DOI: 10.5061/dryad.cvdncjt4f
title: Sunbirds' tendency to hover: the roles of energetic rewards, inflorescence architecture and rain - data

description: Although the Old World sunbirds are generally considered to be an
 ecological analogue of the New World hummingbirds, it is commonly believed
 that in contrast to hummingbirds, sunbirds perch while feeding.
 Nevertheless, recent studies have shown that Old World nectarivores hover
 while feeding more frequently than previously thought, and some Old World
 plants seem to have adapted to hovering bird pollinators. To reveal the
 importance of sunbird foraging behavior in nectar acquisition and to test
 whether this behavior is determined by plant architecture and rain
 intensity, we focused on the specialized West African pollination system
 of Impatiens sakeriana and its two major pollinators, the Cameroon Sunbird
 (Cyanomitra oritis) and the Northern Double-collared Sunbird (Cinnyris
 reichenowi). C. oritis hovered more often than C. reichenowi while feeding
 on flowers, although both species were observed hovering regularly. For
 both species, hovering reduced the feeding time, but this reduction and
 the consequent estimated changes in energetic intake were
 species-specific. We found that both floral pedicel and peduncle length,
 as well as precipitation, negatively affected the probability of C.
 reichenowi hovering but did not have any significant effect on the
 behavior of C. oritis. Our study demonstrates that hovering behavior is
 common in the studied sunbird taxa and that plant architecture and
 environmental factors can influence sunbird foraging behavior.
 Nevertheless, the extent of hovering versus perching behavior, as well as
 the effects of biotic and abiotic factors, is species-specific.
description: The data
 were collected during August 2017 and August 2019 on Mt. Cameroon
 (Cameroon) in the area around Mann’s Spring. All visitors of the target I.
 sakeriana plants were recorded for four days using VIVOTEK IB8367-T
 security cameras during 12-h day periods. The type of behavior (hovering
 or perching) on the flower and while moving among flowers and the exact
 time spent on each activity was noted. The linear distances between each
 pair of opened flowers (i.e., apertures of their corollas) were measured using
 a measuring tape, the lengths of straightened peduncles and pedicels
 (PedPed length) were measured using Vernier caliper,
 both with an accuracy of 1 mm. The actual precipitation was measured in mm
 by two rain gauges placed in two different forest clearings within the
 area of selected plants; a photo of the water level in each was taken
 every 10 min. The average sugar consumption was estimated as the mean
 difference in sugar amount between non-visited and visited
 flowers. Nectar was collected using 5 µl
 microcapillary tubes. Sugar concentration was measured by
 a pocket refractometer (PAL‐1, Atago
 Co.). To test
 whether the frequencies of the observed types of behavior of each sunbird
 species on a flower differ significantly from each other, we used the
 Chi-square test (performed in R; R Core Team 2019). To investigate the
 effect of sunbird behavior on flower visitation rate, we used nested
 analysis of covariance (nested ANCOVA) with plant identifier as an error
 variable and sum of distance between visited flowers as a covariate
 (performed in R; R Core Team 2019). The visitation rate was
 logarithmically (ln) transformed to normalize its distribution. Because of
 the many zero values and impossibility of improving the data distribution,
 we tested the effects of bird species and their behavior on the nectar
 amount left after the bird visit using nonparametric mixed effect
 PERMANOVA with the plant identifier as a random factor. PERMANOVA was
 performed in the PERMANOVA program, which is an extension of the software
 PRIMER (Anderson et al. 2008). To determine the effect of behavior and
 sunbird species on the time spent per flower and on energy intake in time
 we used a generalized linear mixed model (GLMM) with plant ID nested in
 year as a random factor (performed in R; R Core Team 2019). For analysis
 of the effects of sunbird species, PedPed length and precipitation on the
 type of sunbird behavior, we used a binomial GLMM (package lme4; Bates et
 al. 2015) with an assumed Bernoulli distribution, setting flower
 identifiers nested within an individual plant nested within a year as
 random factors. Average precipitation was logarithmically (ln+1)
 transformed to reduce the skewness towards larger values, as we obtained
 many hours of recordings and visit events during light rain but only a few
 visit events in heavy rain. Both analyses were performed in R (R Core Team
 2019).