When plasticity is costly, it can trade off with allocation to other traits, such as fecundity or flight muscle. At the same time, nutrition can affect the total resource pool that affects such allocation decisions. This talk first reviews recent work that explores what happens when nutrient availability varies over millions of years -- allocation to plasticity (brain size) versus other traits (fecundity) can be set by historical nutrient availability, regardless of current diet. At the same time, humans are causing drastic changes to the availability of once limited nutrients, and understanding responses to such nutrient change has implications for conservation. This talk next reviews work on responses to changing availability of nitrogen and sodium, for instance in roadside or agricultural environments, and how plastic responses vary across species.