Birds At Airports - Internet Center for Wildlife Damage Management

146 Pages·1994·5.9 MB·English

by  Alfred J. Godin

BIRDS
E-1 Birds at Airports Alfred J. Godin
E-5 Bird Damage at Aquaculture Facilities W. Paul Gorenzel, Fred S. Conte, and Terrell P. Salmon
E-19 Bird Dispersal Techniques Thurman W. Booth
E-25 Blackbirds Richard A. Dolbeer
E-33 Crows, American Ron J. Johnson
E-41 Eagles Bart W. O’Gara
E-49 Gulls Victor E. F. Solman
E-53 Hawks and Owls Scott E. Hygnstrom and Scott R. Craven
E-63 Horned Larks Jerry P. Clark and Scott E. Hygnstrom
E-67 House Finches (Linnits) Jerry P. Clark and Scott E. Hygnstrom
E-71 Jays, Scrub (California) Jerry P. Clark and Scott E. Hygnstrom
E-75 Kites, Mississippi William F. Andelt
E-79 Magpies Thomas C. Hall
E-87 Pigeons (Rock Doves) David E. Williams and Robert M. Corrigan
E-97 Sparrows, Crowned Jerry P. Clark and Scott E. Hygnstrom
E-101 Sparrows, House William D. Fitzwater
E-109 Starlings Ron J. Johnson and James F. Glahn
E-121 Swallows W. Paul Gorenzel and Terrell P. Salmon
E-129 Waterfowl Edward C. Cleary
E-139 Woodpeckers Rex E. Marsh
Alfred J. Godin BIRDS AT AIRPORTS
State Director (retired)
USDA-APHIS-
Animal Damage Control
Augusta, Maine 04330
Birds are a serious hazard to aviation. this problem worldwide makes bird ated by bird impact with a fast-moving
A bird or a flock of birds that suddenly strike a serious economic problem. aircraft is tremendous. The newer tur-
rises from a runway or surrounding bine engines use light-weight, high-
Birds have been a hazard to aircraft
area may collide with incoming or speed mechanical parts which are
from the first powered flight. During
departing aircraft and cause the air- vulnerable to bird strike damage.
the early days of aviation, when air-
craft to crash, possibly resulting in the
craft flew at slow speeds, birds had The Federal Aviation Administration
loss of human life. Bird collision with
little difficulty in getting out of the (FAA) prescribes rules governing
aircraft is commonly known as “bird
way. Bird strikes were infrequent and wildlife hazard management at certi-
strike.”
damage was mainly confined to fied airports in the Federal Aviation
Damage caused to aircraft usually cracked windshields. The likelihood of Regulations: Part 139. The USDA-
results from collision of one or more the loss of aircraft and/or human lives APHIS-ADC program recognizes the
birds with the engines and/or fuse- was remote. With the development potential for aircraft accidents and loss
lage. Although most bird strikes do and introduction of jet aircraft, bird of human life and considers bird haz-
not result in crashes, they do involve strikes became a serious hazard and ards to aircraft a top priority. This pro-
expensive structural and mechanical costly problem. Faster speeds mean gram provides technical assistance to
damage to aircraft. The incidence of birds have less time to react to alleviate bird hazards to civilian air-
approaching aircraft. The force gener- ports and military airbases.
PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994
Cooperative Extension Division
Institute of Agriculture and Natural Resources
University of Nebraska - Lincoln
United States Department of Agriculture
Animal and Plant Health Inspection Service
Animal Damage Control
E-1
Great Plains Agricultural Council
Wildlife Committee
Legal Status birds, and small mammals. Seeds and sources of water provide a variety of
berries are sought by several migra- bird foods, including small fish, tad-
Most bird species are protected by fed- tory and resident birds such as spar- poles, frogs, insect larvae, other inver-
eral and state laws. The legal status of rows, finches, starlings, blackbirds, tebrates, and edible aquatic plants.
