Do Parents and Helpers Discriminate between Related and Unrelated Nestlings in the Cooperative Breeding Silver‐Throated Tit?

Abstract When benefits exceed costs, natural selection may favor adults that develop the ability to recognize and preferentially direct care toward their own offspring to maximize their fitness. Investigations into the ability of adults to recognize offspring in offspring's early development period may help to understand when the ability of kin recognition starts to develop. In birds, studies of offspring recognition have mainly been conducted on bi‐parental breeding species, but relatively seldom on cooperative breeding species, despite that kin recognition may be of particular importance for cooperative breeders. The silver‐throated tit Aegithalos glaucogularis is a small passerine in which some nests have helpers during breeding. We tested whether silver‐throated tit parents and helpers were able to distinguish between their own and alien nestlings 2–5 d before fledging when recognition mechanisms were likely to have been developed. Through two forced choice experiments, of which one was conducted right beside the experimental nests (<0.8 m) and the other far away from the experimental nests (~6 m), we found that neither parents nor helpers discriminatively fed their own and alien nestlings, which suggested that at least during the experimental nestling age, and within the 6‐m‐radius area around the nests, they might not have the ability to recognize offspring. The possibility that silver‐throated tits use a larger area (>6 m radius) around their nests as a location‐based cue for offspring recognition, or would develop an offspring recognition ability at an older nestling age and/or even after fledging, warrants future studies.