Aim

Much research has quantified species responses to human-modified ecosystems. However, there has been relatively limited work on how human-modified ecosystems may reshape competitive interactions between species. Using extensive data gathered over 19 years across an area exceeding three million ha, we asked: Are levels of interference competition between bird species context-dependent and influenced by habitat structure and productivity? We focussed on the hyper-aggressive behaviour of the Noisy Miner, which has been recognised as a Key Threatening Process for other woodland bird species.

Location

Temperate woodlands of south-eastern Australia

Methods

We constructed Bayesian multi-species occupancy/detection models of bird species in woodland patches and tested the fixed and interactive effects of Noisy Miner presence, the amount of tree cover, net primary productivity, and time. We quantified the responses of 31 species, many with known interactions with the Noisy Miner documented in previous studies at fine spatial scales. However, whether environmental conditions such as amount of forest cover and net primary productivity mediate the impact of Noisy Miners remains untested at large spatial scales and over decadal time scales.

Results

We identified negative associations between the Noisy Miner and 18 bird species, including, unexpectedly, both small- and large-bodied taxa. Site occupancy in some species was influenced by interactions between Noisy Miner presence and increasing amounts of tree cover or productivity. Our results suggest that for some species, interference competition by the Noisy Miner is context-dependent and mitigated by increasing tree cover and/or increasing net primary productivity

Main conclusions

Areas of high productivity or tree cover may be important refugia for some species of woodland birds. Vegetation clearing that reduces tree cover could likely strengthen interference competition by the Noisy Miner on parts of the remaining woodland bird community, including species of conservation concern.

Dataset contains data collected by on-the-ground bird surveys, then used in as part of a Bayesian multi-species occupancy/detection model, used to attempt to answer the question: 

Are levels of interference competition between the Noisy Miner and other bird species context-dependent and influenced by habitat structure and productivity?