problem bird species at airports mourning doves, common pigeons, Temporary and permanent waters,
should be determined before control is and waterfowl. Geese are attracted to including ponds, borrow pits, sumps,
attempted. Migratory birds are pro- open expanses of grasses. Gulls, star- swamps, and lakes, attract gulls,
tected under the Migratory Bird Treaty lings, robins, and crows often feed on waterfowl, shorebirds, and marsh
Act of 1918 (16 USC 703-711), while earthworms on the surface of the birds. Fresh water is especially attrac-
nonmigratory species are protected ground following a rain. Gulls are tive in coastal areas.
under state laws. Some species are fur- opportunistic feeders and frequently
Cover. Birds need cover for resting,
ther protected by the Endangered Spe- feed on grasshoppers and ground-
loafing, roosting, and nesting. Trees,
cies Act of 1973 (Pub. Law 93-205). nesting birds. Raptors are attracted to
brushy areas, weed patches, shrubs,
These laws state make it unlawful to airports because of rodents, birds, and
and airport structures often provide
pursue, capture, take, kill, or possess other small animals that harbored by
suitable habitat to meet these require-
migratory birds or endangered and tall, poorly maintained grass stands
ments. Almost any area that is free
threatened species, except as permit- and borders.
from human disturbance may provide
ted by regulations adopted by the
Occasionally, food becomes available a suitable roosting site for one or more
secretary of the interior. Permits to
through careless waste disposal prac- species of birds. Starlings, pigeons,
take nonendangered migratory birds
tices by restaurants and airline flight house sparrows, and swallows often
are issued only when the birds are
kitchens. Airport personnel have been roost or nest in large numbers in air-
causing, or have the potential to cause,
known to feed birds during their lunch port buildings or nearby trees, shrubs,
a serious threat to public health and
breaks. Many airports have inadequate or hedges. Large concentrations of
safety and when nonlethal methods
garbage disposal systems that permit blackbirds and starlings are attracted
have failed to solve the problem. A
access to various food items. These are to woody thickets for winter roosting
state permit also may be required to
a favorite of several species of birds, cover. Gulls often find safety on or
control migratory and nonmigratory
especially gulls. Nearby landfills or near runways of coastal airports when
birds protected by the state.
sewage outlets may also provide food storms prevent their roosting at sea, on
for birds and other wildlife. islands, or on coastal bays.
Airports
Landfills are often located on or near
Migration
airports because both are often built on
No two airports are exactly alike. publicly owned lands. In these circum- Many airports are located along tradi-
Accordingly, bird hazards vary from stances, landfills contribute to bird tional annual bird migration routes.
airport to airport, even when the same strike hazards by providing food Birds may suddenly appear in large
species are involved. The occurrence sources and loafing areas that attract flocks on or over an airport on their
of birds at airports varies according to and support thousands of gulls, star- annual migration, even when the air-
habitat availability, weather, season of lings, pigeons, and other species. Gen- port itself offers no particular attrac-
year, and time of day. erally, landfills are a major attraction tion. Dates of migration vary by
for gulls, the most common bird species and area. Flock size of a given
Bird Attractants at Airports
involved in bird strikes. Waste paper, species may vary widely from year to
Airports provide a wide variety of paper bags, and other litter blowing year depending on time of year,
natural and human-made habitats that across the ground attract gulls, pre- weather conditions, and many other
offer food, water, and cover. Many air- sumably because litter is mistaken for factors.
ports are located along migratory other gulls or for food. A gull that is
routes used by birds. One of the first attracted to litter decoys other gulls Local Movements
steps in reducing bird hazards is to and encourages flocking. Shorebirds, waterfowl, gulls, and other
recognize these attractants. Usually, Water. Birds of all types are drawn to birds often make daily flights across
several attractants acting in combina- open water for drinking, bathing, feed- airports from their feeding, roosting,
tion are responsible for the presence of ing, loafing, roosting, and protection. nesting, and loafing areas. Airports
birds and their behavior at an airport. Rainy periods provide temporary near cities may experience early
Food. Birds require relatively large water pools at many airports. Many morning and late afternoon roosting or
amounts of food. Most airports sup- airports have permanent bodies of feeding flights of thousands of
port an abundance and variety of water near or between runways for starlings.
