Interplay between the energetics of foraging and thermoregulatory costs in the green‐backed firecrown hummingbird Sephanoides sephaniodes

Abstract

In response to the interplay between variation in food quality and energetic demands, the foraging behaviour of captive green-backed ®recrown hummingbirds Sephanoides sephaniodes was studied. Hummingbirds were exposed to two temperatures (25 8C vs 15 8C), two food qualities (0.5 vs 0.75 m sucrose solutions), and two costs of feeding (birds were provided with feeders with and without a perch). Food selection and consumption were measured, as well as time budgets and metabolic rate while feeding. We predicted that when given a choice, birds would minimize the cost of feeding by selecting feeders with a perch and with a high sugar concentration. However, rather than increasing energy consumption when energy availability was low and thermoregulatory demands were high, hummingbirds remained perched. They reduced feeding and spent most of their time perching. Our results identify a novel behavioural and physiological strategy in hummingbirds. These birds seem to shift their foraging behaviour depending on thermoregulatory and feeding costs. When these costs are high, rather than matching them with increased energy consumption, hummingbirds reduce energy costs by reducing activity. They seemed to adopt the following strategy: when food quality was high and thermoregulatory demands were low, they adopted a high-expense lifestyle. In contrast, when thermoregulatory costs were high, they adopted an energy conserving strategy even when food quality was high. We hypothesize that limitations imposed by physiological processes may explain why animals do not forage during all available time and why under some circumstances they choose foraging behaviours with lower rates of net energy gain.

Short‐term energy regulation in nectar‐feeding birds: the response of Whitebellied Sunbirds (Nectarinia talatala) to a midday fast

“…Increased dietary intake in response to increased thermogenic demands has been demonstrated for two sunbird species (Fleming et al . 2004c; Lotz 1999) and for some but not all hummingbird species examined (Beuchat, Chaplin & Morton 1979; McWhorter & Martínez del Rio 2000; Fernández et al . 2002; Fleming et al .…”

“…Additionally, behavioural changes (such as the use of torpor, decreased flying time or reduced perching metabolic rate) also play a role in the maintenance of body mass at low T a (Beuchat et al . 1979; Hiebert 1991; Fernández et al . 2002).…”

Flexibility of Foraging Behavior in Hummingbirds: The Role of Energy Constraints and Cognitive Abilities

“…Those differences could produce fitness variability in an energetically demanding context. Hummingbird species that inhabit temperate zones, such as S. sephaniodes in central and southern Chile, experience a wide range of temperatures and, consequently, their thermoregulatory costs and foraging demands vary greatly (López-Calleja andBozinovic 1995, Fernández et al 2002). In this context, the rate of net energy gain is important because high metabolic rates make energy storage more difficult for hummingbirds (Hainsworth 1978).…”

“…For example, 1989, Martinez del Rio andKarasov 1990). However, the effect of they experience physiological and ecological constraints on food individual foraging preferences on foraging frequencies, the influ-harvesting and exceptionally high metabolic demands because enceofindividual cognitive performance on foraging frequencies, of their small body size and low environmental temperatures and the degree of flexibility of individual foraging behavior have (Fernández et al 2002). The maintenance of high and constant E-mail: plgonzalezgomez@ucdavis.edu…”

Ampliación de la distribución de Sephanoides sephaniodes (Trochilidae: Aves) en Argentina

“…El Picaflor Rubí puede cambiar de estrategias comportamentales de forrajeo, dependiendo de las condiciones de termorregulación y costos de la alimentación que deba enfrentar (Fernández et al 2002). Además, puede evitar la pérdida de agua corporal ante la escasez de la misma en el ambiente (Bakken & Sabbat 2006).…”