Editor: Karl Evans
Does fragmentation increase extinction thresholds? A European-wide test with seven forest birds
Article first published online: 4 JUN 2013
© 2013 John Wiley & Sons Ltd
Global Ecology and Biogeography
Volume 22, Issue 12, pages 1282–1292, December 2013
How to Cite
Rueda, M., Hawkins, B. A., Morales-Castilla, I., Vidanes, R. M., Ferrero, M. and Rodríguez, M. Á. (2013), Does fragmentation increase extinction thresholds? A European-wide test with seven forest birds. Global Ecology and Biogeography, 22: 1282–1292. doi: 10.1111/geb.12079
- Issue published online: 8 NOV 2013
- Article first published online: 4 JUN 2013
- Ministry of Economy and Competitiveness of Spain. Grant Number: CGL2010-22119
- University of Alcalá and the Spanish Ministry for Education and Science. Grant Number: BVA-2010-0596
- Extinction threshold hypothesis;
- forest amount;
- forest bird species;
- forest fragmentation;
- fragmentation theory;
- species-specific traits
Theory predicts that fragmentation aggravates habitat loss, increasing the extinction threshold of habitat specialists. However, contradictory empirical results have fuelled claims that fragmentation has been overemphasized, and more attention should be given to habitat loss for preserving species. We assess variation in species sensitivity to forest amount and fragmentation and evaluate if fragmentation is related to extinction thresholds in seven forest bird species.
We use the percentage of forest cover and the proportion of cover occurring in the largest patch to partition effects of forest amount versus fragmentation, and apply logistic regression to model the presence–absence of 17 forest bird species. For seven species showing robust models, we define two fragmentation scenarios, low and maximum, across the forest cover gradient and quantify species' sensitivity to forest contraction with no fragmentation, and to fragmentation under constant forest cover. Finally, we develop two tests of the extinction threshold hypothesis by comparing the occurrence probability of each species under the two fragmentation scenarios at different forest covers.
As expected, forest contraction had negative impacts on the occurrence probability of all seven species modelled, but – in line with theory – fragmentation also led to a higher extinction threshold for three (Western capercaillie, Hazel grouse and Eurasian pygmy-owl). One species (Black woodpecker) exhibited the opposite pattern indicating that it probably benefits from fragmentation. Differences among species responses may reflect dispersal abilities, specializations in resources/habitat characteristics and/or sensitivity to potential modifications of interspecific interactions.
Although forest amount is of primary importance for the persistence of forest specialist birds, fragmentation is also relevant for some, and neglecting forest fragmentation would be a mistake for these species. Species-specific traits can be helpful for interpreting species' reactions to fragmentation, and it should not be assumed that it always, or never, matters.