Illinois Natural History Survey - University of Illinois

Double-crested comorant
Phalacrocorax auritus

 

Taxonomy
Occurence in Illinois
Status
Habitat associations
Guilds
Food-habits
Environmental associations
Life history
Management practices
References


TAXONOMY

 

  • Phylum: Chordata
  • Class: Aves
  • Order: Pelecaniformes
  • Family: Phalacrocoracidae
  • Genus: Phalacrocorax
  • Species: Phalacrocorax auritus
  • Authority: Lesson

Comments on taxonomy:
Other names: crow duck, lawyer, shag, taunton turkey, farallon cormorant *02*. Several subspecies, only P. a. auritus occurs in Ill *27,28*.

 


OCCURENCE IN ILLINOIS

Uncommon migrant along Mississippi and Illinois Rivers. Elsewhere in in state an occasional migrant. Rare summer resident along upper Mississippi River, including an annual nesting colony in Carroll Co. A nesting pair also noted in Dekalb Co. *01,08*.

 


STATUS

Items in bold indicate applicable categories
Forest Service Categories: S = recommended for regional sensitive status, F = forest listed species, M = management indicator species

Federal Status:

Endangered Threatened Proposed for listing
Candidate for proposal Recovery plan approved Recovery plan received (USFWS)
Recovery plan in preparation Under notice of review Delisted
Migratory EPA indicator Forest Serv.- Shawnee species

State Status:

Endangered Threatened Proposed

Other:

Game Furbearer Nongame protected
Sportfish Commercial Pest None of the above

Comments on status:
Population in state is low, Bowles et al. (1981) states that in Carrol County a slight increase occurred since 1977 from 12 nests and 30 birds to 39 nests with 83 immature birds in 1980.

 


HABITAT ASSOCIATIONS

Items in bold indicate applicable categories

General habitat:

Unknown Terrestrial Aquatic Riparian

USFS timber inventory forest size class:

Unknown Unstocked Seedling Sapling
Seedling/sapling Pole Mature Over mature

Land use and land cover:

Unknown   Urban Residential
Commercial
Industrial
Transportation, communication
Complex industrial/commercial
Mixed
Other
Agricultural Crop, pasture
Orchards, groves, nurseries
Feedlot
Other
Rangeland Herbaceous
Shrub and brush
Mixed
Forestland Deciduous
Evergreen
Mixed
Water Stream
Lake
Reservoir

Bay
Wetland Forest
Non-forest
Barren Salt flat
Beach
Sand
Rock
Mine
Transit
Mix

 


Forest cover types:

Cover typeStructural stageCanopy closureSeason
Oak-pine Young tree
(1-9" dia.)
All (0-100%) All
Oak-pine Mature
(9" dia. & 100 yrs. old)
All (0-100%) All
Elm-ash-cottonwood Young tree
(1-9" dia.)
All (0-100%) All
Elm-ash-cottonwood Mature
(9" dia. & 100 yrs. old)
All (0-100%) All
Aspen-birch Young tree
(1-9" dia.)
All (0-100%) All
Aspen-birch Mature
(9" dia. & 100 yrs. old)
All (0-100%) All

Associated tree species:

  • Cedar
  • Cottonwood
  • Oak
  • Olive Willow

National wetland inventory classifications:

SystemSubsystemClassSubclassWater regime modifiersWater chemistry
Lacustrine Limnetic Beach/bar Cobble/gravel Unknown/unspecified Unknown/unspecified
Lacustrine Limnetic Open water of unknown botton type   Unknown/unspecified Unknown/unspecified
Lacustrine Littoral Beach/bar Cobble/gravel Unknown/unspecified Unknown/unspecified
Palustrine   Forest Dead trees Unknown/unspecified Unknown/unspecified
Palustrine   Forest Deciduous Unknown/unspecified Unknown/unspecified
Palustrine   Forest Evergreen Unknown/unspecified Unknown/unspecified
Riverine Unknown perennial Beach/bar Cobble/gravel Unknown/unspecified Unknown/unspecified
Riverine Unknown perennial Forest Dead trees Unknown/unspecified Unknown/unspecified
Riverine Unknown perennial Forest Deciduous Unknown/unspecified Unknown/unspecified
Riverine Unknown perennial Forest Evergreen Unknown/unspecified Unknown/unspecified

