Population and demographic synchrony in European land birds.
Abstract
Understanding the drivers of spatially and temporally correlated
(synchronous) fluctuations in abundance is a fundamental challenge in
ecology and conservation. Synchronous fluctuations in different
demographic rates can potentially drive or dampen abundance synchrony,
but demographic synchrony is generally poorly understood. Using
long-term count and demographic data for breeding land-birds at sites
across Europe, we show that the strength and scale of synchrony are
greatest in productivity, followed by adult survival rates and then
counts. However, count fluctuations are more synchronous with survival
than with productivity. Despite migratory and resident species having
similar periodicities of count synchrony, synchrony in both demographic
rates was more common over long-timescales in resident species and
short-timescales in migrant species. These findings suggest local
impacts of synchronous fluctuations in adult survival rates on count
synchrony, potentially dampening effects of large-scale synchrony in
productivity, and that the environmental drivers of synchrony may differ
between residents and migrants.