1. Spa$al memory and learning correlate with plumage ornamenta$on
in male Anna’s hummingbirds (Calypte anna)
Daniel J. Francescon, Melissa G. Meadows and Kevin J. McGraw
School of Life Sciences, Arizona State University, Tempe, AZ 85287, USA
Background
• Colorful ornaments in animals oPen predict an individual’s quality as a mate, compeLtor, or parent
(Badyaev 2007)
• Ornaments place a resource and energy burden on their possessors
• OpLmal foraging theory predicts that organisms will strive to spend the minimum amount of Lme
and energy possible obtaining the maximum amount of resources (Macarthur and Pianka 1966)
• SpaLal memory and learning are used by a variety of organisms in a foraging context (e.g. Johnson
1991; Prior and Gunturken 2001)
• Learning and memory has been shown to affect mate preference in songbirds (Airey et al. 2000)
• We know of no previous studies examining relaLonships between morphological ornaments and
cogniLon
Goals
• To assess the spaLal memory and learning abiliLes of Anna’s hummingbirds under controlled lab
condiLons, and measured the size, hue, chroma, brightness, and direcLonality of their plumage
ornaments (Figure 2)
• To determine whether ornamentaLon can be an accurate predictor of an organism’s ability to
learn and remember the locaLon of profitable food sources
This research was supported in part by funds from the Howard Hughes Medical
InsLtute through the Undergraduate Science EducaLon Program and from the
ASU School of Life Sciences.
Results
• Crown size is posiLvely correlated with improvement from Day 1 to Day 3 (Model F=8.98 p=0.026;
crown size t=‐4.12, p=.0146; Fig. 3; Table 1).
• Crown brightness is posiLvely correlated (t=‐3.01, p=0.040) and crown red chroma is negaLvely
correlated (t=2.94, p=0.043) with improvement from Day 1 to Day 3 (Table 1).
• Crown size is posiLvely correlated with total errors (Model F=5.34 p=0.033; crown size t=4.18,
p=0.006; Table 2; Fig. 4).
• Gorget red chroma is negaLvely correlated with total errors (t=‐2.66, p=0.038; Table 2).
25
20
15
10
5
0
Figure 4
6
5
4
3
2
1
0
‐1
‐2
‐3
Figure 3
Discussion
• Birds with smaller crowns and high gorget red chroma learn and remember the locaLons of profitable and
unprofitable food sources more quickly
• Birds with larger, brighter, less chromaLc crowns improved their performance on the memory task from
Day 1 to Day 3 more than birds with smaller, less bright, less chromaLc crowns
• Birds with smaller crowns and more chromaLc gorgets are more efficient foragers
• Smaller crowns in Anna’s hummingbirds are also linked to more Lme spent chasing in aggressive
interacLons (Meadows, in prep)
• Control of learning and memory could be developmental or geneLc, with potenLal for pleiotropic links to
ornament
• Females would benefit from selecLng males with smaller, redder ornaments
• Plumage ornaments may join song as predictors of learning ability in birds (Airey et al. 2000)
• Further study necessary to determine role of ornaments in sexual selecLon
Acknowledgements
We would like to thank C. Singer, K. Youngs, B. Youmans, and C. Montes for their help in
conducLng experimentaLon for this project. We would like to thank D. Dellergo for help
trapping birds, and E. Tourville for support throughout the project.
Figure 1
Abstract
Costly ornamental traits oPen reveal the health, condiLon, geneLc quality, or foraging ability of
animals. In species that complete complex tasks that are criLcal for survival, such as memory‐driven
foraging on widely spaced, profitable foods, it is also conceivable that sexual signals indicate
cogniLve or learning‐based task performance. Because cogniLve task performance is oPen
geneLcally determined, females selecLng colorful males with good genes would benefit indirectly
by passing these good genes to offspring. Hummingbirds, which are excepLonally colorful and
sexually dichromaLc and that feed on nectar resources from flowers, are an ideal group in which to
test for correlaLons between degree of ornamentaLon and learning‐and‐recall in a foraging
context. Here, we experimentally invesLgated the relaLonship between an individual’s ability to
locate and remember rewarding feeding locaLons and the size and color of iridescent plumage
ornamentaLon in capLve male Anna’s hummingbirds (Calypte anna).