foods such as seeds, berries, grass, landscaping, flood control, or waste-
insects, grubs, earthworms, small water purposes. These permanent
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Damage Prevention and An early priority in reducing bird haz- calls can be recorded on tape cassettes
Control Methods ards is to establish a bird dispersal and played through a loudspeaker
patrol team to harass and scare birds located on the patrol vehicle. Distress
and provide immediate protection for calls supplement shellcrackers and
Bird strike hazards reoccur regularly at
aircraft within the airport perimeter. noise bombs.
many airports and require constant
The patrol team must consist of highly
attention. Before attempting to reduce Automatic exploders or gas cannons,
motivated and knowledgeable person-
bird hazards at an airport, it is important operated by acetylene, propane, or LP
nel with adequate equipment, such as
to assess the problem, identify contribut- gas, produce a noise louder than a
radio-equipped vehicles, shotguns,
ing factors, and analyze the threat to shotgun blast. Exploders can be set up
and frightening devices consisting of
aircraft and human safety. A wildlife and left to operate continuously, but
bird distress calls, live ammunition,
hazard management plan should be for best results, the exploders should
and pyrotechnic devices (automatic
implemented (and may be required by be operated for limited periods of time
gas exploders, shellcrackers, and
FAA) to make the airport unattractive only, unless birds are moving into the
racket bombs). Patrol personnel must
to birds. Scaring or dispersing birds airport. Exploders should be moved
be trained in bird identification and
away from airports is usually difficult periodically so that the birds do not
dispersal methods. Clear communica-
because birds are tenaciously attracted become accustomed to the blasts.
tion between the patrol team and the
to available food, water, and cover. As
control tower is essential.
long as these attractants exist, birds Repellents
will be a problem. Birds react to unfamiliar sounds and
Research has been conducted on the
objects. They learn, however, to ignore
In most situations, a wildlife biologist efficacy of methyl anthranilate (ReJeX-
sounds and objects that have proven
trained in bird hazard assessment iT, Peter Vogt, PMC Corp., pers.
harmless, especially if they are used
should be selected to conduct a thor- commun.) for repelling gulls and wa-
often and for long periods of time.
ough ecological study of the airport terfowl from standing pools of wtaer
Birds should not be allowed to accli-
and its vicinity. The study should on airport runways. Results are prom-
mate to a scare device through
determine what species of birds are ising and registration of ReJeX-iT by
repeated exposure without an associ-
involved, what attracts them, abun- the Environmental Protection Agency
ated adverse effect. The use of shoot-
dance and peak use periods and spe- is currently pending. Methyl anthrani-
ing to reinforce frightening techniques
cial hazard zones. It should also late is a grape-flavored food additive.
can be effective and should occur
include control recommendations to
simultaneously with the scare devices
reduce the frequency of bird occur- Shooting
often enough to maintain fear in the
rence at the airport.
birds. In most cases, an integrated Shooting birds with shotguns or rifles
Habitat Modification approach that incorporates several can be a highly selective and useful
frightening devices will produce the form of hazard control under certain
Several habitat management practices best results. conditions. Federal, state, and possibly
can make an airport less attractive to municipal permits are required. Shoot-
birds. These include eliminating stand- The shellcracker fires a projectile from a ing has been used to reduce hazards
ing water, removing or thinning trees, 12-gauge shotgun. It travels up to 100 caused by birds that habitually fly over
removing brush and managing grass yards (90 m) and explodes with a loud airport runways. Caution must be
height. Buildings can be modified to noise and a flash. Noise bombs are simi- used so that shooting does not disturb
reduce or eliminate roosting or nesting lar and can supplement shellcrackers, nontarget species. Shooting is not prac-
sites. but their range is much shorter. Racket tical or desirable as a method for
bombs are propelled by a special pistol
reducing large numbers of birds.
FAA Order 5200.5A provides guide-
and travel approximately 100 yards
lines for the establishment, elimination,
(90 m); they do not explode.
