The pine processionary moth (Thaumetopoea pityocampa, PPM) is gregarious insect that defoliates pine and cedar species in southern and central Europe. Migratory coal tits (Periparus ater) are a known generalist predator of the third instar larvae in the autumn, and arrive in variable numbers to mountain passes where PPM overwinters in silk nests. Using long-term datasets, this thesis assesses the co-occurrence of these two species over time, and the impact of coal tit predation on PPM to better understand their predator-prey interactions and temporal dynamics. A field survey was also conducted in the Italian Alps to elucidate the insect’s defence mechanism against these avian predators. The relationships between the temporal variation in PPM density and coal tit abundance at three major bird migratory sites in the French and Italian Alps (Col de Bretolet (F), Bocca di Caset (IT), and Passo del Brocon (IT)) were analyzed via linear regression models to test two hypotheses, that: 1) local PPM density predicts coal tit abundance, and 2) coat tit abundance predicts local or regional PPM populations the following year. Main findings include synchronous and irruptive migration patterns of coal tits across the Alps, while PPM densities fluctuate more locally and are not synchronized across different areas. The abundance of migrating coal tits varies independently of the local density of its potential insect prey (hypothesis 1). However, at least for some sites and especially in peak years of coal tit migration, higher numbers of birds captured in autumn correspond to lower densities of PPM nests and adult moths in the following spring or summer (hypothesis 2), confirmed by higher PPM nest predation with increasing coal tit abundance. Predator-prey dynamics of coal tit and PPM are not tightly linked; however, coal tits are important predators during peak migration years and at higher PPM densities. These findings provide insights into the periodic nature of the ecological interactions between migrating coal tits and PPM, and highlight the role of bird predation in population regulation of forest insect pests.
The pine processionary moth (Thaumetopoea pityocampa, PPM) is gregarious insect that defoliates pine and cedar species in southern and central Europe. Migratory coal tits (Periparus ater) are a known generalist predator of the third instar larvae in the autumn, and arrive in variable numbers to mountain passes where PPM overwinters in silk nests. Using long-term datasets, this thesis assesses the co-occurrence of these two species over time, and the impact of coal tit predation on PPM to better understand their predator-prey interactions and temporal dynamics. A field survey was also conducted in the Italian Alps to elucidate the insect’s defence mechanism against these avian predators. The relationships between the temporal variation in PPM density and coal tit abundance at three major bird migratory sites in the French and Italian Alps (Col de Bretolet (F), Bocca di Caset (IT), and Passo del Brocon (IT)) were analyzed via linear regression models to test two hypotheses, that: 1) local PPM density predicts coal tit abundance, and 2) coat tit abundance predicts local or regional PPM populations the following year. Main findings include synchronous and irruptive migration patterns of coal tits across the Alps, while PPM densities fluctuate more locally and are not synchronized across different areas. The abundance of migrating coal tits varies independently of the local density of its potential insect prey (hypothesis 1). However, at least for some sites and especially in peak years of coal tit migration, higher numbers of birds captured in autumn correspond to lower densities of PPM nests and adult moths in the following spring or summer (hypothesis 2), confirmed by higher PPM nest predation with increasing coal tit abundance. Predator-prey dynamics of coal tit and PPM are not tightly linked; however, coal tits are important predators during peak migration years and at higher PPM densities. These findings provide insights into the periodic nature of the ecological interactions between migrating coal tits and PPM, and highlight the role of bird predation in population regulation of forest insect pests.
Pine processionary moth and coal tit: Implications for population dynamics in the Alps
MACEACHERN, HALLIE ANNA
2023/2024
Abstract
The pine processionary moth (Thaumetopoea pityocampa, PPM) is gregarious insect that defoliates pine and cedar species in southern and central Europe. Migratory coal tits (Periparus ater) are a known generalist predator of the third instar larvae in the autumn, and arrive in variable numbers to mountain passes where PPM overwinters in silk nests. Using long-term datasets, this thesis assesses the co-occurrence of these two species over time, and the impact of coal tit predation on PPM to better understand their predator-prey interactions and temporal dynamics. A field survey was also conducted in the Italian Alps to elucidate the insect’s defence mechanism against these avian predators. The relationships between the temporal variation in PPM density and coal tit abundance at three major bird migratory sites in the French and Italian Alps (Col de Bretolet (F), Bocca di Caset (IT), and Passo del Brocon (IT)) were analyzed via linear regression models to test two hypotheses, that: 1) local PPM density predicts coal tit abundance, and 2) coat tit abundance predicts local or regional PPM populations the following year. Main findings include synchronous and irruptive migration patterns of coal tits across the Alps, while PPM densities fluctuate more locally and are not synchronized across different areas. The abundance of migrating coal tits varies independently of the local density of its potential insect prey (hypothesis 1). However, at least for some sites and especially in peak years of coal tit migration, higher numbers of birds captured in autumn correspond to lower densities of PPM nests and adult moths in the following spring or summer (hypothesis 2), confirmed by higher PPM nest predation with increasing coal tit abundance. Predator-prey dynamics of coal tit and PPM are not tightly linked; however, coal tits are important predators during peak migration years and at higher PPM densities. These findings provide insights into the periodic nature of the ecological interactions between migrating coal tits and PPM, and highlight the role of bird predation in population regulation of forest insect pests.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/70753