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Shadow Darner - Aeshna umbrosa

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Global Rank: G5
State Rank: S4S5

Agency Status
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FWP Conservation Tier:


 

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General Description
The Shadow Darner is a common and widespread member of the family Aeshnidae. Darners are among the largest and fastest-flying North American dragonflies, 2 1/4-4 3/4" (57-120 mm) long. Shadow Darners are found state wide from the mountians to the prairies with a subspecies in the east and in the western part of the state. Preferred habitat includes small slow-flowing forested streams, as well as shaded lakes, ponds, bogs, fens, swamps and ditches (Nikula et al. 2002, Paulson 2009, Dunkle 2000). In eastern Montana shaded riparian areas are probably key for this species to be present. Of the wedge shaded cerci darners with straight thoracic stripes, the shadow darner is more brown in color and narrower T-stripes, no face line, eastern form with small green abdominal spots, while western form has larger blue abdominal spots. Associated Wetland and Lotic ecological systems are numerous: Western Emergent Marsh, Northern Rocky Mountain Wooded Vernal Pool and the Rocky Mountain Subalpine-Montane Fen, Great Plains Open Freshwater Depressional Wetland, Perennial Praire Streams.

Diagnostic Characteristics
Of the wedge shaded cerci darners with straight thoracic stripes, the shadow darner is more brown in color and narrower T-stripes, no face line, eastern form with small green abdominal spots, while western form has larger blue abdominal spots.

General Distribution
Montana Range

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Distribution Comments
The Shadow Darner has two distinctive subspecies, both of which occur in Montana. Aeshna umbrosa umbrosa occurs across the eastern plains and A. u. occidentalis is distributed in and west of the Rocky Mountains (Paulson 2009).

Summary of Observations Submitted for Montana
Number of Observations: 80

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

Recency

 

(Records associated with a range of dates are excluded from time charts)



Habitat
Shadow Darners occupy small slow-flowing forested streams, as well as shaded lakes, ponds, bogs, fens, swamps and ditches (Dunkle 2000, Nikula et al. 2002, Paulson, 2009). This species is also found far from water in clearings, forest edges, and forested roads (Nikula et al. 2002).

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 (high, medium, or low) 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 2001, 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 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 associated as using 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 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.  High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the 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 assignments of habitat quality.  If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at bmaxell@mt.gov or (406) 444-3655.

    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: http://mtnhp.org/requests/default.asp) 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.  2001.  The wild mammals of Montana.  Special Publication No. 12.  Lawrence, KS: The American Society of Mammalogists.  278 p.
    • 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
Larvae feed on a wide variety of aquatic insects, such as mosquito larvae, other aquatic fly larvae, mayfly larvae, and freshwater shrimp. They will also eat very small fish and tadpoles.
Adult- The dragonfly will eat almost any soft-bodied flying insect including mosquitoes, flies, small moths, mayflies, and flying ants or termites.

Ecology
This species is mostly active in shaded areas, hence the name Shadow Darner. It is known to feed out in the open very late into the evening even into darkness (Dunkle 2000, Paulson 2009).

Reproductive Characteristics
Shadow Darner males patrol close to the shoreline over open water often hovering for extensive periods. Females oviposit in the decaying wood of floating logs or submerged twigs and branches, even into moist trunks of trees and earthen banks of shoreline. This ovipositing behavior tends to lead to older females with missing or damages ceri (Dunkle 2000, Nikula et al. 2002, Paulson, 2009).

References
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Citation for data on this website:
Shadow Darner — Aeshna umbrosa.  Montana Field Guide.  Montana Natural Heritage Program.  Retrieved on October 20, 2014, from http://FieldGuide.mt.gov/speciesDetail.aspx?elcode=IIODO14190
 
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