Mediterranean storm petrels rely on nest position for homing after migration: a test with artificial nestboxes

Parental dependence on the nest's spatial cues in offspring recognition decreases with nestling growth in the azure-winged magpie

In altricial birds, to address which cues are used by parents to recognize their offspring, and when they switch between cues during reproduction, it has not been well determined. In this study, we address this question in a Tibetan population of the azure-winged magpie Cyanopica cyanus, by examining the dependence of parents on a nest's spatial position in offspring recognition. During the egg and nestling phases, azure-winged magpie nests were translocated to new positions across various distances from their original site, and parental responses to the translocated nests were investigated. Our findings show that a nest's spatial position is not connected with the survival of its young, but might be used as a cue in parental offspring recognition. When nests are translocated to a new position within a certain distance, parents could recognize their nests and returned to resume their parenting behaviors. Parental dependence on the nest's spatial position in offspring recognition is higher during the egg phase than during the nestling phase, and it decreases with the growth of nestlings. After nestlings reach a certain age, the nest' s spatial position was no longer used by parents as the single cue for offspring recognition. These findings suggest that azure-winged magpies switch their cues in offspring recognition during the different stages of reproduction. After parent-offspring communication has been established, the offspring's phenotypic traits may become a more reliable cue than the nest's spatial position in offspring recognition.

Oceanographic drivers and mistiming processes shape breeding success in a seabird

Understanding the processes driving seabirds' reproductive performance through trophic interactions requires the identification of seasonal pulses in marine productivity. We investigated the sequence of environmental and biological processes driving the reproductive phenology and performance of the storm petrel (Hydrobates pelagicus) in the Western Mediterranean. The enhanced light and nutrient availability at the onset of water stratification (late winter/early spring) resulted in annual consecutive peaks in relative abundance of phytoplankton, zooplankton and ichthyoplankton. The high energy-demanding period of egg production and chick rearing coincided with these successive pulses in food availability, pointing to a phenological adjustment to such seasonal patterns with important fitness consequences. Indeed, delayed reproduction with respect to the onset of water stratification resulted in both hatching and breeding failure. This pattern was observed at the population level, but also when confounding factors such as individuals' age or experience were also accounted for. We provide the first evidence of oceanographic drivers leading to the optimal time-window for reproduction in an inshore seabird at southern European latitudes, along with a suitable framework for assessing the impact of environmentally driven changes in marine productivity patterns in seabird performance.