Cognitive biologists from my alma mater published a paper on "Goffin cockatoos wait for qualitative and quantitative gains but prefer ‘better’ to ‘more’" in Biology Letters.
The abstract reads: "
Evidence for flexible impulse control over food consumption is rare in nonhuman animals. So far, only primates and corvids have been shown to be able to fully inhibit the consumption of a desirable food item in anticipation for a gain in quality or quantity longer than a minute. We tested Goffin cockatoos (Cacatua goffini) in an exchange task. Subjects were able to bridge delays of up to 80 s for a preferred food quality and up to 20 s for a higher quantity, providing the first evidence for temporal discounting in birds that do not cache food."
The science daily has a nice article on it: Doing Business With a Parrot: Self-Control Observed in Cockatoos
"The ability to anticipate a delayed gain is considered cognitively challenging since it requires not only the capacity to control an direct impulse but also to assess the gain's beneficial value relative to the costs associated with having to wait as well as the reliability of the trader. Such abilities can be considered precursors of economic decision making and are rarely found outside humans. Only few, typically large-brained animals, have been shown to be able to inhibit the consumption of an immediate food reward in anticipation for a bigger one for more than one minute."