Comments on species-habitat associations:
Nesting done in both living and dead coniferous or deciduous trees, between 1 and 65 ft above the surface of the ground or water *08,11, 13,21,22,28,30,32*. May also nest on the tops of cliffs or on rocky to cobble shores *13,28,29,30,31,32*. Species found along rivers, lakes, ponds or in older swamps *01,02,04,08,10,11,13,15,32*.

Important plant and animal association: Herons, egrets, gulls, and crows.
gulls and crows responsible for significant egg and young predation *06,07,09,13,28,29,30,31*. Species often nest in same areas or trees as great blue herons, black-crowned night-heron, cattle egret, or snowy egrets *11,13,15,28,30*.

High value habitats

HabitatStructural stageSeason
Forested wetland Young tree
(1-9" dia.)
Spring/summer
Forested wetland Mature
(9" dia. & 100 yrs. old)
Spring/summer
Lakes Not applicable
(HVAL-HAB cover)
Spring/summer
Streams and canals Not applicable
(HVAL-HAB cover)
Spring/summer
Bare exposed rock Special habitat Spring/summer
Wet floodplain forest Young tree
(1-9" dia.)
Spring/summer
Wet floodplain forest Mature
(9" dia. & 100 yrs. old)
Spring/summer
Swamp Mature
(9" dia. & 100 yrs. old)
Spring/summer
Lakes and ponds Not applicable
(HVAL-HAB cover)
Spring/summer
Large river Not applicable
(HVAL-HAB cover)
Spring/summer
Cliff Special habitat Spring/summer
Cliff Special habitat Fall
Beach Special habitat Spring/summer
Beach Special habitat Fall
Forested wetland Young tree
(1-9" dia.)
Fall
Forested wetland Mature
(9" dia. & 100 yrs. old)
Fall
Lakes Not applicable
(HVAL-HAB cover)
Fall
Streams and canals Not applicable
(HVAL-HAB cover)
Fall
Bare exposed rock Special habitat Fall
Wet floodplain forest Young tree
(1-9" dia.)
Fall
Wet floodplain forest Mature
(9" dia. & 100 yrs. old)
Fall
Swamp Mature
(9" dia. & 100 yrs. old)
Fall
Lakes and ponds Not applicable
(HVAL-HAB cover)
Fall
Large river Not applicable
(HVAL-HAB cover)
Fall

Species-habitat interrelations: High-value habitat includes areas undisturbed by human activity *11, 18,19,32*. Flooded dead timber stands important, see Meier (1981). Areas to provide colonization are essential *02,09,11,13,14*. Barren, rocky islands of lakes and rivers or the tops of cliffs overlooking open water may also be useful nesting sites *02,10,13,28, 29,30,31,32*.

 


GUILDS

Feed-guilding:

HabitatStructural stageSeasonFeed-guilds
Water Special habitat All Water column- fish
Water column-amphibians
Wetland Special habitat All Water column- fish
Water column-amphibians
Lakes and ponds Special habitat All Water column- fish
Water column-amphibians
Large river Special habitat All Water column- fish
Water column-amphibians

Comments on feed-guilding:
A diving species that feeds mainly on non-commercial fish. Amphibians, crustaceans and mollusks are minor sources of food *02,13,18*.

