Impact of nest sanitation behavior on hosts’ egg rejection: an empirical study and meta-analyses

Abstract

Egg rejection in birds is a specific adaptation toward avian brood parasitism, while nest sanitation is a general behavior for cleaning the nest and avoiding predation. However, both behaviors refer to the action of ejecting objects out of the nest, and nest sanitation has been proposed as a pre-adaptation for egg rejection. Here we tested the eliciting effect of nest sanitation on egg rejection in the red-whiskered bulbul Pycnonotus jocosus, a potential host species that is sympatric with parasitic cuckoos. We conducted meta-analyses of previous studies on both nest sanitation and egg rejection, in order to evaluate the consistency of our conclusions. Our results showed that nest sanitation did not elicit egg rejection in P. jocosus. The conclusions concerning such an eliciting effect from previous studies were mixed, while the methodologies were inconsistent, making the studies unsuitable for comparisons. However, the ejection frequency of nest sanitation was consistently higher than the frequency of egg rejection across different host species or populations. These results suggest that nest sanitation, which is an ancient behavior, is more fundamental than egg rejection, but the effect of the former on the latter is complex and needs further study. Standardized methodologies and the integration of behavior, physiology, and modeling may provide better opportunities to explore the relationship between nest sanitation and egg rejection.

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

“…As a result, they could have evolved a high level of egg recognition over the course of a long‐term coevolution, ultimately winning the ‘arms race’, with egg recognition abilities remaining as a residual behaviour. In contrast, nest sanitation behaviour of parents may also be a factor driving host rejection of foreign eggs (Feng et al., 2019; Li et al., 2021; Yang, Wang, et al., 2015). Nest sanitation behaviour is mainly directed towards irregular, non‐ovoid objects in nests (Guigueno & Sealy, 2009; Hauber et al., 2021; Underwood & Sealy, 2006), which is distinct from egg rejection behaviour.…”

Nest sanitation as an effective defence against brood parasitism

“…The idea was first proposed by Rothstein (Rothstein 1975a) because egg ejection uses motor patterns identical to the removal of non-egg-shape debris (Swynnerton 1918;Rothstein 1975a). While this hypothesis has generally received poor support (reviewed in Li et al 2021), it must be noted that all studies to date have only investigated correlations between nest sanitation and egg removing behaviour (Peer and Sealy 2004;Yang et al 2015b;Luro and Hauber 2017) or whether nest sanitation elicits egg ejection (Yang et al 2015a;Luro and Hauber 2017;Peer 2017;Su et al 2018;Stratton and Dearborn 2021) without an evolutionary perspective. Therefore, further investigation of the potential relationship between the evolution of nest sanitation behaviour and foreign egg ejection is needed (Guigueno and Sealy 2017;Yang 2021).…”