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Effectiveness of barriers, pyrotechnics, flashing lights, and Scarey Man for deterring heron predation on fish

September 1997
Wildlife Society Bulletin 25(3):686-694

Authors:

William F. Andelt

Colorado State University

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Techniques

DETERRING HERON PREDATION ON FISH

Scarey

Man Fall

Guy. Photo

by William Andelt. Great blue heron. Photo

by William Andelt.

Effectiveness

barriers,

pyrotechnics,

flashing

lights,

and

Scarey

Man?

for

deterring

heron

predation

fish

William

F. Andelt, Timothy P. Woolley, and Stuart N. Hopper

Pyrotechnics are effective, but flashing lights and Scarey Man? are

ineffective in deterring heron predation on trout

Authors' address

during

this research:

Department

of Fishery

and

Wildlife

Biology,

Colorado State

University,

Fort

Collins,

CO 80523,

USA. Current address for

Timothy

P. Woolley:

Wyoming

Game and Fish

Department,

P.O. Box 111, Savery,

82332, USA.

Key

words: Ardea

herodias,

black-crowned

night-herons,

Colorado,

control,

frightening, great

blue herons,

hatchery,

Nycticorax

nycti-

corax,

wildlife

damage

Wildlife

Society Bulletin 1997, 25(3):686-694

686

Peer edited

Deterring

heron predation

on fish * Andelt

et al. 687

Fish-eating birds are significant predators at fish-

culture facilities (Scanlon et al. 1978, Parkhurst et al.

1987, Stickley and Andrews 1989, Stickley et al.

1995a). Black-crowned night-herons (Nycticorax

nycticorax; BCNH) and great blue herons (Ardea

berodias; GBH) have been estimated to capture an

average of 79,000 rainbow trout (Oncorhynchus

mykiss) annually from 1985 to 1989 at the Watson

Lake Fish Rearing Unit near Bellvue, Colorado (D. C.

Smeltzer, Colo. Div. Wildl., Bellvue, pers. commun.).

Several techniques have been used or recom-

mended to reduce heron predation on fish in hatch-

eries (Salmon and Conte 1981, Draulans 1987,

Parkhurst et al. 1987). Parkhurst et al. (1987) re-

ported limited success with hand-fired

pyrotechnics,

but Stickley and Andrews (1989) observed that py-

rotechnics were the most effective technique used

by Mississippi farmers

for frightening fish-eating

birds

from catfish ponds. Naggiar (1974) reported that

flashing lights with reflectors were effective during a

short period, for deterring BCNH and GBH foraging

at night. However, pyrotechnics and oscillating

lights have not been thoroughly evaluated.

Lagler

(1939) and Parkhurst et al. (1987) reported

limited to intermediate success with scarecrows in

frightening herons from hatcheries. A relatively new

technique, the Scarey Man' Fall Guy (R. Royal, P.O.

Box 108, Midnight, MS 39115), a 1.46-m-tall,

plastic

mannikin that intermittently

inflates with air, bobs up

and down, illuminates with an internal light, and

emits a high-pitched wail (Stickley et al. 1995b), has

been developed but has not been evaluated for fright-

ening BCNH and GBH. Stickley

et al. (1995b) reported

that Scarey Man reduced numbers of double-crested

cormorants (Phalacrocorax auritus) at catfish ponds

in Mississippi,

but the birds became habituated to the

devices at 3 of 4 sites. We evaluated the effectiveness

of nylon-mesh barriers,

pyrotechnics, bright rotating

(flashing) lights, and Scarey

Man for reducing number

of herons and predation on fish at a rearing unit near

Bellvue, Colorado.

Study area

The study was conducted at the Colorado Division

of Wildlife's Watson Lake Fish Rearing Unit (Fig. 1)

near Bellvue, Colorado. The raceways were formed

by concrete walls averaging 1.30 m high and extend-

ing about 11-18 cm above the ground. The water in

the raceways averaged 70 cm (range = 49-89 cm)

deep and 60 cm (range = 35-83 cm) below the top of

the raceway walls. Eight steel-mesh crosswalks and

140 fish feeders were located on the raceways (Fig.

1). The number of trout (10-23 cm long) maintained

152.9m

I - I

T - .- T -

ii!

Fl -H

I rI_

- !

; 1 -I- 1 -- I

I I U

[~~~ II. I H I I

f~~~~ I 7

0 Raceway

wall

Fig. 1. Location of raceways, raceway walls, fish feeders, nylon-

mesh barriers behind feeders, crosswalks, and Scarey Man (black

rectangles), at the Watson Lake Fish Rearing

Unit in Colorado dur-

ing 1990-1992.

in the raceways during periods when herons were

present was similar during 1990-1992 and ranged

from about 320,000 in April to 120,000 in July.

Methods and materials

We observed herons (Table 1) with lOx binoculars

or a Javelin night-viewing device (avelin Electronics,

Los Angeles, Calif.) equipped with a 300-mm tele-

photo lens from a vehicle on a public road 2 m higher

than and 35-58 m north of the raceways. Hatchery

personnel attached nylon netting (2-mm diameter

and 7- x 7-cm mesh, 2.3 m long, 0.5 m high, and

slanted toward the water at 30-40? from vertical) be-

hind the fish feeders in 1991 and 1992, but not in

1990, to deter herons from capturing fish (Fig. 1).

We hid in a blind 10 m south of the raceways and

fired pyrotechnics at herons immediately after they

landed. We used a single-shot pistol (Record PTB

113, imported through Sutton Ag Enterprises,

Salinas,

Calif.) to fire 17-mm exploding projectiles (Pest Con-

trol Devices, Stoneco, Inc., Trinidad, Colo.) from

2000 to 2200 hours and 15-mm whistling projectiles

(Bird Whistlers', Zink-Feuerwerk, GmbH, Clee-

bronn, Germany)

from 2200 to 0700 hours. We used

the exploding projectiles before 2200 hours because

we surmised that they would more effectively frighten

herons, whereas the whistling projectiles were used

after 2200 hours to limit disturbances to neighbors.