Airport Assistance
or monitoring of landfills, open
dumps, or waste disposal sites on or in Shellcrackers and racket bombs may USDA-APHIS-ADC provides technical
the vicinity of airports. lose their effectiveness when used fre- and operational assistance to airports
quently. It may be necessary to use live
on all aspects of wildlife hazard man-
Frightening ammunition to kill an occasional bird.
agement, including workshops on bird
Remaining birds then become more
Frightening is a reliable and expedi- hazard management, conducting envi-
responsive to the noise devices.
tious means of repelling birds. Fright- ronmental assessments, and develop-
Remember that a permit is required to
ening programs, however, provide ing airport wildlife hazard
take protected species.
only temporary relief and require con- management plans.
stant monitoring. Distress calls are sounds emitted by
birds under conditions of stress. The
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Acknowledgments
I thank James Forbes, USDA-APHIS-ADC, and
Eugene LeBoeuf, Federal Aviation Administra-
tion, for reviewing the manuscript.
For Additional
Information
Arnold, K. A. 1981. Environmental control of
birds. Pages 499-505 in D. Pimentel, ed. CRC
handbook of pest management in agriculture,
vol. 1. CRC Press, Boca Raton, Florida. 597 pp.
Brough, T., and C. J. Bridgman. 1980. An evalua-
tion of long grass as a bird deterrent on Brit-
ish airfields. J. Appl. Ecol. 17:243-253.
Pearson, Erwin W. 1967. Birds and airports.
Proc. Vertebr. Pest Conf. 3:79-86.
Solman, Victor E. F. 1981. Birds and aviation.
Environ. Conserv. 8:45-51.
Thompson, Richard L. 1983. Bird hazards at air-
ports. Proc. Eastern Wildl. Damage Control
Conf. 1:331.
Editors
Scott E. Hygnstrom
Robert M. Timm
Gary E. Larson
E-4
W. Paul Gorenzel BIRD DAMAGE AT
Staff Research Associate
Department of Wildlife, Fisheries
and Conservation Biology AQUACULTURE
University of California
Davis, California 95616
FACILITIES
Fred S. Conte
Aquaculture Extension Specialist
Department of Animal Science
University of California
Davis, California 95616
Terrell P. Salmon
Wildlife Extension Specialist
Department of Wildlife,
Fisheries and
Conservation Biology
University of California
Davis, California 95616
Fig. 1. Great blue heron, Ardea herodias
Damage Prevention and Frightening Trapping
Control Methods Various devices available include Except for some blackbirds, trapping is
reflecting tapes, eyespot balloons, not allowed without a permit from
Exclusion scarecrows, automatic exploders, the US Fish and Wildlife Service
pop-up scarecrows with exploders, and upon recommendation by the
Completely enclose small ponds,
pyrotechnics, alarm or distress calls, USDA-APHIS-Animal Damage
tanks, and/or raceways with screen
lights, water spray devices. Control. Permits are issued to
or netting.
compliment ongoing nonlethal
Aerial harassment with ultralight
Impediments methods. Check county or state
aircraft, radio-controlled model
permit requirements.
Partially covered systems with airplanes; ground harassment with
overhead wire, line, screen, or vehicle patrols. Shooting
netting. Perimeter fencing or wires.
Roost dispersal may move Same as for trapping, except that some
Metal spines, cones, or electrified depredating birds from the area. blackbirds may be shot. Ducks
wires for roosting problems. may be hunted during waterfowl
Avitrol® is a chemical frightening
hunting seasons.
Cultural Methods agent for herring gulls and
blackbirds.
Consideration of local bird
populations, construction of pond Toxicants
margins and bottom profile,
None are approved for use by federal
location of fingerling ponds, and
or state agencies.
feeding techniques may lessen
damage.
PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994
Cooperative Extension Division
Institute of Agriculture and Natural Resources
University of Nebraska - Lincoln
United States Department of Agriculture
Animal and Plant Health Inspection Service
Animal Damage Control
E-5
Great Plains Agricultural Council
Wildlife Committee
Table 1. Bird species reported as predators at aquaculture sites in North America.
Common Name Species Common Name Species
Common loon Gavia immer Red-breasted merganser Mergus serrator
Western grebe Aechmophorus occidentalis Hooded merganser Lophodytes cucullatus
Eared grebe Podiceps nigricollis Bald eagle Haliaeetus leucocephalus
Pied-billed grebe Podilymbus podiceps Osprey Pandion haliaetus
American white pelican Pelecanus erythrorhynchos Red-tailed hawk Buteo jamaicensis
Brown pelican Pelecanus occidentalis Northern goshawk Accipter gentilis
Double-crested cormorant Phalacrocorax auritus Northern harrier Circus cyaneus
Anhinga Anhinga anhinga American coot Fulica americana
Least bittern Ixobrychus exilis Yellowlegs Tringa spp.
