Illinois Natural History Survey - University of Illinois

Forster's tern
Sterna forsteri

 

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


TAXONOMY

 

  • Phylum: Chordata
  • Class: Aves
  • Order: Charadriiformes
  • Family: Laridae
  • Genus: Sterna
  • Species: Sterna forsteri
  • Authority: Nuttall

Comments on taxonomy:
Historically there has been much confusion between Forster's and common terns. For years S. forsteri in summer plumage was not recognized as a separate species because of the close resemblance. Audubon gave the name of Havell's tern (S. havelli) to this species while in winter plumage. Coues was first to distinguish Havell's tern was actually the winter plumage of Forster's tern *13*. Other names: Havell's tern (Audubon), marsh tern, sea-swallow *03,13*.

 


OCCURENCE IN ILLINOIS

Forster's tern occurs in Illinois from late April-mid May, and late July-mid October *01*. This species is a common migrant and occassional summer resident in the NE part of Illinois *01,02*. In 1979 several summered at Lake Calumet and suggested possible nesting activity. The first Illinois nesting record in years was in 1982 at Chain of Lakes State Park where 16 pairs nested producing at least 9 young *22*.

 


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:
The Forster's tern appeared on the Illinois endangered species list's last revision in 1977. This species apparently depends upon larger inland lakes with marsh borders for nesting and its numbers have probably declined with the loss of this preferred habitat. The Forster's tern still satisfies the 3 requirements for inclusion as an endangered species 1) small population numbers in Illinois, 2) preferred habitat threatened, 3) history of decline *02*. The Forster's tern is also protected under the Migratory Bird Treaty Act, 1918 *19* and the Illinois Wildlife Code. 1971 *24*.

 


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: No records.

Associated tree species: No records.

National wetland inventory classifications:

SystemSubsystemClassSubclassWater regime modifiersWater chemistry
Lacustrine Littoral Emergent vegetation Persistent Intermittently exposed/permanent nontidal Freshwater
Lacustrine Littoral Emergent vegetation Narrowleaved persistent Intermittently exposed/permanent nontidal Freshwater
Lacustrine Littoral Flat Cobble/gravel Intermittently exposed/permanent nontidal Freshwater
Lacustrine Littoral Flat Sand Intermittently exposed/permanent nontidal Freshwater
Lacustrine Littoral Flat Mud Intermittently exposed/permanent nontidal Freshwater
Lacustrine Littoral Open water of unknown bottom type   Intermittently exposed/permanent nontidal Freshwater
Palustrine   Emergent vegetation Persistent Intermittently exposed/permanent nontidal Freshwater
Palustrine   Emergent vegetation Narrowleaved persistent Intermittently exposed/permanent nontidal Freshwater
Palustrine   Flat Cobble/gravel Intermittently exposed/permanent nontidal Freshwater
Palustrine   Flat Sand Intermittently exposed/permanent nontidal Freshwater
Palustrine   Flat Mud Intermittently exposed/permanent nontidal Freshwater
Riverine Lower perennial Emergent vegetation Persistent Intermittently exposed/permanent nontidal Freshwater
Riverine Lower perennial Emergent vegetation Narrowleaved persistent Intermittently exposed/permanent nontidal Freshwater
Riverine Lower perennial Flat Cobble/gravel Intermittently exposed/permanent nontidal Freshwater
Riverine Lower perennial Flat Sand Intermittently exposed/permanent nontidal Freshwater
Riverine Lower perennial Flat Mud Intermittently exposed/permanent nontidal Freshwater
Riverine Lower perennial Open water of unknown bottom type   Intermittently exposed/permanent nontidal Freshwater

Comments on species-habitat associations:
During the breeding season the Forster's tern is strongly associated with marshes, while outside of nesting it is known to frequent beaches and more open water *03,05*. Breeding habitats in Illinois feature fairly large lakes bordered with marshes *02*.

Important plant and animal association: Muskrat lodges, cattails, black terns.
Though the Forster's tern nests in marshes it prefers dry nesting sites and is often associated with muskrat houses as a nesting substrate *02*. Cattail stands and detrital cattail mat seem an important factor of breeding habitat *02,04*. Forster's tern comes into contact with black terns during breeding season due to their similar habitat preference, but apparently no competition exists *23*.