The projectiles flew about 40-50 m.

I - I - * it I I - -

-- i

688 Wildlife

Society

Bulletin

1997,

25(3):686-694

Table 1. Chronology

of research conducted on black-crowned

night-herons

and great

blue herons

at the Watson

Lake Fish

Rearing

Unit in Colorado

during

1990, 1991, and 1992.

Nighta Number

of nights

Year

activity Beginning Ending Observing Frightening

1990

Pretreatment counts May

19-20 May

21-22 3

Pyrotechnics

fired for

14 nights May

22-23 Jun

4-5 14

Posttreatment and

pretreatment

counts Jun 5-6 Jun

26-27 8

Pyrotechnics

fired

every

fifth

night Jun

26-27 Jul

29 14 7

Posttreatment counts Aug

2 Sep

25 6

1991

Pretreatment counts Jun

15b Jun

19-20b 6

Rotating lights Jun

21-22C Jul

14-15c 8 24

Posttreatment and

pretreatment

counts Jul 16 Jul

22 4

Pyrotechnics

fired

for 7 nights Jul

23-24 Jul

29-30 7

Posttreatment

counts Jul 31 Aug

21 7

1992"

Pretreatment

1 May

26-2 7 May

31-1 Jun 6

Scarey

Man

1 Jun 1-2 Jun

18-19 8 18

Posttreatment

1/Pretreatment

2 Jun

19-20 Jun

28-29 5

ScareyMan2 Jun 29-30 Jul

12-13 6 14

Posttreatment 2 Jul 13-14 Jul

22-23 5

Two dates

following

the month

indicate observation

throughout

the night;

1 date indicates observation

during

the early

morning.

Frightening

occurred

throughout

the night.

bCounts

occurred

hourly

from 0200 to 0700 on 15, 16, 17, and 18 June,

2200 to 0700 on 18-19 June,

and 2100 to 0700 on 19-20 June.

CCounts

occurred

hourly

from

2100 to 0700 on 21-22 and 22-23 June,

and

0200 to 0700 on 26 and 29 June,

and

2, 6, 10, and

14 July.

Counts occurred

hourly

from

2100 to 0200 during

all 5 periods.

We placed 4 2-beam rotating beacons with clear

acrylic domes and 75,000 candle-power spotlamps

(Tripp Lite

Model Mark-12,

Tri Lite, Inc., Chicago, Ill.)

at the 4 corners of the western half of the rearing

unit. Plywood was placed immediately east of the 2

eastern lights to minimize flashing into the eastern

half of the rearing unit. One 2-beam rotating beacon

with a clear acrylic dome (Tripp Lite Model RF-6,

Tri

Lite, Inc., Chicago, Ill.) and 70,000 candle-power

halogen spotlamps (No. H7616, Wagner Div., Cooper

Industries, Inc., Parsippany, NJ.) was positioned in

the center of the western half of the rearing unit.

Each beacon rotated 45 times and produced 90

flashes per minute.

We used the night-viewing device to count herons

on the eastern half of the rearing

unit during pretreat-

ment, treatment, and posttreatment periods, and on

the western half during pretreatment and posttreat-

ment of the flashing-light experiment. We used

binoculars to count herons on the western half of the

rearing unit while lights were flashing (treatment pe-

riod) because bright lights could have damaged the

night-viewing device. To determine if we biased our

counts by using different viewing devices, we painted

2-L,

plastic, beverage bottles to simulate juvenile and

adult BCNH and placed them in the rearing unit; our

observer counted similar proportions of bottles on

lighted (24/26) and unlighted (20/26) sides.

We evaluated the effectiveness of 2 Scarey Man

mannikins by conducting hourly counts of herons

during 5 consecutive periods (Table 1). The man-

nikins were placed at the northwestern site on the

east half and at the southwestern site on the western

half of the rearing unit (Fig. 1) during the first 2

nights and then rotated counter-clockwise on each

half of the rearing unit every other night to minimize

habituation. Each Scarey Man activated for 35-40

seconds every 9-10 minutes from about 1700 or

2045 through 0800 hours. To evaluate habituation to

Scarey Man, we determined the proportion of BCNH

and GBH

that remained on the half of the rearing

unit

where a Scarey Man activated; we divided the num-

ber of BCNH and GBH

observed <2 minutes after the

Scarey Man activated by the number of BCNH ob-

served <2 minutes before it activated.

Data analyses

The effect of nylon-mesh barriers on altering the

distribution of BCNH and GBH behind feeders was

determined by comparing the nightly proportions of

BCNH and GBH behind feeders without barriers in

1990 to the nightly proportions of BCNH and GBH

Deterring

heron predation

on fish * Andelt

et al. 689

behind feeders with barriers

in 1991 and 1992. The

comparisons were made with ANOVA (GLM proce-

dure) after weighting the nightly proportions by the

total number of herons observed in the rearing unit.

We used linear regression (GLM procedure, SAS

Inst., Inc. 1988:549-640) to examine the effect of

time (nights) on the number of pyrotechnics fired,

number of BCNH and GBH frightened during py-

rotechnic experiments, number of BCNH and GBH

that returned after the 14- and 7-night pyrotechnic

experiments, number of herons present during all 5

periods of the Scarey Man experiment, and propor-

tion of herons present <2 minutes after each Scarey

Man activated. The average numbers of herons pres-

ent each night before and after the 14- and 7-night-py-

rotechnic experiments were compared with t-tests

(TTEST procedure, SAS Inst., Inc. 1988:941-947). If

the variances were unequal, an approximate t was

calculated. Satterwaite's (1946) approximation was

used to compute the degrees of freedom and the

probability level for the approximate t. When py-

rotechnics were fired every fifth night, the numbers

of herons observed the nights before and after fright-

ening were compared with a paired t-test (MEANS

procedure, SAS Inst., Inc. 1988:946-947).