Breed-guilding:

HabitatStructural stageSeasonBreed-Guilds
Forested wetland Young tree
(1-9" dia.)
Spring/summer Artificial structure (e.g. telephone and power poles, chimney, antenna)
Tree canopy, large branches of live broad-leaved deciduous trees
Tree canopy, large branches of live needle-leaved evergreen trees
Tree canopy, large branches of dead broad-leaved deciduous trees
Tree canopy, large branches of dead needle-leaved evergreen trees
Forested wetland Mature
(9" dia. & 100 yrs. old)
Spring/summer Artificial structure (e.g. telephone and power poles, chimney, antenna)
Tree canopy, large branches of live broad-leaved deciduous trees
Tree canopy, large branches of live needle-leaved evergreen trees
Tree canopy, large branches of dead broad-leaved deciduous trees
Tree canopy, large branches of dead needle-leaved evergreen trees
Swamp Young tree
(1-9" dia.)
Spring/summer Artificial structure (e.g. telephone and power poles, chimney, antenna)
Tree canopy, large branches of live broad-leaved deciduous trees
Tree canopy, large branches of live needle-leaved evergreen trees
Tree canopy, large branches of dead broad-leaved deciduous trees
Tree canopy, large branches of dead needle-leaved evergreen trees
Swamp Mature
(9" dia. & 100 yrs. old)
Spring/summer Artificial structure (e.g. telephone and power poles, chimney, antenna)
Tree canopy, large branches of live broad-leaved deciduous trees
Tree canopy, large branches of live needle-leaved evergreen trees
Tree canopy, large branches of dead broad-leaved deciduous trees
Tree canopy, large branches of dead needle-leaved evergreen trees
Cliff Special habitat Spring/summer Terrestrial surface
Beach Special habitat Spring/summer Surface of water column-river/lake/marsh, unconsolidated cobble substrate

Comments on breed-guilding:
Species breeds on land, on or near the nest, see Mendall (1936). Nesting done in trees, on cobble shores of lakes and islands or on top of cliff overlooking open water *13,22,28,29,30,31,32*. There has been good success in the use of artificial nesting structures, see Meier (1981), Bowles et al. (1981).

 


FOOD-HABITS

Trophic level is CARNIVORE

Food itemLife stage/plant part
Mollusca Adult
Crustaceans Adult
Cypriniformes (carps, minnows, loaches) Adult
Siluriformes (catfishes) Adult
Gasterosteiformes (sticklebacks, pipefishes, seahorses) Adult
Perciformes (basses, sunfishes, perches, sculpins) Adult
Caudata (salamanders,newts,sirens,mudpuppies,hellbenders) Adult
Salientia (frogs, toads) Adult
Important:
Cypriniformes (carps, minnows, loaches) Adult
Siluriformes (catfishes) Adult
Perciformes (basses, sunfishes, perches, sculpins) Adult
Juvenile:
Mollusca Adult
Crustaceans Adult
Cypriniformes (carps, minnows, loaches) Adult
Siluriformes (catfishes) Adult
Gasterosteiformes (sticklebacks, pipefishes, seahorses) Adult
Perciformes (basses, sunfishes, perches, sculpins) Adult
Caudata (salamanders,newts,sirens,mudpuppies,hellbenders) Adult
Salientia (frogs, toads) Adult
Adult:
Mollusca Adult
Crustaceans Adult
Cypriniformes (carps, minnows, loaches) Adult
Siluriformes (catfishes) Adult
Gasterosteiformes (sticklebacks, pipefishes, seahorses) Adult
Perciformes (basses, sunfishes, perches, sculpins) Adult
Caudata (salamanders,newts,sirens,mudpuppies,hellbenders) Adult
Salientia (frogs, toads) Adult

Comments on food habits: 
General: Prefers fish, see comments on feed-guilding. Sprunt et al. (1970) reports that about 99% of diet is fish.
Juvenile: Young eat regurgitated food from parents until old enough to capture own prey *02,07,14,16,19,28*.
Adult: Dive from the surface of the water to depths between 5 and 25 ft., staying under about 30 seconds but as long as 70 seconds *02,05,13, 18*.


