CHIRPS – CHanges In bird Reproductive Performance and Song along land-use gradients
Passerines are strongly affected by land-use intensity, mainly through habitat loss and reduced food resources. In particular, the availability and quality of arthropod prey are likely important drivers of bird condition and breeding success. Along land-use gradients, variation in resource availability can lead birds to adjust their foraging strategies, with consequences for parental provisioning efficiency and ultimately breeding success, as predicted by the food limitation hypothesis.
Prey availability and quality can also influence vocal activity. In food-poor environments, individuals may face trade-offs between time spent foraging and time allocated to singing. These trade-offs likely vary over time as birds adjust their behaviour to meet energetic demands. Because vocal activity plays a crucial role in mate attraction and territory defence, it is often considered an honest signal of individual condition, as only individuals in good condition can afford sustained singing.
CHIRPS aims to study how land-use intensity and prey availability jointly shape bird vocal activity across communities, and breeding success in a focal species, the great tit (Parus major). The project tests whether vocal activity and reproductive success are linked because they share common environmental drivers, and whether breeding success in P. major can be predicted from vocal activity and acoustic traits.
We hypothesize that :
- 1. Land-use intensity reduces arthropod prey availability and quality for birds.
- 2. Bird vocal activity and acoustic traits vary with land-use intensity and prey availability across time.
- 3. Higher land-use intensity and reduced arthropod prey resources decrease breeding success in P. major
- 4. Probability of good breeding success in P. major can be predicted from vocal activity and acoustic traits.
The project combines field experiments with existing datasets from the Biodiversity Exploratories, including arthropod surveys from the core project and BEsound acoustic recordings. Analyses of vocal activity along land-use and resource gradients will be conducted using these existing datasets from both forest and grassland plots. A food supplementation experiment will be conducted on great tits (Parus major) in forest MIPs using nest boxes equipped with cameras and feeding stations. Arthropod availability will be measured in trees near nest boxes, and bird vocal activity will be monitored using autonomous acoustic recorders.
These data will be integrated to link prey availability, parental provisioning behaviour, vocal activity, and breeding success across a land-use gradient.
Scientific assistants
