Tuesday, April 9, 2019

Episode 467 (4-8-19): Considering Cormorants

Click to listen to episode (4:08).

Sections below are the following:
Transcript of Audio
Audio Notes and Acknowledgments
Extra Information
Related Water Radio Episodes
For Virginia Teachers (Relevant SOLs, etc.).

Unless otherwise noted, all Web addresses mentioned were functional as of 4-5-19.


From the Cumberland Gap to the Atlantic Ocean, this is Virginia Water Radio for the week of April 8, 2019.

This week, we feature a water-bird mystery sound.  Have a listen for about 10 seconds, and see if you can guess this long-necked, diving, fish-eating creature.  And here’s a hint: a double-feature on its crest forms a core part of this bird’s name.

SOUNDS - ~12 sec

If you guessed a Double-crested Cormorant, you’re right!  The Double-crested Cormorant is the most common of six species of cormorants in North America and two species in Virginia.  Virginia’s other cormorant, the Great Cormorant, is the world’s most widespread cormorant but is a relatively infrequent visitor to the Commonwealth.

The Double-crested is typically found along Virginia’s Atlantic coastline and around the Chesapeake Bay, and it’s also seen on inland ponds, lakes, and rivers, often resting on rocks, trees, or human structures.  The two head crests that give this species part of its name are not regularly visible; much more noticeable are its long dark neck, its orange throat, its large nesting colonies, and its habit of holding out its wings to dry out feathers following a diving and feeding foray.  Like other cormorants and the related Anhinga, the Double-crested Cormorant uses diving and powerful swimming ability to get its preferred food of fish along with many species of bottom-dwelling invertebrates.  Cormorant feathers have less water-resistant oils, though, compared to other diving species like various diving ducks; this may make cormorants faster underwater, even as it leads to their on-land wing-spreading behavior.

The word “cormorant” has Latin roots meaning “sea crow.”  That’s appropriate, because like crows, cormorants also have a reputation in some areas and situations as a pest.  The Cornell University Lab of Ornithology’s Web site, Birds of North America, has noted that, although cormorants typically feed on non-commercial fish, they have had documented economic impacts of commercial fisheries.  The Cornell site states that “real and perceived resource conflicts have resulted in substantial federal policy changes regarding cormorant management in the United States.”

Big, behaving distinctively, and bound up in policy decisions: cormorants may make you do a double-take, even if you don’t see a double crest.

Thanks to Lang Elliott for permission to use the Double-crested Cormorant sounds, from the Stokes Field Guide to Bird Songs.  We close with about 15 more seconds of cormorant sounds, mixed in with some other bird species, from a series of recordings made by David Moroz within a colony reportedly of over 1000 cormorant nests.

SOUNDS - ~ 13 sec


Virginia Water Radio is produced by the Virginia Water Resources Research Center, part of Virginia Tech’s College of Natural Resources and Environment.  For more Virginia water sounds, music, or information, visit us online at virginiawaterradio.org, or call the Water Center at (540) 231-5624.  Thanks to Stewart Scales for his banjo version of Cripple Creek to open and close this show.  In Blacksburg, I’m Alan Raflo, thanking you for listening, and wishing you health, wisdom, and good water.


The first Double-crested Cormorant sounds were taken from the Stokes Field Guide to Bird Songs-Eastern Region CD set, by Lang Elliott with Donald and Lillian Stokes (Time Warner Audio Books, copyright 1997), used with permission of Lang Elliott, whose work is available online at the “Music of Nature” Web site, http://www.musicofnature.org/.

The ending cormorant sounds were taken from David Moroz, “Soundholder - Cormorants,” online at http://soundholder.com/product/sound-library-cormorants/,” sample provided for public use by Freesound.org, online at https://freesound.org/people/Soundholder/sounds/425375/, under Creative Commons Attribution 3.0 License.

Click here if you’d like to hear the full version (1 min./11 sec.) of the “Cripple Creek” arrangement/performance by Stewart Scales that opens and closes this episode.  More information about Mr. Scales and the group New Standard, with which Mr. Scales plays, is available online at http://newstandardbluegrass.com.


Double-crested Cormorant painting originally published between 1827 and 1838 by John James Audubon in Birds of America (plate 257), as reprinted in 1985 by Abbeville Press, New York.  Photo taken April 8, 2019, from the reprint copy (no. 6 of 350 copies printed in 1985) owned by Special Collections of Virginia Tech Libraries.  Virginia Water Radio thanks Special Collections for permission to photograph their copy and for their assistance. Information about Birds of America is available from the National Audubon Society, online at http://www.audubon.org/birds-of-america.

Two Double-crested Cormorants at the Virginia Tech Duck Pond in Blacksburg on April 3, 2019.

Double-crested Cormorant, location and date unidentified.  Photo by Rodney Krey, made available for public use by the U.S. Fish and Wildlife Service's National Digital Library, online at http://digitalmedia.fws.gov (specific URL for the photo is https://digitalmedia.fws.gov/digital/collection/natdiglib/id/4280/rec/3), accessed 4-8-19.