ENVIRONMENTAL ASSOCIATIONS

General:

  • Aquatic habitat zone: pelagic- needs open water
  • Flood plain: see comments
  • Cliffs/ledges: see comments
  • Aquatic habitats: rocky offshore islands
  • Aquatic habitats: island inhabitant
  • Aquatic habitats: swamp
  • Ecotones: woodland/water
  • Preferred trees: see comments
  • Vegetation successional stage: bare rock
  • Human associations: wildlife refuges/sanctuaries
  • Unknown

Limiting:

  • Aquatic habitats: island inhabitant
  • Aquatic habitats: swamp
  • Ecotones: woodland/water
  • Vegetation successional stage: bare rock

Egg

  • Unknown

Feeding juvenile:

  • Aquatic habitat zone: pelagic- needs open water
  • Flood plain: see comments
  • Cliffs/ledges: see comments
  • Aquatic habitats: rocky offshore islands
  • Aquatic habitats: island inhabitant
  • Aquatic habitats: swamp
  • Ecotones: woodland/water
  • Preferred trees: see comments
  • Vegetation successional stage: bare rock
  • Human associations: wildlife refuges/sanctuaries

Resting juvenile:

  • Aquatic habitat zone: pelagic- needs open water
  • Flood plain: see comments
  • Cliffs/ledges: see comments
  • Aquatic habitats: rocky offshore islands
  • Aquatic habitats: island inhabitant
  • Aquatic habitats: swamp
  • Ecotones: woodland/water
  • Preferred trees: see comments
  • Vegetation successional stage: bare rock
  • Human associations: wildlife refuges/sanctuaries

Feeding adult:

  • Aquatic habitat zone: pelagic- needs open water
  • Aquatic habitats: swamp
  • Ecotones: woodland/water
  • Human associations: wildlife refuges/sanctuaries

Resting adult:

  • Aquatic habitat zone: pelagic- needs open water
  • Flood plain: see comments
  • Cliffs/ledges: see comments
  • Aquatic habitats: rocky offshore islands
  • Aquatic habitats: island inhabitant
  • Aquatic habitats: swamp
  • Ecotones: woodland/water
  • Preferred trees: see comments
  • Vegetation successional stage: bare rock
  • Human associations: wildlife refuges/sanctuaries

Breeding adult:

  • Flood plain: see comments
  • Cliffs/ledges: see comments
  • Aquatic habitats: rocky offshore islands
  • Aquatic habitats: island inhabitant
  • Ecotones: woodland/water
  • Preferred trees: see comments
  • Vegetation successional stage: bare rock
  • Human associations: wildlife refuges/sanctuaries

Comments on environmental associations:
General: Species has close association to water such as larger lakes and rivers, ponds or swamps where it is found nesting on nonvegetated shores, on top of cliffs or in trees *01,02,04,08,28,29,30,31,32*. Meier (1981) states that species nests primarily in flooded dead timber over most of the midwest. Tree species mentioned from various localities as possible nesting sites include paper birch, maple, elm, cottonwood, willow, oak, cedar and Russian olive *06,22,28,30*.
Egg: Habitat deterioration and pesticides are other causes of population declines *09,10,11,20,21*.
Feeding juvenile: Young fed a semi-liquid, regurgitated food by both parents for about 2 weeks after which whole or partially digested food is left at the nest. Young are fed until old enough to feed themselves at 42 days at which time they accompany adults in fishing *02,07,13,14 16,28*. Older juveniles assumed to feed like adults *00*.
Resting juvenile: Young assumed to rest at nest site, older juveniles assumed to rest like adults (see comments on resting adults).
Feeding adult: Feed in open water *02,05,13,18* capturing prey below the surface *18,19*.
Resting adult: Return to colony after sundown, sleep standing up or sitting down, waking in the early morning, see Mendall (1936). Also rest on snags near water *01*. Sleep frequently in day for short intervals, see Lewis (1929).
Breeding adult: Breed on land, near or on nest, at undisturbed sites *13,19*.


LIFE HISTORY

Origin: Native *01*.

