How dependent are bell miners (Manorina melanophrys) on lantana (Lantana camara) as part of their habitat?

Abstract

Context: The bell miner (Manorina melanophrys) is thought to prefer the dense vegetation of Lantana camara, a dominating noxious weed, to nest in compared with native plant communities in northern New South Wales and south-eastern Queensland. As miner numbers seemed to have increased with increased availability of nesting habitat, larger numbers of despotic bell miners territorially reduce native avian diversity. The resultant high insect numbers in the canopy lead to dieback. It is unknown to what extent the native bell miner relies on lantana for nesting sites and if restoration through removal of lantana, resulting in an influx of native species, changes food availability and thus foraging behaviours. Aims: The objective of our study was to understand the relationship between the presence of lantana and bell miners by determining: (1) bell miner behaviours in response to different understorey types; (2) bell miner nesting choices on a broad scale; (3) nesting preference for each site on a broad scale; and (4) whether nest height is related to fledging success. Methods: Fifty individual bell miners were observed within five colonies (four containing comparison quadrats of treated and intact lantana as part of a restoration study and one containing water vine for comparison as a pristine site; n = 10 per treatment) during four seasons. Five bouts of gleaning, probing or sallying were observed, noting height and plant species. Nest sites were examined over a large area, noting plant species present, nest height and plant height. Key results: Bell miners used gleaning as the primary foraging tactic primarily in eucalypts (93%; n = 600, mean = 13.6 m ± 0.29, s.e.). Bell miners generally nested in understorey vegetation (83.5% of nests observed) at a mean height of 2.7 m in 37 different plant species, native and exotic. Nest height did not influence the probability of broods fledging. Conclusions: Bell miners exhibit considerable nest plasticity, and the removal of lantana as an oft-used nesting habitat is unlikely to lead to relocation by this species. Implications: Instead, future research needs to focus on canopy insect assemblages in bell miner colonies, a potentially more important determinant of bell miner distribution.