High value habitats

HabitatStructural stageSeason
Lakes Not applicable
(HVAL-HAB cover)
Fall
Lakes Not applicable
(HVAL-HAB cover)
Spring/summer
Reservoirs Not applicable
(HVAL-HAB cover)
Fall
Reservoirs Not applicable
(HVAL-HAB cover)
Spring/summer
Nonforested wetland Special habitat Fall
Nonforested wetland Special habitat Spring/summer
Wetland Special habitat Fall
Wetland Special habitat Spring/summer
Lakes and ponds Not applicable
(HVAL-HAB cover)
Fall
Lakes and ponds Not applicable
(HVAL-HAB cover)
Spring/summer
Lake Michigan Not applicable
(HVAL-HAB cover)
Fall
Lake Michigan Not applicable
(HVAL-HAB cover)
Spring/summer
Streams Special habitat Fall
Streams Special habitat Spring/summer
Beach Not applicable
(HVAL-HAB cover)
Fall
Beach Not applicable
(HVAL-HAB cover)
Spring/summer
Marsh restoration Special habitat Fall
Marsh restoration Special habitat Spring/summer

Species-habitat interrelations: See [HA] pg. 4.


GUILDS

Feed-guilding:

HabitatStructural stageSeasonFeed-guilds
Wetland Special habitat All Terrestrial surface- arthropods
Terrestrial surface- invertebrates other than arthropods
Terrestrial surface- amphibians
Water surface- arthropods
Water surface- invertebrates other than zooplankton or arthropods
Water surface- fish
Water surface- amphibians
Water column- arthropods
Water column- invertebrates other than zooplankton or arthropods
Water column- fish
Water surface- carrion
Terrestrial surface- carrion
Air- arthropods
Lakes and ponds Not applicable
(HVAL-HAB cover)
All Terrestrial surface- arthropods
Terrestrial surface- invertebrates other than arthropods
Terrestrial surface- amphibians
Water surface- arthropods
Water surface- invertebrates other than zooplankton or arthropods
Water surface- fish
Water surface- amphibians
Water column- arthropods
Water column- invertebrates other than zooplankton or arthropods
Water column- fish
Water surface- carrion
Terrestrial surface- carrion
Air- arthropods
River Not applicable
(HVAL-HAB cover)
All Terrestrial surface- arthropods
Terrestrial surface- invertebrates other than arthropods
Terrestrial surface- amphibians
Water surface- arthropods
Water surface- invertebrates other than zooplankton or arthropods
Water surface- fish
Water surface- amphibians
Water column- arthropods
Water column- invertebrates other than zooplankton or arthropods
Water column- fish
Water surface- carrion
Terrestrial surface- carrion
Air- arthropods

Comments on feed-guilding:
The Forster's tern eats a more varied diet than other tern spp. Because of its marsh existence it eats more insects than most tern spp., but fish are their principle food item *05,14,15,23*. This species feeds aerially, picks food off surface, and plunges into water after prey *04,05,08,09*. This tern also eats limited amounts of carrion (dead fish and frogs) and bird eggs; sometimes conspecifics *05,11,14*.

Breed-guilding:

HabitatStructural stageSeasonBreed-Guilds
Wetland Not applicable
(HVAL-HAB cover)
Spring/summer Terrestrial surface, herbaceous litter
Terrestrial surface, beaches (mud, sand, rock) without hydrophytes
Terrestrial surface, marshy areas with hydrophytes but not hydric soils
Terrestrial surface, grass and grasslike vegetation
Lakes and ponds Not applicable
(HVAL-HAB cover)
Spring/summer Terrestrial surface, herbaceous litter
Terrestrial surface, beaches (mud, sand, rock) without hydrophytes
Terrestrial surface, marshy areas with hydrophytes but not hydric soils
Terrestrial surface, grass and grasslike vegetation

Comments on breed-guilding:
Forster's terns invariably breed in inland lakes or marshes placing nests near open water but prefers a high, dry substrate (muskrat lodge, piles of vegetation). Exact location of copulation unknown. See *23* for habitat description.