American bittern Botaurus lentiginosus Franklin’s gull Larus pipixcan
Black-crowned night-heron Nycticorax nycticorax Ring-billed gull Larus delawarensis
Yellow-crowned night-heron Nycticorax violaceus California gull Larus californicus
Green-backed heron Butorides striatus Herring gull Larus argentatus
Little blue heron Egretta caerulea Glaucous gull Larus hyperboreus
Great blue heron Ardea herodias Caspian tern Sterna caspia
Cattle egret Bubulcus ibis Common tern Sterna hirundo
Snowy egret Egretta thula Forster’s tern Sterna forsteri
Great egret Casmerodius albus Black tern Chlidonias niger
White-faced ibis Plegadis chihi Great horned owl Bubo virginianus
White ibis Eudocimus albus Barred owl Strix varia
Wood stork Mycteria americana Belted kingfisher Ceryle alcyon
Mallard Anas platyrhynchos American crow Corvus brachyrhynchos
Northern pintail Anas acuta Fish crow Corvus ossifragus
Blue-winged teal Anas discors Common raven Corvus corax
Wood duck Aix sponsa Black-billed magpie Pica pica
Redhead Aythya americana American dipper Cinclus mexicanus
Greater scaup Aythya marila European starling Sturnis vulgaris
White-winged scoter Melanitta fusca Common grackle Quiscalus quiscula
Surf scoter Melanitta perspicillata Boat-tailed grackle Quiscalus quiscula
Bufflehead Bucephala albeola Brown-headed cowbird Molothrus ater
Common merganser Mergus merganser
Identification production efforts. Damage and Damage
Identification
Table 1 lists 61 species of birds
Reduction of the damage caused by
reported as pests at aquaculture sites.
fish-eating birds requires accurate bird
The open-water areas and large con-
Table 2 presents a brief description of
identification and some knowledge of
centrations of aquatic livestock at
the appearance, characteristic feeding
avian biology and habits. Responsible
aquaculture facilities are natural attrac-
habits, and behavior of birds respon-
bird management requires knowledge
tants to many birds. Birds can have a
sible for damage. Although some birds
of both the problem species and other
significant economic impact on the cul-
are limited in the way they feed and
birds that use the aquatic habitat with-
ture of aquatic products including fish,
may be easily deterred by control
out harming aquaculture efforts. Not
shellfish, crustaceans, and other inver-
measures, many birds have a reper-
all birds are harmful to production
tebrates. For our purpose here, we will
toire of feeding behaviors available to
efforts. Birds only become a problem if
refer to these birds as fish-eating birds,
overcome various damage reduction
their activities directly or indirectly
and the aquatic products as fish.
schemes. As an example, Table 3 illus-
result in fish loss. Many species benefit
from the association with production trates the variety of feeding behaviors Fish-eating birds are highly mobile and
facilities without interfering with used by six species of herons. adaptable predators, able to rapidly
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Table 2. Identification and description of the feeding habits and behavior of birds commonly responsible for damage
at aquaculture facilities.
Herons
Description:
• Body length varies, 11 to 38 inches (28 to 97 cm).
• Long legs and toes, short tail, large wings.
• Wingspan varies; great blue heron, 70 inches (178 cm); black-crowned night-heron, 44 inches (112 cm);
snowy egret, 38 inches (96 cm); green-backed heron 25 inches (64 cm).
• Neck usually long, bent in S shape when flying; beak long, pointed.
Black-crowned Green heron • Plumage variable: all white, brown, gray, blue; or pattern of stripes and streaks.
• Sexes colored alike; immatures duller than adults.
night-heron
Feeding and Other Habits:
• Various methods used depending on species. See Table 3 for more details.
• Feed mostly during day or at dusk; black-crowned night-herons feed mostly at dusk or night.
• Most nest in colonies; often perch or nest in trees near water.
