Figure 3: Recognizability of host eggs is correlated with cuckoo egg mimicry and predicts host rejection behaviour.

(a) The relationship between the degree of cuckoo pattern mimicry (data taken from the study by Stoddard and Stevens¹³) and the recognizability of the host pattern signature. Weighted linear regression, P=0.005. (b) The relationship between the recognizability of the host egg signature and the frequency with which hosts reject non-mimetic eggs. Rejection rates are from the study by Avilés and Garamszegi³⁶. Weighted linear regression, P=0.004. These results indicate that hosts of the common cuckoo have evolved modified egg patterns in response to cuckoo mimicry (a), leading to recognizable pattern signatures that facilitate rejection of parasitic eggs (b). Recognizability of the host signature is measured as the likelihood that a host egg will be correctly identified to its own clutch (see text for details).