Portal de Periódicos da CAPES

Foraging Efficiencies and Time Budgets in Nectar-Feeding Birds

1975; Wiley; Volume: 56; Issue: 1 Linguagem: Inglês

10.2307/1935304

1939-9170

Larry L. Wolf, F. Reed Hainsworth, Frank B. Gill,

Plant Parasitism and Resistance

EcologyVolume 56, Issue 1 p. 117-128 Article Foraging Efficiencies and Time Budgets in Nectar-Feeding Birds Larry L. Wolf, Larry L. WolfSearch for more papers by this authorF. Reed Hainsworth, F. Reed HainsworthSearch for more papers by this authorFrank B. Gill, Frank B. GillSearch for more papers by this author Larry L. Wolf, Larry L. WolfSearch for more papers by this authorF. Reed Hainsworth, F. Reed HainsworthSearch for more papers by this authorFrank B. Gill, Frank B. GillSearch for more papers by this author First published: 01 January 1975 https://doi.org/10.2307/1935304Citations: 85AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract We examined the relationship between time budgeting for major activities of nectar—feeding birds and the foraging efficiency (total energy intake divided by total energy spent foraging) required to maintain an energetically balanced, 24—h energy budget. The hyperbolic shape of the curve relating this "required foraging efficiency" to percent time foraging (percent of daylight hours) suggests that at low percent times for foraging a major change in foraging efficiency would be required to decrease substantially the time for feeding, whereas at low foraging efficiency small changes in foraging efficiency would produce major changes in time budgeting for foraging. For hummingbirds, which usually hover while foraging, and for sunbirds, which usually perch while foraging the required foraging efficiency increased at a given percent time for foraging with (1) decreasing body size, (2) decreasing day length, (3) lower average temperatures, and (4) increasing nonfeeding flying time (such as for feeding young and territorial defense). The sunbirds would require a higher foraging efficiency (all other conditions being equal) than hummingbirds because of their lower foraging costs per unit time. However, the generally lower extraction efficiency of hummingbirds, due to their higher costs for feeding, tends to balance their lower required foraging efficiency, resulting in foraging time budgets similar to those for sunbirds. Actual foraging efficiency of these nectar—feeding birds is an increasing function of energy available per flower. The asymptotic relationship of empirical measures of this "achieved foraging efficiency" and nectar volume obtained per flower derives from a combination of coast and benefit terms relating to (1) rate of energy extraction per flower, and (2) time spent not probing flowers on a foraging bout. This relationship suggests that at low initial nectar volumes substantially more foraging efficiency results from slight increases in average nectar volumes per flower, whereas at high initial volumes virtually no change occurs in foraging efficiency with similar nectar availability changes. Thus, slight increases of nectar availability per flower should produce no obvious change in percent—time foraging at high initial volumes, but a marked decrease in percent—time foraging at low initial volumes. Similarly, the benefits achieved from an equivalent increase in average nectar volumes per flower through additional defense costs are proportionately higher and increase faster at low initial volumes than at high initial volumes. The general concept of foraging efficiency, or profitability, seems to be an important component of theories dealing with prey selection, especially in relation to foraging time. Citing Literature Volume56, Issue1January 1975Pages 117-128 RelatedInformation