Physical description: Length between 29-36 in *02,04,07,16,17*. Slender, straight, tip curved *04,07*. Weight between 4 and 4.5 lbs up to 6 lbs *02,07*. Color is black with no white flank patches, yellow-orange throat patch *02,04,07*; legs and feet also black. Immatures with lighter upperparts, grayish and cream breast *02,16,17, 28*. Double-crest visible during short breeding season *02,17,19*.

Reproduction: Species breeds from Alaska to Alberta and Newfoundland, south as far as Mexico and the Bahamas *08,17,27*. Spring migration brings species to various locations within the state from mid-March to mid-May *01,24*. Breeding seasons in various states from mid-April through June *09,10,13,15*. Territory selected and defended by male, but not over-aggressively *13,19,22*. Courtship takes place on land or in water. Majority of displays occur on land and include song and accompanying gestures such as bowing, upstretching, swelled neck, open and closing bill, caressing and a snake-like movement of the head and neck that is performed by the female also *13,14,19*. Copulation takes place on land, on or near the nest *13*. Nesting done in colonies *02,07,09,10,11,14,29,30,31,32*. Nest construction shared by both mates. Nest made of sticks and stems, lined with leafy twigs, grasses, and assorted trash found in area *02, 13,15,32*. Approx. 4 days to complete nest *02.28,32*. May reuse nest of previous year *02,28,32*. Usually one brood per season. Will renest if nest or eggs destroyed *02,13,28,32*. Eggs layed over a couple of days between April and July *02,11,14,22*; pale ,chalky blue in color *02,13,14*. Incubation performed by both sexes soon after first egg is layed; 24-30 days *02,13,22,28,32*. Between 1.06 And 2.83 young per nest from studies done in Utah and Wisconsin *28,11*. Ellison et al. (1978) found in a study of 36 nests that 0.75 young fledged per nest. A 30-66% hatching success has been reported *28*. Young are altricial, dark and skinny, covered with short black "wool" at 2 weeks *02,07,13,14,18,28*. Eyes open at 4-5 days *02,19,22,28*. Both parents take care of young. Are meticulous when feeding regurgitated food. Young covered by parents in extreme weather *02,07,13,14, 16*. If nesting in trees, young climb out of nest on to limbs between 14-22 days *28*. If ground nesting, young may join together at 3-4 weeks to wander around the colony *02*. Swimming is acheived before flight, usually between 3-6 weeks *28*; flight at approx. 35-42 days *02*. Young achieve independence at 10 weeks *02,13,19*. Sexual maturity acheived at 3 yrs, rarely 2 yrs *19,32*.

Behavior: This species is territorial and aggressive in nest defense *28,31*. Other authors mention that territorial defense is not overly aggressive *13,19,22*. Palmer (1962) reports a 5-10 mi foraging radius. Fall migration takes place from mid-August through November in various states, including Illinois *01,14,19,22,23*. Young disperse at approx. 10 weeks at which time they may remain in the colony to roost, may roost alone, or join other juveniles elsewhere *02,13,14*. Foraging strategies involve swimming on surface of open water where it may dive (between the depths of 5-25 ft) to capture prey *02,13,18,19*. Ross (1973) states that bottom dwelling fishes are preferred prey. Flight patterns of flocks are similar to those of geese *14,18,19*. Cormorants sit on snags along rivers or lakes. Roosting occurs from approx. Sunset to daylight if undisturbed *01,13*.

Limiting factors: Eggshell thinning due to exposure to DDE, DDT, and PCB's; predation of eggs and young by crows, ravens, and gulls; human disturbances that cause abandonment of eggs or young; natural deterioration or human destruction of habitat; and temporary food shortages all mentioned as possible limiting factors *09,11,20,21,28,29,30,31*. Verbeek (1982) reports that crows were responsible for the destruction of 22% of cormorant eggs (first clutch) in B.C. human disturbance often mentioned *08,11,21,24,30,32*.

