CORRELATIONS OF DAILY ACTIVITY WITH AVIAN CHOLERA MORTALITY AMONG WILDFOWL Author(s): Shawn M. Combs and Richard G. Botzler Source: Journal of Wildlife Diseases, 27(4):543-550. Published By: Wildlife Disease Association DOI: http://dx.doi.org/10.7589/0090-3558-27.4.543 URL: http://www.bioone.org/doi/full/10.7589/0090-3558-27.4.543

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Journal

of Wildlife

Diseases,

27(4),

© Wildlife

CORRELATIONS

OF DAILY

MORTALITY Shawn

AMONG

M. Combs1

(Pasteurella (USA). in

Avian

flock

of

wildfowl:

mallards wildfowl on

bird

land,

density,

cholera

in

use

(Fulica

American

land

or

of

cholera,

thousands

of

America among

(Rosen, affected

mented is known

(Titche, about

disease

or

Anas

spp.,

americana,

avian

tundra

directly in

wildfowl throughout 1971). While annual species are well 1979; Friend, the factors

1945,

its

seven

may

the

defined columbianus),

(Cygnus shovelers The

(A. clypeata)/ position of these flock size, time

mean

that

predisposing

variations

factors

in

to

and

1987), initiating

three

more

Humboldt

use

generally

ler,

than

avian

(Cygnus relation

no

relation

epi-

(a)

their

docA se-

or

(b)

1977

and

January

1978

zootics, umented

two distinctive features were among affected wildfowl.

quence

in species

mortality

American coot (Fulica tality started and reached epizootics,

American

clypeata), and

A. cyanoptera), 1978; Mensik suffered

teal

(A.

respectively

and

habitat Mayr,

morearly

in

swans

Botzler,

mallards

(A.

discors,

A. crecca,

cies sen

(Oddo et a!., 1989). Secondly,

disproportionately

of

high

wildfowl

no

many

to

fowl

be due

could

behavior.

has

avian

sequence

disproportionate

wildlife

on

(Delacour 1965, 1975; assessed use

site,

spe-

in relation cholera. Ro-

variation

cholera

and Bell-

variation

of several

to avian

that

in suswild-

among

in habitat

to differences

If Rosen

if be and

densities

at a single

proposed

that would

studies

habitat

susceptibility

(1969)

or

of

one

and

that

mortality

and behavior Johnsgard,

ceptibility use 543

there

wildfowl

to their

platy-

predicted

1980),

sta-

a density-in-

We

are

no

hypothesized

correct,

there

in behavior

had

in

occurrence

extent tundra

populations

was

use 1945;

rose,

and

(Anas americana), (A. acuta), northern

pintails

(A.

by

mortality. While

observed.

americana) a peak

followed wigeon

rhynchos),

was

the

the

live

the

Botz-

among

their

in the

of

and

that

and

between

other

frequenuse

fashion.

position

the

their

functioned

(1969)

of

of

Mensik

mortality

period,

85%

in contrast,

from

to

to 55%

at lower

observed

cholera

Rosen

to

columbianus)

a 13-yr

avian

site;

1978;

cholera

tistical

45

died

et a!.,

swans over

sus-

County,

on this

1989). Rosen (1969)

the

January

columbi-

80

only

predicted

(Oddo

of avian

epizo-

composed but

wildfowl area

little the

Coots

wildfowl cies

in

cholera

Cygnus

ecology,

mortality,

dependent

coots

variations

empirically

propose

behavioral

California (USA) (Titche, 1979; R. G. Botzler, unpubl. data). None have been reported since 1979. Based on evaluations of

shovelers

as

cholera California

with

six

We

serve

cholera,

North losses docu-

transmission

avian

confirmed

northern

correlated

with

water.

of avian

County,

among

correlated

shallow

risk

swans.

by the bacterium annually kills

at Centerville,

the

were

mortality.

caused multocida,

facilitating

were

pected

epizootics behaviors

grazing

INTRODUCTION

otics

past

the

Humboldt

americana),

was

on

frequency

coots,

Fulica

epizootiology,

wildfowl. Since

influence

tundra swans northern pintails (A. acuta), northern teal (A. discors, A. crecca, A. cyanoptera).

grazing

and

can

USA

wildfowl.

words:

