Stephens & Foraging - Behavior and Ecology - Chapter 8 doc

Part III Modern Foraging Theory [...]... three rate-maximizing currencies McNamara and Houston (1997) give a general derivation and discussion of this important point Thus, a provisioning model can accommodate rate-maximizing and efficiency-maximizing behavior within a single framework Few studies have tested this critical prediction (Figures 8. 1 and 8. 2 show measured behavior as well as predictions about behavior based on central place foraging. .. items at the collection site, but always before beginning to collect a load for delivery (Brooke 1 981 ; Kacelnik 1 984 ; Krebs and Avery 1 985 ) Central place foraging models simply ignore this self-feeding, and none of these studies accounted for it in making model predictions 281 282 Ronald C Ydenberg Figure 8. 2 Number of prey (mealworms) collected for delivery to a nest by parent starlings from a feeding... expenditure Daily self-feeding Figure 8. 5 Hypothetical scheme of relationships between total daily delivery (on y-axis), resting metabolic rate (r), self-feeding rate, daily energy expenditure, and maximum daily energy expenditure (k) (all on x-axis) Total daily self-feeding and total daily energy expenditure must balance As self-feeding increases, the provisioner can expend and deliver more The lower... this capacity to clutch and brood size, and the possible significance of predation danger to provisioners remain unresolved 8. 8 Suggested Readings The basic central place foraging models with which this account begins are best described and interpreted by Stephens and Krebs (1 986 ) The ideas of my own that I present in this essay build on two previous accounts (Ydenberg 1994, 19 98) that also describe provisioning... depends on the self-feeding rate The term di /ci in equation (8. 2) represents the efficiency of option i: at low self-feeding rates, the total delivery is determined largely by its value, and behavior (i.e., choice of i) should match that predicted by an efficiency (or efficiency-like) currency As the self-feeding rate increases, it becomes possible to sustain a higher workload, and the measured behavior should... larger prey (tactics 1–6) (B) The expected means and standard deviations in total daily delivery resulting from each prey selection tactic are shown here, and the “z-score” method of Stephens and Charnov (1 982 ) applied to find the tactic minimizing the probability of a shortfall for brood sizes of 1, 3, and 5, indicated by tangents The model predicts that as demand (brood size) rises relative to the expected... point create demand that affects provisioning behavior, but central place foraging models do not take account of this Integrating provisioning models with results from metabolic capacity studies and variance sensitivity models greatly expands the range of phenomena that our models can explain and suggests many interesting avenues for investigation Nevertheless, important and long-standing questions... Figure 8. 3 The dependence of total daily delivery on the self-feeding rate and the tactical options available, as described in equations (8. 1) and (8. 2) The three lines labeled i = 1, 2, 3 represent three successively higher-workload delivery tactics For each tactic, open circles indicate the delivery time attainable if the provisioner adopts a low self-feeding rate; solid circles, an intermediate self-feeding... separately for the energy delivered to nestlings and the energy parents consume and expend (Ydenberg and Schmid-Hempel 1994) Only one central place foraging study published before Houston’s (1 987 ) paper recognized this key Provisioning distinction In a model of flight speed for parent birds delivering food to offspring, Norberg (1 981 ) separated parent and offspring accounts by requiring that provisioners... for a “down-regulated” metabolism, and the upper curve for an “up-regulated” metabolism Up-regulation gives higher deliver capacity, but also generates a higher resting metabolic rate, and so is more expensive to maintain In the example shown, the provisioner benefits from up-regulated metabolism when the attainable self-feeding rate exceeds the rate labeled s∗ (1994; see also Hogstad 1 987 ) interpret . accommodate rate-maximizing and efficiency-maximizing behavior within a single frame- work. Few studies have tested this critical prediction. (Figures 8. 1 and 8. 2 show measured behavior as well. (Brooke 1 981 ; Kacelnik 1 984 ; Krebs and Avery 1 985 ). Central place foraging models simply ignore this self-feeding, and none of these studies accounted for it in making model predictions. 282 Ronald. data Provisioning 285 Figure 8. 3. The dependence of total daily delivery on the self-feeding rate and the tactical options avail- able, as described in equations (8. 1) and (8. 2). The three lines