Use of alternate upland nesting habitat reduces brood parasitism in an endangered bird

Parasites can cause great fitness cost to their hosts, however, their impact on host populations is often unknown. In healthy populations, parasites are not expected to cause declines, but they can be devastating to small and/or declining populations. Nest ectoparasites can have detrimental impacts on the breeding output of their hosts and are emerging as a threat to several endangered bird species. Therefore, finding cost‐effect ways to reduce the impact of parasites on endangered hosts is crucial. Although ‘close‐order’ management techniques available to manage nest parasites are effective, they are often expensive and might not be suitable for species that are intolerant of intensive manipulation. We tested a low cost, ‘close‐order’ management technique to control parasites and boost nest productivity in an endangered passerine. The endangered forty‐spotted pardalote Pardalotus quadragintus is exploited by an ectoparasitic fly Passeromyia longicornis, an obligate subcutaneous parasite of nestling birds. We offered adult pardalotes the opportunity to ‘self‐fumigate’ their nests by supplying feathers treated with insecticide with which to line their nests and tested whether this boosted nest productivity. Pardalotes readily incorporated the experimental feathers in nest building, and survival of hatchlings was significantly higher in nests lined with treated feathers (95%) compared to nests lined with control feathers (8%). This represents a substantially greater improvement in reproductive success than in previous experimental studies, offering the strongest evidence yet that self‐fumigation is a highly effective, simple and low cost ‘close‐order’ management technique for defending endangered birds against ectoparasites.

Haematophagous parasites can negatively impact breeding success and their control is often the target of management for threatened bird species. Mitigating parasitism can be difficult and certainly should only be done if parasite control is possible and if successful control improves host species fitness. Here, we use an experiment to test the effect of two alternative chemical methods ofOrnithonyssus bursamanagement in nests of a threatened host species, the New Zealand hihiNotiomystis cincta. We compared a reactive management alternative using Frontline®(active ingredient fipronil) to controlO. bursainfestations after detection to a preventative management alternative using Avian Insect Liquidator (AIL) spray (active ingredients piperonyl butoxide (PBO), permethrin and methoprene) before egg laying. We found that AIL‐treated nests were less likely to be parasitized and parasitism occurred later in nestling development if nests did become parasitized. We also found no difference in egg hatchability nor nestling condition between alternative management approaches but did find nest success was higher in preventative AIL‐treated nests. Our approach highlights the value of an experimental approach in assessing management alternatives in threatened species conservation and the host fitness benefits that can be achieved from control of costly parasitism.

Confronting the invasive species crisis with metamodel analysis: An explicit, two-species demographic assessment of an endangered bird and its brood parasite in Puerto Rico

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Antiparasite behavior

Learning from parents during early development may crucially influence future mate choice decisions of birds. Such sexual imprinting is thought to be important to many fields of evolutionary ecology, including sexual selection, hybridization, speciation, and interspecific brood parasitism. Most results have been obtained from controlled experiments on captive birds. Hence, there is a need to study sexual imprinting and the development of species recognition under more natural circumstances. I have cross-fostered a migratory bird, the pied flycatcher Ficedula hypoleuca, to nests of two resident species, the larger great tit Parus major, and the smaller blue tit P. caeruleus, by adding a single egg to the clutch, or by swapping whole clutches. No cross-fostered bird recruited to the local breeding population from the mixed brood treatment but sample size was small. However, for the whole brood treatment, cross-fostering had no apparent effect, compared to controls, on local recruitment, natal dispersal, mating success, breeding success, or sexual display responses to intruders. Hence, there were no signs that the cross-fostered birds were sexually imprinted on the host. The results are discussed in relation to sexual imprinting, natal dispersal, interspecific brood parasitism, and conservation of endangered birds.

The Shiny Cowbird (Molothrus bonariensis) is an avian brood parasite that could represent a threat for the survival of some endangered birds. To evaluate this potential problem for threatened or endemic wetland species, we estimated the abundance of Molothrus bonariensis and studied its behavior, its association with vegetation and its interspecific interactions in 19 wetlands located in the Bogotá area, Colombia. We found densities between 0 and 2.24 ind./ha, which are significantly lower than those of the Yellow-hooded Blackbird (Chrysomus icterocephalus), a known host. Urban wetlands presented higher cowbird densities than semiurban and rural wetlands together. The cowbirds showed a strong association with introduced trees between 10.1 and 15 m high, isolated from other trees and with medium foliage densities, as well as with stands of bulrush. Only 4.5% of the cowbirds observed were interacting with individuals of other species, mostly the blackbird, which sometimes evicted the cowbird from its territories. We conclude that the abundance of Molothrus bonariensis may not yet represent a serious threat for most species it parasitizes with the exception of Apolinar’s Wren (Cistothorus apolinari), which is in such a precarious situation that the presence of only a few cowbirds could be disastrous for its persistence.