The effect of flashing lights on herons was deter-

mined by subtracting the number of herons observed

per hour each night on the eastern half of the rearing

unit from the number observed on the western half

and then comparing the differences among pretreat-

ment, treatment, and posttreatment with a paired

analysis of variance (ANOVA; GLM procedure, SAS

Inst., Inc. 1988:549-640). The average number of

herons observed each night at the entire rearing unit

during pretreatment, treatment, and posttreatment of

the flashing-light and Scarey Man experiments were

compared with ANOVA. We conducted this research

following animal welfare protocol number 90-071,

which was approved by the Colorado State Univer-

sity Animal Care and Use Committee.

Results

Diurnal and seasonal activity patterns

BCNH and GBH arrived at the rearing unit between

2000 and 2100 hours, and most birds of both species

departed by 0700 hours. BCNH and GBH started ar-

riving in April (D. C. Smeltzer, Colo. Div. Wildl., Bell-

vue, pers. commun.) and only a few of either species

remained by mid-to-late September.

Barriers

The nightly proportions of BCNH counted behind

feeders, compared to all areas, were similar (Contrast

F = 0.09; 1, 80 df; P = 0.765) before (2%

of 2,215 ob-

servations during 1990) and after (2% of 11,579 ob-

servations during 1991 and 1992) barriers

were pres-

ent. The proportions of GBH

counted behind feeders

varied (F = 76.70; 2,79 df; P < 0.0001) among years

and were higher during 1990 (32% of 584 observa-

tions) without barriers compared to 1991 (10% of

1,356 observations) and 1992 (4% of 1,521 observa-

tions) with barriers. The barriers were associated

with an increase in hourly counts of GBH

at the rear-

ing unit.

Frightening with pyrotechnics for 14

nights

The average number of pyrotechnics fired (x =

4.0, SE = 0.5) and BCNH (x = 3.1, SE = 0.7) and GBH

(x = 2.0, SE = 0.3) frightened per hour decreased

from nights 1 through 14 of the experiment (Fig.

2a). The average number of BCNH (x = 55.9, SE =

12 -- -.

10o

03 8

2c 6

I 4

U) cO

0 4

cc 2

X1 l I I

I i

i , I I I I I . I

1 2 3 4 5 6 7 8 9 10 11 12 13 14

NIGHT

30 | PRETREATMENT POSTTREATMENT I BCNH B

0 -

rO H

T ~ GBH

t0 - BCNH

= 0.63 + 0.45

x night,

r2 = 0.79,

P = 0.003

GBH

= 0.47 + 0.15

x night,

r2= 0.78,

P= 0.004

O I

2L\. _

3 2 1 1 2 4 7 10 14 18 22

NIGHT

Fig.

2. (a)

Average

number of pyrotechnics

fired,

black-crowned

night-herons

(BCNH)

frightened,

and great blue herons (GBH)

frightened per hour (2100-0700) during

14 consecutive nights

(22-23 May to 4-5 Jun 1990) at the Watson

Lake Fish

Rearing

Unit in Colorado. (b) Average

numbers of BCNH

and GBH

ob-

served

per hour

(2100-0700) before

(19-20 to 21-22 May

1990)

and after

(5-6 to 26-27 Jun

1990)

firing pyrotechnics

for 14 nights.

PYROTECHNICS

FIRED BCNH FRIGHTENED GBH FRIGHTENED

- A

Pyrotechnics

= 6.98

- 0.39

x night,

r2 = 0.68,

P = 0.0003

BCNH

= 7.07

- 0.53 x night,

r2 0.66,

P = 0.0004

i~?

mma,A GBH = 3.26 - 0.17 x night, r2 = 0.44, P= 0.010

'.?,,

.^..v . '

i J ! , , , , , , , , , ,

690 Wildlife

Society Bulletin

1997, 25(3):686-694

9.4) and GBH (x = 7.0, SE = 1.0) observed per hour

each night before firing pyrotechnics for 14 consec-

utive nights was higher (BCNH:

t = -5.4, 2.1 df, P =

0.031; GBH: t = -5.3, 9 df, P = 0.0005) than the av-

erage number (BCNH: x = 5.0, SE = 1.4; GBH:

x =

1.9, SE = 0.5) observed after frightening (Fig. 2b).

After firing pyrotechnics, the average number of

BCNH and GBH increased slowly from nights 1

through 22 (Fig. 2b).

Frightening with pyrotechnics for 7

nights

The average number of pyrotechnics fired (x =

1.2, SE

= 0.2) and BCNH

(x = 1.5, SE

= 0.3) and GBH

(x = 0.3, SE = 0.1) frightened per hour did not

change from nights 1 through 7 (Fig. 3a). The aver-

age number of BCNH

(x = 10.4, SE

= 1.7) and GBH

= 4.7, SE = 1.4) observed per night after firing py-

PYROTECHNICS

FIRED BCNH

FRIGHTENED GBH FRIGHTENEDI

-% Pyrotechnics = 1.90 - 0.17x night, r2 = 0.42, P= 0.113

\ BCNH = 2.47 - 0.24 x night, r2 = 0.33, P = 0.181

% GBH = 0.53 - 0.05 x night, r = 0.23, P= 0.276

NIGHT

40 - l -----.---

PRETREATMENT POSTTREATMENT BCNH B

[ GBH

r 1 BCNH

= 6.00 + 0.51 x night,

r2 = 0.71,P = 0.017

GBH = 0.60 + 0.47x night, r2= 0.89, P= 0.001

MIKE~

g g ;;40k1k40 |

0~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Efl

Fig.

3. (a)

Average

number of pyrotechnics

fired,

black-crowned

night-herons

(BCNH)

frightened,

and great blue herons (GBH)

frightened

per

hour

(2100-0700, except

2100-0530 on 27-28 Jul

1991) during

7 consecutive

nights

(23-24 to 29-30 Jul 1991) of

frightening

herons from

the Watson Lake

Fish

Rearing

Unit

in Col-

orado. (b) Average

numbers of BCNH and GBH

observed

per

hour (0200-0700) before (16-22 Jul 1991) and after

(31 Jul-21

Aug 1991) firing

pyrotechnics

for 7 nights.

