Understanding how resource use and life history variation influence a population's response to modified, fragmented landscapes is a major challenge for ecologists. We investigated the phenology, life history decisions and provisioning behaviour of a generalist passerine-the great tit-across a heavily managed woodland landscape. Contrary to most previous studies on this species, reproductive investment and success were lower in deciduous than in coniferous woodland fragments. This could not be explained by differences in provisioning behaviour; instead population density was considerably higher in deciduous woodlands, suggesting birds did not follow an ideal free distribution. Clutch size declined with lay date amongst populations breeding in coniferous woodland fragments, but these populations also displayed pronounced seasonal declines in the proportion of fledglings produced per egg and fledgling mass. In contrast, and against patterns observed in other similar study systems, clutch size did not change with lay date in mixed-species deciduous woodland fragments. Furthermore, the proportion of young fledged and fledgling condition remained stable throughout the season, even though the quality of food provisioned to nestlings increased over the season. Local recruitment was negligible, suggesting that plasticity rather than natural selection played a key role in driving the patterns observed. The unusual patterns we report are likely explained by the fragmented nature of the landscape, and unreliable phenological cues in a mixed-species tree community coupled with low food availability. They contrast with those reported from most other populations situated in continuous woodland, demonstrating that caution is needed when generalising across different contexts and ecosystems.
Personality research suggests that individual differences in risk aversion may be explained by links with life-history variation. However, few empirical studies examine whether repeatable differences in risk avoidance behaviour covary with life-history traits among individuals in natural populations, or how these links vary depending on the context and the way risk aversion is measured. We measured two different risk avoidance behaviours (latency to enter the nest and inspection time) in wild great tits (Parus major) in two different contexts—response to a novel object and to a predator cue placed at the nest-box during incubation---and related these behaviours to female reproductive success and condition. Females responded equally strongly to both stimuli, and although both behaviours were repeatable, they did not correlate. Latency to enter was negatively related to body condition and the number of offspring fledged. By contrast, inspection time was directly explained by whether incubating females had been flushed from the nest before the trial began. Thus, our inferences on the relationship between risk aversion and fitness depend on how risk aversion was measured. Our results highlight the limitations of drawing conclusions about the relevance of single measures of a personality trait such as risk aversion.
Context Collisions between birds and aircraft (bird strikes) are a serious threat to aviation safety and these negative human–wildlife interactions are predicted to increase. As the wider spatial use of landscapes by birds can affect aviation safety (e.g. location of foraging and roosting sites), there is a clear need to implement effective management strategies at sites adjacent to airfields to reduce ingress of avian taxa across airfield boundaries. Aims In the present study, we assessed the efficacy of both an acoustic deterrent (sonic net) and a visual simulated predator effigy, in the form of a fox-shaped model, to disturb and reduce bird accumulations on: (1) agricultural foraging sites; (2) an active airfield; and (3) problematic roof-top roosts. Methods These non-lethal scare technologies were assessed separately and in combination by using a factorial design. Bird abundances, species richness and behavioural changes were considered. Key results Although the scare technologies did not reduce bird species richness at treated sites, in most cases, a significant reduction in bird abundances was observed. Equally, the number of birds observed to forage or roost was also generally significantly reduced, as was time spent by birds within treated sites. However, the effects of treatments were not universally across species. For example, a reduction in the abundance of gulls tended to be paired with an increase in the number of corvids for foraging sites. Nevertheless, the combined application of the sonic net and fox effigy caused a considerable reduction in foraging bird numbers, whereas singular treatment types appear to work best for roof-top roosts. Data also indicate that the sonic-net technology can be used to deter night-time roosting on an active airfield. Conclusions When taken together, treatments resulted in substantial and often significant reductions in bird abundance, foraging and roosting activity, as well as site residency time. However, treatment efficacy tended to be context and taxon specific. Implications Sonic net and mobile simulated predator effigies represent promising experimental scare technologies. Following further testing, the integration of these technologies into bird management interventions could yield substantial risk reductions for bird strikes, as well as improved non-lethal management of problematic roosting and nesting sites.
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