Information use in foraging flocks of songbirds - no evidence for social transmission of patch quality

Abstract

10Animals use behavioural cues from others to make decisions in a variety of contexts. There is 11 growing evidence, from a range of taxa, that information about the locations of food patches can 12 spread through a population via social connections. However, it is not known whether information 13 about the quality of potential food sources transmits similarly. We studied foraging behaviour in a 14 population of wild songbirds with known social associations, and tested whether flock members use 15 social information about the profitability of patches to inform their foraging decisions. We provided 16 artificial patches (ephemeral bird feeders) that appeared identical but were either profitable (contained 17 food) or unprofitable (contained no food). If information about patch profitability spreads via social 18 associations, we predicted that empty feeders would only be sampled by individuals that are less 19 connected to each other than expected by chance. In contrast, we found that individuals recorded at 20 empty feeders were more closely associated with each other than predicted by a null model simulating 21 random arrival of individuals, mirroring pattern of increased connectedness among individuals 22 recorded at full feeders. We then simulated arrival under network-based diffusion of information, and 23 demonstrate that the observed pattern at both full and empty feeders matches predictions derived from 24 this post-hoc model. Our results suggest that foraging songbirds only use social cues about the 25 location of potential food sources, but not their profitability. These findings agree with the hypothesis 26 that individuals balance the relative economic costs of using different information, where the costs of 27 personally sampling a patch upon arrival is low relative to the cost of searching for patches. This 28 study extends previous work on information spread through avian social networks, by suggesting 29 important links between how animals use information at different stages of the acquisition process 30 and the emerging population-level patterns of patch use. 32Key words: collective animal behaviour, economic decision-making, group foraging, local 33 enhancement, Paridae, social information, social network 103 whether a patch contains food or not. We provided artificial patches (bird feeders) that appeared 104 identical but were either empty or stocked with seed, and calculated the connectedness of individuals 105 arriving at each feeder using the edge strength from independently-recorded social association 106 network data. We then compared the order in which birds discovered these feeders with a null model 107 simulating random arrival of birds, to test two distinct hypotheses.