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![Twelve-day-old tropical mockingbird nestling with approximately 70 subcutaneous Philornis trinitensis larvae [Photo by Jordan Herman].](profile/Sarah-Knutie/publication/313018521/figure/fig1/AS:455505211596800@1485612313986/Twelve-day-old-tropical-mockingbird-nestling-with-approximately-70-subcutaneous-Philornis.png)
Twelve-day-old tropical mockingbird nestling with approximately 70 subcutaneous Philornis trinitensis larvae [Photo by Jordan Herman].
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Introduced parasites threaten host populations around the world. For example, introduced parasitic nest flies (Philornis downsi) have contributed to the decline of several species of Darwin's finches in the Galápagos Islands. Introduced parasites are thought to have severe effects on native hosts because the hosts do not have effective defenses aga...
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... days. After the eggs hatch, nestlings spend about 15 days in the nest prior to fledging (Ffrench 1991). Adult P. trinitensis flies, which are not parasitic, lay their eggs in the nests of both grassquits and mocking- birds. Once the fly eggs hatch, the larvae burrow beneath the skin of the nestlings, where they feed on blood and other fluids (Fig. ...
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Citations
... The copyright holder for this preprint this version posted September 28, 2024. ; https://doi.org/10.1101/2024.09.26.615210 doi: bioRxiv preprint partial explanation for its invasiveness (74). The main known enemies of Philornis spp. in their native range are parasitoid wasps that attack the pupal stage (51,74,75). ...
... ; https://doi.org/10.1101/2024.09.26.615210 doi: bioRxiv preprint partial explanation for its invasiveness (74). The main known enemies of Philornis spp. in their native range are parasitoid wasps that attack the pupal stage (51,74,75). In contrast, parasitoids of Philornis are exceedingly rare in Galápagos and only include generalist species (24, 76). ...
Invasive species disrupt island ecosystems, posing significant threats to native species. The avian vampire fly (Philornis downsi), introduced into the Galapagos Islands, has become a major threat to endemic birds including Darwins finches, yet the genetic mechanisms of its invasion remain unclear. This study used whole-genome sequencing of P. downsi populations from Galapagos and its native range in mainland Ecuador, revealing reduced genetic diversity in Galapagos, indicative of a recent bottleneck. We found evidence of ongoing gene flow among island populations and identified regions under positive selection near genes related to neural signaling, muscle development, and metabolic processes, which may have contributed to the fly invasion success in Galapagos. These findings highlight the importance of genomic research for mitigating the impact of P. downsi on Galapagos biodiversity.
... Thus, any reduction in the body mass of parasitized nestlings may have been masked by the weight of the parasites themselves. Similarly, P. trinitensis parasites of tropical mockingbirds in Tobago, which are also subcutaneous, reduce tarsus growth but not the apparent body mass of nestlings (Knutie et al., 2017). By comparison, P. downsi larvae, which are not subcutaneous but live in the nest, do significantly reduce the body mass of Galápagos mockingbird nestlings (Knutie et al., 2016). ...
Co‐parasitism is ubiquitous and has important consequences for the ecology and evolution of wild host populations. Studies of parasite co‐infections remain limited in scope, with few experimental tests of the fitness consequences of multiple parasites, especially in natural populations.
We measured the separate and combined effects of Philornis seguyi nest flies and shiny cowbirds Molothrus bonariensis on the fitness of a shared host, the chalk‐browed mockingbird (Mimus saturninus) in Argentina.
Using a two‐factor experimental approach, we manipulated the presence of nest flies and cowbirds in mockingbird nests and assessed their effects on mockingbird haemoglobin levels, begging and provisioning rates, body size, and fledging success. We also monitored rates of nest predation in relation to parasitism by flies and cowbirds.
Nest flies reduced the haemoglobin concentration, body size, and fledging success of mockingbirds, likely because mockingbirds did not compensate for parasitism by begging more or feeding their nestlings more. Cowbirds also reduced the fledging success of mockingbirds, even though they had no detectable effect on haemoglobin or body size. Nests with cowbirds, which beg more than mockingbirds, attracted more nest predators. There was no significant interaction between the effects of flies and cowbirds on any component of mockingbird fitness. The combined effects of nest flies and cowbirds were strictly additive.