8 7 5 2 1 2

NIGHT 4 7 10 15 22

rotechnics was lower (BCNH: t = -6.46, 9 df, P = <

0.0001; GBH t = -1.78, 9 df, P = 0.109) than the av-

erage number (BCNH x = 29.0, SE = 2.3; GBH x =

8.7, SE = 1.5) observed before frightening (Fig. 3b).

After firing pyrotechnics, the average number of

BCNH and GBH increased from nights 1 through 22

(Fig. 3b). A lower proportion (posttreatment di-

vided by pretreatment) of BCNH and GBH were ob-

served after 14 nights of frightening during 1990

than after 7 nights of frightening during 1991 (Figs.

2b, 3b).

Frightening with pyrotechnics every

fifth night

The average number of pyrotechnics fired (x = 3.9,

= 0.3) and BCNH

(x = 3.5, SE

= 0.3) and GBH

(x =

1.1, SE

= 0.2) frightened per hour did not change dur-

ing 7 consecutive nights (separated by 4 nights with-

out frightening; Fig. 4a). The average number of

BCNH

( = 16.2, SE = 2.2) and GBH

(x = 5.9, SE = 1.1)

observed per hour each night before frightening was

greater (BCNH:

paired t = 5.6, 6 df, P = 0.001; GBH:

paired t = 3.4, 6 df, P = 0.014) than the average num-

ber (BCNH:

x = 6.0, SE = 1.0; GBH:

x = 2.2, SE

= 0.7)

observed per hour each night after frightening (Fig.

4b). The average number of BCNH and GBH in-

creased during the treatment (nights before frighten-

ing: BCNH:

x = 16.9; GBH:

x = 5.8; Fig. 4b) compared

to an average of 7.9 BCNH and 4.6 GBH on nights 5,

9, and 13 before treatment. This was likely related to

a continuing increase in herons following the 14

nights of frightening with pyrotechnics in the previ-

ous experiment. The average number of BCNH

(counted at 0400 and 0500 hrs) continued to increase

on nights 5 (x = 31.0) and 11 (x = 50.5) after treat-

ment and then decreased on nights 23 (x = 32.0), 35

(x = 16.0), 47 (x = 5.5), and 59 (x = 0.5) after treat-

ment. The average number of GBH

(counted at 0400

and 0500 hrs) also increased or remained similar to

treatment numbers on nights 5 (x- = 5.5), 11 (x =

10.5), 23 (x = 3.5), 35 (x = 7.5), and 47 (x = 5.0), but

decreased on night 59 (x = 1.5) after treatment. The

decreases in numbers of BCNH and GBH during the

latter posttreatment period likely was related to mi-

gration from the study area.

Bright flashing lights

The number of BCNH on the western half of the

rearing unit was higher than on the eastern half dur-

ing pretreatment (western x = 16.0, SE

= 1.5; eastern

x = 12.3, SE = 0.9) and posttreatment periods (west-

ern x = 16.5, SE = 1.3; eastern x = 12.4, SE = 1.5),

whereas the number of BCNH was lower on the

lighted western half of the rearing unit (x = 12.9, SE

, 30

z In g

*g I P

i I W ii r ' ** * -

I -

Deterring

heron

predation

on fish * Andelt

et al. 691

6 l PYROTECHNICS

FIRED BCNH

FRIGHTENED

23 .v. BCNH = 4.19.0.16 x night,

r2 =

1 2 3 4

PERIOD

oc a:

I 25

I 20

015

w 10

m 5

. BCNH

BEFORE

E BCNH

AFTER

2 GBH

F - V

-F-

,ir if ~

F t 7

1 2 3 4

PERIOD

Fig.

4. (a) Average

number of pyrotechnic

night-herons

(BCNH)

frightened,

and gre

frightened

per hour (2100-0700) during;

27-28 Jul

1990),

each separated

4 nights

fka XA/ti-crn I l-^o

F:ick Pn3rin: I Init in

:- nlnr

GBH FRIGHTENED A

t, r2 0.27, P= 0.228 4.

0.17,

P - 0.355

!.42,

P= 0.114

treatment (x = 29.4, SE = 3.4), and posttreatment (x

= 28.9, SE = 2.3) periods (F = 0.04; 2,15 df; P =

0.958). The average number of GBH on the western

and eastern halves of the rearing unit combined was

greater during pretreatment (x = 11.8, SE = 0.8) than

during treatment (x = 8.5; SE = 0.8) and posttreat-

ment (x = 8.7, SE = 1.5) periods (F = 3.87; 2,15 df; P

= 0.044).

.....I

Frightening with Scarey Man

The average number of BCNH at the rearing unit

5 6 7 varied (F = 16.00; 4,25 df; P < 0.0001) among the 5

pretreatment, treatment, and posttreatment periods

(Fig. 6), and was lower during the first treatment than

3EFORE

~ GBHAFTER

B during the first pretreatment or first posttreatment

periods (Table 2). The number of BCNH also was

lower during the second treatment and second post-

treatment periods than during the second pretreat-

I ment period. The average number of GBH varied (F

= 4.55; 4,25 df; P = 0.007) among the 5 periods and

generally was lowest during treatment periods (Fig.

7 ( j 6, Table 2). The average numbers of BCNH and GBH

/ j( I increased with time (nights) during the first treat-

:t '? g ment period, but did not change with time during the

other periods (Table 2).

5 6 7 The proportion of BCNH that remained (<2 min af-

ter frightening) on the half of the rearing unit where

a Scarey Man activated increased with time (propor-

fired,

black-crowned

at blue herons (GBH) tion BCNH = 0.66 + 0.03 x night, n = 75, r2 = 0.26, P

7 nights

(27-28 Jun

to < 0.0001) from day 1 (n = 13, x no. before = 6.9, x

without

frightening,

at no. after = 4.1) through day 14 (n = 12, x no. before

-Ar . !. A/, rrn\ n... ....

