Ecological correlates of territory and home range size in
North American dabbling ducks
T H O M A S D. N U D D S A N D C. D A V I S O N A N K N E Y
Socio-ecology’s main focus is upon correla­
tions betw een social organization and spe­
cies’ differences in ecology (C rook 1970).
A m ong w aterfow l biologists there has been
considerable disagreem ent concerning the
existence and function of territories (see
R yder 1975, M ineau & C ooke 1979, Owen
& Wells 1979, for reviews of the literature
and the nature of the problem for geese).
M cKinney (1965) reviewed the literature
about ducks. F or exam ple, H ochbaum
(1944) thought th at intraspecific aggression
by ducks (frequently referred to as ‘spacing
behaviour’) ‘fit’ the definition of classical
avian territoriality, but Sowls (1955) prop­
osed that ducks had broadly overlapping
hom e-ranges and did not exhibit territo r­
iality. A m ain problem has been the use of
the word ‘territo ry ’ w here a defended area
was not obvious (D zubin 1955; M cKinney
1965).
O ne interpretation of intraspecific
aggression is that it functions in m ate
attraction and pair-bonding. B road com ­
parisons of species’ natural histories with
plumage and behavioural characteristics in
different environm ents support that view
(e.g., Siegfried 1976, for oxyurids). A ddi­
tionally, intraspecific aggression might en ­
sure undisturbed feeding, copulation or
incubation for breeding pairs. B road com ­
parisons support that hypothesis also (see
T itm an & Seym our 1980 for review).
A s a third alternative, M cKinney (1965,
1973) hypothesized th a t the degree of in­
traspecific aggressive behaviour of ducks
would be a positive function of the degree
of defendability (Brown 1964) of their re­
spective food resources. M cKinney’s com ­
parisons support that view. N orthern
Shoveler A nas clypeata, for example,
which feed prim arily on abundant cladoceran arthropods or on planorbid snails
(Swanson et al. 1979), show frequent male
intolerance of other males and the pair­
bond is long-lasting. Shovelers approach
the case of classical avian territoriality;
their food resources are relatively easy to
defend and the areas frequented by pairs
are small. In contrast, Pintail A . acuta are
m ore prom iscuous and males are more
tolerant of one another. T he food re­
sources they use are ‘patchy’, being locally
58
W ildfowl 33 (1982):58—62
abun d an t but variable in tim e and space
(K rapu 1974), and economical defence of
such a resource is less likely. M allard A .
platyrhynchos ap p ear to occupy an in­
term ediate position on this continuum of
duck social organization. D errickson
(1978, 1979), D w yer et al. (1979), G ilm er
et al. (1974), and M cH enry (1971) reiter­
ated the im portance of resource ‘patchi­
ness’ in understanding differences in the
mobility and social behaviour of ducks.
A ny general theory to account for the
diversity of social organizations of ducks
m ust take into account both resource
‘patchiness’ and the positive relationship
betw een body size and territory size in
birds (Schoener 1968). G enerally, larger
organism s require m ore energy and need
larger foraging areas because they feed
optim ally on large prey which are relatively
scarce. Thus, interspecific variation in sizes
of areas used by breeding ducks may be
due to (1) differences in body size and (2)
the spatial and tem poral variability of re­
sources. F or exam ple, M allard and similar­
sized Black D uck A . rubripes are consi­
dered ecological equivalents by Bellrose
(1976). T erritories of Black Duck con­
form ed to the configurations of habitat in
an A tlantic coast m arsh (Seym our & T it­
m an 1978). M ales defended entire ponds,
the largest of which was 4-0 ha, and all
nests w ere closer to defended ponds than
to any o th er w ater body. Neighbouring
pairs avoided each o th e r’s areas after
boundaries w ere established. M allard in
the prairie-pothole region, in contrast,
occupied large overlapping areas, and loaf­
ing and feeding sites were considerable
distances from the nest (D w yer et al. 1979).