Population parameters: Moratality rate reported by Palmer (1962) was 22-26% after the first year. Palmer also reported that 25% of population at breeding grounds were composed of pre-breeders. Average lifespan reports range from 8 yrs 4 mo to 23 yrs after banding *02,19*. Meier (9181) states that in the George W. Mead wildlife area of central Wisconsin, the cormorant population "expanded at an annual rate of approx. 25% since 1968". Bowles et al. (1981) report that a slight increase was recorded in 1980 for Carroll Co., Illinois. A 454% population increase from 1977 to 1980 in the U.S. Great Lake regions was found by Scharf et al. (1981).

 


MANAGEMENT PRACTICES

Beneficial:

  • Maintaining undisturbed/undeveloped areas
  • Maintaining natural areas and nature preserves
  • Maintaining unique or special habitat features (wetlands, snags, caves, cliffs, talises, etc.)
  • Preserving endangered species habitat
  • Preserving sensitive species habitat
  • Performing special survey prior to prescription
  • Performing field survey prior to prescription
  • Controlling land use and human activities
  • Seasonal restriction of human use of habitats
  • Controlling pollution
  • Practices other than those included on the ifwis list (see comments)
  • Controlling pollution in aquatic habitats
  • Developing/maintaining snags
  • Developing/maintaining lakes and ponds
  • Creating/maintaining islands within permanent impoundments
  • Developing/maintaining wetlands
  • Protecting existing wetlands
  • Restoration of wetlands (return flooded or drained areas to previous wetland conditions)
  • Riparian habitat management practices other than those included on ifwis list (see comments)
  • Deferred cutting of forest areas
  • Developing/maintaining mature hardwood forest
  • Providing food and cover for species under consideration
  • Restricting human disturbance during migration, breeding, and nesting
  • Constructing nesting structures for birds
  • Providing artificial nesting and roosting sites (platforms, nest boxes, cones, baskets, burro)
  • Fish stocking

Adverse:

  • Removing gravel from stream beds
  • Providing public access (develop roads, trails, parking areas or provide legal access)
  • Draining ponds/lakes
  • Drawdown of ponds/lakes
  • Draining wetlands
  • Removing bank vegetation
  • Applying pesticide on agricultural land
  • Applying herbicide
  • Applying insecticide
  • Strip mining
  • Applying pesticides
  • Applying herbicides
  • Applying insecticides
  • Removal of old trees
  • Application of pesticides
  • Application of insecticides
  • Removing unwanted fish
  • Drawdown of ponds/lakes

Existing:

  • Practices other than those included on the ifwis list (see comments)
  • Applying pesticide on agricultural land
  • Applying pesticides
  • Constructing nesting structures for birds
  • Providing artificial nesting and roosting sites (platforms, nest boxes, cones, baskets, burro)

Comments on management practices:
See [FH] for beneficial fish species. Larger lakes, ponds, rivers, and swamps with older dead timber provide essential habitat *01,02,04,08, 11,32*. Artificial nesting structures have proven to be beneficial *08, 11*. Snags are useful for resting sites along lakes and rivers *01*. Gravel/cobble shorelines along islands, lakes, and rivers are important for nesting *10,13*. Public access disrupts needed privacy *08,11, 19,29*. Draining lakes/ponds eliminates the "undesirable" fish that the cormorant feeds on, see [FG]. DDT, DDE, and PCB's cause eggshell thinning *09,20*. Double-crested cormorants are protected under the Illinois Endangered Species Protection Act, 1972, the Illinois Wildlife Code, 1971, and the Federal Migratory Bird Treaty Act, 1918 *08, 25,26*.

 


REFERENCES

0. IRISH, J. 1984. ILL. NAT. HIST. SURV., 607 E. PEABODY DR., CHAMPAIGN, ILL. (217)333-6846.

1. BOHLEN, H. 1978. AN ANNOTATED CHECK-LIST OF THE BIRDS OF ILLINOIS. ILLINOIS STATE MUS. POP. SCI. SER., VOL. IX. 156 P.