Avian Pasteurella

CHOLERA

at Centerville,

nonfeeding

sequences

spent

activities birds

and

coots

mortality

time

habitat

among

Key anus,

past

and

95521,

from

feeding

American

groups

spent

11

California

wildfowl

susceptible

characteristics

and

wigeon (Anas americana), (A. platyrhynchos), and

American

Arcata,

that for

mortality use

University,

hypothesis

infection)

habitat

AVIAN

1991

G. Botzler2

State

the

cholera

size,

groups

Humboldt

We tested multocida

ABSTRACT:

WITH

Association

WILDFOWL

and Richard

‘Department of Wildlife, 2Author for correspondence

ACTIVITY

pp. 543-550

1991,

Disease

(1969)

was

cor-

544

JOURNAL

rect,

we

OF WILDLIFE

predicted

DISEASES,

there

would

tent behavioral differences that died early in avian or had disproportionately compared with water is a likely pasteurellae, early or mortality

which would

be

that

birds

along response

we observed of carcasses mudflats and to prevailing

pected

that

time in greatest

epizootics. we predicted

Thus,

spending

If this the

hypothesis groups

differences

partly in we exthe

in

flock

high the

of correlations

hypothesis

fluence ceptib!e

would

that

the risk birds.

avian

STUDY

with in-

for

sus-

AREA

The study was conducted at Centerville, 26 km southwest of Eureka, Humboldt County, California 40#{176}30’N, 124#{176}10’W). Two seasonal ponds (Ponds One and Two), approximately 3.9 and 5.5 ha, respectively, were separated from the Pacific Ocean by a 700-m strip of pasturelands

and

included

pus

sp.,

sp.,

and

coastal

dunes.

Juncus sp., Potamogeton assorted

water

Pond

and

1.2

by

cattle

was

to

grazed

October

January,

each hunting

hunting club. site is provided

Ruppia

sp.,

depths m

in

rights

ScirLemna

sp.,

sp.,

(Combs,

ranged

and

year.

vegetation

Rubus

sp.,

Gramineae

Maximum One

Dominant

Rumex

Pond sheep

From were

1988).

up to

0.5

The

from

February

October leased

Additional information by Combs (1988).

m

Two.

in

area

through to

a

about

Based

on

quence, defined: mallards, daylight

15

mortalcoots. An

cholera

are present from avian

each year cholera at

AND METHODS

their

positions

in

the

six wildfowl groups coots, wigeon, swans, and teal. Observations hours (0600-1800) through

mortality

se-

were empirically pintails, shoveler! were limited to on non-hunting

March,

1982-83

and

scans (Altmann, 1974) were made every hour each day. A scan to determine the flock size of each wildfowl group within each of the 76 observation units of the site was made

habitat

activities

study died

The ponds and adjacent land area were divided into 76 observation units to facilitate locating birds on the study site (Combs, 1988). Sizes and shapes of these units were determined by natural boundaries of shoreline, and water depth (0.15 m, >0.15 m). Mean area of units was 1855 m2 (SE = 215); median size was 1,470 m2.

days, October 1983-84. Four

at Cenposition were re-

conflict

wildfowl

of

mormost

determine size,

lated to the high disproportionate ity from avian cholera among the

most

was correct, died early

that

use and behavior among wildfowl terville were correlated with their in the sequence of mortality, or

absence

at conwater

at Ceneach (Combs,

unpubl. data). Specific popfor the years of this study by Combs (1988). The wildfowl

MATERIALS

water would receive the to P. multocida during

and suffered disproportionately tality would be the ones spending time in shallow water. Our objectives were to whether

are summarized evaluated in this and have regularly Centerville.

epizootics

shorelines, winds.

R. C. Botzler, characteristics

be-

the greatest in shallow

wildfowl

shallow exposure

1988; ulation

dying

suffered disproportionate have different feeding

haviors than other wildfowl. During past avian cholera Centervil!e, centrations

Wildfowl generally begin to arrive terville from late October to mid-November year, and have departed by early March

consis-

wildfowl. Because for transmitting

expect

1991

27, NO. 4, OCTOBER

among species cholera epizootics high mortality,

other medium we

VOL.

local

this

mm

before

locations also (pond locations

the

hour.