Cormorants are a family of birds within the bird order Suliformes, which also includes frigatebirds, boobies, gannets, anhingas, and shags, according to the Cornell Laboratory of Ornithology’s “All About Birds” Web site (https://www.allaboutbirds.org/guide/browse/taxonomy/Phalacrocoracidae).

The scientific names of the two cormorant species typically found in Virginia are as follows:
Double-crested Cormorant – Phalacrocorax auritus;
Great Cormorant – Phalocrocorax carbo.

Here are some points about the Double-crested Cormorant, excerpted from the Virginia Department of Game and Inland Fisheries (VDGIF), “Fish and Wildlife Information Service/Double-crested Cormorant,” online at https://vafwis.dgif.virginia.gov/fwis/booklet.html?&bova=040024&Menu=_.Taxonomy&version=17991.  (The VDGIF site has relatively little information about the Great Cormorant, which is less commonly found in Virginia than the Double-crested.)

Occurrence in Virginia

“This species is a transient, irregular, local winter resident and common summer visitor near the coast. It is a rare transient in Piedmont, Mountain and Valley regions. Peak counts occur at Chincoteague during the fall…. Cormorants are highly adapted to aquatic environments, both fresh water and marine for breeding and foraging.  This is the only cormorant species likely to be seen on inland freshwater lakes and rivers.”

Physical Description

“This is a medium-sized cormorant…length 29-36 inches, wingspread 54 inches, weight 6 pounds.”


“The breeding season is from December-October, with a peak from April-June.… Breeding behavior is colonial and monogamous…. They express territorially during the breeding season, over nest sites and the adjoining perch.… The nest site may be on rocky or vegetated coastal islands, on bare ground among boulders, on cliff tops, or in trees.  They also nest on inland freshwater lakes with swampy regions, in live or dead trees, on islands (including salt and brackish marsh islands), or rocky reefs.  They will accept artificial nesting structures…. They may use old nests or those of great blue herons…. This species is also known to nest with brown pelicans, as on S. Marsh Point [Virginia]…. This species is [characterized by] highly colonial nesters with colonies ranging in size from a few nests to thousands.”


“The foraging strategy is to dive from the surface, and swim underwater near the surface or deeper using their feet for propulsion.  They are usually a bottom feeder, opportunistic and prefer schooling prey in the littoral zone in inland waters and rocky reefs.  They have symbiotic feeding relationships with mergansers, egrets, and pelicans.  The diet consists of small brackish/saltwater and freshwater fishes, amphibians, and crustaceans such as spider crabs, shrimp, crayfish, some reptiles, mollusks, and sea worms.  Like many other avian species that consume whole prey, cormorants regurgitate indigestible food parts in the form of pellets.  After feeding, [they] frequently perch in the sun with their wings spread for the sole purpose of drying off their wings.  They perform this behavior because they lack oils in their feathers to repel water.”

Impacts on Populations

“Predators of the eggs and young include gulls, crows, and ravens…. During the middle of the Twentieth Century, double crested cormorant populations declined because of exposure to DDT and other toxins.  Upon the ban of these pesticides, double crested cormorant numbers increased to the point where Canada and the US passed legislation allowing the killing of cormorants on islands where their nesting habits destroy local vegetation or those found feeding in aquaculture ponds.  Many of the claims made by fish farmers that cormorants are destroying fish stocks in aquaculture ponds are unfounded as double crested cormorants typically forage in fish with no commercial value.  Other threats to double crested cormorants include incidental capture in gill nets, oil spills that have resulted in the deaths of tens of thousands of cormorants and human disturbance in nesting colonies.”


Used for Audio

John James Aububon, Birds of North America, “Double-crested Cormorant,” plate 257, online at https://www.audubon.org/birds-of-america/double-crested-cormorant.

Chesapeake Bay Program, “Field Guide/Birds/Double-crested Cormorant,” online at https://www.chesapeakebay.net/discover/field-guide/entry/double_crested_cormorant.

Cornell Laboratory of Ornithology, “All About Birds, online at https://www.allaboutbirds.org/. The Double-crested Cormorant entry in online at https://www.allaboutbirds.org/guide/Double-crested_Cormorant/; the Great Cormorant entry is online at https://www.allaboutbirds.org/guide/Great_Cormorant/.

Kevin J. McGowan/Cornell Laboratory of Ornithology, “Frequently Asked Questions About Crows,” online at http://www.birds.cornell.edu/crows/crowfaq.htm.

Cornell University Lab of Ornithology and American Ornithologists’ Union, “Birds of North America Online/ online at http://bna.birds.cornell.edu/bna (subscription required). The Double-crested Cormorant entry (Introduction) is online at https://birdsna.org/Species-Account/bna/species/doccor/introduction.

Richard King, “When Dams and Dredging Alter an Ecosystem, Blame It on Cormorants,” Living Bird, August 2014, republished by the Cornell Laboratory of Ornithology, “All About Birds” Web site, online at https://www.allaboutbirds.org/when-dams-and-dredging-alter-an-ecosystem-blame-it-on-cormorants/.

