Dependence of the azure-winged magpie on nest spatial cues in offspring recognition decreases with nestling growth

Various cues have been identified as the basis for animals' discrimination between kin and non-kin. In altricial birds, these cues show temporal and spatial variations, implying that kin recognition might be condition-dependent. In this study, we hypothesize that parents might be sensitive to the changes in nest spatial position, and that their dependence on the nest spatial cue in offspring recognition decreases with offspring growth. We tested this hypothesis in a Tibetan population of the azure-winged magpie, Cyanopica cyanus, by designing a nest translocation experiment. We found that adults could return to their nest and continue caring for their offspring even if the nest had been moved to a new position. Their sensitivity to the spatial change in nest position not only varied with distance but also relied on the offspring life-history stage. Breeders were more likely to recognize their nest and offspring during the nestling period than during the incubation period, indicating that the dependence of parents on the spatial cue of the nest is higher when offspring are in the form of eggs than in the form of nestlings. Our findings suggest that azure-winged magpies mainly depend on the spatial position of the nest to recognize their nest and offspring. After nestlings establish communication with their parents, their phenotypic characteristics may replace the nests' spatial cue to play a greater role in the offspring recognition of parents.