“…Such coordinated feeding visits have been found in a number of observational studies (Johnstone et al, 2014;Bebbington and Hatchwell, 2016;Koenig and Walters, 2016;Iserbyt et al, 2017Iserbyt et al, , 2018Savage et al, 2017;Leniowski and Wegrzyn, 2018;Wojczulanis-Jakubas et al, 2018), but the number of studies testing the significance of conditional cooperation for conflict resolution remains limited (but see Griffioen et al, 2019;Iserbyt et al, 2019). Experiments are vital for our understanding of conditional cooperation given the analytical difficulties faced in observational studies that may prevent to prove whether parents actively take turns (Schlicht et al, 2016;Ihle et al, 2019;Santema et al, 2019). That is, turn taking could also arise from variation in the refractory period (Johnstone et al, 2014;Savage et al, 2017) or from correlated male and female inter-visit intervals (Schlicht et al, 2016; but see Johnstone et al, 2016;Savage et al, 2017).…”