Abstract
Abstract Anti-predator behaviour is common among birds, but little research exists on whether differences in the predator landscape between urban and rural habitats results in differential anti-predator behaviour. We compared nest-defence behaviour of mountain chickadees (Poecile gambeli) in urban and rural habitats in Kamloops, BC, Canada to a simulated predator model (snake) on top of nest boxes while incubating females were away from nests on foraging bouts. Upon their return, we recorded proximity to the predator model, latency to contact the nest box and enter the nest, and number of gargle and chick-a-dee calls as measures of anti-predator behaviour and compared multivariate “predator aversion scores” across birds occupying either rural or urban landscapes. Rural-nesting birds had more aversive reactions to the predator model than the urban-nesting birds, which may suggest differences in perceived threat of the model, in combination with increased boldness associated with urban-nesting birds.
Highlights
Prior nesting experience of females did not affect their response to predator models, but there was a strong effect of habitat on response — Rural birds exhibited stronger aversion towards the model, staying at greater distance while calling, and taking much longer to approach and enter the nest than the Urban birds
Our results partially suggest this; Urban birds approached closer and were faster to approach the nest box on which the predator model was placed, but this meant they were less likely to vocalize during predator presentations than Rural birds
Did Rural birds call more than Urban birds, but the number of dee notes in chick-a-dee calls did not differ among females from either habitat type
Summary
Nest predation is an important factor that reduces offspring survival in avian species (Ricklefs, 1969; Martin, 1993; DeGregorio et al, 2014; Groenewoud et al, 2019), and selects for anti-predator behaviour in adult birds to help reduce offspring mortality (Ricklefs, 1969; Montgomerie & Weatherhead, 1988; Martin, 1995; Meilvang et al, 1997, Veen et al, 2000). Indirect anti-predator response may include cryptic placement of nests, false incubation, or concealing movement to and from nests to reduce likelihood of predators detecting nests. These indirect behaviours may be less energetically costly than direct behaviours, the latter of which may incur greater costs to parents by increasing their exposure to, or causing detection by, predators. Prey species must balance how they respond to predators based on perceived level of threat, as engaging in excessive direct anti-predator behaviour could either give cues to predators about the location of nests they had not previously detected, or reduce parental attention to nests and nestlings (e.g., incubation and feeding rates). Adult birds may modify the intensity of their anti-predator response based on other considerations, such as: their own physical condition to mount a response; their prior breeding experience and previous encounters with predators; the age or number of nestlings and how much energy they have already invested into the nest; or, the proximity of the predator to the nest and how likely it is to
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