Figure 2. Ecological variation and diversity in signalling systems.

(a) In unpredictable environments, parents may produce a larger brood than future environmental conditions will support. This selects for parents to preferentially feed the offspring with the highest chance of survival. We predict parents will assess quality by cues such as body size, or structural signals such as dark mouths. Offspring may still beg, but parents should ignore begging in favour of other information. (b) In contrast, in predictable environments, parents will lay an appropriate number of eggs and food will be plentiful enough to rear all their offspring. Here parents will be selected to preferentially feed offspring in the worst condition. We predict offspring should signal need through begging, and parents will feed those begging more.