highly significantp <0.001
We found a highly significant difference in the number of chicks visible between the mid- and late-nestling periods (χ 2 1 = 138.12, p <0.001): on days 6–7, an average proportion of 0.81±0.02 SE of the brood was visible to carers, while only 0.19±0.01 of the brood was visible to carers at day 10–12.