In summary, we show that nest flies and cowbirds both reduce host fitness, but do not have interactive effects in co‐parasitized nests. Our results further suggest that predators exacerbate the effects of nest flies and cowbirds on their hosts. Our study shows that the fitness consequences of co‐parasitism are complex, especially in the context of community‐level interactions.
... Despite their widespread distribution (Teixeira 1999), there is little information about Philornis ecology in their native range. On Tobago, the native parasitic fly Philornis trinitensis decreased reproductive success of black-faced grassquits (Tiaris bicolor) while having almost no effect on that of tropical mockingbirds (Mimus gilvus; Knutie et al. 2017). This difference in the effect of parasitism seemed to be due to a behavioral response by infected mockingbirds that served to mitigate the cost of parasitism on nestlings. ...
... We defined abundance of larvae as the number of larvae per live nestling on a given date. We defined prevalence of infestation as the presence of at least one nest fly larva or pupa in a Ridgway's hawk nest, either detected on a nestling or within the nest substrate after the death of a nestling (see Knutie et al. 2017). We measured age as nestling age in days and visit date is the day of year as a decimal number (001-366). ...
... Another possibility is that prevalence or abundance of P. pici in Los Haitises is influenced by some other reservoir host species. Knutie et al. (2016Knutie et al. ( , 2017 found that mockingbird spp. in the Galápagos and on Tobago were tolerant of Philornis infestations, thus possibly promoting Philornis parasitism of nestlings in their corresponding ecosystem. The northern mockingbird is native to Hispaniola, where it is common (BirdLife International 2017). ...
Understanding parasite-host ecology is increasingly important for conservation efforts in a changing world. Parasitic nest flies in the genus Philornis (Diptera: Muscidae) have been implicated in the decline of endemic island species and are also known to negatively impact breeding success of the critically endangered Ridgway’s hawk (B. ridgwayi) on the island of Hispaniola. Despite the importance of these effects on hosts, and extensive research of Philornis downsi in the Galápagos, the ecology of most species of philornid nest flies is poorly understood. We examined biotic factors related to Philornis pici infestations of nestling Ridgway’s hawks in the Dominican Republic, where both fly and hawk are native. We found grass-cover was negatively associated with P. pici infestations, while coverage and height of other vegetation classes (tree, shrub, herbaceous, and bare ground) had no association, which is interesting considering recent landscape-level changes to Ridgway’s hawk habitat. Anthropogenic activities in Los Haitises National Park, the last strong-hold of Ridgway’s hawk, have shifted the landscape from primary forest to a fragmented secondary forest with smallholder or subsistence farms and grassy patches. New information on the ecology of nest flies in their native habitat can inform conservation efforts and allow us to make recommendations for future research.
... Ants are known as population regulatory agents of many insects (Finnegan, 1969;Cerdá & Dejean, 2011;Fernandes et al., 2012;Platner et al., 2012;Brown et al., 2015;Campolo et al., 2015) and have been reported to predate various stages of insect development (Morris et al., 1998;Urbaneja et al., 2006;Fernandes et al., 2012;Campolo et al., 2015), including ectoparasite pupae (Kaunisto et al., 2016). The presence of ants in bird nests has been previously recorded but poorly studied (Hanmer et al., 2017;Knutie et al., 2017;Gibson et al., 2019). Knutie et al. (2017) detected ants and wasps as possible predators of the bird nestlings' parasite Philornis trinitensis (Diptera: Muscidae), when sampling grassquits (Genus Tiaris) and mockingbirds (genus Mimus) nests in Tobago island, and Gibson et al. (2019) found a negative association between Tapinoma sessile presence and fly larvae abundance in Brown thrasher nests (Toxostoma rufum). ...
... The presence of ants in bird nests has been previously recorded but poorly studied (Hanmer et al., 2017;Knutie et al., 2017;Gibson et al., 2019). Knutie et al. (2017) detected ants and wasps as possible predators of the bird nestlings' parasite Philornis trinitensis (Diptera: Muscidae), when sampling grassquits (Genus Tiaris) and mockingbirds (genus Mimus) nests in Tobago island, and Gibson et al. (2019) found a negative association between Tapinoma sessile presence and fly larvae abundance in Brown thrasher nests (Toxostoma rufum). ...
1. Parasites are one of the main actors in host–parasite interactions. Still, their role as a prey and the related consequences for such interactions and in other respects, such as food webs, are frequently overlooked.
