Urban living can rescue Darwin's finches from the lethal effects of invasive vampire flies

Human activity changes multiple factors in the environment, which can have positive or negative synergistic effects on organisms. However, few studies have explored the causal effects of multiple anthropogenic factors, such as urbanization and invasive species, on animals and the mechanisms that mediate these interactions. This study examines the influence of urbanization on the detrimental effect of invasive avian vampire flies (Philornis downsi) on endemic Darwin's finches in the Galápagos Islands. We experimentally manipulated nest fly abundance in urban and non-urban locations and then characterized nestling health, fledging success, diet, and gene expression patterns related to host defense. Fledging success of non-parasitized nestlings from urban (79%) and non-urban (75%) nests did not differ significantly. However, parasitized, non-urban nestlings lost more blood, and fewer nestlings survived (8%) compared to urban nestlings (50%). Stable isotopic values (δ15 N) from urban nestling feces were higher than those from non-urban nestlings, suggesting that urban nestlings are consuming more protein. δ15 N values correlated negatively with parasite abundance, which suggests that diet might influence host defenses (e.g., tolerance and resistance). Parasitized, urban nestlings differentially expressed genes within pathways associated with red blood cell production (tolerance) and pro-inflammatory response (innate immunological resistance), compared to parasitized, non-urban nestlings. In contrast, parasitized non-urban nestlings differentially expressed genes within pathways associated with immunoglobulin production (adaptive immunological resistance). Our results suggest that urban nestlings are investing more in pro-inflammatory responses to resist parasites but also recovering more blood cells to tolerate blood loss. Although non-urban nestlings are mounting an adaptive immune response, it is likely a last effort by the immune system rather than an effective defense against avian vampire flies since few nestlings survived.

Female in-nest attendance predicts the number of ectoparasites in Darwin's finch species

Selection should act on parental care and favour parental investment decisions that optimize the number of offspring produced. Such predictions have been robustly tested in predation risk contexts, but less is known about alternative functions of parental care under conditions of parasitism. The avian vampire fly (Philornis downsi) is a myasis-causing ectoparasite accidentally introduced to the Galápagos Islands, and one of the major mortality causes in Darwin's finch nests. With an 11-year dataset spanning 21 years, we examine the relationship between parental care behaviours and number of fly larvae and pupae in Darwin's finch nests. We do so across three host species (Camarhynchus parvulus, C. pauper, Geospiza fuliginosa) and one hybrid Camarhynchus group. Nests with longer female brooding duration (minutes per hour spent sitting on hatchlings to provide warmth) had fewer parasites, and this effect depended on male food delivery to chicks. Neither male age nor number of nest provisioning visits were directly associated with number of parasites. While the causal mechanisms remain unknown, we provide the first empirical study showing that female brooding duration is negatively related to the number of ectoparasites in nests. We predict selection for coordinated host male and female behaviour to reduce gaps in nest attendance, especially under conditions of novel and introduced ectoparasites.

House finches with high coccidia burdens experience more severe experimental Mycoplasma gallisepticum infections

Parasites co-infecting hosts can interact directly and indirectly to affect parasite growth and disease manifestation. We examined potential interactions between two common parasites of house finches: the bacterium Mycoplasma gallisepticum that causes conjunctivitis and the intestinal coccidian parasite Isospora sp. We quantified coccidia burdens prior to and following experimental infection with M. gallisepticum, exploiting the birds' range of natural coccidia burdens. Birds with greater baseline coccidia burdens developed higher M. gallisepticum loads and longer lasting conjunctivitis following inoculation. However, experimental inoculation with M. gallisepticum did not appear to alter coccidia shedding. Our study suggests that differences in immunocompetence or condition may predispose some finches to more severe infections with both pathogens.

Within-Lineage Divergence of Avian Haemosporidians: A Case Study to Reveal the Origin of a Widespread Haemoproteus Parasite

Avian haemosporidian parasites are particularly diverse and widespread. To date, more than 3,000 distinct cytochrome b lineages have been recorded, of which some present extremely wide geographical distributions, even including multiple continents. Whether these isolates represent one or several cryptic species remains unknown. Here we carried out a case study of SISKIN1, a common haemosporidian parasite lineage belonging to the morphologically described species Haemoproteus tartakovskyi. To shed light on its evolutionary origin, we investigated the divergence between SISKIN1 isolates obtained from siskins and redpolls in Europe (Russia and Sweden) and house finches in North America (Mexico). First, we used sequence capture of a small data set (2 Russian isolates and 1 Mexican isolate) to investigate the genetic structure based on the full-length mitochondrial genome and ∼1,000 genes. The mitochondrial genomes of Russian isolates were identical with each other but differed from the Mexican one at 6 positions. The nuclear divergence between Russian and Mexican isolates was on average 2.8%, close to what has been observed between 2 species of malaria parasites that respectively infect humans (Plasmodium falciparum) and gorillas (Plasmodium praefalciparum). Second, we used the expanded data set (15 samples in total) to investigate the genetic structure in 3 genes known to be involved in host invasion. The European isolates were identical across all sequenced genes, whereas the Mexican isolates were highly diverse. The lack of shared alleles between European and Mexican populations suggests that they might have diverged in isolation without gene flow. From the MalAvi database we examined the lineages most similar to the SISKIN1 barcode fragment (part of the cyt b gene) and found that most of them had been recorded in North and South America. This suggests that the lineage SISKIN1 originated in North America and subsequently spread to Europe. Our analyses support that the cyt b gene barcoding region is a useful marker for identification of avian haemosporidian lineages that can classify them into clusters of closely related parasites, but to further investigate species limits and evolutionary history, molecular data from multiple faster-evolving genes are required.