D espite the similarity in body size, Black
D uck conform b etter to the classical defini­
tion of territorial behaviour than do M al­
lard.
A t a gross level of com parison, large
m arshes are less heterogeneous environ­
m ents th an pothole habitats. Large m ar­
shes may ‘draw dow n’ during drought
periods b u t seldom disappear com pletely,
so tem poral fluctuations in resources may
be dam ped. Potholes are extrem ely vari­
able and seasonal and annual variation in
pothole abundance is large (Smith 1971;
Ecological correlates in N orth A m erican dabbling ducks
Stoudt 1971). Large m arshes are structur­
ally an interspersion of w ater and aquatic
vegetation. Pothole habitats contain patch­
es of w ater and aquatic vegetation dis­
persed am ong upland habitats.
T able 1 is a com pilation of quantitative
data from the literature on territory and
hom e-range sizes of A nas spp., classified
according to the type of breeding habitat.
Body-weight are data from Bellrose
(1976). T he data suggest (Figure 1) a com ­
ponent of territory/hom e-range
size
variance th at is related to body-size (r =
0-44, P < 0-06, all data; r = 0-60, P < 0-01,
‘pothole’ data only). In addition there is a
com ponent of intraspecific variation that
suggests that larger areas are, in general,
necessary to produce adequate resources
for breeding in ‘patchy’ environm ents.
A reas are larger in pothole than marsh
habitats (t = 2-47, P < 0-05).
T he pattern is m ost striking, considering
the variability inherent in published data
such as differences in the tim e when terri­
tory or hom e-range was m easured, in de­
finition of territory and hom e-range, and in
population size (which may affect territory/
hom e-range size).
T he pattern of intraspecific variation in
territory/hom e-range size both clarifies and
reinforces M cKinney’s hypothesis that the
diversity of duck social systems is related to
the characteristics of resources in breeding
habitats. W e explicitly account for the con­
tributions that variability of body-size and
of food resources separately m ake to
59
variance in the size of areas used by breed­
ing dabbling ducks.
T he hypothesis that intraspecific vari­
ation in territory/hom e-range size is related
to resource dispersion is n ot new. Trautman (1949, cited by Sowls 1955) w ondered
if ‘. . . changing w ater levels or other fac­
tors m ake territory hunting m ore difficult’.
Dzubin (1955) realized th at geographic
variation in territorial behaviour existed
and might be attributable to variation in
the type of breeding habitats occupied, and
that territory should n ot be rigidly defined.
Smith (1971) observed th at M allard and
Pintail territorial behaviour was consider­
ably different in eastern and w estern re­
gions of the prairies and suggested that
‘breeding habitat requirem ents of the east­
ern populations may produce a different
spatial distribution than th at of western
populations’.
A lthough differences in the social o r­
ganization displayed by ducks are appa­
rent, they may grade into one another as
dictated by the costs of defending re­
sources in different environm ents, and
different body sizes and/or diets. Wiens
(1976) proposed a continuum of social
organizations from rigid territoriality
w here resources are spatially and tem por­
ally predictable and the cost of resource
defence is low, to flocks and nomadism
w here resources are unpredictable and the
expense of defence is high. A m ong the
A natinae reviewed here loose territorial­
ity, hom e-ranges, and coloniality represent
Table 1. Body weights and territory or home-range sizes of ducks in pothole and marsh habitats.
