Twinkling lights or turning down the dimmer switch? Are there two patterns of extinction debt in fragmented landscapes?

Abstract

The decline and local extinction of many woodland birds across southern Australia is continuing and seems likely to continue for a long time even though broad-scale clearing has ceased in many regions. The small proportion of remaining vegetation and its fragmented and degraded nature will probably mean that a long-term extinction debt will have to be paid. For some species this will be through the process of successive extinctions of sub-populations and lack of recolonization due to poor dispersal ability, leading to ultimate extinction of the metapopulation. However, many bird species in Australia travel locally and regionally to exploit resources that vary in time and space (rich-patch nomads), and appear to be quite capable of dispersing in fragmented landscapes. Many of these too are declining and we need to understand the processes involved in their decline. Making the matrix more hospitable may reverse the declines of the poor dispersers. However, a different approach may be needed to assist the rich-patch nomads, such as re-establishing key resources. This will involve a better understanding of their natural history.