2. TERRES, J. 1980. AUDUBON SOCIETY: ENCYCLOPEDIA OF NORTH AMERICAN BIRDS. ALFRED KNOPF, NEW YORK. 1109 P.

3. AMER. ORNITHOLOGISTS UNION. 1982. THIRTY-FOURTH SUPPLEMENT TO THE AMERICAN ORNITHOLOGISTS' UNION CHECKLIST OF NORTH AMERICAN BIRDS. SUPPLEMENT AUK 99(3).

4. PETERSEN, R. T. 1980. A FIELD GUIDE TO THE BIRDS EAST OF THE ROCKIES, HOUGHTON MIFFLIN CO., BOSTON. 384 PP.

5. ROSS, R. K. 1973. A COMPARISON OF THE FEEDING AND NESTING REQUIREMENTS OF THE GREAT CORMORANT (PHALACORCORAX CARBO L.) AND DOUBLE-CRESTED CORMORANT (P. AURITUS LESSEN) IN NOVA SCOTIA. PROC. N. J. INST. SCI. (1974-76). 27: PP. 114-132.

6. ELLISON, L. N. AND L. CLEARY. 1978. EFFECTS OF HUMAN DISTURBANCE BREEDING OF DOUBLE-CRESTED CORMORANTS. AUK 95(3):510-517.

7. AUDUBON, J.J. 1967 REPRINT. THE BIRDS OF AMERICA. DOVER PUBLICATIONS, INC. VOL. 6. 457 PP.

8. BOWLES, M.L., V.E. DIERSING, J.E. EBINGER AND H.C. SHULTZ 1981 ENDANGERED AND THREATENED VERTEBRATE ANIMALS AND VASCULAR PLANTS OF ILLINOIS. THE DEPT. CONSERV. 189 PP.

9. GRESS, F., R.W. RISEBROUGH, D.W. ANDERSON, L.F. KIFF AND J.R. JEHL, JR. 1973. REPRODUCTIVE FAILURES OF DOUBLE-CRESTED CORMORANTS IN SOUTHERN CALIFORNIA AND BAJA CALIFORNIA. WILSON BULL. 85(2):197- 208.

10. SCHARF, W.C. 1979. NESTING AND MIGRATION AREAS OF BIRDS OF THE U.S. GREAT LAKES (30 APRIL TO 25 AUGUST 1976). U.S. FISH AND WILDLIFE SERVICE, OFFICE OF BIOLOGICAL SERVICES. FWS/OBS-77/2. 113 PP.

11. MEIER, T.L. 1981. ARTIFICIAL NESTING STRUCTURES FOR THE DOUBLE- CRESTED CORMORANT. TECHNICAL BULL. NO. 126. DEPT. OF NATURAL RESOURCES, MADISON, WIS. 12 PP.

12. ILL. DEPT. OF CONSERVATION. 1978. (OFFICIAL LIST OF ENDANGERED AND THREATENED VERTEBRATE SPECIES OF ILL.) ILL. END SPECIES PROT. ACT SEC. 337 ART. CXXVIII.

13. MENDALL, H.L. 1936. THE HOME LIFE AND ECONOMIC STATUS OF THE DOUBLE- CRESTED CORMORANT, PHALACROCORAX AURITUS AURITUS (LESSON) THE MAINE BULLETIN. VOL. XXXIX NO. 3. 143 PP.

14. BENT, A.C. 1922. LIFE HISTORIES OF NORTH AMERICAN PETRELS AND PELICANS AND THEIR ALLILES. DOVER PUBL., INC., NY. 335 PP.

15. ANDERSON, D.W. AND J.W. ELLIS. 1966 CORMORANT NESTING IN NORTHWESTERN MINNESOTA. THE LOON 38(1):5-8.

16. SPRUNT, A. AND E. CHAMBERLAIN. 1970. SOUTH CAROLINA BIRD LIFE. UNIV. SOUTH CAROLINA PRESS, COLUMBIA. 655 P.

17. PEARSON, T.G., C.S. BRIMLEY AND H.H. BRIMLEY. 1942. BIRDS OF NORTH CAROLINA. BYNUM PRINTING CO., RALEIGH, NORTH CAROLINA. 416 PP.