Species
Body weight
(kg)
A . platyrhynchos
1-18
A . rubripes
A . streperà
A . acuta
1-18
0-90
0-95
A . crecca
A . discors
0-32
0-42
A . cyanoptera
A . c/ypeata
0-34
0-66
H om e range size
(ha)
283*
468
203t
230
4
28
486
509
243}
8*
103
65
36
7
0-7
8*
8*
3
20
H abitat
Source
pothole
pothole
pothole
pothole
marsh
marsh
pothole
pothole
pothole
marsh
pothole
pothole
pothole
pothole
pothole
m arsh
m arsh
marsh
pothole
Dzubin 1955
D w yer et al. 1979
T itm an 1973
G ilm er et al. 1975
Seym our & T itm an 1978
G ates 1962
D rew ien 1968
D errickson 1978
D rew ien 1967
G ates 1962
Dzubin 1955
D rew ien 1968
E vans & Black 1956
M cHenry 1971
Stewart & T itm an 1980
G ates 1962
G ates 1962
Seym our 1974
Poston 1974
* M axim um (m arsh) or m inim um estim ates (p o th o le); t C alculated; i B ased on a sin gle pair on ly .
60
T hom as D. N u d d s and C. D avison A n k n e y
LOG
BODY
W E I G H T (g)
Figure 1. The relationship between body weight and home-range size for some North American
Anatinae. Triangles are pothole data, circles are m arsh data. Species are coded as follows: A nas
crecca, open triangle; A . cyanoptera, open circle; A . discors, closed; A . clypeata, left-shaded; A .
streperà, right-shaded, A . acuta, upper-shaded; A . platyrhynchos (and A . rubripes), lower-shaded.
interm ediate types of organization adapted
to increasingly variable or unpredictable
resources. A dditionally, D zubin (1955)
observed that in the arid and unpredictable
short-grass prairie region, ducks nest in
colonies, and Frith (1959) described the
nom adic m ovem ents of waterfowl in the
unpredictable habitats of inland New
South Wales. On the other hand, Ball et al.
(1978) speculated that the stability of river
habitats prom oted the evolution of rigid
territoriality in African Black Duck A.
sparsa.
We may speculate about several addi­
tional points concerning Figure 1. First, if
the abscissa w ere transform ed to convey
the size of the food ducks eat, Shoveler
would occupy the extrem e left-hand posi­
tion and the fit of the data would be
im proved. A p art from the Shoveler, there
is a regular increase in the num ber of
lamellae per cm of bill (i.e., finer spacing)
and decrease in bill size with decreasing
body size within the A nas (Nudds &
Kaminski, unpub. ). This suggests that the
underlying selective force favouring larger
areas being used by ducks with larger
bodies is the lesser availability of food of
the preferred size for the larger birds.
Second, the lowest data points for Blue­
winged Teal A . discors, reported by
M cH enry (1971) and Stew art & Titm an
(1980), w ere both estim ates for the pothole
region
near
M innedosa,
M anitoba.
M cH enry said that his estim ate of homerange size was less than that reported by
others because, in his region, pothole den­
sity was high. We suggest that smaller
areas are affordable by Blue-winged Teal
in habitats comprising closely-spaced
potholes which are m ore marsh-like with
respect to resource dispersion.
Third, Black D uck in A tlantic coast m ar­
shes occupy areas in the sam e size-range as
do Shoveler, a species about half their
weight, in oth er m arsh habitats. Perhaps
an increase in the num ber of potential
com petitors may reduce resource levels
and force the use of larger areas (Y eaton &
Cody 1974). Black D uck in A tlantic coast
marshes of low com petitor diversity may
thus benefit, this being reflected in the
small areas they occupy there. O ther vari­
ation in Figure 1 might be accounted for if
we knew of the num ber of coexisting Anas
species at each study site.
W e have necessarily been less concerned
with the historical sem antic argum ents ab­
out w hat constitutes territories or homeranges, have sacrificed some detail in
favour of discovering broadly applicable
principles, and have concerned ourselves
Ecological correlates in N orth A m erican dabbling ducks
with the biological significance of observed
patterns of variation in the size of areas
used by pairs of breeding ducks. This re­
view goes som e distance tow ards reconcil­
ing differences of opinion regarding ‘te r­
ritorial’ behaviour and its function in
ducks. Because duck populations appear to
be in evolutionary equilibria with resource
levels (Nudds 1980), we hypothesize that
interference com petition has evolved a
diversity of forms depending on the
heterogeneity of resources in space and
ecological tim e. In the future, consistent,
operational definitions of territory and
hom e-range, im proved diet analysis, radio­
telem etric techniques, and quantification
of tem poral and spatial resource variability
for several species am ong different habitats
will enable us to assess the various hypoth­
eses regarding the function of intraspecific
aggression by ducks.
