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Despite its prevalence across bird taxa, avian vocal mimicry remains a poorly studied field of animal behaviour. In order to advance our understanding of the function of avian vocal mimicry, the field requires that the range of vocal mimicry in birds is described. The Tawny Lark (or Sykes's Lark, Galerida deva) is endemic to central and western India. Recent work on other Galerida larks has found that the mimetic vocalisations match the biodiversity of their acoustic environment, thereby conferring a significant novel function in study of individual mimetic variation linked to biodiversity. Here, we provide a detailed account of the variety of mimetic sounds produced by the Tawny Lark. We also describe acoustic and peer-based analyses that gauge the accuracy of the mimicry. By providing a detailed description of mimicry, we provide a basis for future study of the function of mimicry in this species.

Successful reproduction often depends upon parents providing offspring with resources and protection. In birds, reproductive success can often be enhanced by parents engaging in antipredator behaviors, but these behaviors can be costly. Theoretically, individuals should temporally modify the intensity of nest defense behavior to balance the costs and benefits of current and future reproductive success. More specifically, nest defense should vary throughout a nesting attempt to maximize fitness of the adults. Here, we consider the relationship between nest defense behavior and chick vulnerability in the herring gull (Larus argentatus), where chicks are under high predation risk. We estimated chick vulnerability by quantifying survival probabilities at different periods of the nestling stage. Simultaneously, we quantified changes in parental aggression throughout the nesting cycle by simulating predation attempts using a human predator model. We found that chick survival probabilities were lowest (i.e., vulnerability was highest) and parental aggression in nest defense was greatest during the first 10 days after hatching. Thus, we show that parents are most defensive when chicks are most vulnerable and that adults optimize nest defense behaviors in a way that maximizes their fitness.