 


FOOD-HABITS

Trophic level is CARNIVORE

Food itemLife stage/plant part
Insecta Unknown
Odonata (dragonflies, damselflies) Larva
Odonata (dragonflies, damselflies) Adult
Orthoptera (grasshoppers, crickets, cockraoches) Unknown
Coleoptera (beetles) Unknown
Tricoptera (caddisflies) Adult
Osteichthyes (bony fishes) See comments
Salientia (frogs, toads) Unknown
Birds Egg/fetus
Podicipedidae (grebes) Egg/fetus
Laridae (gulls, terns) Egg/fetus
Important:
Insecta Unknown
Odonata (dragonflies, damselflies) Adult
Tricoptera (caddisflies) Adult
Osteichthyes (bony fishes) See comments
Juvenile:
Osteichthyes (bony fishes) See comments
Adult:
Insecta Unknown
Odonata (dragonflies, damselflies) Larva
Odonata (dragonflies, damselflies) Adult
Orthoptera (grasshoppers, crickets, cockraoches) Unknown
Coleoptera (beetles) Unknown
Tricoptera (caddisflies) Adult
Osteichthyes (bony fishes) See comments
Salientia (frogs, toads) Unknown
Laridae (gulls, terns) Egg/fetus

Comments on food habits: 
General: Because of its breeding habitat the Forster's tern has a more varied diet than the common tern *05,14*. Insects make up a significant proportion of the diet which the Forster's tern may catch on the wing or pick up from the water. Small fishes are their principle food and are caught from the waters surface or by diving into water from a perch or a hover *04,05,13,14,15*. Forster's terns are known to eat dead fish and frogs revealed by receeding ice and also are known to occassionally eat bird eggs *11,14,15,23*.
Juvenile: The only mention of juvenile food habits available was of parent terns carrying small fishes in their bills back to nesting areas *10, 11*. It is assumed juveniles adopt adult habits upon fledging and independence *00,09*.
Adult: See [FH] general and important food habits.


ENVIRONMENTAL ASSOCIATIONS

General:

  • Biodegradable organics: clean waters that have not been polluted
  • Aquatic habitat: shallows with emergent vegetation (littoral zone)
  • Aquatic habitat zone: pelagic- needs open water
  • Water level: see comments
  • Aquatic habitats: typha-scirpus marsh
  • Aquatic habitats: freshwater marsh
  • Aquatic habitats: sandy beaches
  • Aquatic habitats: sandbars
  • Aquatic habitats: island inhabitant
  • Aquatic habitats: sloughs, bayous
  • Aquatic habitats: marsh
  • Aquatic habitats: backwaters
  • Grasses: see comments
  • Unknown

Limiting:

  • Biodegradable organics: clean waters that have not been polluted
  • Aquatic habitat: shallows with emergent vegetation (littoral zone)
  • Aquatic habitat zone: pelagic- needs open water
  • Water level: see comments
  • Aquatic habitats: typha-scirpus marsh
  • Aquatic habitats: freshwater marsh
  • Aquatic habitats: marsh

Egg

  • Unknown

Feeding juvenile:

  • Unknown

Resting juvenile:

  • Aquatic habitat: shallows with emergent vegetation (littoral zone)
  • Aquatic habitat zone: pelagic- needs open water
  • Aquatic habitats: typha-scirpus marsh
  • Aquatic habitats: freshwater marsh
  • Aquatic habitats: sandy beaches
  • Aquatic habitats: sandbars
  • Aquatic habitats: sloughs, bayous
  • Aquatic habitats: marsh
  • Grasses: see comments

Feeding adult:

  • Aquatic habitat zone: pelagic- needs open water
  • Aquatic habitats: typha-scirpus marsh
  • Aquatic habitats: freshwater marsh
  • Aquatic habitats: sloughs, bayous
  • Aquatic habitats: marsh

Resting adult:

  • Aquatic habitat zone: pelagic- needs open water
  • Aquatic habitats: typha-scirpus marsh
  • Aquatic habitats: freshwater marsh
  • Aquatic habitats: sandy beaches
  • Aquatic habitats: sandbars
  • Aquatic habitats: sloughs, bayous
  • Aquatic habitats: marsh
  • Grasses: see comments

Breeding adult:

  • Aquatic habitat: shallows with emergent vegetation (littoral zone)
  • Water level: see comments
  • Aquatic habitats: typha-scirpus marsh
  • Aquatic habitats: freshwater marsh
  • Aquatic habitats: sandy beaches
  • Aquatic habitats: sandbars
  • Aquatic habitats: island inhabitant
  • Aquatic habitats: sloughs, bayous
  • Aquatic habitats: marsh
  • Aquatic habitats: backwaters
  • Grasses: see comments

