The forty-spotted pardalote is an endangered and highly specialised species. Forty-spotted pardalotes are endemic to eastern Tasmania where they co-occur with two other pardalotes (the spotted and striated). Their historical range covered the east coast and some offshore islands but they are now restricted to small offshore islands, headlands and peninsulas in south-eastern Tasmania and Flinders Island in the north. Forty-spotted pardalotes use small tree hollows for nesting, in which they build a dome shaped nest out of grass, tree bark and feathers. They also are dependent on white gum (Eucalyptus viminalis) where they forage for arthropods and manna (sugary exudates from leaves and branches). Forty-spotted pardalotes are threatened by habitat loss and degradation, introduced predators like sugar gliders, competitors, drought and poor dispersal ability. Our research discovered a new threat for this species- parasites. A screw worm fly (Passeromyia longicornis) lays its eggs in the nests of forty spotted pardalotes, and the maggots burrow into the skin of nestling pardalotes, where they drink the blood of the baby birds. Unsurprisingly, this leads to very high mortality rates of fly-struck pardalote nestlings and is the primary cause of nesting failure identified in this species.
Why it’s difficult
Forty-spotted pardalotes are elusive because are smaller than a matchbox and live high in the canopy of E. viminalis dominant or subdominant forests. These small birds can go unnoticed if the observer is not able to recognize their quiet call and monitoring the nests of wild birds in tiny tree cavities is extremely challenging.
What we are doing
Since 2010 we have been conducting a monitoring program for Forty-spotted pardalotes over their entire remaining range (North Bruny Island, Maria and Flinders Island) to track changes in their population patterns of occupancy and abundance. Our monitoring program recently led to the discovery of a new population of forty spotted pardalotes in a location beyond their known range- a major conservation win for this species. We use this monitoring to identify what habitat characteristics are most important for supporting pardalote populations, and identify ways to make new populations safe from known threatening processes. This research will be used to develop a framework and feasibility analysis of the potential for experimental reintroduction of the species to parts of its historic range. Further our monitoring program has allowed us to derive the first robust population estimates for this poorly known species.
We have been monitoring the breeding success of Forty-spotted pardalotes at a network of nest boxes on North Bruny Island since 2012. This array of nest boxes allowed us to discover that parasitic fly larvae are responsible for high nestling mortality. Our group tested and now implement techniques to manage the incidence of fly parasitism using bird-safe insecticide to fumigate nests, which substantially improves nestling survival. We are using the existing network of nest boxes already occupied by pardalotes to investigate their sensitivity to different management interventions (fly control) and experimentally deploying new nesting boxes into relict populations of unmanaged pardalotes to establish whether they respond to management intervention.