Fig. 7.5. (a) The four patterns of feeder quality: (1) halves, (2) quarters, (3) checkerboard, (4) Random. Solid circles represent feeders containing sucrose; the remaining circles represent feeders that were empty.
Spatial patterns or point locations?
Wolf & Hainsworth (1990, 1991) could find little evidence for memory for reward locations in the five male hummingbirds (rufous and broad-tailed) they observed foraging at clumps of Ipomopsis aggregata inflorescences. However, rufous hummingbirds do display memory for both spatial pattern and point locations in experiments. Sutherland & Gass (1995) used an array of 64 feeders (11 cm apart), 32 of which contained reward, to test learning and memory of a range of spatial patterns in female rufous hummingbirds. The array was presented in one of four patterns: (1) halves; (2) quarters; (3) checkerboard; or, (4) random (see Fig. 7.5a) on four consecutive days, with birds having 40 trials at each pattern.
Performance on all arrays began at 50% (chance), but performance improved much more quickly and reached higher levels after 40 trials in the halves and quarters arrays than in the more complex checkerboard and random arrays. Birds' performances were, however, still improving
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