18. POUGH, R.N. 1951. AUDUBON BIRD GUIDES: SMALL LAND BIRDS DOUBLEDAY AND COMPANY, INC., GARDENCITY. P. 24 312 PP.& 48 PLS.

19. PALMER, R.S. 1962. HANDBOOK OF NORTH AMERICAN BIRDS. NEW HAVEN AND LONDON, YALE UNIVERSITY PRESS. VOL. 1. 567 PP.

20. ANDERSON, D.W., J.J. HICKEY, R.W. RISEBROUGH, D.F. HUGHES AND R.E. CHRISTENSEN. 1969. SIGNIFICANCE OF CHLORINATED HYDROCARBON RESIDUES TO BREEDING PELICANS AND CORMORANTS. CAN. FIELD. NAT. 83(2):91-112.

21. LEWIS, H.F. 1931. ADDITIONAL INFORMATION CONCERNING THE DOUBLE-CRESTED CORMORANT (PHALACROCORAX AURITUS AURITERS (LESSON)). THE AUK 48(2):207-214.

22. LEWIS, H.F. 1929. THE NATURAL HISTORY OF THE DOUBLE-CRESTED CORMORANT (PHALACROCORAX AURITUS AURITUS (LESSON). RU-MI-LOU BOOKS OTTAWA, CANADA. 94 PP.

23. KLEEN, V. M. 1983. FIELD NOTES: FALL MIGRATION. ILLINOIS AUDUBON BULL. 204: 45-56.

24. KLEEN, V. M. 1983. FIELD NOTES: SPRING MIGRATION. ILLINOIS AUDUBON BULL. 206: 28-41.

25. U.S. FISH WILDLIFE SERVICE. 1983. CODE OF FEDERAL REGULATIONS. TITLE 50. WILDLIFE AND FISHERIES. CHAPTER 1. PP. 11-18. 50 CFR 10.13. LIST OF MIGRATORY BIRDS. SPECIAL PUBL. FEDERAL REGISTER. GENERAL SERVICES ADMIN. OCTOBER 1.

26. ILLINOIS DEPARTMENT OF CONSERVATION. 1980. CONSERVATION LAWS, CH. 61. WILDLIFE. ART. II. PAR. 2.2. REPRINTED FROM ILLINOIS REVISED STATUTES, 1979. WEST PUBL. CO., ST. PAUL, MN. 120P.

27. AMERICAN ORNITHOLOGIST'S UNION. 1957. CHECK-LIST OF NORTH AMERICAN BIRDS, 5TH ED. LORD BALTIMORE PRESS, INC., BALTIMORE, MD.

28. MITCHELL, R. M. 1977. BREEDING BIOLOGY OF THE DOUBLE-CRESTED CORMORANT ON UTAH LAKE. GREAT BASIN NATUR. 37(1): 1-23.

29. VERBEEK, N. A. M. 1982. EGG PREDATION BY NORTHERN CROWS: ITS ASSOCIATION WITH HUMAN AND BALD EAGLE ACTIVITY. AUK 99(2): 347-352.

30. SCHARF, W. C. AND G. W. SHUGART. 1981. RECENT INCREASES IN DOUBLE- CRESTED CORMORANTS IN THE UNITED STATES GREAT LAKES. AM. BIRDS 35(6): 910-911.

31. SIEGEL-CAUSEY, D. AND G. L. HUNT, JR. 1981. COLONIAL DEFENSE BEH- VIOR IN DOUBLE-CRESTED AND PELAGIC CORMORANTS. AUK 98(3): 522-531.

32. HARRISON, H. H. 1979. A FIELD GUIDE TO WESTERN BIRD'S NESTS. HOUGHTON MIFFLIN CO., BOSTON. 279 PP.

 


 

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