Specialists maintained their preference for the target cue;Foraging initiation by naïve sparrows was slower than by specialists only in the first session;Naïve individuals experienced higher success using the alternative cue;The calculation of the observed-to-expected ratio from Competitive advantage of rare behaviours induces adaptive diversity rather than social conformity in skill learning
Creators: name: Aljadeff, Naama
name: Luc-Alain Giraldeau
name: Lotem, Arnon
Publisher: name: The Royal Society
Year: 2020
Subjects: subject: Ecology
subject: FOS: Biological sciences
subject: FOS: Biological sciences
subject: 60801 Animal Behaviour

description: The distribution (probability density plot) of specialist preference for colour over shape (the number of choices in the rewarding colour / total number of choices in rewarding colour and shape) during the four sessions of Stage 2 experiment. We used exact binomial tests to reject the null hypothesis of no preference (i.e. that the proportion of choices in the rewarding colour equals 0.5). All distributions significantly differed from those expected by our null hypothesis: (a) colour specialist groups; significant preference for the rewarding colour (one-tailed p&lt; 0.02 in all cases, n=13,16,16,15), (b) mixed specialist groups; significantly different than 0.5, with individuals preferring either colour or shape (two-tailed p&lt; 0.001 in all cases, n=22,21,22,21), and (c) shape specialist groups; significant preference for the rewarding shape (one-tailed p&lt;0.001 in all cases, n=16,16,17,17).;Latency to first peck in intact wells by specialists (grey boxplots) and naïve sparrows (white boxplots) during the four sessions of Stage 2 experiment (session 1: n=70, 10, session 2: n=72, 16, session 3: n=69, 14, session 4: n=69, 17, for specialists and naive, respectively. We included only naïve sparrows that made six or more choices per session and whose data was thus further analysed). Naïve sparrows were slower to start pecking in intact wells, compared to the specialists, only in the first session (Mann-Whitney test, p=0.008). In the following sessions foraging initiation did not differ between specialists and naïve individuals. Data are represented as median, 25%, and 75% quantiles, and data points outside this range.;The estimated proportion of successful pecks in the rewarding colour wells (white boxplots) and the rewarding shape wells (grey boxplots) by naïve individuals (top panel a-c) and by specialists (bottom panel d-f) in the 3 group types (colour specialists, mixed specialists, and shape specialists) and during the four foraging sessions of Stage 2 experiment. The proportion of successful pecks was estimated as the proportion of pecks in intact rewarding wells (that contained 7 seeds in half of the cases) out of the total number of pecks for that cue (including open wells that were already empty). Data are represented as median, 25%, and 75% quantiles, and data points outside this range.;An example of calculating the observed-to-expected ratio for a particular naïve sparrow (#15601) in a shape specialist group, during the last (4th) foraging session. Each row in the Table depicts a single peck by the focal sparrow, from the first (top row) to the last (next to the bottom row). (a) and (b) show the number of available intact wells in the rewarding colour and shape (respectively) that were available for the focal sparrow prior to each peck (based on a step-by-step video analysis). A foraging session starts with 36 intact wells in each of the rewarding cues (colour and shape), and the availability of intact wells during the session is then affected by the pecks of all foraging individuals, including the focal sparrow (which explains why in this example the number of available intact wells does not start with 36). (c) and (d) show the choice made by the focal individual in the rewarding colour and shape (1 for choosing and 0 for not choosing); note that the availability of intact wells immediately before this decision is that depicted in (a) and (b) of the same row. (e) and (f) indicate the proportion of intact rewarding wells of colour and shape out of the total number of available intact wells, which is calculated based on columns (a) and (b) (e.g. ‘e’ of the first row: 34/(34+33)=0.51). Note that these proportions represent a focal bird's probability of choosing at random each of the rewarding cues at each of the pecks. To calculate the observed-to-expected ratio over the entire session we summed up (bottom row, in bold) the actual number of choices (columns c and d), which is the ‘observed’ number; and the expected probabilities of each peck (columns e and f), which gives the expected number of choices during the entire session (i.e. the sum of probabilities of scoring 1 in each peck). Thus, for the sparrow in this example, the expected number of choices in the rewarding colour is 5.21, the actual number of choices is 8, and the observed-to-expected ratio is therefore 8/5.21= 1.54. Clearly, in this case, it would appear that the sparrow preferred colour over shape but we did not test the statistical significance of this individual preference. Rather, we used this ratio as an unbiased data score instead of the absolute number of choices, or the proportion of choices, which may be biased by food depletion (see Methods).