IIn

1 VVdLUI I LdlKe r

Is INerdlIg I J IIIL II I ,UIUIdUU. tU) Averadge inumI-

bers of BCNH

and GBH observed per hour (0100-0200 and

0400-0600) the night

before

and the night

after

firing pyrotech-

nics.

= 1.7) than on the unlighted eastern half (. = 16.5, SE

= 1.7) during treatment (paired ANOVA, F = 19.52;

2,15 df; P < 0.0001; Fig. 5). Similarly, the number of

GBH on the western half of the rearing unit was

higher than on the eastern half during pretreatment

(western x = 7.3, SE = 0.4; eastern x = 4.5, SE = 0.5)

and posttreatment periods (western x = 5.2, SE = 0.8;

eastern x = 3.5, SE = 0.9), whereas the number of

GBH was lower on the lighted, western half of the

rearing unit (x = 2.3, SE = 0.3) than the unlighted

eastern half (x = 6.2, SE = 0.7) during treatment

(paired ANOVA, F = 32.34; 2,15 df; P < 0.0001; Fig.

5). These changes in numbers of herons indicate that

some of the 21% of BCNH and 63% of GBH were re-

distributed from the western half to the eastern half

of the rearing unit while the lights were flashing.

However, the average number of BCNH on the com-

bined western and eastern halves of the rearing unit

did not vary among pretreatment (x = 28.2, SE = 2.2),

a 20

0 15

W 10

0 7 6 5 4 3 2 1 2 5 8 11 151923 1 2 4 7

NIGHT

Fig.

5. Average

numbers of black-crowned

night-herons

(BCNH)

and great

blue herons

(GBH)

observed

per hour

(0200-0700) on

the western

and eastern

halves

of the Watson Lake

Fish

Rearing

Unit in Colorado before

(15-20 Jun

1991, pretreatment,

denoted

as no. of nights

before

treatment)

bright

flashing lights

were

placed

on the western

half,

while the lights

were flashing

(22 Jun-14

Jul

1991, treatment

counts, but lights flashed 21-22 Jun through

14-15 Jul 1991), and after

the lights

were removed

(16-22 Jul

1991, posttreatment,

denoted as number of nights

after

treatment).

_ _ I? __ _L_ II I

11 L [

f .

I I i -- - I I -R

f~ LI

i I I

692 Wildlife

Society Bulletin

1997, 25(3):686-694

100

? 80

LuJ

co 60

o 40

cc:

m 20

~_ C~~~

BCNH

? GBH

PRETREAT. TREATMENT POSTTREAT. TREATMENT POSTTREAT.

_ ~i

-q

- rr

' I

i v I i

6 4 2 2 7 14 18 1 4 10

NIGHT 2 7 14 1 4 10

Fig.

6. Average

numbers

of black-crowned

night-herons

(BCNH)

and great

blue herons

(GBH)

observed

per hour

(2100-0200 hr)

before

(26-27 May

to 31 May-1

Jun

1992, pretreatment,

denoted

as no. of nights before treatment

1), during

(1-2 to 18-19 Jun

1992, treatment

1),

after

(19-20 to 28-29 Jun

1992, posttreatment

1/pretreatment

2, denoted as no. of nights

after

treatment

1), dur-

ing (29-30 Jun

to 12-13 Jul

1992, treatment

2), and after

(13-14

to 22-23 Jul

1992, posttreatment

2, denoted

as no. of nights

after

treatment

2) 2 Scarey

Man mannikins were used to frighten

herons

from the Watson Lake

Fish

Rearing

Unit

in Colorado.

= 16.8, x no. after = 17.7) of the first treatment pe-

riod. The proportion of GBH that remained on the

half of the rearing unit where a Scarey Man activated

did not increase with time (proportion GBH = 0.96 +

0.002 x night, n = 53, r2 = 0.00, P = 0.866) from day

1 (n = 6, x no. before = 2.3, x no. after = 1.5) through

day 14 (n = 12, x no. before = 3.2, x no. after = 3.0)

of the first treatment period.

Estimates of trout captured by herons

We estimate that BCNH and GBH captured a mini-

mum average of 31,000 and 25,000 trout, respec-

tively, annually during 1990, 1991, and 1992 (Andelt,

unpubl. data). These captures occurred while we

frightened herons with pyrotechnics, flashing lights,

and Scarey Man during some periods that herons

were present. Hatchery personnel (D. C. Smeltzer,

Colo. Div. Wildl., Bellvue, pers. commun.) estimated

that BCNH and GBH combined captured an average

of 40,000 trout annually during 1990, 1991, and

1992. These losses of fish to herons were lower than

the estimated average annual losses (79,000) of fish

that hatchery personnel attributed to herons during

the previous 5 years when frightening devices were

not used.

Discussion

BCNH and GBH were the only avian species that

we observed capturing trout at the Watson Lake Fish

Rearing Unit. In contrast, Parkhurst et al. (1992) re-

ported 7 major avian predators of fish at hatcheries in

Pennsylvania and reported that GBH were not ob-

served foraging in concrete raceways.

The presence of barriers behind fish feeders was

associated with a significant reduction in the number

of GBH that were behind feeders and an increase in

the number of GBH at the rearing unit. Great blue

heron fish-capture rates were highest from behind

fish feeders (Andelt, unpubl. data); this suggests that

GBHs were forced to stay longer at the rearing unit to

capture fish after barriers were installed.

We were more successful in decreasing numbers

of BCNH and GBH by firing pyrotechnics for 14 com-

pared to 7 consecutive nights, and we speculate that

more herons adopted alternate food sources during

the longer period of frightening. Although frighten-

ing herons every fifth night decreased the number of

herons the following night relative to the night be-

fore frightening, the lack of reduction in herons with

each subsequent fifth night of frightening indicates

this effort was not successful.

Our data indicate that heron predation could be re-

duced substantially by firing pyrotechnics during re-

Table 2. Numbers and changes

in numbers

(with

time [nights])

of black-crowned

night-herons

and great

blue herons

before,

during,

and

after

frightening

with

Scarey

Man at

the Watson

Lake Fish

Rearing

Unit in Colorado

during

1992.

