CAPTURE METHODS FOR BLACK-Bn l.P.r MAGPIES

A number of characteristics contribute to the difficulties involved in capturing Black-billed Magpies (Pica pica). They are extremely wary, tend- ing to avoid unusual objects (e.g., wire traps or mist-net poles) that have been recently introduced into their environment. Some are particularly reluctant to walk into enclosed traps (Birkhead 1991, J. M. Marzluff pers. comm.). Magpies also tend to be opportunistic feeders, making it virtually impossible to predict flight paths for the placement of mist nets. Finally, they learn very quickly and will avoid any trap in which they have previously been caught or nearly caught. They may even avoid traps in which they have merely seen other birds captured. Researchers have coped with these problems in several ways. Variations of funnel-entrance traps (e.g., Alsager et al. 1972) have been used with considerable success in some populations (Erpino 1968, Reese and Kadlec 1985) but with little or no success in others (Birkhead 1991, J. M. Marzluff pers. comm.). Buitron (1983) has used nooses hidden in grass and baited with suet to capture adult magpies, while Marzluff (pers. comm.) has used modified mammal leg-hold traps hidden under vegetation and baited with eggs. Unfortunately, individuals may learn to avoid any of these traps. To overcome this problem, one can use an arsenal of different traps, introduc- ing new varieties as individuals learn to avoid those currently employed. Another common solution (e.g., Birkhead 1991) has been simply to aban- don efforts to capture adults and rely on the banding of juveniles in the nest. Of course, this solution is practical only for those conducting relatively long- term studies of magpies dispersing only short distances. We experienced the difficulties involved in capturing adult magpies while trying to color-band a small population near Reno, Nevada. We came to rely on two trapping methods, one a modified traditional trap (the noose carpet), the other a modified method of mist-netting. Based on the design of the bal- chatri trap (Berger and Mueller 1959) traditionally used for raptors, a noose carpet is a flat piece of wire mesh to which have been tied numerous monofilament nooses. Noose carpets have been used to capture raptors and galliforms (Bloom 1987, Bub 1991), but their design and use for corvids has not previously been described in detail in the literature. We also developed and refined a capture technique using mist nets that we call the "bait-and- chase" method. We were able to rely on these two methods exclusively because magpies were relatively slow to learn to avoid them. Both methods had the further advantages of allowing the capture of multiple birds simulta- neously and the targeting of desired individuals; they should be useful for capturing other corvids and trap-shy species.