Brood parasitism of rosefinches by cuckoos: suitable host or accidental parasitism?

Abstract

The arms race between avian brood parasites and their hosts is a classic model of co-evolution. Parasitic breeding by the common cuckoo (Cuculus canorus) in the nests of the Chinese beautiful rosefinch (Carpodacus davidianus) was found from May to July 2017 in Saihanba National Forest Park, Heibei, China. To understand whether the rosefinch is a suitable host species for the common cuckoo, egg recognition, chick recognition, brood rearing, and brood diets were studied. The results showed that rosefinches fully accepted non-mimetic white model eggs and parakeet (Melopsittacus undulatus) eggs, and also did not reject the similar-looking eggs of cinereous tits (Parus cinereus). Chinese beautiful rosefinches did not demonstrate any ability to recognize or discriminate between parasitic eggs or nestlings, and provisioned nestlings of cinereous tit, coal tit (Periparus ater), dusky warbler (Phylloscopus fuscatus), and common cuckoo within their nests. However, Chinese beautiful rosefinches were unable to rear the parasitic nestlings; dissections of deceased nestlings revealed that the food provided by Chinese beautiful rosefinch parents was largely composed of plant seeds and young plant shoot materials. This suggested that the high cross-fostered nestling mortality was due to unsuitable food provisioning from the host parents to the parasitic chicks. Therefore, we concluded that the Chinese beautiful rosefinch is not a suitable host for the common cuckoo, and this parasitic breeding system does not represent a co-evolutionary relationship.