Potential cuckoo hosts have similar egg rejection rates to parasitized host species

Abstract

Background: Thrush species are rarely parasitized by cuckoos, but many have a strong egg recognition ability. To date, there is a limited understanding of the relationship between host egg rejection and cuckoo parasitism rate. Methods: By using egg experiments in the field, we compared egg rejection between two non-parasitized potential host species and two parasitized hosts of cuckoos in the same region. Results: The White-bellied Redstart (Luscinia phoenicuroides), a host of the Common Cuckoo (Cuculus canorus), rejected 66.6% of blue model eggs; the Elliot's Laughingthrush (Trochalopteron elliotii), a host of the Large Hawk Cuckoo (Hierococcyx sparverioides), rejected 25% of blue model eggs and 46.1% of white model eggs; and the Chestnut Thrush (Turdus rubrocanus) and the Chinese Thrush (T. mupinensis), in which cuckoo parasitism has not been recorded, rejected 41.1 and 83.3% of blue model eggs, respectively. There were no significant differences in the egg rejection among them, although the Chinese Thrush showed the highest rate of egg rejection. Conclusions: This study indicates that the egg recognition ability of cuckoo hosts has no correlation with the actual parasitism rate of cuckoos. We suggest that the egg recognition ability of the two potential host species may have been retained from a parasitic history with the cuckoo, while the two common host species have developed their egg rejection abilities due to current parasitism pressure. In addition, our study highlights the importance of the multicuckoo parasite system for better understanding the selection pressure of parasitism on the evolution of host egg recognition abilities.

Brood parasitism and egg recognition in three bunting hosts of the cuckoos

“…Previous studies have shown that the degree of egg rejection by the host of cuckoos was significantly and positively correlated with the degree of parasitism rate (Røskaft et al, 2002), which was not supported by the results of the present study as all three bunting species had strong egg recognition but low cuckoo parasitism rates (for comparison, 9% in corn bunting, n = 90, Antonov et al, 2006;11.5% in Jankowski's bunting, n = 95, Zhang et al, 2020). Similarly, the findings of Yi et al (2020) showed no difference in egg recognition ability between potential hosts and currently used hosts. Since some host species have a strong ability to reject eggs in the absence of parasitism (Lahti, 2006;Medina & Langmore, 2015;Underwood et al, 2004), brood parasitism rates may not be a primary indicator of host egg recognition ability, or that they were once subjected to parasitism pressure and egg recognition ability is retained.…”

“…Similarly, the findings of Yi et al. (2020) showed no difference in egg recognition ability between potential hosts and currently used hosts. Since some host species have a strong ability to reject eggs in the absence of parasitism (Lahti, 2006; Medina & Langmore, 2015; Underwood et al., 2004), brood parasitism rates may not be a primary indicator of host egg recognition ability, or that they were once subjected to parasitism pressure and egg recognition ability is retained.…”

“…The egg mass and sizes are shown in Table 1. Either one red or one blue model egg was placed in an experimental nest before mid‐incubation (Yi et al., 2020). Nest checks were conducted every 3 days for a 6‐day experimental cycle, and the results of the parent's response to the foreign egg were recorded (Yi et al., 2020).…”

“…Either one red or one blue model egg was placed in an experimental nest before mid‐incubation (Yi et al., 2020). Nest checks were conducted every 3 days for a 6‐day experimental cycle, and the results of the parent's response to the foreign egg were recorded (Yi et al., 2020). If the model egg was pecked by the parent, thrown out of the nest, or if the nest was abandoned, the host response was recorded as rejection.…”

“…For example, Yi et al. (2020) compared the egg recognition ability of different hosts breeding in the same area to explore the correlation between egg rejection and cuckoo parasitism. However, given that there are many species of passerine birds suitable for cuckoo parasitism breeding within the same area, only a very few species are regularly parasitised by cuckoos, and there are few studies on why these potential hosts are not, or seldom, parasitised (Davies, 2000; Grim et al., 2011; Grim & Honza, 2001; Honza et al., 2004).…”