Implications of floral orientation for flight kinematics and metabolic expenditure of hover‐feeding hummingbirds

Abstract

Summary1. Nectar-bearing flowers are characterized by many different shapes, sizes and orientations, which may affect the way hummingbirds feed from them. Many hummingbird-pollinated flowers are oriented downwards, thereby requiring that trochilids feed while hovering with the bill oriented vertically upward. 2. We measured body orientations, wingbeat kinematics and hovering metabolic rates for Anna's Hummingbirds (Calypte anna) feeding from artificial flowers that were oriented horizontally, tilted 45°downwards and pointing vertically downwards. 3. When feeding from vertically oriented flowers, hummingbirds employed an upright body position combined with dorsal head flexion. Additional kinematic adjustments included an increased stroke plane angle relative to the longitudinal body axis and an increased stroke amplitude deriving from increases in the minimum positional angle of the wingbeat. 4. By contrast, wingbeat frequency, the stroke plane angle relative to horizontal, the ratio of the minimum to maximum positional angles of the wingbeat and the upstroke/downstroke ratio did not vary during feeding from different flower orientations. 5. Metabolic rates increased by an average (±SD) of 10Á8 (±8Á8)% for feeding from vertically compared to horizontally oriented flowers. 6. Feeding from pendent flowers comes with a substantial metabolic cost that may influence floral selection by hummingbirds and thus the evolution of associated pollination syndromes.

Biomechanics of hover performance in Neotropical hummingbirds versus bats

“…1B ) that adapted to the different flowers foraged ( 23 ). Therefore, we wondered whether the hover pose required for each flower angle ( 24 ) would modify upstroke support. To test how the flower angle affects upstroke force production, we made aerodynamic force recordings for horizontal (45°) and vertical flower orientations.…”

Into turbulent air: size-dependent effects of von Kármán vortex streets on hummingbird flight kinematics and energetics

“…Interestingly, von Kármán vortex streets persist as a dominant flow structure within vegetational canopies [10], even amidst the complexity of interacting wakes, and thus represent a well-characterized unsteady regime with which to probe biomechanical responses of volant taxa to natural flow fluctuations. In this regard, hummingbirds are of particular utility because of their capacity to engage in sustained feeding bouts from flowers over a range of orientations [11] and under challenging environmental conditions, including reduced air density [12], fast forward flight [13] and while flying in rain [14,15]. Thus, the associated maintenance of stability more generally is an obvious feature of flight in this taxon.…”

The use of a Low Cost High Speed Camera to Monitor Wingbeat Frequency in Hummingbirds (Trochilidae)

“…1975), and so hummingbirds may prefer flowers orientated in a given position and direction (Fenster et al, 2009;Sapir and Dudley, 2013). In the present study, the nectar hole was in the base of the feeder, only slightly angled towards the approaching hummingbird, so that it would have to tilt its body to some extent during nectar feeding.…”

“…The body masses were used in the figure presentation. In addition, for the purple-throated mountain-gem and violet sabrewing I measured inclination to the body axis with respect to a reference point (Sapir and Dudley, 2013), both while hover-feeding and hovering in front of the feeder (fig. 1b).…”