2. This paper analyses predation pressure on a ubiquitous avian ectoparasitic fly, Carnus hemapterus, identifies their main natural enemies and quantifies their relative effect on the abundance of the parasite. Also, the effect of nest‐site type on their main enemies' predation pressure was analysed.
3. Several ant species were found in the nest boxes of the host species, the European roller (Coracias garrulus), during the breeding season and preyed upon adult and larval stages of Carnus.
4. Ants were also the putative predators of carnid pupae after the breeding season, when significant reduction (on average, by half) in the abundance of carnid pupae occurred in 75% of nest boxes within few months.
5. Carnid pupae are also reported here, for the first time, to be parasitised by the parasitoid wasp Chartocerus conjugalis, whose prevalence was around 21%.
6. Nest‐site type had no clear effect on the predation rate of carnid pupae after the breeding season.
7. It was concluded that predation is an important factor regulating the abundance of ectoparasites, and thus, it may influence the outcome of host–parasite relationships.
... The probability of a nest becoming infected depends primarily on host taxa, a fact that is apparent when the infection rates of two or more host species living in a same area are compared (Lopes and Marini 2005, Rabuffetti and Reboreda 2007, Knutie et al. 2017. Infection is usually linked with decreased body condition of nestlings (Uhazy and Arendt 1986, Norris et al. 2010, O'Connor et al. 2010a, Hayes et al. 2019. ...
... Additionally, when the larvae move to the bottom of the nest for pupation, a denser nest wall protects them from removal attempts by the parents Dudaniec 2016, Ursino et al. 2019) or by predators, such as ants (O'Connor et al. 2010b, Knutie et al. 2017. Secondary components in some plant species can act as parasite repellents and may be used in nest construction (Wimberger 1984, Clark 1990, Quiroga et al. 2012. ...
Parasitic botfly larvae (Philornis ssp., Diptera: Muscidae) are found in nests of several bird taxa, although prevalence and impact on nestling survival vary considerably among species. Here we describe patterns of botfly infestation in Blue‐black grassquit (Volatinia jacarina) nestlings. We identified the most typically affected nestling body parts and assessed parasite prevalence, impact on nestling survival, changes in nestling body shape. Additionally, we tested whether climatic conditions, nest morphology and habitat characteristics are associated with larvae abundance. Blue‐black grassquits had low breeding success (16% of eggs/nestlings survive to fledge; 19% of the nests fledge at least one), but most failures resulted from predation by vertebrate predators. We estimated that 1% of nestlings died due to botfly infestation, and the number of subcutaneous larvae (range 1‐18) in a nestling's body did not predict fledging success. Infected chicks exhibited a higher tarsus asymmetry. Thus, we argue that although botflies had a small impact on offspring survival, they may reduce fitness in adulthood. There was no evidence that environmental conditions and nest morphology are linked to the number of larvae on nestlings. Nesting areas with higher food supply had lower infestation rates. Possibly, food‐rich habitats allow parents to invest more time in offspring care (brooding nestlings), thus protecting them from fly attacks. Alternatively, vegetation composition could influence local invertebrate diversity, which could provide a natural trophic buffer against adult Philornis. The present study brings to light new perspectives concerning bird‐botfly interaction.
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... Permethrin is also used for experimentally manipulating ectoparasite load in nests for research purposes. Species whose nests have been treated with permethrin include purple martins (Progne subis; Moss and Camin, 1970), cliff swallows (Hirundo pyrrhonota; Brown and Brown, 1986), barn swallows (Hirundo rustica; Møller, 1990), blue tits (Cyanistes caeruleus; Tomás et al., 2007;Lobato et al., 2008), pied flycatchers (Ficedula hypoleuca; Lobato et al., 2008), red grouse (Lagopus lagopus; Mougeot et al., 2008), tropical mockingbirds (Mimus gilvus; Knutie et al., 2017), blackfaced grassquits (Tiaris bicolor; Knutie et al., 2017) and barn owls (Tyto alba; Efstathion et al., 2019). ...