Acknowledgements
W e thank K. F. A braham , R. O . Bailey, R. W.
C ole, F. M cK inney, P. M ickelson, J. S. M illar,
61
T. W. Schoener, and R. D. T itm an for critical
reviews of a draft of the m anuscript. This work
was supported by the N atural Sciences and
Engineering Research Council of Canada,
C anadian W ildlife Service, US Fish and Wildlife
Service, U niversity of W estern O ntario Founda­
tion of New Y ork, D epartm ent of Indian and
N orthern A ffairs, and the C anadian National
Sportsm en’s Fund. The senior author was sup­
ported by N atural Sciences and Engineering
R esearch Council of C anada Postgraduate, and
O ntario G rad u ate, Scholarships.
Summary
A review of published, quantitative data sug­
gested that the sizes of areas used by breeding
A nas spp. is related to both body-size and
resource dispersion. M cK inney’s hypothesis did
not distinguish the separate contributions of
each of those factors. The variability in social
systems am ong dabbling ducks is correlated with
the spatial and tem poral variability of breeding
habitats; social systems can be arranged along a
continuum with ‘rigid’ territoriality comm on in
stable habitats, but ‘loose’ territoriality and
hom e-ranges prevailing in variable habitats.
References
Ball, I. J ., Frost, P. G . H ., Siegfried, W. R. & M cKinney, F. 1978. T erritories and local m ovem ents
of A frican Black D ucks. W ildfowl 29: 61-9.
Bellrose, F. C. 1976. Ducks, geese, and swans o f North America. H arrisburg, Pa.: Stackpole Co.
B row n, J. L. 1964. T he evolution of diversity in avian territorial systems. Wilson Bull. 76: 160-9.
D errickson, S. R. 1978. The m obility of breeding Pintails. A u k 95: 104-14.
D errickson, S. R. 1979. Social interactions and spacing behaviour in breeding dabbling ducks
(A bstract). Pp. 45 in T. A . B ookhout (ed.). Waterfowl and wetlands—an integrated review.
LaCrosse, W is.: LaCrosse Printing Co.
C rook, J. H . 1970. Social organization and the environm ent: aspects of contem porary social
ethology. A nim . Behav. 18: 197-209.
D rew ien, R. C. 1968. Ecological relationships of breeding Blue-winged Teal to prairie potholes.
M.Sc. Thesis, S. D akota State Univ.
D zubin, A . 1955. Some evidences of hom e range in waterfowl. Trans. N. A m er. Wildl. Conf. 20:
278-98.
D w yer, T. J ., K rapu, G. L. & Janke, D. M. 1979. Use of prairie pothole habitat by breeding
M allards. J. Wildl. M anage. 43: 526-31.
Evans, D. C. & Black, K. E. 1956. D uck production studies on the prairie potholes of South D akota.
U.S. Fish and Wildl. Serv. Spec. Sci. Rept. ( W ildlife) No. 32.
Frith, H. J. 1959. T he ecology of wild ducks in inland New South W ales. II. M ovem ents. C .S .l.R .O .
Wildl. Res. 4: 108-30.
G ates, J. M. 1962. B reeding biology of the Gadwall in northern U tah. Wilson Bull. 74: 43-67.
G ilm er, D . S., Ball, I. J ., C ow ardin, L. M ., R eichm ann, J. H . & T ester, J. R. 1975. H abitat use and
hom e range of M allards breeding in M innesota. J. Wildl. Manage. 39: 781-9.
H ochbaum , H . A . 1944. The Canvasback on a prairie marsh. W ashington, D . C.: A m er. Wildl. Inst.
