Double-crested Cormorant - Nannopterum auritum
Large, dark cormorant. Typical length 70 to 90cm, body mass 1.2 to 2.5 kg. Sexes are alike. Males are slightly larger than females. Adults have black or dark-brown plumage, with a dull greenish or bronze gloss. The orange-yellow skin of face and throat is distinctive throughout the year. The "double crest" feathers are variable and are fully developed for only a short time early in the year. This is the only seasonal change. Has totipalmate feet in which all 4 toes are connected by web (Hatch and Weseloh 1999).
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.
Western Hemisphere Range
Observations in Montana Natural Heritage Program Database
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
SUMMER (Feb 16 - Dec 14)
Direct Evidence of Breeding
Indirect Evidence of Breeding
No Evidence of Breeding
WINTER (Dec 15 - Feb 15)
Not Regularly Observed
(Observations spanning multiple months or years are excluded from time charts)
Birds breeding east of the Rocky Mountains generally winter along the Gulf of Mexico from Florida to Texas (Dolbeer 1991). In the Bozeman area they are seen during spring migration from April 10 to May 30 and intermittently from July to October 10, with a peak in the fall around September 6.
Occupies diverse aquatic habitats in all seasons. Requires, in addition to feeding habitats, suitable places for daytime resting or loafing and nighttime roosts (Hatch and Weseloh 1999).
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:
- 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);
- Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
- Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
- 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: mtnhp.org/requests
) 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.
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At most sites eats almost entirely fish preferring slow-moving or schooling species. (Hatch and Weseloh 1999).
Typically a single brood. Second broods per season are rare. Clutch size is 1 to 7 eggs with 4 being normal. Nesting is done in colonies (Hatch and Weseloh 1999). Nesting occurs in late May to early June.
- Literature Cited AboveLegend: View Online Publication
- Dolbeer, R.A. 1991. Migration patterns of Double-crested Cormorants east of the Rocky Mountains. Journal of Field Ornithology 62(1):83-93.
- Marks, J.S., P. Hendricks, and D. Casey. 2016. Birds of Montana. Arrington, VA. Buteo Books. 659 pages.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
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- Additional Sources of Information Related to "Birds"