1. FORAGING (PART II)

2. Foraging Decisions Feeding holes (24/log) -seeds placed in 0, 6, 12, and 24 holes After a bird samples a log, how does it decide to stay or move on? Currency: maximize rate of intake

3. Foraging Decisions After a bird samples a log, how does it decide to stay or move on? If 0 or 24 holes with seeds -- average of 1.7 ‘looks’ If 6 or 12 holes with seeds -Model predicts 3 or 6 ‘looks’ per log Experiments – 3.5 and 6.3 ‘looks’ per log

4. Fixed portion – 10 nuggets/day Variable portion – 5 or 20 nuggets/day WHICH IS THE BETTER OPTION?

5. “BETTER” depends on benefit of eating different numbers of nuggets If need 10 nuggets to survive – should use 10 nugget option If need >10 nuggets to survive – lose nothing by going to 5/20 option Therefore – animals should be sensitive to both mean rate of return AND variability

6. Caraco et al (1980’s – 1990’s) Juncos - Junco phaenotus Feeders Every visit OR NOTE: Same average reward Constant reward Variable reward

7. Caraco et al (1980’s – 1990’s) Juncos - Junco phaenotus Feeders Every visit OR Juncos behave as if they are risk adverse

8. Caraco et al (1980’s – 1990’s) Juncos - Junco phaenotus OR Second question: Is there a level of food at which juncos start to become risk prone? Add food to variable feeder < Reward = 3Average reward = 6

9. Caraco et al (1980’s – 1990’s) Juncos - Junco phaenotus OR When Reward constant = ½ Reward variable 50% of juncos chose the variable

10. Caraco et al (1980’s – 1990’s) Did experiment at 1 and 19ºC Feeders OR Constant reward Variable reward Adequate at 19ºC but not at 1ºC Option preferred at 1ºC

11. A MODEL FOR THIS 1 0 5678910 Survival Energy level at dusk (arbitrary units)

12. A MODEL FOR THIS Foraging options: 1) Provides 1 unit of energy with a probability of 1.0 2) Provides 2 units of energy with a probability of 0.5 and 0 units of energy with a probability of 0.5 Option chosen depends on current hunger state Energy level if choosing: Best to chooseState(i)(ii) 6 7 7 8 8 or 6 9 or 7 (ii) – take risk (i) – play it safe

13. FOOD STORAGE Clark’s nutcracker - can store about 30,000 seeds in 2500 – 4000 locations Paridae - can store between 100,000 and 500,000 seeds

14. FOOD STORAGE Imagine two strategies HoarderFreeloader Cost - high Benefit - high Cost - low Benefit - high AN ESS ONLY IF MEMORY IS INVOLVED

15. Willow tit Seeds labelled with 35 S Number with labelled feathers Given 35 S seeds Not given 35 S seeds

16. Optic chiasma

17. Time Visits Percentage Same eye Other eye Marsh tit

18. Clark’s nucracker Memory in Corvids Pinyon jay Mexican jay Western scrub jay High Low Reliance on stored food High Low Spatial memory

19. Hippocampal size Groups that don’t store foodGroups that store food

20. Hippocampal size Shorter daylength Milder winter

21. Cognition Western scrub jay Store nuts Store worms Retrieve 0 0 120 124 PREFER NUTS PREFER WORMS

22. Cognition Western scrub jay Food delivered when lights come on Food delivered 2 hours after lights come on

23. Cognition – variety in the diet Western scrub jay Fed nuts Fed dog food

24. Feeding and vigilance

25. Heller & Milinski, 1979

26. Feeding and vigilance