Comments on environmental associations:
General: See species habitat associations.
Feeding juvenile: No available information but assume when fledged to utilize feeding.
Resting juvenile: No available information but assumed to use nesting area (marsh habitat, tall vegetation) until independent *00*.
Feeding adult: Adults are known to feed over open water and in vegetated marshes *04,05,09*. In California it was noted that adults did not fish in their nesting area because it was too limited by vegetation for good fishing and travelled to more open water *11*.
Resting adult: No available information but assume rests in and near nest when incubating *00*.
Breeding adult: During breeding season the Forster's tern is essentially a bird of marshes *05,15,21*. In Illinois this species is primarily found on marsh bordered lakes slightly larger than those preferred by black terns *02*. For nest sites, higher dry substrates are preferred, i.e. muskrat houses, driftage or matted vegetation *02,21,23*. A stable water level may be important as many nests are lost to flooding *10, 23*. Marshes vegetated with phragmites, typha and scirpus grasses seem to be good habitats *06*.


LIFE HISTORY

Origin: Native *01,02*.

Physical description: 14-16 1/2 in. length; 30 in. wingspread. Forster's tern is easily mistaken for the common tern, however their calls are very different. In summer it is black-capped with a white breast, light grey mantle. The deeply forked tail is pale grey with white outer edges and a dark border along the inside of fork. Wing tips are silvery white or frost grey. Bill is orange-red with black tip, orange-red feet, and eyes are dark brown. In winter plumage, the head lacks the black cap but is distinguished by narrow black band through and back of the eyes and black spot near ear. The feet are yellowish and bill is dark *03,13,18*.

Reproduction: No information is available for Illinois and little available for other areas. Forster's tern is a migrant species in Illinois and throughout C. U.S. from great lakes to New England. It winters from C. Calif. and Baja, Calif. to S.W. Mexico from E. Mexico north and east along shores of gulf to W. Fla., and from N. Fla. north to Va. Forster's terns arrive approx. late April in Ill., early April in KY, and Minn. in early april *02,05,12*. No information is available on courtship activities but Salt & Willard (1971) reported a "heightened social interaction" from courtship and nesting in San Francisco *09*. Portnoy (1977) reported Forster's terns nested earlier than other terns (early March-July compared to early April- Aug.) in Louisiana *21*. No information is available on choice of territory or nest site. The Forster's tern varies the family custom of nesting by constructing a real nest of vegetation, in rank growths of grass or on drifted mats of sedge *05,13*. Nests vary in construction from a well made structure on an assembled heap of vegetation to a mere hollow in a pile of reeds, muskrat house or muddy or sandy shore. Nests may also be placed in dead reeds or flag being held several feet above water *05,03,13*. Forster's terns may appropriate nests from other birds, i.e. grebes *03*. Construction of the nest remains undescribed. Egg dates: VA, 30 May-12 July (5-28 June); Manitoba, 7 June-12 July (8-21 June); Utah, 5 June-3 July (11-26 June); Calif., 26 May-12 July (27 May-15 June) *05*. Forster's tern usually lays 3-4 (2-5) eggs, 43.0 x 31.0 mm *05,07,13,23*. Eggs may vary from tawny olive to buff having small lavender and grey spots *05,07*. Incubation is apparently done by both sexes and may last from 23-25 days *03,05,06,23*. McNicholl (1983) reports eggs hatch within 1 day of each other in the order laid. Eggs hatched over a 1-5 day period *06*. In San Francisco, many multiple layings were observed and it is assumed that the larger clutches observed are a product of more than 1 female *05*. Forster's tern is known to raise only 1 brood per year *05,13,14*. Upon hatching young are downy, clay colored to buff and heavily streaked or spotted with black *05*. Chicks hatch with eyes open but remain in nest for first day or 2 *03,05*. Young are fed by parents until fully grown and able to fly after which they are recruited into the hunting population *05,06*. Flight age is unknown.

