Feeding behavior by hummingbirds (Aves: Trochilidae) in artificial food patches in an Atlantic Forest remnant in southeastern Brazil

ABSTRACT During flight, hummingbirds achieve the maximum aerobic metabolism rates within vertebrates. To meet such demands, these birds have to take in as much energy as possible, using strategies such as selecting the best food resources and adopting behaviors that allow the greatest energy gains. We tested whether hummingbirds choose sources that have higher sugar concentrations, and investigated their behaviors near and at food resources. The study was conducted at Atlantic forest remnant in Brazil, between June and December 2012. Four patches were provided with artificial feeders, containing sucrose solutions at concentrations of 5%, 15%, 25% and 35% weight/volume. Hummingbird behaviors were recorded using the ad libitum method with continuous recording of behaviors. The following species were observed: the Brazilian ruby Clytolaema rubricauda (Boddaert, 1783), Violet-capped woodnymph Thalurania glaucopis (Gmelin, 1788), Scale-throated hermit Phaethornis eurynome (Lesson, 1832), White-throated hummingbird Leucochloris albicollis (Vieillot, 1818), Versicoloured emerald Amazilia versicolor (Vieillot, 1818), Glittering-bellied emerald Chlorostilbon lucidus (Shaw, 1812) and other Phaethornis spp. C. rubricauda, P. eurynome and Phaethornis spp. visited the 35%-sucrose feeders more often, while the T. glaucopis visited the 25%-sucrose feeders more often. L. albicollis and A. versicolor visited more often solutions with sugar concentration of 15%. C. lucidus visited all patches equally. Three behavioral strategies were observed: 1) C. rubricauda and T. glaucopis exhibited interspecific and intraspecific dominance; 2) the remaining species exhibited subordinance to the dominant hummingbirds, and 3) P. eurynome and Phaethornis spp. adopted a hide-and-wait strategy to the dominant hummingbird species. The frequency of aggressive behaviors was correlated with the time the hummingbird spent feeding, and bird size. Our results showed that hummingbirds can adopt different strategies to enhance food acquisition; that more aggressive species feeding more than less aggressive species; and that the birds, especially if they were dominant species, visited high quality food resources more often.

摘要 飞行过程中，蜂鸟具备脊椎动物界最高的有氧代谢速率。为满足此类极端能量需求，这类鸟类必须尽可能多地摄取能量，其策略涵盖筛选最优食物资源，以及采取能最大化能量收益的行为模式。本研究旨在测试蜂鸟是否会选择糖浓度更高的食物源，并调查它们在食物源附近及取食阶段的行为表现。
本研究于2012年6月至12月间，在巴西的大西洋森林残余斑块中开展。实验设置了4个人工喂食器位点，分别盛放浓度为5%、15%、25%和35%的蔗糖溶液（质量体积比）。蜂鸟的行为记录采用连续记录的任意取样法（ad libitum method）。
本次观察到的蜂鸟物种包括：巴西红玉蜂鸟（Clytolaema rubricauda，Boddaert, 1783）、紫顶林蜂鸟（Thalurania glaucopis，Gmelin, 1788）、鳞喉隐蜂鸟（Phaethornis eurynome，Lesson, 1832）、白喉蜂鸟（Leucochloris albicollis，Vieillot, 1818）、杂色翠蜂鸟（Amazilia versicolor，Vieillot, 1818）、闪绿蜂鸟（Chlorostilbon lucidus，Shaw, 1812）以及其他隐蜂鸟属（Phaethornis spp.）物种。
其中，巴西红玉蜂鸟、鳞喉隐蜂鸟及其他隐蜂鸟属物种更频繁地造访35%浓度的蔗糖喂食器；紫顶林蜂鸟更偏好25%浓度的喂食器；白喉蜂鸟与杂色翠蜂鸟则更常光顾15%浓度的溶液；而闪绿蜂鸟对所有浓度的喂食器造访频率无显著差异。
本次研究共观察到三类行为策略：1）巴西红玉蜂鸟与紫顶林蜂鸟表现出种间与种内支配行为；2）其余物种均对优势蜂鸟类群表现出从属行为；3）鳞喉隐蜂鸟及其他隐蜂鸟属物种会采取躲避等待策略，以避开优势蜂鸟类群。
攻击行为的发生频率与蜂鸟的取食时长及体型大小呈显著相关。本研究结果表明：蜂鸟可采取多样化策略以提升食物获取效率；具有更强攻击性的物种取食频率高于攻击性较弱的物种；且蜂鸟（尤其是优势物种）会更频繁地造访高品质食物资源。