The energetics of nestling birds

The nestling energy budget is examined with particular reference to the Dipper. Dippers showed an adaptive strategy of differential growth allowing premature fledging. Sex-specific differences in energetics and growth dynamics were observed which may result in differential mortality between the sexes. Field thermoregulation costs were lower than laboratory estimates, however heat loss did not obey the 0.67 exponent rule in the Dipper. Adults appear to adjust their brooding behaviour in response to nestling body temperature. Activity costs measured directly were only about 10% of previous indirect estimates. Brood activity costs increased exponentially with increasing brood-size thus offsetting any reduction in thermoregulation costs through huddling; implications of these results are discussed. Time-activity-laboratory estimates of daily energy expenditure provided excellent agreement with field measurements using doubly-labelled water on 'mature* Dipper nestlings. TAL estimates, however, progressively over-estimated daily metabolised energy (DME) in younger nestlings. Sources of this error are evaluated, and a predictive equation for nestling DME presented. Influences of brood DME on parental care are discussed. Energetic implications of hatching asynchrony were examined in the House Martin. Four hypotheses are discussed. (1) Nest failure; (2) Brood reduction; (3) Peak load reduction, and (4) Reduced sibling rivalry. The latter two were modelled and tested in the field. Little evidence was found for the hypotheses considered, lending support to the view that hatching asynchrony is an incidental trait, and moreover one in which costs may outweigh benefits

Stock Options and Chief Executive Officer Compensation

Although stock options are commonly observed in chief executive o±cer (CEO) compensation contracts, there is theoretical controversy about whether stock options are part of the optimal contract. Using a sample of Fortune 500 companies, we solve an agency model calibrated to the company-specific data and we find that stock options are almost always part of the optimal contract. This result is robust to alternative assumptions about the level of CEO risk-aversion and the disutility associated with their effort. In a supplementary analysis, we solve for the optimal contract when there are no restrictions on the contract space. We find that the optimal contract (which is characterized as a state-contingent payoff to the CEO) typically has option-like features over the most probable range of outcomes