Genetic assignment of P. downsi individuals across three islands using Bayesian clustering analysis. Two genetic clusters are identified: (a) including all individuals from Santa Cruz (n = 62) (bottom left) and Isabela (n = 9) (centre top), and (b) all individuals from Floreana Island (n = 76) (bottom right). Black dots represent independent geographic sampling points (i.e. location of bird nests). Note that two geographic sampling points on Isabela Island were within 5 m of each other and are not distinguishable.