Reconsideration of the determinants of clutch size, asynchronous incubation, and nest building in birds using computer simulations

Adaptations for breeding in birds have long been an important area of study in evolutionary ecology. Because the breeding season is the most dangerous period to not only offspring but also parent birds, predators and anti-predator responses of bird play a crucial role in avian reproduction. Despite much effort, predators as a determinant of some breeding traits often remain unclear due to too many ways in which predators might affect reproduction. Computer simulations allow one to control many factors and to look into the effect of each factor on breeding adaptations even under complex situations. In this study, I examined the determinants of avian breeding adaptations under the risk of predation with computer simulations. The first portion of my research focused on why birds invest or do not invest time in the construction of a safe nest. When parent birds build a safe nest in a short time, then an investment in nest building will be favored. However, even when a nest provides a great increase in survival rate, nest construction is often not favored if it requires a substantial investment of time.;Secondly, I used computer simulations to examine and expand the Nest Failure Hypothesis for hatching asynchrony, in which the distribution of the risk of nest predation across the nesting cycle determines the optimal onset of incubation. Long-standing theory on this matter assumes only a single nesting attempt per season. However, allowing for multiple nesting attempts per season greatly changes the expectations of previous theoretical/empirical studies focused on the Nest Failure hypothesis. The most important insight here is that the daily probabilities of survival across the entire nesting cycle will influence the optimal onset of incubation, not just a few key probabilities as argued in classic theoretical papers on this topic.;Lastly, to address how egg viability influences clutch size in birds, I used computer simulations to determine optimal clutch sizes under various scenarios. As many birds begin incubation after the clutch has been completed, eggs laid early go a long time un-incubated and are less likely to hatch (i.e., they are less viable). Current conceptual theory suggest implies that these drops in egg viability could be a strong determinant of optimal clutch size in birds. However, my simulations show that a drop in egg viability alone cannot determine the optimal clutch sizes. A drop in viability will be a strong determinant of clutch size, but only in conjunction with factor as other factors like multiple nesting attempts per season, limitation in the total eggs produced per season, and the risk of nest predation.