At

Pond

were categorized >0.15 m deep), 0.15 m), and

Two,

bird

as deep water shallow water land (land sur-

(pond locations face adjacent to the pond). The location and behavior of individual coots were recorded on scans every half hour. Scans of all other wildfowl were made 15 mm past each hour. All behavioral surveys were done with a 36 x spotting scope mounted on a 1.5-m ladder located 75 m north of the ponds. Eleven behaviors were defined: (a) grazing or ripping off tops of vegetation on land area or in shallow water; (b) dipping or feeding with the head and neck underwater but with the body horizontal on the water surface; (c) tipping or feeding with the body perpendicular to the water surface, and only the feet and tail visible; (d) gleaning or skimming the water surface with the bill; (e) preening or cleaning feathers with the bill, (f) bathing; (g) swimming; (h) walking; (i) taking-off; (j) landing; and (k) inactive such as roosting, loafing, or motionless on water or land. The Statistical Package for the Social Sciences (SPSS) software (Nie et al., 1975; Hull and Nie, 1981)

was

used

nonparametric

to test behaviors

for

statistical

analyses

differences

between

in

analyses. (Zar,

wildfowl

wildlife

1974)

Standard were

used

habitat use and groups, and com-

COMBS

1.

TABLE

size maintained to March 1982-83,

Average

Rankin

Mean flock Size per observation Unit’ Ranking

based

those

with

both

species

“Means

on Oddo

a rank on

et al.

(1978)

died

last.

“6”

received

based

pare

of

a rank

three

units

mortality

or more and

2.5

Coots

Swans

Wigeon

20.7

28.7

19.1

and

Mensik the

with

from

and

peak

at least

past

days,

with

day.

Both

ple

sizes

to

large

tests

(Botzler

mortality

one

bird,

to

corrected

U-statistic

to

sums

significant

termine

of

from

each

icance

level

for

Hypotheses in

the

using

other

Spearman’s

rank

TABLE

and

2.

County,

Botzler,

Percentage California,

Land

past

6.2

6.3

dying

first

in the

both

species abilities

de-

dif-

The

signif-

a

= 0.05. position

epizootics

and

were

tested

test

wildfowl

6

epizootics

before

have

and

after

a rank

wigeon

of

(Zar,

Swans followed

directly to the

Coots 32,1O&

n

and

Wigeon = 4,231

mean

size,

highest

past

wigeon, of

of past

flock

was

spite

having

not mortality

teal, (Tasize

(Oddo 1989). and the

among

less

was

P = 0.036) 111 the mor-

epizootics

mortality

epizootics

highest the highest

on three

mean

Mensik and Botzler, between flock size

the second swans had high

flock pintails,

respectively

disproportionate

observed

=

coots,

sequence

of total time birds were October to March 1982-83

and

the

by

al., 1978; relationship

of wildfowl

of

prob-

correlated (r = 0.84, position of these Species

both

1978)

had

Ranking

after

that

of 2.5. Exact all correlations.

RESULTS

swans,

1989)

from 1 (coots) mortality oc-

a rank for

clear.

coots Coots

mean flock size. mean flock size, had

Swans = 1,040

of

observations

made

for

disproportionately

wigeon and swans used land sigmore than did pintails, shoveler/ and teal (Table 2). The position in the

habitats

of Pond

mortality

Two,

sequence

Centerville,

was

Humboldt

n

Pintails = 3,149

Shoveler/ Mallards n = 2,659

2.0

n

Teal = 979

21.9

28.8

39.6

3.8

39.0

40.7

11.4

57.6

31.0

48.9

39.1

30.5

49.0

38.6

67.0

44.7

each

group.

But de-

at Centerville.

1983-84.

n

in had

6.4

water

m)

et The high

water

(>0.15

1;

mortality,

group.

were assigned were calculated

Coots, nificantly mallards

varied wigeon et al.,

(0.15m)

‘Number

at

behavior

area

Deep

set

correlation

n

Shallow

9.4

occurred

respective

tality

rank to

between

and

1974). Mortality rankings to 6 (teal). Because peak curred both before (Oddo (Mensik

1974). was

of

size

use used

significantly

(Zar, tests

sequence in flock

distest

which

of correlations

differences

County,

Teal

1).

between

were

were

these

mortality

Humboldt

Pintails

ble

comparisons

but means,

samples

ferent

has

545

5 Shoveler! mallards

Due

a normally

multiple

rank

which

Those

CHOLERA

mortality

4

shoveler/mallards,

SPSS.

differences

Newman-Keuls,

instead

Ponds,

cholera

and

Kruskal-Wallis

nonparametric

similar

a vian

sam-

Mann-Whitney into

When

each

both

unequal

within

the

transformed

statistic.

indicated

samples,

ties

sizes,

was

Z

for

for

For

of replication was units and time of

weighted

sample

(1989). of swans

for

epizootics

samples.