Black-crowned

night-herons Great blue herons

Change

with time Change

with time

Periods x SE Intercept Slope P x SE Intercept Slope P

Pretreatment

1 66.7A" 5.8 87.0 -5.8 0.074 12.4A 1.7 7.2 1.5 0.153

Treatment

1 23.8C 5.3 3.6 2.2 <0.0001 5.5C 1.3 0.7 0.5 0.0002

Posttreatment

1/Pretreatment

2 49.8B 3.2 56.8 -1.5 0.136 8.2BC 1.4 5.1 0.6 0.141

Treatment

2 32.1C 3.1 36.8 -0.7 0.344 7.5BC 0.7 6.4 0.2 0.323

Posttreatment 2 27.7C 1.1 29.9 -0.5 0.195 9.8AB 0.7 11.4 -0.3 0.149

Numbers in a column

followed

by the same

letter did not

differ

(P> 0.05).

Deterring heron predation on fish * Andelt et al. 693

peated 14-night periods followed by 22 nights with-

out frightening. Assuming (as we observed) no

herons will capture fish during frightening and 9%

the BCNH

and 27%

of the GBH

would be present dur-

ing the 22-night periods following frightening, we es-

timate that the number of herons and heron preda-

tion on fish could be reduced to only 10%

(9%

BCNH

and 27% GBH present during 61% of the season) of

pretreatment losses by firing pyrotechnics during 4

14-night periods from mid-April through early Sep-

tember. This amount of frightening (4 periods x 14

nights/period x 10 hrs/night) would cost $3,920

@$7/hr for labor and $840 for pyrotechnics (assum-

ing 4.0 pyrotechnics @$0.375 each [with firing cap]

are fired/hr). The costs of frightening ($4,760) and

fish lost (0.10 x 79,000 fish lost/yr during the 5 yrs be-

fore our study x $0.30/fish = $2,370) would be only

30% of the value of fish lost (79,000 x $0.30/fish =

$23,700) without frightening.

Bright rotating lights reduced the numbers of

BCNH and GBH on the western half of the rearing

unit by redistributing

some of the birds to the eastern

half where flashing lights were not operating. We

speculate the numbers of herons would not have

been reduced as much on the western half if flashing

lights had been placed on both sides because herons

traveled only a short distance to forage on the eastern

half. Although we hypothesized that the bright flash-

ing lights would inhibit the birds' ability to see and

capture fish, the lights did not affect the number of

attempted and successful captures of fish (Andelt, un-

publ. data).

Two Scarey Man mannikins reduced the numbers

of BCNH

and GBH at the rearing unit during the first

4 nights of the first treatment period, but the num-

bers of both species then increased substantially

through the eighteenth night of use. This trend, in

addition to the increased proportion of BCNH that re-

mained <2 minutes after a Scarey Man activated dur-

ing the first treatment period and the ineffectiveness

of Scarey Man during the second application, indi-

cated that herons quickly habituated to the devices.

We determined the effects of treatments by com-

paring counts of herons between pretreatment and

posttreatment or among pretreatment, treatment,

and posttreatment. Ideally, another rearing unit

should be used as a control to ascertain if changes in

numbers of herons were affected by treatments

rather than outside factors such as reproduction, in-

cubation, and feeding of young (Vos 1984). How-

ever, we believe our data adequately assessed the ef-

fects of treatments because: (1) our treatments lasted

<24 days, (2) numbers of herons remained fairly sta-

tic during 1993, 1 year after our study when we

tested a rather unsuccessful frightening device dur-

ing a short period (11 nights; Andelt and Hopper

1996), (3) numbers of herons generally were similar

during pretreatment periods of the 3 years of our

study and during 1993, (4) numbers of herons gener-

ally decreased during treatment compared to both

pretreatment and posttreatment periods, and (5) the

effects of pyrotechnics were similar during 1990 and

1991 although applied during late May through early

June 1990 versus late July 1991.

Management recommendations

Our data indicate that nylon-mesh barriers can be

used in fish-rearing

facilities to reduce GBH

foraging

on fish. However, the adaptability

of GBH

in choos-

ing alternate foraging sites suggests that barriers will

need to be placed at most if not all foraging sites to

greatly reduce predation. Bright rotating lights and

Scarey

Man were ineffective in frightening BCNH and

GBH from the Watson Fish Rearing

Unit.

We reduced numbers of BCNH 91%

and GBH

73%

during a 22-night period following 14 nights of haz-

ing, but we were less effective when employing py-

rotechnics for a 7-night period. We believe fishery

managers can effectively reduce the costs of moder-

ate to substantial heron predation at fish-rearing

facil-

ities by employing pyrotechnics for 14-night periods

followed by periods without frightening.

Acknowledgments. We thank G. G. Schoonveld

and D. C. Smeltzer, Colorado Division of Wildlife, for

funding the study. D. C. Smeltzer provided data on

heron predation on fish and encouraged the evalua-

tion of pyrotechnics for deterring heron predation.

We thank M. M. Robinette for conducting most of the

field work during the second year and L. S. Butler for

summarizing data. K. P. Burnham provided sugges-

tions on statistical analyses. L. H. Carpenter provided

the night-vision device. B. A. Knopf and K. M. Giesen

reviewed the manuscript.

Literature cited

ANDELT,

W. F., AND S. N. HOPPER.

1996. Effectiveness of alarm-dis-

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Prog. Fish-Cult.

58:258-262.

DRAULANS,

D. 1987. The effectiveness of attempts to reduce pre-

dation by fish-eating birds: a review. Biol. Conserv. 41:219-

232.

LAGLER,

K. F. 1939. The control of fish predators at hatcheries and

rearing stations. J. Wildl. Manage. 3:169-179.

NAGGIAR, M. 1974. Man vs. birds. Fla. Wildl. 27:2-5.

PARKHURST,

J. A., R. P. BROOKS,

AND

D. E. ARNOLD.

1987. A survey of

wildlife depredation and control techniques at fish-rearing

fa-

cilities. Wildl. Soc. Bull. 15:386-394.