Crown
Gorget
Figure 2: Anna’s Hummingbird ornament location.
Photo by Maria Jose Fernandez
R² = 0.639
‐5
0.8 1 1.2 1.4 1.6 1.8
Total errors
Crown size (cm2)
R² = 0.243
‐4
0.8 1 1.2 1.4 1.6 1.8
Day 3 errors ‐ Day 1 errors
Crown size (cm2)
• Error – return visit by bird to previously visited (known) unprofitable feeder
Note: Raw data for memory scores are presented here for clarity. Square root transforma;ons of
memory scores were used for sta;s;cal analysis.
Works Cited
Airey, D. C., H. CasLllo‐Juarez, G. Casella, T. J. DeVoogd, and E. J. Pollack. "VariaLon in the Volume of Zebra Finch Song Control Nuclei Is Heritable:
Developmental and EvoluLonary ImplicaLons." Proceedings of the Royal Society of London Series B‐Biological Sciences 267.1457 (2000): 2099‐104
Alexander, Badyaev V. "Evolvability and Robustness in Color Displays: Bridging the Gap between Theory and Data." EvoluLonary Biology 34. (2007):
61‐67
Johnson, R. A. "Learning, Memory and Foraging Efficiency in Two Species of Desert Seed‐harvester Ants." Ecology (1991): 1408‐1419
Macarthur, R. H., and E. R. Pianka. "On OpLmal Use of a Patchy Environment." American Naturalist 100.916 (1966): 603‐+
Prior, H., and O. Gunturken. "Parallel Working Memory for SpaLal LocaLon and Food‐related Object Cues in Foraging Pigeons: Binocular and
Lateralized Monocular Performance." Learning and Memory (2001): 44‐51
Figure 1: Experimental apparatus consisLng
of a 269 cm x 147 cm x 274 cm outdoor
aviary. Access to the five feeders (1‐5) on
the opposite wall was controlled by a rope
and pulley system linking the observer to a
verLcally moving door.
Methods
• Sixteen male Anna’s hummingbirds were individually exposed to an array of one profitable
(nectar‐containing) feeder randomly inserted among four unprofitable (water‐containing) feeders
(Figure 1)
• APer locaLng the profitable feeder, a door was closed over the array for 10 minutes, prevenLng
access
• For each trial, the door was opened again, allowing access to the feeder array. We recorded the
order and number of visits to each unprofitable feeder before the profitable feeder was visited.
These visits to unprofitable feeders consLtuted errors. Once the profitable feeder was located
again, the door was closed for 10 minutes.
• The above process was repeated 2 more Lmes each day, with the profitable feeder in the same
locaLon, for a total of 3 trials.
• We repeated this series of 3 trials every other day for a total of 3 days with the profitable feeder in
a different locaLon each Lme.
• We performed separate mulLple regressions to examine color variables, body size, and days in
capLvity as predictors of 1) total number of errors over the 9 trials and 2) task learning – the
difference in number of errors between days 1 and 3. We used AIC model selecLon to choose the
most parsimonius models.
Table 2 DF
Sum of
Squares
Mean
Square F value p
Model 5 11.58 2.32 5.34 0.033
Error 6 2.60 0.43
Table 1 DF
Sum of
Squares
Mean
Square F value p
Model 7 4.79 0.68 8.98 0.026
Error 4 0.30 0.08
Parameter Es$mates t p
Crown Area 4.18 0.006
Gorget Area ‐2.42 0.052
Crown Red Chroma ‐1.42 0.204
Crown Hue 1.83 0.117
Gorget Red Chroma ‐2.66 0.038
Parameter Es$mates t p
Crown Area ‐4.12 0.015
Gorget Area 2.25 0.088
Crown Brightness ‐3.01 0.040
Crown Red Chroma 2.94 0.043
Crown Hue 1.730 0.159
Gorget Red Chroma ‐1.060 0.349
Gorget Hue 0.930 0.406