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for comparing use with availability on an individual animal basis (although it
performed poorly in McClean et al.'s 1998 evaluation). This method (compo-
sitional analysis) has become increasingly popular because it enables assess-
ment of both second-order and third-order selection and yields statistical com-
parisons (rankings) among habitats (Donázar et al. 1993; Carroll et al. 1995;
Macdonald and Courtenay 1996; Todd et al. 2000). Additionally, because the
data are arranged analogous to an
ANOVA
, in which between-group differences
can be tested against within-group variation among individuals, it provides a
means of testing for differences among study sites (e.g., with different habitats,
different animal density, or different predators or competitors), seasons or
years (e.g., with different food conditions), sex-age groups, or groups of ani-
mals with different reproductive outputs or different fates (Aebischer et al.
1993a; Aanes and Andersen 1996).
SITE ATTRIBUTE DESIGN
Site attribute studies differ from use-availability studies in that they measure a
multitude of habitat-related variables at specific sites and attempt to identify
the variables and the values of those variables that best characterize sites that
are used (often for a specific activity). With this design, the dependent variable
is not the amount of use (as with use-availability studies) but simply whether
each site was used or unused (or a random location with unknown use); the
independent variables can be many and varied. Use-availability studies gener-
ally just deal with broad habitat types, or if more variables are considered, they
are analyzed individually (Gionfriddo and Krausman 1986; Armleder et al.
1994).
A site attribute design was used in 45 (29 percent) of the habitat selection
studies I reviewed. Of these, 28 were on birds and 17 on mammals. This design
requires measurement of habitat variables at some defined site, usually one that
serves some biological importance to the animal. Nest sites of birds are easily
defined and biologically important, and hence are often the subject of studies
of this nature. Habitat characteristics of breeding territories (Gaines and Ryan
1988; Prescott and Collister 1993), drumming sites (Stauffer and Peterson
1985; Thompson et al. 1987), and roosting sites (Folk and Tacha 1990) also
have been investigated. Among mammals, studies have focused on characteris-
tics of feeding sites (e.g., as evidenced by browsed or grazed vegetation; Edge et
al. 1988), food storage sites (e.g., squirrel middens; Smith and Mannan 1994),
resting sites (e.g., deer beds; Huegel et al. 1986; Ockenfels and Brooks 1994),
shelters (such as cliff overhangs, cavities, burrows, lodges, or dens; Lacki et al.
