Individual study: Anna’s hummingbirds Calypte anna rapidly learn to use feeders supplying sugar solution and may show a preference for red-dyed solutions in California, USA
Wheeler T.G. (1980) Experiments in Feeding Behavior of the Anna Hummingbird. The Wilson Bulletin, 92, 53-62
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Provide supplementary food for hummingbirds to increase adult survival
A controlled study in mountainous pine forests in California, USA, in July 1976 (Wheeler 1980) found that Anna’s hummingbirds Calypte anna fed more on red-dyed sugar solutions than solutions on other colours (17 visits/hour for red solution vs. 13 for yellow, eight for green, four for blue and five for uncoloured). However, birds did not show a preference when solutions were presented one after another. A separate experiment found that, after 40 minutes, approximately 80% of hummingbirds visiting a feeding area went to a feeder containing sugar solution, rather than a control feeder containing water. Solutions consisted of saturated solutions of cane sugar in water and were supplied from a 250 ml feeder with small holes near the base. The feeder had been used for several years before the experiment.