Behavior: No information is available on territoriality or home range. Forster's terns are known to nest in loose colonies or solitarily *03*. Bent (1921) describes one colony as having 12 nests in 30 yds. square *05*. Scharf (1979) noted 35-40 pair on .012 ha *04*. Outside of nesting season Forster's tern frequents bays, beaches and oceans, but during breeding season prefers marsh habitat (i.e. phragmites, Typha and Scirpus spp.). Van Rossen (1933) reported this species traveling 2 miles to feeding areas *11*. This particular colony never fed in their nesting area for it was too limited by vegetation for good fishing. The Forster's tern may prefer open water for fishing. Salt & Willard (1971) reported this species fishing with a specialized mode of flying over water and diving which made it able to capitalize on the small fishes which live in shallow waters or in upper levels of larger bodies of water *09*. The Forster's tern is radically hostile to other bird species but sociable to its own kind (except during breeding season) *05*. A strong suggestion of nesting may be the attack behavior of the parents *22*.

Limiting factors: Probably, the most limiting factor to the Forster's tern as a breeding bird in Illinois and other areas is the loss of nesting habitat. In Illinois this species seems dependent on larger lakes with marsh borders for nesting *02*. Developmental and recreational use of lakes and marshes may prevent the Forster's tern from nesting in Illinois *02*. In the Green Bay, Wisc. area this species is a regular nester in dense cattail and detrital cattail mat. 80% of this habitat was lost between 1966-1976 *04*. Another threat to terns has been the massive spraying of marshes with insecticides (mainly DDT) for mosquito control. Terres (1980) reports large numbers of terns, some 5 to 12 yrs. old, had been found dead on New England beaches; killed by DDT acquired from minnows *03*. Vandalism and intentional human disturbance still occur. Portnoy (1977) reported the abandonment of the largest Forster's tern colony (Grassy I) in Louisiana *21*. Natural enemies include: muskrat, mink, other gulls, foxes, racoons, weasels, rats *03,05*. Changing water levels destroys nests and eggs *SEE 23*.

Population parameters: No information is available on population size, relative trends, survival and mortality rates, sex ratio and average lifespan. This species has probably declined in Illinois with the loss of its preferred nesting habitat *02*. Bergman et al. (1970) reported 12% nesting success (N=107) *23*.

 


MANAGEMENT PRACTICES

Beneficial:

  • Maintaining undisturbed/undeveloped areas
  • Maintaining early stage of ecological succession
  • 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
  • Controlling pollution in aquatic habitats
  • Controlling water levels
  • Maintaining streams
  • Developing/maintaining lakes and ponds
  • Developing/maintaining wetlands
  • Creating/maintaining wetlands from non-wetlands
  • Developing/maintaining mudflats
  • Protecting existing wetlands
  • Burning of wetlands to maintain successional stages
  • Restoration of wetlands (return flooded or drained areas to previous wetland conditions)
  • Seeding aquatic plants
  • Restricting human disturbance during migration, breeding, and nesting
  • Developing/maintaining spawning and nesting areas and structures

Adverse:

  • Recreational development
  • Channelization
  • Dredging
  • Controlling aquatic plants
  • Draining ponds/lakes
  • Draining wetlands
  • Applying pesticide on agricultural land
  • Strip mining
  • Applying insecticides

Comments on management practices:
Apparently the Forster's tern in Illinois is dependent on larger inland lakes with marsh borders for nesting *02*. Developmental & recreational use of lakes and marshes may prevent this species from nesting in Illinois *02*. The Forster's tern has a sporadic history in the great lakes. In a known nesting area (Green Bay) 80% of its preferred habitat has been lost between 1966-1976 *03*. A latest threat to terns has been massive spraying of marshes with insecticides (mainly DDT) for mosquito control *03*. Human vandalism and disturbance is an extreme limiting factor. Intruders into colonies may crush young and eggs and in some areas of the country still shoot individuals *03,21*. Management in Illinois must include the maintainance of natural marsh conditions along borders of large inland lakes that provide potential nest habitat for the Forster's tern. Also, as with other marsh species, control of water quality may also play a critical role in maintaining breeding populations *02*. The Forster's tern is protected by the Illinois Endangered Species Act 1973 *02*, the Migratory Bird Treaty Act *19*, and the Illinois Wildlife Code, 1921 *21*.

 


REFERENCES

0. MALMBORG, PATTI L. 1984. IL. NAT. HIST. SURV., 607 E. PEABODY DR., CHAMPAIGN, ILL. (217)333-6846.

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

2. BOWLES, M. 1981. ENDANGERED & THREATENED VERTEBRATE ANIMALS & VASCULAR PLANTS OF ILLINOIS. ILLINOIS DEPT. OF CONSERV. P. 47.

