Fig. 2

A Conditional Inference Tree characterizing flights of GPS-logger-equipped great skuas incubating eggs on Bjørnøya. a Total trip duration. b. Maximal ranges of flights. c Total distance covered. d Minimal convex polygon. The following characteristics of recorded great skua flights: sex (F – female, M - male), Bird_ID (individuals A-P) were used as initial explanatory variables. Encircled variables have the strongest association to the response variable (maximal ranges of flights). The p values listed at each encircled node represent the test of independence between the listed variable (sex, Bird_ID) and the response variable (maximal ranges of flights). Terminal nodes indicate which variable levels characterizing the great skua flights ranges and n indicates the number of flights corresponding to specific Bird_ID levels. Boxplots show the median (band inside the box), the first (25%) and third (75%) quartile (box), the lowest and the highest values within 1.5 interquartile range (whiskers) and outliers (circles)