K rapu, G . L. 1974. Foods o f breeding pintails in N orth D akota. J. Wildl. Manage. 38: 408-17.
M cH enry, M. G . 1971. B reeding and post-breeding m ovem ents of Blue-winged Teal (A nas discors)
in southw estern M anitoba. P h.D . Thesis, Univ. of O klahom a.
M cKinney, F. 1965. Spacing and chasing in breeding ducks. W ildfowl 16: 92-106.
M cKinney, F. 1973. Ecoethological aspects o f reproduction. Pp. 6-21 in D . S. F arner (ed.). Breeding
biology o f birds. W ashington, D .C .: National A cad. Sci.
M ineau, P. & C ooke, F. 1979. T erritoriality in Snow G eese or the protection of parenthood—
R yder’s and Inglis’s hypotheses re-assessed. W ildfowl 30: 16-19.
62
T hom as D. N u d d s and C. D avison A n k n e y
N udds, T. D . 1980. R esource variability, com petition and the structure of w aterfowl comm unities.
Ph.D . Thesis, Univ. of W estern O ntario.
O w en, M ., & W ells, R. 1979. T erritorial behaviour in breeding geese— a re-exam ination of R yder's
hypothesis. W ildfow l 30: 20-26.
Poston, H . J. 1974. H om e range and breeding biology of the Shoveler. Can. Wildl. Ser. Rept. Ser'.
25.
R yder, J. P. 1975. T he significance of territory size in colonial nesting geese— an hypothesis.
W ildfowl 2 6:114-16.
Schoener, T. W.
1968. Sizes of feeding territories am ong birds. Ecology 49: 123-41.
Seym our, N. R. 1974. T erritorial behaviour of wild Shovelers at D elta, M anitoba. W ildfow l 25:
49-55.
Seym our, N. R. & T itm an, R. D . 1978. Changes in activity patterns, agonistic behaviour, and
territoriality of Black D ucks (A nas rubripes) during the breeding season in a Nova Scotia tidal
m arsh. Can. J. Zool. 56: 1773-85.
Siegfried, W. R . 1976. Social organization in R uddy and M accoa Ducks. A u k 93: 560-70.
Sm ith, A . G. 1971. Ecological factors affecting waterfowl production in the A lberta parklands. U.S.
Fish and Wildl. Serv. Resour. Pubi. 98.
Sowls, L. K. 1955. Prairie ducks. W ashington, D .C .: Wildl. M anage. Inst.
Stew art, G . R. & T itm an, R. D . 1980. T erritorial behaviour by prairie pothole Blue-winged Teal.
Can. J. Zool. 58: 639-49.
Stoudt, J. H . 1971. Ecological factors affecting waterfowl production in the Saskatchewan parklands.
U.S. Fish and Wildl. Serv. Resour. Pubi. 99.
Swanson, G. A ., K rapu, G. L. & Serie, J. R. 1979. Foods of laying female dabbling ducks on the
breeding grounds. Pp. 47-58 in T. A . B ookhout (ed.). W aterfowl and wetlands— an integrated
review. LaC ross, W is.: LaCrosse Printing Co.
T itm an, R . D . 1973. T he role of the pursuit flight in the breeding biology of the M allard. Ph.D .
T hesis, U niversity of New Brunswick.
T itm an, R. D . & Seym our, N. R. 1980. A com parison of pursuit flights by six N orth A m erican ducks
of the genus Anas. W ildfow l 32: 11-18.
W iens, J. A . 1976. Population responses to patchy environm ents. A nn. Rev. Ecol. Syst. 7: 81-120.
Thomas D. Nudds, D epartm ent of Z oology, University of W estern O ntario, L ondon, O ntario N6A
5B7, C anada. Present address: D epartm ent of Zoology, University of G uelph, G uelph, O ntario,
N IG 2W 1, Canada.
C. Davison Ankney, D epartm ent of Z oology, University of W estern O ntario, London, O ntario,
N6A 5B7, C anada.