Size or quality. What matters in vegetation restoration for bird biodiversity in endangered temperate woodlands?

Vegetation restoration is a globally important form of management intervention designed to both remediate degraded land and to restore biodiversity. Using a 15-year controlled experimental study in endangered Australian temperate woodlands, we quantified the response of bird biota to vegetation enhancement leading to the re-establishment of an understorey, an increase in woodland patch size, or a combination of both. Our empirical results were characterized by marked variation in species richness and in the response of individual species to both time since enhancement and type of enhancement. For example, overall bird species richness initially responded negatively to enhancements but the effects were mitigated over time. Similar responses were identified for individual species such as the Rufous Songlark (Megalurus mathewsii). In the case of the Noisy Miner (Manorina melanocephala), responses to enhancement were negative and remained so over time. Conversely, the White-plumed Honeyeater (Ptilotula penicillata), Yellow-rumped Thornbill (Acanthiza chrysorrhoa) and Superb Fairy-wren (Malarus cyaneus) responded positively to enhancements. We also found evidence for variable responses to the kind of enhancement with some species responding to increased woodland patch size (e.g. Yellow-rumped Thornbill), others to a combination of enhancements (e.g. White-plumed Honeyeater), whereas yet others were agnostic to the kind of intervention that was implemented (e.g. Noisy Miner). Positive effects of enhancement were often time lagged for 6–8 years following instigation of underplanting and/or increases in woodland patch size. The negative effects of patch enhancement on the Noisy Miner indicate that underplanting and/or increases in woodland patch size may represent ways in which the impacts on other bird taxa of this despotic, hyper-aggressive species might be mitigated.