Memory for location and visual cues in white-eared hummingbirds Hylocharis leucotis

Abstract

In nature hummingbirds face floral resources whose availability, quality and quantity can vary spatially and temporally. Thus, they must constantly make foraging decisions about which patches, plants and flowers to visit, partly as a function of the nectar reward. The uncertainty of these decisions would possibly be reduced if an individual could remember locations or use visual cues to avoid revisiting recently depleted flowers. In the present study, we carried out field experiments with white-eared hummingbirds Hylocharis leucotis, to evaluate their use of locations or visual cues when foraging on natural flowers Penstemon roseus. We evaluated the use of spatial memory by observing birds while they were foraging between two plants and within a single plant. Our results showed that hummingbirds prefer to use location when foraging in two plants, but they also use visual cues to efficiently locate unvisited rewarded flowers when they feed on a single plant. However, in absence of visual cues, in both experiments birds mainly used the location of previously visited flowers to make subsequent visits. Our data suggest that hummingbirds are capable of learning and employing this flexibility depending on the faced environmental conditions and the information acquired in previous visits.

How scent and nectar influence floral antagonists and mutualists

“…Hummingbirds, in contrast to hawkmoths, have smaller territories and pollinate flowers only in a small area close to their nests ( Norton et al, 1982 ). This allows them to learn cues and plant positions which are correlated with the presence of food sources ( Ackerman et al, 1994 ; Campbell et al, 1997 ; Hurly and Healy, 2002 ) or even with the quality of the food ( Pérez et al, 2011 ). In contrast to hummingbirds, large hawkmoths like M. sexta cover much larger distances each night and rely more on direct perception rather than memory in visiting their food sources ( Raguso and Willis, 2003 , 2005 ), as they most likely never visit the same plant twice in nature, although moths are also known to learn when exploring new food sources ( Riffell et al, 2013 ).…”

Differential response to colour tasks on resident and migratory hummingbirds: a field test

“…Individuals that repeatedly foraged on few rewarding flowers might have memorized their spatial location in the array. There is evidence indicating that hummingbirds are more influenced by the position of the nectar source than its colour (BENÉ 1945;COLLIAS & COLLIAS 1968;MILLER & MILLER 1971;MILIAR et al 1985;BROWN & GASS 1993;BROWN 1994;SUTHERLAND & GASS 1995), and that hummingbirds use both location and visual cues (HURLY & HEALY 1996) to remember previously rewarding flowers hierarchically or independently depending on environmental conditions (PÉREZ et al 2011). Therefore, our interpretation of differential sensitivity to colour must be interpreted with caution.…”

“…Hummingbirds can deal simultaneously with memory of floral characteristics (colour) and memory of place (SUTHERLAND & GASS 1995;PÉREZ et al 2011); we do not distinguish the two groups.…”

“…The responses of individuals to a given task, although a possible fundamental axis of hummingbird behavioural variation, have been investigated only in a few hummingbird species, particularly Selasphorus species. To date, most studies have explored species differences in their abilities to discriminate colour (LYERLY et al 1950;COLLIAS & COLLIAS 1968;MILLER & MILLER 1971;STILES 1976;GOLDSMITH & GOLDSMITH 1979;GOLDSMITH 1980;MITCHELL 1989), learning spatial cues to find food (COLE et al 1982;HAINSWORTH et al 1983;MILIAR et al 1985;WOLF & HAINSWORTH 1986;BROWN & GASS 1993;BROWN 1994;HEALY & HURLY 1995;SUTHERLAND & GASS 1995;HURLY 1996;IRWIN & BRODY 1999) and memory use for location and/or visual cues for tracking changes in the environment TAMM 1987TAMM , 1989HURLY & HEALY 1996;PÉREZ et al 2011). However, there is scanty evidence of whether they make use of their foraging experience to solve foraging tasks, and modify their foraging behaviour based on their past experience (BACON et al 2010), the taste of food (BACON et al 2011), the variance of nectar volume and concentration ) and/or the use of floral resources by conspecifics and heterospecifics (ALTSHULER & NUNN 2001;LARA et al 2009), and which species of hummingbirds perform more precisely in such behavioural tasks.…”

“…The uncertainty of these decisions in a novel environment may possibly be reduced if an individual can quickly associate a rewarding flower with its colour and discriminate non-rewarding flowers to avoid their 2 J.F. Ornelas and C. Lara revisitation (MILIAR et al 1985;PÉREZ et al 2011), as this colour use by individuals affects not only their foraging choices but also population-level responses to competition (SANDLIN 2000a(SANDLIN , 2000b. Although hummingbirds typically pollinate primarily red, tubular flowers, they also feed from flowers that are neither tubular nor red throughout their ranges (GRANT 1966;ALTSHULER 2003), and they are flexible in moving quickly to rewarding colours other than red once they are sampled (MILLER & MILLER 1971;STILES 1976;GOLDSMITH & GOLSMITH 1979;MELÉNDEZ-ACKERMAN et al 1997;LARA et al 2009;GONZÁLEZ-GÓMEZ et al 2011).…”