3. TERRES, J.K. 1980. THE AUDUBON SOCIETY: ENCYCLOPEDIA OF NORTH AMERICAN BIRDS. ALFRED A. KNOPF, NEW YORK. 1109 P.

5. BENT, A.C. 1921. LIFE HISTORIES OF NORTH AMERICAN GULLS & TERNS. U.S. NATL. MUS. BULL. #113. PP. 229-236.

6. MCNICHOLL, M.K. 1983. HATCHING OF FORSTER'S TERNS. CONDOR 85:50-52.

7. HARRIS, A.T. 1933. THE FORSTER TERN. THE OOLOGIST 50:31-34.

8. REED, J.M., H.E. HAYES, & D.A. ZEGERS. 1982. FEEDING BEHAVIORS AND EFFICIENCIES OF COMMON & FORSTER'S TERNS. WILSON BULL. 94(4):569-571.

9. SALT, G.W. & D.E. WILLARD. 1971. THE HUNTING BEHAVIOR AND SUCCESS OF FORSTER'S TERN. ECOLOGY 52:989-998.

10. SIBLEY, C.G. 1952. FORSTER TERNS BREEDING ON SAN FRANCISCO BAY, CALIFORNIA. CONDOR 55:278-279.

11. VAN ROSSEM, A.J. 1933. TERNS AS DESTROYERS OF BIRDS' EGGS. CONDOR 35(2):49-51.

12. MENGEL, R.M. 1965. THE BIRDS OF KENTUCKY. ORNITHOL. MONOGR. NO. 3. P. 261.

13. SPRUNT, A. & E.B. CHAMBERLAIN. 1970. SOUTH CAROLINA BIRD LIFE. UNIVERSITY OF SOUTH CAROLINA PRESS, COLUMBIA. P. 266-267.

14. FORBUSH, E.H. 1929. BIRDS OF MASSACHUSETTS. VOL. I. NORWOOD PRESS, NORWOOD, MASS. PP. 103-105.

15. BURLEIGH, T.D. 1958. GEORGIA BIRDS. UNIVERSITY OF OKLAHOMA PRESS. NORMAN. PP. 288-289.

16. STONE, W. 1937. BIRD STUDIES AT OLD CAPE MAY. VOL. II. THE DELAWARE VALLEY ORNITHOLOGICAL CLUB. PHILADELPHIA. P. 578.

17. MARTIN, A.C., H.S. ZIM, & A.L. NELSON. 1951. AMERICAN WILDLIFE & PLANTS. MCGRAW-HILL BOOK CO., INC., NEW YORK.

18. PETERSON, R.T. 1980. A FIELD GUIDE TO THE BIRDS. HOUGHTON MIFFLIN CO., BOSTON. P. 96.

19. U.S. FISH & WILDLIFE SERVICE. 1980. CODE OF FEDERAL REGULATIONS. TI- TLE 50. WILDLIFE AND FISHERIES. CHAPTER 1. PP 11-18. 50CFR10.13. LIST OF MIGRATORY BIRDS. SPECIAL PUBL. FEDERAL REGISTER. GENERAL SER- VICES ADMIN. OCTOBER 1.

20. AMERICAN ORNITHOLOGIST'S UNION. 1982. THIRTY-FOURTH SUPPLEMENT TO THE AMERICAN ORNITHOLOGIST'S UNION'S CHECK-LIST TO NORTH AMERICAN BIRDS. SUPPL. TO AUK VOL. 99(3).

21. PORTNOY, J.W. 1977. NESTING COLONIES OF SEABIRDS AND WADING BIRDS - COASTAL LOUISIANA, MISSISSIPPI & ALABAMA. U.S. FISH & WILFLIFE SERVICE, BIOLOGICAL SERVICES PROGRAM. FWS/OBS-77/07. 126 PP.

22. KLEEN, V. 1982/1983. FIELD NOTES: BREEDING SEASON. ILLINOIS AUDUBON SOCIETY. WAYNE, IL. P. 31.

23. BERGMAN, R.D., P. SWAIN & M.W. WELLER. 1970. A COMPARATIVE STUDY OF NESTING FORSTERS AND BLACK TERNS. WILSON BULL. 82(4):435-444.

24. 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. 120 P.

 


 

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