Timing in Free-Living Rufous Hummingbirds, Selasphorus rufus

Abstract

Animals organize their lives around circannual and circadian rhythms, but little is known of their use of much shorter intervals. In the laboratory, some animals can learn the specific duration (seconds or minutes) between periods of food access. It has been supposed that wild nectarivores, such as hummingbirds, might also learn short time intervals so as to avoid revisiting emptied flowers until the nectar has been replenished. We provided free-living, territorial rufous hummingbirds each with eight artificial flowers containing sucrose solution. Four flowers were refilled 10 min after the bird emptied them, and the other four were refilled 20 min after being emptied. Throughout the day, birds revisited the 10 min flowers significantly sooner than they revisited the 20 min flowers, and return visits to the flowers matched their refill schedules. Hummingbirds remembered the locations and timing of eight rewards, updating this information throughout the day. Not only is this the first time that this degree of timing ability has been shown in wild animals, but these hummingbirds also exhibit two of the fundamental aspects of episodic-like memory (where and when), the kind of memory for specific events often thought to be exclusive to humans.

What hummingbirds can tell us about cognition in the wild

“…As we did not know how long it would take for a bird to learn the refill rates (if at all), we presented each of three territorial birds with an eight-flower array for 11 days. It turned out that the birds had, in fact, learned the refill rates quite well by the end of the first day (our expectations of their performance vastly underestimated their abilities) but the key finding was that all three birds returned to the 10-minute refilling flowers at around 10 minutes and to the 20-minute refilling flowers at around 20 minutes (Henderson et al, 2006a). Although these time periods are much shorter than typical refilling times for real flowers and birds may defend up to a couple of thousand flowers in their territories, we considered that the Henderson et al (2006a) data at least showed 'proof of principle' and that these birds could learn refill rates, for multiple flowers and relatively quickly.…”

“…It turned out that the birds had, in fact, learned the refill rates quite well by the end of the first day (our expectations of their performance vastly underestimated their abilities) but the key finding was that all three birds returned to the 10-minute refilling flowers at around 10 minutes and to the 20-minute refilling flowers at around 20 minutes (Henderson et al, 2006a). Although these time periods are much shorter than typical refilling times for real flowers and birds may defend up to a couple of thousand flowers in their territories, we considered that the Henderson et al (2006a) data at least showed 'proof of principle' and that these birds could learn refill rates, for multiple flowers and relatively quickly. Furthermore, not only were the duration of the refill rates longer and the number of flowers that the birds could track more than has been tested in the laboratory, all of the birds were living a very active life throughout their foraging on the array, defending their territory from intruding males and displaying to females.…”

“…They can also remember pairs of these components: they can remember when and where (Henderson et al, 2006a) and they can remember what and where (e.g., Healy & Hurly 1995; 1998) although we have not explicitly looked for whether they can remember what and when together. The question then was whether they could remember all three components together.…”

“…Food storing did, however, lead to perhaps the greatest recent flurry of excitement and effort in comparative cognition (Clayton & Dickinson, 1999): the examination of cognitive abilities in corvids. Subsequent work is now ranging from examination of episodic-like memory in a number of species including rats (Babb & Crystal, 2005), magpies Pica pica (Zinkivskay, Nazir, & Smulders, 2009), chickadees Poecile atricapillus (Feeney, et al, 2009), hummingbirds (Henderson, Hurly, Bateson, & Healy, 2006a), and meadow voles Microtus pennsylvanicus (Ferkin, Combs, Delbarco-Trillo, Pierce, & Franklin, 2008) to examination of problem-solving in a variety of contexts, typically by corvids but not always (Auersperg, Huber, & Gajdon, 2011;Dally, Emery, & Clayton, 2010;Schmidt, Scheid, Kotrschal, Bugnyar, & Schloegl, 2011;Taylor, Elliffe, Hunt, & Gray, 2010;Teschke & Tebbich, 2011;Weir, Chappell, & Kacelnik, 2009). …”

Floral reward production is timed by an insect pollinator

“…Interval timing-sensitivity to elapsing durations-is thought to function in many different contexts, including communication (von Frisch 1967;Seeley & Tovey 1994), navigation (Srinivasan et al 2000) and foraging (Stephens & Krebs 1986;Gill 1988;Gallistel 1990;Seeley & Tovey 1994;Clayton & Dickinson 1998;Ohashi 2002;Henderson et al 2006). Interval timing ability is known to occur in several vertebrates, including humans (Richelle & Lejeune 1980;Lejeune & Wearden 1991), and was recently discovered in bumble-bees, Bombus impatiens (Boisvert & Sherry 2006).…”