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

2) What, exactly, did the researchers do to try to answer their question?

They first used a regression equation to determine the independent effects of gaping and calling in regards to effect on parental care. They then correlated these 2 factors and determined that both factors in tandem appear to be the most optimized means of conveying nutritional needs. To determine the effect of the begging call they compared to responses of the parents subjected to 49 nests with either 2 or 4 chicks that were 6/7 days old. They then amplified the call in the experimental groups with either a playback of 1 or 4 additional chicks and compared these results to the control groups that did not have any vocal augmentation. Once they created a regression model that best quantified these results they then applied this formula to chicks of other ages.The compared the parental response by transposing blackbird and song thrush chicks into warblers nests as they rival the cuckoo chicks in size. They then tested the response of the parents in the presence of these experimental species performing their  natural displaying (large gaping) that was augmented by a cuckoo call.