... Permethrin is also used for experimentally manipulating ectoparasite load in nests for research purposes. Species whose nests have been treated with permethrin include purple martins (Progne subis; Moss and Camin, 1970), cliff swallows (Hirundo pyrrhonota; Brown and Brown, 1986), barn swallows (Hirundo rustica; Møller, 1990), blue tits (Cyanistes caeruleus; Tomás et al., 2007;Lobato et al., 2008), pied flycatchers (Ficedula hypoleuca; Lobato et al., 2008), red grouse (Lagopus lagopus; Mougeot et al., 2008), tropical mockingbirds (Mimus gilvus; Knutie et al., 2017), blackfaced grassquits (Tiaris bicolor; Knutie et al., 2017) and barn owls (Tyto alba; Efstathion et al., 2019). ...
Permethrin is increasingly used for parasite control in bird nests, including nests of threatened passerines. We present the first formal evaluation of the effects of continued permethrin exposure on the reproductive success and liver function of a passerine, the zebra finch (Taeniopygia guttata), for two generations. We experimentally treated all nest material with a 1% permethrin solution or a water control and provided the material to breeding finches for nest building. The success of two consecutive clutches produced by the parental generation and one clutch produced by first-generation birds were tracked. Finches in the first generation were able to reproduce and fledge offspring after permethrin exposure, ruling out infertility. Permethrin treatment had no statistically significant effect on the number of eggs laid, number of days from clutch initiation to hatching, egg hatch rate, fledgling mass or nestling sex ratio in either generation. However, treating nest material with permethrin significantly increased the number of hatchlings in the first generation and decreased fledgling success in the second generation. Body mass for hatchlings exposed to permethrin was lower than for control hatchlings in both generations, but only statistically significant for the second generation. For both generations, an interaction between permethrin treatment and age significantly affected nestling growth. Permethrin treatment had no effect on liver function for any generation. Permethrin was detected inside 6 of 21 exposed, non-embryonated eggs (28.5% incidence; range: 693–4781 ng of permethrin per gram of dry egg mass). Overall, results from exposing adults, eggs and nestlings across generations to permethrin-treated nest material suggest negative effects on finch breeding success, but not on liver function. For threatened bird conservation, the judicious application of this insecticide to control parasites in nests can result in lower nestling mortality compared to when no treatment is applied. Thus, permethrin treatment benefits may outweigh its sub-lethal effects.
... Differences in infection risk between nestlings and adults may also occur because altricial nestlings are developing an immune response to parasites and therefore might not be immunocompetent while still in the nest Knutie et al. 2017). Birds can produce an immunoglobulin Y (IgY) antibody-mediated immune response to Philornis spp. ...
... Birds can produce an immunoglobulin Y (IgY) antibody-mediated immune response to Philornis spp. and other similar parasitic flies (Koop et al. 2013;Knutie et al. 2016;Knutie et al. 2017;DeSimone et al. 2018;Grab et al. 2019;Knutie 2020). However, this response is likely an acquired immune response, which often requires repeated exposures to the host to become effective. ...
Philornis flies Meinert (Diptera: Muscidae) have been documented parasitizing over 250 bird species, some of which are endemic species threatened with extinction. Philornis parasitism is hypothesized to affect nestlings disproportionately more than adult birds because limited mobility and exposed skin of nestlings increase their vulnerability to parasitism. We used a comprehensive literature review and our recent fieldwork in the Dominican Republic, Puerto Rico, and Grenada to challenge the idea that parasitism by subcutaneous Philornis species is a phenomenon primarily found in nestlings, a fact that has not been quantified to date. Of the 265 reviewed publications, 125 (49%) reported incidences of parasitism by subcutaneous Philornis, but only 12 included the sampling of adult breeding birds. Nine of these publications (75%) reported Philornis parasitism in adults of ten bird species. During fieldwork in the Dominican Republic, Puerto Rico, and Grenada, we documented 14 instances of parasitism of adult birds of seven avian species. From literature review and fieldwork, adults of at least fifteen bird species across 12 families and four orders of birds were parasitized by at least five Philornis species. In both the published literature and fieldwork, incidences of parasitism of adult birds occurred predominantly in females and was frequently associated with incubation. Although our findings indicate that Philornis parasitism of adult birds is more common than widely presumed, parasite prevalence is still greater in nestlings. In the future, we recommend surveys of adult birds to better understand host-Philornis relationships across life stages. This information may be essential for the development of effective control measures of Philornis to ensure the long-term protection of bird species of conservation concern.
