Pollock et al. 1994). Another off-site approach involves contacting hunters
before the hunting season and asking them to keep records of each hunt during
the season (e.g. Caithness 1982; Pollock et al. 1994). Off-site surveys provide
more opportunity for biased estimates resulting from such factors as poor
memory, rounding error, false reporting associated with prestige or other moti-
vations for deceit, question misinterpretation, species misidentification, and
nonresponse.
13.4.3Harvest estimation when harvest is illegal
Illegal harvest can be of two types that sometimes require different methods of
estimation and investigation. One type of illegal harvest occurs during open
hunting seasons and involves violations of bag limits (shooting more birds than
legally permitted) and of species regulations (shooting protected species of birds
in addition to birds for which the season is open). The other type of illegal har-
vest does not occur within the context of an open season and includes virtually
any other type of illegal hunting activity, such as targeting protected species, ille-
gal commercial harvest, and hunting at illegal times (e.g. at night).
Illegal harvest during the hunting season is frequently investigated by clan-
destine observation of hunters. North American studies of illegal activities in
waterfowl hunting often employ a “spy blind” technique (e.g. Mikula et al. 1972;
Martin and Carney 1977; Nieman and Caswell 1989). Roving hunter checks by
conservation officers can also provide information on certain types of violations
(e.g. harvested birds exceeding the bag limit). Mail questionnaire hunter surveys
have been used to estimate illegal activity as well (Gray and Kaminski 1989,
1994), and may be useful when respondent anonymity is ensured.
Illegal harvest occurring outside the context of a legal hunting season typical-
ly cannot be investigated using hunter observation methods, as participants in
illegal activities are secretive. One method for estimating the magnitude of ille-
gal activities and harvest is sometimes termed “violation simulation” (Gray and
Kaminski 1989). The approach uses investigators who pose as illegal hunters and
harvest birds “illegally”. The number of these simulated violators detected by
conservation officers is used with the number of actual violators detected to esti-
mate total violations under a capture-recapture approach. Another approach is
for investigators to infiltrate the societal subset of interest (e.g. commercial
poachers) in order to obtain information about the magnitude of harvest (Gray
and Kaminski 1989). It is worth noting that in some countries, laws regarding
hunting are so infrequently enforced that participants in illegal activities may not
worry about being secretive. In such cases, the off-site surveys described above
(13.4.2) may work.
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