Alice Jane Lippson and Robert L. Lippson, Life in the Chesapeake Bay, Johns Hopkins University Press, Baltimore, Md., 2006.

Oxford Dictionary and Thesaurus-American Edition, Oxford University Press, New York, N.Y., and Oxford, England, 1996.

Chandler S. Robbins et al., A Guide to Field Identification of Birds of North America, St. Martin’s Press, New York, N.Y., 2001.

Stan Tekiela, Birds of Virginia Field Guide, Adventure Publications, Inc., Cambridge, Minn., 2002.

Virginia Department of Game and Inland Fisheries, “Fish and Wildlife Information Service/Double-crested Cormorant,” online at https://vafwis.dgif.virginia.gov/fwis/booklet.html?&bova=040024&Menu=_.Taxonomy&version=17991; “Great Cormorant,” online at https://vafwis.dgif.virginia.gov/fwis/booklet.html?&bova=040023&Menu=_.Taxonomy&version=17994; and “Anhinga,” (online at https://vafwis.dgif.virginia.gov/fwis/booklet.html?Menu=_.Taxonomy&bova=040025&version=17991).

For More Information on Cormorants or Other Birds in Virginia and Elsewhere

BirdNote®, a daily broadcast/podcast on birds, online at http://birdnote.org/.

Cornell University Lab of Ornithology, “E-bird,” online at https://ebird.org/home.  This program was featured in Virginia Water Radio Episode 440, 10-1-18.

Cornell University Lab of Ornithology, “Merlin Photo ID,” online at http://merlin.allaboutbirds.org/.  The application for mobile devices allows users to submit a bird photograph to get identification of the bird.

Virginia Society of Ornithology, online at http://www.virginiabirds.org/.  The Society is non-profit organization dedicated to the study, conservation, and enjoyment of birds in the Commonwealth.

Xeno-canto Foundation Web site, online at http://www.xeno-canto.org/.  The site provides bird songs from around the world.


All Water Radio episodes are listed by category at the Index link above (http://www.virginiawaterradio.org/p/index.html).  See particularly the “Birds” subject category.


The episode—the audio, extra information, or sources—may help with the following Virginia Standards of Learning (SOLs).

2010 English SOLs

Reading Theme
6.4 and 7.4 – meanings of unfamiliar words - a. word origins and derivations.
8.4, 9.3, 10.3, 11.3, and 12.3 – knowledge of word origins, analogies, and figurative language to extend vocabulary development within authentic texts.

2010 Science SOLs

Grades K-6 Earth Resources Theme
3.10 – impacts on survival of species, including effects of fire, flood, disease, and erosion on organisms.
4.9 – Va. natural resources, including watersheds, water resources, and organisms.
6.9 – public policy decisions related to the environment (including resource management and conservation, land use decisions, hazard mitigation, cost/benefit assessments).

Grades K-6 Life Processes Theme
K.7 – basic needs and processes of plants and animals.
1.5 – animals’ basic needs and distinguishing characteristics.
3.4 – behavioral and physiological adaptations.

Grades K-6 Living Systems Theme
2.5 – living things as part of a system, including habitats.
3.5 – food webs.
3.6 – ecosystems, communities, populations, shared resources.
4.5 – ecosystem interactions and human influences on ecosystem.
5.5 – cell structures and functions, organism classification, and organism traits.

Life Science Course
LS.4 – organisms’ classification based on features.
LS.8 – community and population interactions, including food webs, niches, symbiotic relationships.
LS.9 – adaptations for particular ecosystems’ biotic and abiotic factors, including characteristics of land, marine, and freshwater environments.
LS.11 – relationships between ecosystem dynamics and human activity.

Biology Course
BIO.1 – current applications to reinforce science concepts.
BIO.8 – dynamic equilibria and interactions within populations, communities, and ecosystems; including nutrient cycling, succession, effects of natural events and human activities, and analysis of the flora, fauna, and microorganisms of Virginia ecosystems.

Virginia’s SOLs are available from the Virginia Department of Education, online at http://www.doe.virginia.gov/testing/.

Following are links to Water Radio episodes (various topics) designed especially for certain K-12 grade levels.

Episode 250, 1-26-15 – on boiling, for kindergarten through 3rd grade.
Episode 255, 3-2-15 – on density, for 5th and 6th grade.
Episode 282, 9-21-15 – on living vs. non-living, for kindergarten.
Episode 309, 3-28-16 – on temperature regulation in animals, for kindergarten through 12th grade.
Episode 333, 9-12-16 – on dissolved gases, especially dissolved oxygen in aquatic habitats, for 5th grade.
Episode 403, 1-15-18 – on freezing and ice, for kindergarten through 3rd grade.
Episode 404, 1-22-18 – on ice on ponds and lakes, for 4th through 8th grade.
Episode 406, 2-5-18 – on ice on rivers, for middle school.
Episode 407, 2-12-18 – on snow chemistry and physics, for high school.