694 Wildlife

Society Bulletin 1997, 25(3):686-694

PARKHURST,J. A., R. P. BROOKS, AND D. E. ARNOLD. 1992. Assessment

of predation at trout hatcheries in central Pennsylvania. Wildl.

Soc. Bull. 20:411-419.

SALMON, T. P., AND F. S. CONTE. 1981. Control of bird damage at

aquaculture facilities. U.S. Fish and Wildl. Serv. Wildl. Manage.

Leafl. No. 475. llpp.

SAS

INSTITUTE,

INC. 1988. SAS/STAT

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SATTERWAITE,

F. W. 1946. An approximate distribution of estimates

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SCANLON, P. F., L. A. HELFRICH,

AND R. E. STUITZ. 1978. Extent and

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Wildl. Agencies 32:470-473.

STICKLEY,

A. R., AND K.

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fish farmers on means, effort, and costs to repel fish-eating

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STICKLEY,

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STICKLEY,

A. R., D. F. Morr, ANDJ.

O. KING. 1995b. Short-term ef-

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Wildl. Soc. Bull. 23:73-77.

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orado State Univ., Fort Collins. 65pp.

William (Bill) F. Andelt (photo) is an associate professor and ex-

tension wildlife specialist in the Department of Fishery and Wild-

life Biology at Colorado State University. He received his B.S.

(1974) and M.S. (1976) degrees in wildlife sciences from the Uni-

versity of Nebraska and his Ph.D. (1982) in zoology from Col-

orado State University. Bill's interests include research and exten-

sion related to managing human-wildlife conflicts and the ecol-

ogy of carnivores. Timothy (Tim) P. Woolley is a biologist with

the Wyoming Game and Fish Department. He received his B.S

(1992) in wildlife biology from Colorado State University and his

M.S. (1995) in zoology and physiology from the University of

Wyoming where he evaluated ground and fixed-wing aerial

pronghorn composition surveys. Stuart N. Hopper has nearly

completed a B.S. in wildlife biology at Colorado State University

and recently has worked on a Canada goose monitoring project

for the Colorado Division of Wildlife.

High-frequency and high-amplitude sounds enhance bird deterrence: A case study of the Black- necked Crane

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Oct 2024

Under the global vision of sustainable development, the harmonious coexistence of humans and wildlife has become a crucial topic. Birds are closely related to human life, and bird deterrence technology is not only a necessary measure to maintain human health and economic security but also an important means to protect birds. Although sound-based bird deterrence has been widely used, the effects of different frequencies and combinations have not been systematically explored. The Black-necked Crane ( Grus nigricollis ), a nationally protected wildlife species, shares some of its habitats with human agricultural activities. This study designed sounds of various frequencies and combinations and conducted deterrence experiments on Black-necked Cranes at their wintering sites in northeastern Yunnan Province, exploring how sound frequency and combinations affect the behavioral responses, evasion distances, and escape speeds of the cranes. The results indicate that: (1) in terms of behavioral response intensity, evasion distance, and escape speed, sounds with high frequency and high variability significantly outperformed other sounds (n=479, p < 0.001); (2) there were no significant differences in the response of Black-necked Cranes of different flock types and age combinations to sounds. The study recommends using high-frequency, highly variable sounds for short-term control of Black-necked Cranes. Additionally, this research demonstrates that using either high frequency or high variability combinations can achieve efficient bird deterrence in the short term, and provides a scientific basis for developing and refining bird deterrence strategies for other bird species.

Effects of artificial light on bird movement and distribution: a systematic map

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Background Artificial light is ubiquitous in the built environment with many known or suspected impacts on birds. Birds flying at night are known to aggregate around artificial light and collide with illuminated objects, which may result from attraction and/or disorientation. In other contexts, birds are repelled by light-based deterrents, including lasers and spotlights. Artificial light can also change birds’ perceptions of habitat quality, resulting in selection or avoidance of illuminated areas. Studies documenting aggregation, deterrence, and habitat selection are typically considered separate literature bodies, but they actually study a common set of populations, interventions/exposures, and responses. Our systematic map provides a comprehensive, searchable database of evidence of the effects of artificial light on bird movement and distribution, increasing both the quantity and diversity of studies that are accessible for further comparison and synthesis. We identify and describe the evidence available for four secondary questions relevant to conservation or management: aggregation/mortality at structures with artificial lights, evidence that light attracts and/or disorients birds, light-based deterrent efficacy, and the influence of continuous illumination on habitat selection. Methods Using the principles of systematic reviews and methods published in an earlier protocol, we conducted an extensive and interdisciplinary literature search. We searched multidisciplinary citation indices as well as databases and websites specific to conservation, pest management, transportation, and energy. In our map, we included all studies reporting eligible populations (birds), interventions/exposures (artificial light), and outcomes (movement through space, behaviour preceding movement, or distribution). We evaluated the quantity of available evidence based on meta-data fields related to study context, population traits, light source characteristics, and outcome variables. We used these meta-data to identify relevant evidence for each secondary question and describe aspects of our secondary questions that may support reviews (evidence clusters) and others that require more research (knowledge gaps). Review findings We manually screened 26,208 articles and coded meta-data for 490 eligible studies in a searchable database, organizing the literature to facilitate future reviews and evidence-based management. Much of the evidence was concentrated in particular locations (Northern hemisphere), taxonomic orders ( Passeriformes, Charadriiformes , and others), and light wavelengths (red and white). We identified 56 distinct response variables and organized them into 3 categories (behaviour, distribution, and avian community), showing the diversity in bird responses to light. Conclusions Our database can be used to answer the secondary questions we identified and other questions about the effects of artificial light on bird movement and resulting changes to distribution. There may be sufficient evidence for a review of the weather and lunar conditions associated with collisions, which could help identify nights when reduction of artificial light is most important. Further experiments should investigate whether specific types of light can reduce collisions by increasing the detectability of structures with artificial lights. The efficacy of lasers as deterrents could be evaluated through systematic review, though more studies are needed for UV/violet lasers. To reduce the impacts of outdoor lighting on birds, research should investigate how spectral composition of white light influences bird attraction, orientation, and habitat selection.

