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A drop in immigration results in the extinction of a local woodchat shrike population
Author(s) -
Schaub M.,
Ullrich B.
Publication year - 2021
Publication title -
animal conservation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.111
H-Index - 85
eISSN - 1469-1795
pISSN - 1367-9430
DOI - 10.1111/acv.12639
Subject(s) - biological dispersal , population , shrike , population decline , extinction (optical mineralogy) , geography , population size , endangered species , ecology , population growth , immigration , demography , small population size , biology , habitat , paleontology , archaeology , sociology
Abstract The demographic reasons of local population extinctions are rarely known which hampers learning for preventing extinction of other populations. Here we study the demography of a population of the endangered woodchat shrike Lanius senator at the edge of its distribution range from 1966 to 1992. We recorded the number of breeding pairs and collected reproduction and capture‐recapture data which were analysed with an integrated population model. Population size and most demographic rates fluctuated, but did not show long‐term trends. The most important demographic driver for the variation in the annual population growth rate was immigration. Despite its dependence on immigration, the local population was not necessarily a sink but may have been part of a balanced dispersal system. A population viability analysis showed that the risk was zero for the population to go extinct due to stochastic events during the 10 years after 1992. Yet, the population went extinct 6 years after the end of the study. The only demographic mechanism that can explain the fast extinction is a stop of immigration. The population was always dependent on immigration due to the strong dispersal of the shrikes and became more isolated due to the overall decline of the species. Our results suggest that the reservoir of potential immigrants may have become insufficient to maintain the local population and highlights that local populations can go extinct without the need of local changes in demography. Successful conservation of bird populations with similar demography as woodchat shrikes need to focus on spatial scales that extend significantly beyond the local one.