following hunting activities. Private hunting clubs and estates are frequently
relatively small in area and are under strict control of owners and their gamekeep-
ers. In such situations, it may be possible to obtain exact counts of harvested birds,
as for Red GrouseLagopus lagopuson shooting moors in Great Britain (e.g. Potts
et al. 1984; Hudson 1986). In many situations, however, such tight control is not
possible and sample survey methods must be used to estimate harvest. On-site
surveys involve efforts to contact hunters during or just following hunting activi-
ties, whereas off-site surveys involve other means of contacting hunters at times
subsequent to hunting.
On-site survey methods generally fall into one of two categories: access-point
surveys and roving surveys. Access-point surveys are appropriate for situations in
which hunting takes place in a local area (or series of such areas) to which access is
restricted to a relatively small number of entry points. Wildlife or conservation
officers are then stationed at a sample of these access points during a sample of
possible hunting times, and hunters exiting the area are stopped and their harvests
recorded. Visits to access points by conservation officers can be selected random-
ly with known probability from the possible points and from the possible times
during the hunting season, and harvest can be estimated. Although the statistical
framework for such sampling has been best developed for fisheries (Robson 1960;
Robson and Jones 1989; Pollock et al. 1994), surveys based on encounters at
hunter check stations have been used successfully for birds (e.g. Mikula et al.
1972; Wright 1978).
Roving surveys may be useful in areas for which discrete access points do not
exist or are too numerous to cover. The sampling frame for this design consists of
the set of all possible times (e.g. days, part-days) available for hunting and all pos-
sible locations where hunting can take place (these might be woodlots, moors or
portions of such habitat patches). Conservation officers travel over the selected
sample locations counting, interviewing, and checking encountered hunters.
The statistical framework for this design has again been developed primarily for
fisheries surveys (Robson 1961, 1991; Pollock et al. 1994) but has general
applicability for bird harvest as well.
Off-site surveys typically involve efforts to contact hunters before, during,
or following the hunting season in an effort to obtain information about the
harvest. The sample frame for such surveys is generally based on lists of hunters
(e.g. purchasers of hunting licenses, members of hunting clubs). Questionnaires
may then be mailed to hunters (e.g. Atwood 1956; Martin and Carney 1977;
Wright 1978; Barker 1991; Barker et al. 1992; Dolton and Padding 2002) or
conservation officers may contact and question selected hunters by telephone
(Hayne and Geissler 1977; Barker 1991) or in person (door to door surveys,
Assessing harvest levels| 313