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ANIM COGN

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Human–Wildlife Interactions: From Conflict to Coexistence

Book

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Effectiveness of Alarm–Distress Calls for Frightening Herons from a Fish Rearing Facility

Article

Full-text available

Oct 1996

We evaluated the effectiveness of using alarm-distress calls of the black-crowned night heron Nycticorax nycticorax and the great blue heron Ardea herodias for frightening these piscivorous bird species from a rearing unit for rainbow trout Oncorhynchus mykiss. Heron alarm–distress calls reduced black-crowned night heron numbers 48% during the 11-d treatment period, compared with the pretreatment period, but did not affect the number of great blue herons. The number of black-crowned night herons using the rearing unit and the proportion that remained immediately after the broadcast of alarm–distress calls increased from nights 1 through 11 of the treatment period, which indicates that this predator quickly habituated to the calls. We did not find any differences between the proportions of black-crowned night herons and great blue herons that remained on the rearing unit immediately after playing calls of the respective species. Alarm–distress calls were mostly ineffective in reducing heron predation on rainbow trout fingerlings.

BIRD DAMAGE AT AQUACULTURE FACILITIES

Article

Full-text available

Jan 1994

Reduction of the damage caused by fish-eating birds requires accurate bird identification and some knowledge of avian biology and habits. The open-water areas and large concentrations of aquatic livestock at aquaculture facilities are natural attractants to many birds. Birds can have a significant economic impact on the culture of aquatic products including fish, shellfish, crustaceans, and other invertebrates. For our purpose here, we will refer to these birds as fish-eating birds, and the aquatic products as fish.

A survey of wildlife depredation and control techniques at fish- rearing facilities

Article

Jan 1987

Surveyed 336 fish hatchery managers predominantly from the E USA, of which 85% responded, to assess aspects of hatchery depredation. Most facilities (63%) experienced losses to predators and managers identified 4 species of insects, 13 species of herpetofauna, 18 species of mammals, and 43 species of birds as predators. Control devices were used by 85% of the managers to limit depredation losses; top screens, enclosures, and shooting were rated as most effective in deterring predators and visual scare devices as least effective. Most managers (73%) could not place an economic value on their losses. -from Authors

Assessment of predation at trout hatcheries in central Pennsylvania

Article

Jan 1992

The authors identified seven important predators at ten trout hatcheries and quantified their foraging behaviors. Most species devoted <28% of their total time in a hatchery to foraging for fish. As a group, predators fed on fish of variable lengths, but many factors determined specific lengths of fish taken. Most predators foraged equally at earthen and concrete raceways, but great blue herons Ardea herodias foraged only at earthen raceways. Collectively, common grackles Quiscalus quiscula captured and removed the most fish/day, but because mallards Anas platyrhynchos were present for more days/year, they had the greatest total impact. Secondary infection and injuries sustained during attacks by predators also may be important factors in fish loss. -from Authors

Short-term effects of an inflatable effigy on cormorants at catfish farms

Article

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Survey of Mississippi catfish farmers on means, effort, and costs to repel fish-eating buds from ponds

Article

Sep 1989

Eighty-seven percent of 281 Mississippi catfish farmers felt that fish-eating birds were enough of a problem to warrant harassment. Fanners estimated that they spent an average of 2.6 man-hours per day harassing birds at an average annual cost of

7400. Sixty percent of the farmers who harassed birds did so by driving around the ponds and firing at birds to repel them. Propane exploders and pyrotechnics were also used. Pyrotechnics were judged the most effective repellent technique. The cost of bird harassment according to these farmers is

2.1 million. The value of fish loss to cormorants alone is roughly estimated at

3.3 million. The total annual loss to birds is estimated at

5.4 million.

AS/stat user's guide. Release 6.04

Book

Jan 1988

SAS Institute

Impact of Great Blue Heron Depredations on Channel Catfish Farms

Article

Apr 2007
J WORLD AQUACULT SOC

With the growth of channel caffish Ictalurus punetatus production in the Delta Region of Mississippi over the last 30 years have come concurrent depredation problems caused by great blue herons Ardea herodias. Biomass in stomachs from herons collected at catfish farms averaged 41% catfish, 38% sunfish Lepomis sp., 17% shad Dorosoma cepedianum, and 4% gambusia Gambusia sp.; whereas observations of herons foraging indicated that 45% of the prey taken were gambusia. Our observational data indicate that herons take an average of 12 10-cm catfish fingerlings daily. The diurnal density of foraging herons on catfish ponds averaged 0.17 herons/ha in 1990, which means that the average 127-ha farm supports approximately 22 herons. Nocturnal foraging, especially on dark nights, appears to be minimal. If our data are approximately correct, the average catfish farm could be losing $30/ha per yr to herons, assuming that this catfish fingerling mortality can be attributed solely to heron depredation.

The effectiveness of attempts to reduce predation by fish-eating birds: A review

Article

Dec 1987
BIOL CONSERV

Dirk Draulans

The effectiveness of different types of attempts to control predation by fish-eating birds is reviewed in view of the increased abundance of both fish-farms and several fish-eating bird species, and the consequent increasing number of conflicts between birds and man and fish-farmers and bird protectors. There is, so far, no scientific basis to claim that removal of predators through relocation or killing (the method favoured most by farmers and fishermen) reduces bird abundance or increases fish yields. On the other hand, most bird deterrents (the alternative proposed by many bird protectors) have only a very short-term effect, if any, depending mainly on the availability of alternative resources. ‘Ecological’ measures have not yet been properly tested, but are unlikely to solve the problem. The only reasonable solution to prevent fish from being eaten by piscivorous birds is to make sites inaccessible through wiring and netting. The costs of such measures have to be carefully balanced against the expected reduction of fish losses.

Response of breeding great blue herons to human disturbance in northcentral Colorado /

Article