (Ellison 1992). Fledged young with adults have been observed into early September on the breeding grounds (Wright 1996, P. Hendricks personal observation).

No management activity is currently underway. Grazing may have a negative impact by directly or indirectly altering habitat for nesting and foraging. Nest parasitism by Brown-headed Cowbirds has recently been documented in Montana (P. Hendricks unpublished data).

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Citation for data on this website:
Blue-gray Gnatcatcher — Polioptila caerulea.  Montana Field Guide.  .  Retrieved on , from