Science for Saving Species Research findings factsheet Project 2.2.3

Conservation and management of the Endangered forty-spotted through “self-fumigation” of nests

In brief Background The forty-spotted pardalote has undergone major declines and The forty-spotted pardalote was The also make use of is now Endangered. Larvae of once widespread across Tasmania nest boxes where they are available, the parasitic fly (Passeromyia but has suffered severe population and nest boxes are an important longicornis) is the primary cause of declines and contraction of its management tool given that most nesting failure, killing most chicks in range. It is now largely confined remaining populations of the some areas and severely hampering to two islands off the south-eastern are in second-growth forest where recovery efforts. If not addressed, coast of Tasmania, Bruny Island tree hollows are in short supply. and Maria Island, and is listed this parasite could lead to the In 2012, ANU research discovered nationally as Endangered. extinction of the species. that larvae of the native parasitic Our previous research has shown The cause of its decline is likely a fly (Passeromyia longicornis) are that spraying pardalote nests with number of threats in combination. impacting pardalote chicks. The a bird-safe insecticide can improve The forty-spotted pardalote’s range flies are attracted to the nests chick survival, but finding and is naturally restricted to Tasmanian where they lay eggs. When the accessing forty-spotted pardalote forests where its preferred food chicks hatch, the fly maggots nests is logistically difficult. tree, white gum (Eucalyptus burrow under the skin of nestlings, viminalis), is the dominant or sub- feeding on their blood and causing To overcome this, we developed dominant tree species, as the severe mortality. In areas where the a technique that utilises the bird’s feed both on invertebrates that live fly is most prevalent, the maggots own instinct of collecting feathers in the tree foliage and by “farming” have been found in 87% of forty- to line its nest in order to introduce white gum manna, a sugary gum, spotted pardalote nests. Nestling the insecticide. We placed sterilised by clipping the stalks of leaves forty-spotted pardalotes suffer chicken feathers treated with with their beaks, causing them to 81% mortality in parasitised nests. insecticide in dispensers near exude this nutritious substance. nesting sites over two breeding Key threats to this dietary specialist Healthy forty-spotted pardalote seasons and pardalotes took these species include loss or degradation chicks in a self-fumigated nest. Image: Fernanda Alves back to their nests, effectively of its white gum forest habitat, self-fumigating. alongside competition from other In self-fumigated nests, 95% of birds, including aggressive invasive hatchlings survived to fledging species such as noisy miners. compared to just 8% of hatchlings Forty-spotted pardalotes nest in untreated control nests. between August and January in This novel technique is a highly tree hollows, where they build effective and inexpensive method enclosed dome-shaped nests out of reducing parasitism of chicks. of bark and grass, lined with soft material such as feathers or fur. Background (continued) Research aim The fly is also native to Tasmania and effective ways to reduce the impact We developed and tested the has been recorded also parasitising of the parasitic fly on the forty- effectiveness of an innovative, four other species of bird. spotted pardalote and boost low-cost and low-tech approach its nestling survival rate. to reduce forty-spotted pardalote Although parasites may be very nestling mortality caused by the costly to their hosts, from an A previous trial demonstrated that larvae of the native screw worm evolutionary perspective they are spraying nest boxes with a bird- fly (P. longicornis). not predicted to cause decline of safe insecticide could dramatically the host population, when that reduce parasitism; however, the population is healthy. However, natural tree hollows that forty- when the population is small and/ spotted pardalotes use for nesting or declining and facing multiple tend to be high in the canopy, other threats, as in the case of the making them inaccessible to forty-spotted pardalote, parasites conservation managers and making can emerge as a critical threat. the option of manual fumigation of It is therefore crucial to find cost- large numbers of nests infeasible. Adult forty-spotted pardalote in a nest lined with fumigated chicken feathers. Image: Fernanda Alves

What we did

We used North Bruny Island as on the dispensers to slow the We also switched nests between our study site because of its high degradation of the insecticide from treatment groups for each prevalence of the parasitic fly exposure to sunlight and rain. All successive nesting attempt within P. longicornis. Previous research feather dispensers were hung in a season. (Pardalotes have multiple had shown it to be found in 87% of trees about 4 m from nest boxes. broods per season.) After a nest forty-spotted pardalote nests in that We compared the effectiveness succeeded or failed, we cleaned the location. The area also contained a to feather dispensers in which the nest boxes to encourage the birds network of nest boxes known to be chicken feathers were not treated to rebuild and swapped their feather used by forty-spotted pardalotes. with insecticide (the control). dispenser from control to treatment or vice versa. The timing was very Over two breeding seasons, August To ensure that the results were much aligned between individual 2016 to January 2017 and August not affected by site and/or season, nests, both for when they were built 2017 to January 2018, we conducted we divided the study area in half. by the birds and for their date of a field experiment designed to The half that received treatment success/failure, so it was possible encourage the birds to “self- feather dispensers in the 2016–17 to switch groups of nests between fumigate” their nests. We exploited breeding season for the first clutch experimental treatments with the way forty-spotted pardalotes line received control feather dispensers no risk of overlap. their nests with feathers to introduce for the first clutch in the 2017–18 a commercial bird-safe insecticide season, and vice versa. (composed of Permethrin, Piperonyl Butoxide and Methoprene) to nests via feathers. In the trial, we placed sterilised store- bought chicken feathers treated with the insecticide in “feather dispensers” hung in trees (the treatment). The dispensers were made of double hardware mesh to hold the feathers in place and attached a cover Examining a nest box used by forty-spotted pardalotes on North Bruny Island for the presence of the parasitic fly. Image: Fernanda Alves Setting up the self-fumigation experiment with chicken feather dispensers. The birds Key findings made heavy use of the feathers from these dispensers. Image: Fernanda Alves • Our key finding was that making insecticide-treated feathers available to forty- spotted pardalotes was highly effective at facilitating “self- fumigation” by exploiting the natural behaviours of the species.