Great
• Depending on species, hunt singly but can occur in large, loose flocks that tend toward even distribution
blue
Snowy egret across foraging area.
heron
• Foraging birds attract others.
Cormorants
Description:
• Five species in North America; double-crested cormorant described below is a major pest species at
aquaculture facilities.
• Body length 32 inches (81 cm).
• Wingspan 52 inches (132 cm).
• Plumage uniformly dark, with large, orange throat patch; young with lighter underparts. Sexes colored alike.
• Neck long and snakelike; flies with neck kinked; beak with hooked tip.
• Short legs and webbed toes; short tail often used as prop when perched.
• Swims with body often nearly submerged, but with neck erect and bill pointed at upward angle.
Feeding and Other Habits:
• Dives from surface; pursues fish underwater.
• Daytime feeder; hunts singly or in flocks that may number 500 to 600 birds. Birds in feeding flock form line
that advances on fish.
• Foraging birds attract others.
• Runs across water to take off.
• Nests in colonies; often perches on trees, poles, rocks, or buoys that overhang or project from water.
Gulls
Description:
• Many species; in general, stout body, total length 12 to 32 inches (30 to 81 cm).
• Long, pointed wings; wingspan 36 to 65 inches (91 to 165 cm).
• Bill slightly hooked; webbed feet.
• Adult plumage mostly white, wings white or dark on upper surface with dark tips. Immatures darker,
mostly brown or grayish.
• Sexes colored alike.
Feeding and Other Habits:
• Variable methods: plunges from flight, perches on raceway walls; swoops down to scoop up prey; bobs
while swimming.
• Forages along shoreline; scavenges dead fish.
• Daytime feeder.
• Highly social; breeds in colonies.
• Feeds in flocks.
Terns
Description:
• Streamlined, slender body, total length 9 to 23 inches (22 to 58 cm).
• Long, pointed wings; wingspan 20 to 53 inches (51 to 135 cm).
• Bill slender, sharp and pointed; tail usually forked.
• Plumage mostly whitish with gray on top of wings; black cap present except in winter.
• Sexes colored alike.
Feeding and Other Habits:
• Flies over water, hovers above surface, dives head-first into water.
• Daytime feeder; hunts individually.
• Nests in colonies; does not normally swim.
• Light, graceful flier.
(continued on next page)
E-7
Table 2. Continued
Mergansers
Description:
• Three species in North America: hooded, red-breasted, and common mergansers.
• Body length varies: hooded merganser 16 to 19 inches (41 to 48 cm); larger species 20 to 27 inches (51 to 69 cm).
• Wingspan from 26 to 37 inches (66 to 94 cm).
• Slender, spike-like bill with hooked tip.
• Crested head except for male common merganser.
• Plumage varies with sex: males at distance appear mostly black and white; females appear gray and brown.
Feeding and Other Habits:
• Dives from surface; pursues fish underwater.
• Daytime feeder.
• Normally in small, loose flocks; large concentrations unusual.
• Runs across water to take off.
• In flight, body, head, and neck are horizontal.
Blackbirds
Description:
• Many species: in general, small-bodied, total length 6 to 16 inches (15 to 40 cm); sharp, pointed bill.
• Plumage iridescent black; some species have brightly colored areas of yellow, red, or orange on head or
wings.
• Females smaller-bodied; plumage brownish, often with streaked breast.
Feeding and Other Habits:
• Catches prey in shallow water at impoundment edges, or climbs down raceway screens to water surface.
• All species daytime feeders.
• Gregarious; flocks number from few birds to thousands.
• Some species congregate in huge winter roosts.
Belted kingfisher
Description:
• Compact body, total length 12 to 13 inches (30 to 33 cm).
• Large head, short neck, heavy pointed bill.
• Short legs and toes; wingspan 21 to 24 inches (53 to 63 cm).
• Plumage blue-gray above; males with gray band across white breast, females with gray and rusty band.
Head crested.
Feeding and Other Habits:
• Plunge-dives head first from perch or hovering position.
• Daytime feeder.
• Territorial and solitary.
• Loud rattling call given in flight.
• Uses poles, wires, and other elevated objects as perches to scan foraging areas.
Pelicans
Description:
• Two species in North America: American white pelican described below is pest species at aquaculture sites.