... Permethrin is also used for experimentally manipulating ectoparasite load in nests for research purposes. Species whose nests have been treated with permethrin include purple martins (Progne subis; Moss and Camin, 1970), cliff swallows (Hirundo pyrrhonota; Brown and Brown, 1986), barn swallows (Hirundo rustica; Møller, 1990), blue tits (Cyanistes caeruleus; Tomás et al., 2007;Lobato et al., 2008), pied flycatchers (Ficedula hypoleuca; Lobato et al., 2008), red grouse (Lagopus lagopus; Mougeot et al., 2008), tropical mockingbirds (Mimus gilvus; Knutie et al., 2017), blackfaced grassquits (Tiaris bicolor; Knutie et al., 2017) and barn owls (Tyto alba; Efstathion et al., 2019). ...
... Permethrin is also used for experimentally manipulating ectoparasite load in nests for research purposes. Species whose nests have been treated with permethrin include purple martins (Progne subis; Moss and Camin, 1970), cliff swallows (Hirundo pyrrhonota; Brown and Brown, 1986), barn swallows (Hirundo rustica; Møller, 1990), blue tits (Cyanistes caeruleus; Tomás et al., 2007;Lobato et al., 2008), pied flycatchers (Ficedula hypoleuca; Lobato et al., 2008), red grouse (Lagopus lagopus; Mougeot et al., 2008), tropical mockingbirds (Mimus gilvus; Knutie et al., 2017), blackfaced grassquits (Tiaris bicolor; Knutie et al., 2017) and barn owls (Tyto alba; Efstathion et al., 2019). ...
Philornis downsi is a bird-parasitic fly native to mainland South America that invaded the Galapagos Islands where it is pushing some Darwin’s Finch species over the brink of extinction. Flies lay eggs in bird nests and the larvae feed on nestlings, often killing them. Protecting Galapagos landbirds from this parasite is a conservation priority. A short-term solution involves providing permethrin-treated cotton to the finches or injecting wild nests with permethrin. However, the risk of permethrin to long-term bird health and reproduction has not been formally tested. Our experiment represents a worst-case scenario to determine the effects of exposure to permethrin in Zebra Finches (Taeniopygia guttata) across consecutive generations. The experiment consisted of two treatments. Treatment finches received nesting material sprayed with 1% solution of permethrin and control finches received nesting material sham-fumigated with water. The parental generation laid two clutches of eggs (F1.1 and F1.2). Adults reared from the F1.1 clutch were used to establish a second generation (F2). Blood was drawn to evaluate liver function by assaying aspartate aminotransferase and bile acids levels. Permethrin treatment affected hatching mass for both the F1 and F2 generations. Birds exposed to permethrin produced smaller nestlings than controls. The F2 control birds hatched all nestlings, whereas F2 treatment pairs only fledged 70% of nestlings. Treatment had no effect on liver function tests for any generation. Our study represents a worst-case scenario and permethrin exposure for birds in the field would likely be much lower than doses tested in this experiment.
... The extent to which this activity protects these birds from Philornis infection is not known. In terms of physiological defences, brooding females of Darwin's Finches have been shown to produce antibodies in response to P. downsi infection in some studies (Huber et al. 2010, Koop et al. 2013b) but not others ( Knutie et al. 2016Knutie et al. , 2017. However, even in cases where an immune response was detected, this response was not effective at helping nestlings survive parasitism ( Koop et al. 2013b). ...
... A recent study showed that Mimus parvulus and M. gilvus exhibited high levels of tolerance to P. downsi and P. trinitensis, respectively . Nestlings of these species can tolerate heavy Philornis parasitism without suffering decreased fledging rates or weights although parasitism by P. trinitensis did reduce the length of the primary feather and tarsus of M. gilvus fledglings ( Knutie et al. 2017). In a study of the Galápagos Mockingbird M. parvulus, nestlings in parasitised nests exhibited enhanced begging behaviour and this resulted in increased parental feeding, which can likely compensate for blood lost to parasitism ). ...
... This study showed how a tolerant Philornis host (the Great Kiskadee) can serve as a 'reservoir host' that puts less tolerant hosts (thornbirds) at increased risk of attack by producing high numbers of parasites. A similar argument has been made for P. downsi and P. trinitensis attacking both larger-bodied tolerant host species and smaller host species that suffer more negative fitness effects of parasitism ( Knutie et al. 2016Knutie et al. , 2017Heimpel et al. 2017). ...
