10
RICHARD S. MILLER
and this weakens his argument. He does not define “optimum” and it
is therefore impossible to test this critical hypothesis, but a more serious
objection is the lack of evidence for food as an ultimate limiting factor
in many populations (Andrewartha and Birch, 1954). While we must
accept the fact that territories are rendered incompressible at some point
by psychological factors (Klopfer, 1962) and that competition for space is
a form of limiting convention, it cannot be assumed that all species
require space for the same reasons or that they are ultimately limited
by the same factor. There are numerous examples among birds to show
that territory is related to factors other than food (cf. Hinde, 1956).
The principal area of defense among hole-nesting birds is usually the
immediate vicinity of the nest hole, and the density of breeding pairs
can be increased in most natural habitats by providing artificial nest
boxes (Von Haartman, 1956). Intraspecific and interspecific territorialism exists among closely related species of plovers, but these birds, as
do many others, feed outside the limits of their territories. Simmons
(1956) suggests that the most important function of territory in these
species is the spacing of nests and eggs, as Tinbergen (1956) has shown
for other ground-nesting birds. Hartley (1949) found that the only common requirement among the territories of mourning chats (Oemnathe
lugens) in their wintering quarters in the African deserts was a measure
of shade. This could be provided by broken ground or some artificial
counterpart such as a scar in a hill or hutments of a camp. A structural
feature which is required for breeding or shelter may be more limiting
than food in the habitats of some species, and it is frequently observed
that the limits of population in territorial species are well below the
ultimate limit of food supply, even in years of food scarcity. However,
if we define “territory” simply as any “defended area or space”, regardless of its origin or function, it is evident that territorialism exists both
within and between some species, and leads to competitive exclusion
from particular habitats and niches. This concept can be accommodated
within the broader term “interference”, which may be direct, as in the
case of territoriality or overt aggression, or indirect chemical communication. I n each case the effect of interference is to ensure possession of
a particular array of resources at the possible expense of other individuals
or species.
There is an apparent evolutionary tendency toward more formalized
mechanisms of territorial behavior, with greater emphasis on display
and correspondingly less on physical contact. Wynne-Edwards (1962)
uses the term “epideictic display” to denote conventions that have
evolved away from the direct, primitive contest and have come to
assume a symbolic quality, not even directly implying threat in some
cases, but which nevertheless serve to interfere with intrusion into a
RICHARD S. MILLER
and this weakens his argument. He does not define “optimum” and it
is therefore impossible to test this critical hypothesis, but a more serious
objection is the lack of evidence for food as an ultimate limiting factor
in many populations (Andrewartha and Birch, 1954). While we must
accept the fact that territories are rendered incompressible at some point
by psychological factors (Klopfer, 1962) and that competition for space is
a form of limiting convention, it cannot be assumed that all species
require space for the same reasons or that they are ultimately limited
by the same factor. There are numerous examples among birds to show
that territory is related to factors other than food (cf. Hinde, 1956).
The principal area of defense among hole-nesting birds is usually the
immediate vicinity of the nest hole, and the density of breeding pairs
can be increased in most natural habitats by providing artificial nest
boxes (Von Haartman, 1956). Intraspecific and interspecific territorialism exists among closely related species of plovers, but these birds, as
do many others, feed outside the limits of their territories. Simmons
(1956) suggests that the most important function of territory in these
species is the spacing of nests and eggs, as Tinbergen (1956) has shown
for other ground-nesting birds. Hartley (1949) found that the only common requirement among the territories of mourning chats (Oemnathe
lugens) in their wintering quarters in the African deserts was a measure
of shade. This could be provided by broken ground or some artificial
counterpart such as a scar in a hill or hutments of a camp. A structural
feature which is required for breeding or shelter may be more limiting
than food in the habitats of some species, and it is frequently observed
that the limits of population in territorial species are well below the
ultimate limit of food supply, even in years of food scarcity. However,
if we define “territory” simply as any “defended area or space”, regardless of its origin or function, it is evident that territorialism exists both
within and between some species, and leads to competitive exclusion
from particular habitats and niches. This concept can be accommodated
within the broader term “interference”, which may be direct, as in the
case of territoriality or overt aggression, or indirect chemical communication. I n each case the effect of interference is to ensure possession of
a particular array of resources at the possible expense of other individuals
or species.
There is an apparent evolutionary tendency toward more formalized
mechanisms of territorial behavior, with greater emphasis on display
and correspondingly less on physical contact. Wynne-Edwards (1962)
uses the term “epideictic display” to denote conventions that have
evolved away from the direct, primitive contest and have come to
assume a symbolic quality, not even directly implying threat in some
cases, but which nevertheless serve to interfere with intrusion into a