• Body length 62 inches (158 cm).
• Wingspan 108 inches (274 cm).
• Very large white bird with black wing tips and enormous, orange bill with pouch. Sexes colored alike.
Young grayish colored.
• Swims with great buoyancy; floats high on water.
Feeding and Other Habits:
• Feeds from water surface; does not dive. Plunges head underwater and catches fish in pouch.
• Daytime feeder; hunts singly in deep water; in shallow water forms small flocks that drive fish toward
shore.
• Takes off from water with feet kicking in unison.
• Nests in colonies usually at sites remote from people.
• In flocks most of time; flies with series of slow wing beats followed by glide. Birds in flock fly single file;
may soar to great heights.
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Table 3. Occurrence of feeding behaviors among selected species of herons (from Kushlan 1978).
Species Great Great Snowy Green- Yellow- Black-
blue egret egret backed crowned crowned
heron heron night night
heron heron
Behavior1
Standing X X X X X X
Walking X X X X X X
Hovering X X X X
Dipping X X
Plunging X X X
Diving X
Feet-first diving X X
Jumping X X
Swimming feeding X X X X
1Feeding behaviors defined as follows:
Standing - stands in one place.
Walking - walks at a slow or fast speed.
Hovering - hovers over water or ground, picking up prey.
Dipping - while flying puts head down and catches prey.
Plunging - dives headfirst from air.
Diving - dives headfirst from perch.
Feet first diving - alights on water feet first.
Jumping - jumps from perch feet first.
Swimming feeding - swims or floats on surface of water.
exploit situations of food abundance. have failed to meet coliform bacteria raceways or ponds, hovering overhead
Aquaculture facilities are ideal feeding standards set by health service agen- and then plunging into the water,
sites for these predators. The severity cies due to fecal droppings of birds standing or stalking along the edges of
of bird problems will vary with the roosting on these structures. Bird feces ponds, or swimming and diving in the
species and number of birds present can degrade water quality and, ponds. Some species, including the
and whether the birds reside only sea- through bacterial activity, leads to black-crowned night-heron and the
sonally or tend to remain at the facility reduced oxygen levels. The economic yellow-crowned night-heron in par-
throughout the year. In recent years, impact on the farmer can be extensive ticular, feed at dusk and night, when
populations of normally migratory and, in some cases, devastating. Bird aquaculture personnel may not be
waterbirds have been reported to depredation results in loss of crop and present to observe damage. Because
remain near fish production facilities income. It can result in significant most fish are swallowed whole, often
year-round. The proximity of nearby expenditure of time and funds in few direct signs of damage are left
nesting or roosting sites and the avail- establishing bird management pro- behind. The decrease in the number of
ability of alternative feeding sites are grams and training personnel. remaining fish may not be obvious for
also important factors. Problems are some time. In these cases, the presence
The birds commonly responsible for
compounded when drought impacts of whitewash (bird excrement), bird
most damage are herons, cormorants,
alternative feeding sites, especially as feathers, and/or bird footprints may
pelicans, gulls, egrets, mergansers and
the number and size of available wet- be the only signs of bird predation.
other diving ducks, blackbirds, and
lands continue to diminish due to Additional observations at night
kingfishers. Other problem species
human activities. should be made to verify bird depre-
reported less frequently include dip-
dation. Some fish may show scars
Besides consuming fish, birds can pers, grebes, ospreys, and dabbling
from predatory attempts. Cormorants
injure fish, disrupt their feeding activ- ducks. Because most species of fish-
often injure fish, allowing access to
ity, disturb broodstock, and contribute eating birds are diurnal, or active dur-
fungal and bacterial disease organ-
to the spread of diseases and parasites ing daylight hours, direct observation
isms. Herons sometimes spear but do
in aquaculture ponds and raceways. In is the usual means of confirming bird
not kill or eat larger brood stock.
marine environments, large numbers presence and damage. Obvious signs
Chewed or partially eaten fish may be
of birds often roost on shellfish culture of hunting and feeding birds include
a sign of predatory mammals, includ-
or holding structures. Shellfish lots birds perched on trees or wires near
ing raccoon, mink, and otters.
E-9