Azure‐winged Magpies Cyanopica cyanus trade off reproductive success and parental care by establishing a size hierarchy among nestlings

Abstract

It is common in birds that the sizes of nestlings vary greatly when multiple young are produced in one nest. However, the methods used by parents to establish size hierarchy among nestlings and their effect on parental provisioning pattern may differ between species. In the Azure‐winged Magpie Cyanopica cyanus, we explored how and why parents controlled the sizes of nestlings. Asynchronous hatching was the main cause of size hierarchy within the brood, although the laying of larger eggs later in the laying sequence reduced this effect. Parents with asynchronous broods produced more eggs and fledged more nestlings than those with synchronous broods but their brood provisioning rates, food delivery per feeding bout and feeding efficiency did not differ. We performed a cross‐fostering experiment to synchronize some asynchronous broods. Provisioning rates of asynchronous broods were lower than those of synchronized broods, but the daily growth rates and fledging body mass of their nestlings were not different. Our findings indicate that parents of asynchronous broods can achieve higher reproductive success than those of synchronous broods based on the same parental care, and the same reproductive success as those of synchronized broods based on less parental care. It appears that parent birds can better trade off reproductive success and parental care by establishing a size hierarchy among nestlings.

High level of extrapair fertilization in individual Tibetan azure‐winged magpies and their adaptive responses

“…An inability to discriminate their own offspring from unrelated young may explain this counter-intuitive response of cuckolded males and females. Our cross-fostering experiments in the Tibetan population of the azure-winged magpie show that foster parents do not eject fostered chicks when those fostered chicks are younger than 11-12 d (Da et al 2018). This finding is opposite to the report from the Iberian azure-winged magpies where breeders can reject nearly one half of conspecific eggs (Avilés 2004).…”

Performance of Azure-winged magpies in Aesop’s fable paradigm

“…Nevertheless, from the perspective of cognitive psychology, the results showed that the magpies have the ability of training transfer and analogical problem solving. The performance of the Azure-winged magpies in string-pulling tasks 24 , 27 and mirror tasks 28 also showed that they have a certain, although limited, spatial cognitive ability. We should emphasize that interference among experiments should be avoided in designing experiments to test cognitive ability.…”

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

“…Therefore, it is understandable that parents make no reaction to the change of incubation days during the egg phase ( Table 2 ), but significantly respond to the change of nestling ages during the nestling phase ( Table 3 ). In a previous study on the Tibetan azure-winged magpie that involved a cross-fostering experiment, parents began to reject a foreign nestling after it was 10 days old ( Da et al. 2018 ), indicating that parents can recognize their offspring from unrelated nestlings based on the phenotypic traits of nestlings.…”

“…2005 ) or the great spotted cuckoo Clamator glandarius ( Soler et al. 2003 ), no cases of nest parasitism by cuckoos have occurred in the Tibetan population ( Da et al. 2018 ).…”

“…2019 ). Moreover, a cross-fostering experiment performed in the Tibetan population indicates that foster parents do not reject foreign nestlings until it is 10 days old ( Da et al. 2018 ), suggesting that offspring recognition in the azure-winged magpie may be connected with nestling age.…”