Thesis

Hummingbird choices at artificial flowers made to resemble ornithophiles versus melittophiles

Certain floral characteristics are associated with specific pollinators. Hummingbird-pollinated flowers are usually red, lack a landing platform, lack color patterns on the perianth, and contain a high amount of dilute sucrose-rich nectar compared to bee-pollinated flowers. The goal of this study was to test hypotheses concerning the reasons for these characters to the extent that they involve hummingbird behaviors. An array was set up that contained 16 artificial inflorescences, each with five artificial flowers. In Experiment 1, flowers were made that differed only in color, and birds showed very little preference, slightly preferring red over other colors. In Experiment 2, color was made to be associated with nectar offerings, and birds learned to visit flowers of the color that provided much more nectar (6 versus 2 μL but not 4 versus 2 μL), but generally 2 μL was above the threshold for inclusion in the diet. In Experiment 3, birds were offered bird-nectar (8 μL of 12% sucrose) versus bee-nectar (2 μL of 48% hexose), and birds did not prefer the nectars that were similar to natural bird-adapted flowers even though they could extract bird nectar with less handling time. In Experiment 4, birds were offered flowers with and without landing platforms, and birds preferred flowers that lacked landing platforms, which saved them time. In Experiment 5, birds were offered flowers that were patterned or not, associated with differing nectar volumes, and birds did not associate the higher nectar reward with either flower type. In general, the preferences of birds fall far short of explaining the natural phenomenon of bird- versus bee-pollination syndromes. Other factors, such as adaptation to discourage bees, are discussed as additional causes of the differences between the syndromes. Furthermore, I delve into the possibility that bird behaviors may be based on their drive to sample new and different flowers, i.e., flowers unlike those that are optimally rewarding.

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