The declining-population paradigm holds that small populations are particularly vulnerable to anthropogenic influences such as habitat destruction, pollution and species introductions. While the effects of particular stressors, such as parasitism, may be unimportant in a large, healthy population, they can be serious and even devastating in situations characterised by a restricted geographic range, or by fragmented or reduced population sizes. We apply this idea to nest parasitism of threatened Neotropical bird species that exist in small populations, focusing on dipteran nest parasites in the genus Philornis . We review the literature on Philornis parasitism exerting negative pressure on bird populations that have become small and isolated due to human actions and present a new case of Philornis parasitism of a threatened hummingbird species. Our aim is to raise awareness about the exacerbating effect that nest parasites can have on small and declining bird populations; especially when biological information is scarce. The five reviewed cases involve two species of Darwin’s Finches in the Galápagos Islands attacked by the invasive P. downsi , two species of hawks on islands in the Caribbean attacked by the native P. pici and P. obscura , and the Yellow Cardinal Gubernatrix cristata in southern South America attacked by an unknown Philornis species. We also present new documentation of parasitism of a threatened hummingbird species in mainland Ecuador by an unidentified Philornis species. We recommend more field studies to determine the presence of nest parasites in bird populations worldwide to improve understanding how nest parasites affect bird fitness and population viability and to allow time to act in advance if needed. Parasitism by Philornis may represent a severe mortality factor in most already threatened bird species, putting them at greater risk of extinction. Therefore, parasitism management should be included in all threatened species recovery plans.
... 770 bird species found on Caribbean islands, 73 are threatened with extinction and 12 are considered Critically Endangered (BirdLife International 2016). Although parasitism by Philornis spp. is known to occur in Caribbean birds, parasite-host ecology remains almost completely unquantified except in two native songbird species (see Knutie et al., (2017)). Improving our understanding of Philornis-host relationships may prove important to bird conservation. ...
... In both introduced and native ranges of nest flies, host response to parasitism varies by host species. Mockingbird (Mimus spp.) nestlings in the Gal apagos, where nest flies are introduced, and on Tobago, where they are native, demonstrated immune and behavioral responses to parasitism, and survived heavy nest fly loads (Knutie, 2014;Knutie et al., 2017). In contrast, Darwin's finches (Gal apagos) and blackfaced grassquits Tiaris bicolor, (Tobago) suffered severe declines in productivity due to nest flies (Koop et al., 2011;Knutie et al., 2017). ...
... Mockingbird (Mimus spp.) nestlings in the Gal apagos, where nest flies are introduced, and on Tobago, where they are native, demonstrated immune and behavioral responses to parasitism, and survived heavy nest fly loads (Knutie, 2014;Knutie et al., 2017). In contrast, Darwin's finches (Gal apagos) and blackfaced grassquits Tiaris bicolor, (Tobago) suffered severe declines in productivity due to nest flies (Koop et al., 2011;Knutie et al., 2017). In Puerto Rico, pearly-eyed thrasher Margarops fuscatus nestlings survived infestations of >60 nest fly larvae (Arendt, 1985), whereas infestations as low as two nest fly larvae were associated with mortality in a nonpasserine host, Puerto Rican sharp-shinned hawk Accipiter striatus venator, Delannoy & Cruz, 1991). ...
Parasitic nest flies Philornis spp. are a driving force threatening the extinction of bird species endemic to Neotropical islands such as the Galápagos, where introduced Philornis downsi negatively impacts reproductive success of naïve avian hosts. Elsewhere in the Neotropics, such as in the Caribbean region where Philornis nest flies are native, effects of Philornis on host productivity are poorly known. We manipulated parasitism by the native Hispaniolan nest fly Philornis pici on a critically endangered endemic host, Ridgway's hawk Buteo ridgwayi, to study the impact of nest fly myiasis on hawk breeding success with the goal of providing a management option for endangered species until broad‐scale solutions can be found. Our treatment protocol was enough to reduce P. pici abundance by 89% and increase probability of fledging by 179% for treated nestlings. Our results indicate that parasitism by nest flies decreases survival and fledging success of nestling Ridgway's hawks and is a possible factor in the decline of the species. To the best of our knowledge, this work represents the first quantitative evidence of nest fly impact on survival or productivity in a non‐passerine host.
