<p>In avian brood parasite systems, egg recognition and rejection by hosts represent one of the most prevalent defensive strategies. However, the mechanisms underlying the acquisition or evolution of egg recognition by hosts remain poorly understood. Here, the grey bushchat (<i>Saxicola ferreus</i>), a host bird of the common cuckoo (<i>Cuculus canorus</i>), was used to examine whether short-term learning and memory of foreign egg phenotypes influence host egg rejection decisions. Results indicated that: (1) the emergence of maculation signals from parasitic eggs significantly alters the grey bushchat’s rejection decisions based on its memory of own egg template (shifting from acceptance to rejection); (2) short-term learning and memory, acquired through the rejection of foreign eggs, increased the likelihood of rejecting own eggs that bore similar maculation patterns; and (3) the grey bushchat responded preferentially to spotty signals when exposed to conventional foreign egg features (background color or spotty maculation), but showed increased rejection of linear-marked conspecific eggs when presented with distinct signals (linear markings). Moreover, grey bushchats showed significantly reduced rejection of test eggs (spotty or linear-marked conspecific eggs) in the absence of foreign egg signals. These findings demonstrate that parasitic egg phenotypes can induce short-term imprinting effects (i.e., rejection signals) on the host. This study offers an important mechanistic explanation for how parasitic pressure drives the evolution of egg recognition ability, underscoring the key role of imprinting on parasitic egg templates in shaping host cognitive adaptations.</p>