Signals of Need in Parent-Offspring Communication and their exploitation by the common cuckoo. Part I

1) What question were the researchers trying to answer?

The researchers were trying to discover why common cuckoo chicks are able to successfully parasitize warbler nests. Specifically,  they are researching the complex behavior that is displayed by the cuckoo and warbler chicks in an effort to quantify the effect each signal type (gaping displays and call frequency) has on the parental individuals in regards to how much food they provide. To begin,  they first tested the various impacts of different response levels and discovered that multiple signals offered more precise information regarding how much food the chicks required, the age of the individual as well as the size of the brood. However, they then transition to the effect of a cuckoo parasite on a nest of warblers and note that one cuckoo requires the nutrition needed for approximately 4 warbler chicks. They question how only a cuckoo chick, with its enormous size,  is able to trick the foster parents into continually bringing it large amount of food.