the unit of grid

were

and

tributed results

independent

behavior, a pooling

g of sequential

2.5

Since

TO AVIAN

on the Centerville

1

variation in flock size, habitat use, and behavior. Behaviors and locations were ranked and compared using Mann-Whitney U-tests for two independent samples, and Kruskal-Wallis tests for species

groups

CORRELATED

of “2.5.”

observation

species

BEHAVIOR

by six wildfowl 1983-84.

flock

October

California,

AND BOTZLER-WILDFOWL

546

JOURNAL

weakly time There

correlated spent was

high coots ences and

OF WILDLIFE

DISEASES,

with

on land no evident

(r

VOL. 27, NO. 4, OCTOBER

their

ranking P

0.75,

=

=

relationship

disproportionate during past in time spent

of

0.084). between

mortality epizootics, and on land between

among differcoots

the other wildfowl groups in this We recorded 62,460 behavioral

among

wildfowl

(Table

3). Coots

study. acts

spent

sig-

nificantly more time grazing (73.0%) than all other activities combined (Table 3), and grazed more frequently than other waterfowl (Tables 3, 4). Swimming the next most frequent behavior The remaining for only 15.5% Coots exhibited than any other 4).

(11.5%) for

nine behaviors accounted of coot sightings (Table 3). significantly less inactivity wildfowl group (Tables 3,

Overall, coots and wigeon similarities in behaviors (Table coots, wigeon spent significantly grazing

(62.3%)

than

all

(Tables 3), and second most common

served. mortality directly

The position sequence correlated

(r

to

rank

of

quency

order

(Table

of of

had 3). more

other

combined was the

the

was coots.

behaviors

swimming behavior wildfowl

past

their

also obin

epizootics

P

0.93,

=

some Like time

the was

=

0.008)

grazing

fre-

4).

was

an

exploratory

study

designed

to test hypotheses about the possible roles of wildfowl density, habitat use and behavior, as predisposing factors to avian cholera.

In themselves,

adequate

to establish

lationships.

were

to test

The position ity sequence ville flock

correlations cause

Rather,

used

was

time of

grazing

water. The observation flock sizes died epizootics that avian

are effect

not re-

patterns

hypotheses.

of wildfowl in the mortalof past epizootics at Center-

directly

size,

quency

and

correlation

these

conflicted cholera

correlated spent on

that earlier

independent

fashion.

to their

mean

on land, and freland and shallow species with large in avian cholera

with operates

the hypothesis in a density-

Finding

evidence

a density-dependent relationship surprising, however, since high facilitate the transmission of avian through and

domestic Olney,

bird

Correlation sequence with expected. shallow exposure

populations

(Van

Es

of position time spent

in the mortality on land was un-

Because most carcasses occur in water, we assumed the greatest to infection would occur there.

Thus, we low water avian land.

for

is not densities cholera

1940).

expected would

cholera Perhaps

that time spent be better correlated

mortality pasteurellae land

than time originating

carcasses

on

tion, and centrated

are transmitted dose to birds

are

size for correlated

on

each to

land Our 4) were

(r = 0.89, behavioral consistent

wildfowl Bel!rose,

behavior 1980).

grazing regularly

during trast,

an birds

to

dilu-

in a more grazing or

conscav-

subject

1987). It also is posto time spent on by flock size; rank wildfowl rank of

group time

P = 0.019). observations with earlier

was spent

(Tables reports

3, on

(Johnsgard, 1965, 1975; Because bacteria tend to

near the Baker,

birds posed

on from

have been observed during avian chol-

era epizootics (Pau!lin, sible that the correlation land was confounded of flock directly

in shalwith spent

not

enging on land. Coots scavenging on carcasses

concentrate (Potter and

DISCUSSION

This

1991

surface 1961;

of the Potter,

water 1964),

at the surface would be exto P. multocida in water

avian cholera epizootic. ingesting food or water

the surface, such would be expected

as dippers to receive

to bacteria

water

on

the

Several factors these findings. One

In conbelow

and tippers, less exposure

surface.

added important

uncertainty factor

to is that

avian cholera did not occur during this study; thus, mortality patterns from one set of years were compared to wildfowl activities observed during a second set of years. However, the major variation between years appears to be weather, and Combs minimal

(1988) impact

assumed

that

noted that on wildfowl the

observations

weather activity. of these

had

a We two

COMBS

AND

BOTZLER-WILDFOWL

BEHAVIOR

CORRELATED

TO AVIAN

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CHOLERA

547

548

JOURNAL

OF WILDLIFE

DISEASES,

VOL. 27, NO. 4, OCTOBER

1991

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