Risky decisions: a test of risk sensitivity in socially foraging flocks of Lonchura punctulata

Group foraging allows for individuals to exploit the food discoveriesof other group members. If searching for food and searchingfor exploitation opportunities within a group are mutually exclusivealternatives, the decision to use one or the other is modeledas a producer-scrounger game because the value of each alternativeis frequency dependent. Stochastic producer-scrounger modelsgenerally assume that producer provides a more variable anduncertain reward than does the scrounger and hence is a riskierforaging alternative. Socially foraging animals that are attemptingto reduce their risk of starvation should therefore alter theiruse of producer and scrounger alternatives in response to changesin energy budget. We observed flocks of nutmeg mannikins (L.punctulata) foraging in an indoor aviary to determine whethertheir use of producer and scrounger alternatives were risk sensitive.Analyses of the foraging rewards of three flocks of seven birdsconfirm that producer is a riskier foraging strategy than isscrounger, although the difference in risk is rather small.We then submitted two other flocks to two different energy budgetsand observed the foraging decision of four focal birds in eachflock. All but one bird increased their relative use of theriskier producer strategy in the low food reserve treatment,but the overall use of producer did not differ significantlybetween treatments, providing evidence for a small but consistenteffect.