The five trials to be described herein were all conducted in the same 3.5 x 3.9 m room. The floor was covered with 6 cm of fine sand which was brushed to a smooth surf ace between and within each trial to obliterate all signs of cache making and cache presence. Conspicuous objects such as feces, feathers, and seed hulls were also carefully removed from the sandy substrate. The north wall contained a window in the east corner that was covered during each trial. The east and west walls each contained a wall socket and brackets for the attachment of three 3.5 m long perches. The south wall contained a sink, a small bench, a door, and a light fixture 0.3 m from the ceiling. These features of the room remained constant for each trial.
For all five trials a 15 cm square seed tray was placed near the center of the room. It was not moved between the caching and recovering phases of each trial. In Trials 1 and 2 the seed tray was on the floor while in Trials 3, 4, and 5 it was 1 m above the floor. A water dish was always located next to the seed tray, but remained on the floor.
All trials were conducted with a single semi-tamed Clark's nutcracker that had been in captivity for 7 months prior to the initiation of the trials. The sex and age of this bird were not known. Trials 1 through 3 were conducted between September 1980 and February 1981. Trials 4 and 5 were run in September and October 1981. The bird spent the intervening spring and summer of 1981 in a large outdoor flight cage. During this and other intervals, during which the bird was not in the above described room, it was fed insects, mice, a variety of seeds and a sparse supply of pinyon pine (Pinus edulis) seeds. The bird occasionally cached and recovered seeds in this situation.
All cache-recovery trials were conducted between 06:45 and 10:00 unless stated otherwise (Trial 4). Light and temperature conditions were the same between the cache-recovery phases of all trials.
During the caching and recovery phases of all trials, one of us (RPB) sat on the bench on the south wall and made direct observations in full view of the bird. In all trials RPB recorded the behavior of the bird and plotted the approximate location of each cache, on a map of the floor. Each cache was sequentially numbered as it was made. The time at which caching began and ended was recorded.
All trials followed a similar protocol. The nutcracker was put in the room seven days before each trial. During these seven days, the bird was fed hulled pinyon pine seeds, a mixture of various commercially available seeds, popcorn, and an occasional mouse. Each day the bird was fed 10 to 15 intact pinyon pine seeds in our presence. Intact pinyon pine seeds were never cached and only rarely did we find other food in caches. Eighteen hours before the initiation of a caching session the bird was deprived of all food.
At the beginning of a trial 210 large, intact, pinyon pine seeds were placed in the feeding tray. The bird typically ate four to six seeds before caching seeds in the substrate. After the bird ate or cached all 210 seeds, the lights were turned off, the bird was captured, and removed from the room. The bird was placed in a holding cage for the isolation