• The simple and low-cost method substantially boosted fledging success in self-fumigated nests; 95% of hatchlings survived to fledging in the treatment Adult forty-spotted pardalote in a nest lined with nests compared to just 8% of fumigated chicken feathers. Image: Fernanda Alves hatchlings in the control nests.

• The technique resulted in an immense improvement in the reproductive success of this Endangered pardalote, while avoiding many of survival. The survival rate of $8 per unit plus one hour of the disadvantages of more control nests in both studies assembly and deployment time. intrusive, less feasible and was the same, at 8%. This is such a low-cost approach that it may be feasibly deployed at more expensive techniques • In the self-fumigation trial, large enough scales to be suitable as such as manually spraying the forty-spotted pardalotes an effective conservation tool for the nests. Manual spraying involves made heavy use of the chicken Endangered forty-spotted pardalote. a significant time investment to feathers from the dispensers locate and access nests in tree when constructing their nests, Conservation actions can be hollows, and often requires both as lining for the nest criticised for not considering the challenging tree-climbing. By cup itself and also as a more importance of parasites to healthy contrast, in self-fumigation, general construction material. ecosystems. However, parasite the feathers are deployed just The higher survival rate found control is justifiable in the case of above ground level, so that in our self-fumigation study the forty-spotted pardalote, as it has no tree-climbing is necessary. than in the spray trial might been reduced to small and isolated reflect the use of treated • Our results found that populations that are experiencing feathers as a nesting material self-fumigation is not only the ill effects of cumulative within the nest interior, which substantially more cost- threatening processes, especially is likely to be a more effective effective than manual spraying habitat loss and limited availability defence against the parasitic and also more effective. An of nesting sites. Moreover, the fly larvae than spraying earlier trial involving manual parasite P. longicornis is a generalist outside the dome. The nest spraying forty-spotted that exploits the nestlings of other cavities naturally protect the pardalote nests with insecticide Tasmanian bird species, so control insecticide from degradation resulted in 89% survival of of it is unlikely to have a negative by sunlight and rain. hatchlings to fledging. Our self- conservation impact on fumigation experiment yielded Construction of the feather its populations, as other host a 6% improvement on nestling dispensers costs approximately species are available. Below: A nest box lined with fumigated chicken feathers. The method is not only simple and low-cost, it utilises the natural behaviour of the Endangered forty-spotted pardalote. Image: Fernanda Alves

Implementations and recommendations

The natural behaviour of forty- because parasitic flies are spotted pardalotes can be used widespread and affect a large range to facilitate self-fumigation of of species. The dispensers and nests. By hanging dispensers nesting material could be tailored filled with feathers treated with a to suit the ecology of many other bird-safe insecticide near forty- bird species as well as nest-building spotted pardalote nests, the birds mammals that are also afflicted themselves will take the insecticide by parasites – for example, by back to their nests and incorporate deploying the dispensers on it though the nest structure. the ground or using different nesting material. This method was found to be highly effective at improving This study also demonstrates chick survival in areas impacted the benefit that can be gained by parasitism. The method is by working with and utilising the also simple and low-cost, further natural behaviours of a threatened recommending it as a suitable species when approaching tool for conservation managers. a seemingly insurmountable conservation problem. Our results may have implications for many threatened bird species,

Cited material This factsheet summarises key findings from: Alves, F., Langmore, N., Heinsohn, R., Stojanovic, D. (2020). “Self- fumigation” of nests by an endangered avian host using insecticide-treated feathers increases reproductive success more than tenfold. Conservation. doi:10.1111/acv.12627

Further information Fernanda Alves [email protected] We used double hardware mesh for the dispensers and Imagesattached from a coverthe lives to ofslow cats degradation obtained by of video the insecticide camera collars, including a) fromplaying the with elements. a dragon; Image: b) eating Fernanda a gecko; Alves c) rabbit; and d) a mouse.

This project is supported through funding from the Australian Government’s National Environmental Science Program.