Experimental Infection and Clearance of Coccidian Parasites in Mercury-Exposed Zebra Finches

Mercury is a globally distributed, persistent environmental contaminant that affects the health of many taxa. It can suppress the immune system, which often plays a role in defense against parasites. However, there have been few investigations of whether mercury affects the abilities of animals to resist parasitic infection. Here, we exposed zebra finches to a lifetime dietary exposure of methylmercury (1.2 μg/g wet weight) and experimentally infected them with coccidian parasites to examine the effect of methylmercury exposure on parasitic infection. The mercury-exposed birds did not have an altered immune response (heterophil:lymphocyte ratio) nor a reduced ability to clear the infection. However, mercury-exposed birds tended to have higher parasite loads at the time when we expected the greatest immune response (2-3 weeks post-infection). Although mercury did not greatly influence the infection-course of this parasite in captivity, responses may be more accentuated in the wild where birds face additional immune challenges.

Morpho-functional variety of the coxal glands in cheyletoid mites (Prostigmata). II. Cheyletidae

Trombidiform mites are characterized by the presence of several paired glands in the anterior body portion united by a common conducting duct (podocephalic canal). Apart from the acinous (salivary) glands the podocephalic system includes a pair of tubular coxal glands (CGs) responsible for osmoregulation. The aim of the present study was to figure out how functional changes of acinous glands reflect on the corresponding CG. For this purpose, the anatomy and fine structure of the CG were analyzed in two mite species, Bakericheyla chanayi and Ornithocheyletia sp. (Cheyletidae), which have a different composition of their single acinous gland. The results showed that in both species the CG lacks a filtering saccule. It is composed of the proximal and distal tubes and leads into a cuticle-lined excretory duct. Both tubes demonstrate a similar species-specific fine structure. They are characterized by an extensive system of apical membrane invaginations (internal canals) associated with numerous large mitochondria. Local areas of modified internal canals were regularly observed in both species. They contain structures resembling those constituting filtering slit diaphragms of other animals. In O. sp., CG cells in addition demonstrate features characteristic of protein-like secretion. Apparently this correlates with the loss of true salivary glands in this species, as its acinous gland was previously assumed as silk producing. Contrary to this, the CG of B. chanayi shows no kind of granulation, which coincides with the presence of a salivary portion in its complex acinous gland. The microtubule-rich intercalary cells at the base of the excretory duct were associated with special muscles presumably regulating the dilation of the duct lumen. These cells might represent a basic feature common to different types of podocephalic glands.

Morphological and molecular characterization of Isospora neochmiae n. sp. in a captive-bred red-browed finch (Neochmia temporalis) (Latham, 1802)

A new Isospora (Apicomplexa: Eimeriidae) species is described from a single red-browed finch (Neochmia temporalis) (subspecies N. temporalis temporalis), that was part of a captive population in Western Australia. Sporulated oocysts of this isolate are spherical, 18.3 (18.2-18.9) × 18.2 (18.2-18.6) μm, with a shape index (length/width) of 1.0; and a smooth and bilayered oocyst wall, 1.2 μm thick (outer layer 0.9 μm, inner 0.3 μm). A polar granule is present, but the oocyst residuum and a micropyle are absent. The sporocysts are ovoid-shaped, 13.3 (9.5-16.4) × 8.6 (6.8-10.0) μm, with a shape index of 1.5. An indistinct Stieda body is present, but the substieda body is absent. A sporocyst residuum is present and composed of numerous granules of different size scattered among the sporozoites. Morphologically, the oocysts from this isolate are different from those of all known valid Isospora spp. Molecular analysis was conducted at 4 loci; the 18S and 28S ribosomal RNA (rRNA), the mitochondrial cytochrome oxidase (COI) gene and the heat shock protein 70 (hsp70) gene. At the 18S locus, this new isolate exhibited 99.9%, 99.8%, 99.7%, and 99.5% similarity to I. sp. MAH-2013a from a superb starling (Lamprotornis superbus), I. MS-2003 from a Southern cape sparrow (Passer melanurus), I. sp. Tokyo from a domestic pigeon (Columba livia domestica) and I. MS-2003 from a Surinam crested oropendula (Psarocolius decumanus). At the 28S locus, this new isolate exhibited 99.7% similarity to both an Isospora sp (MS-2003) from a Northern house sparrow (Passer domesticus) and an Isospora sp. (MS-2003) from a Southern cape sparrow. At the COI locus, this new isolate exhibited 98.9% similarity to an Isospora sp. ex Apodemus flavicollis. At the hsp70 locus, this new isolate exhibited 99% similarity to isolate MS-2003 (AY283879) from a wattled starling (Creatophora cinerea). Based on morphological and molecular data, this isolate is a new species of Isospora, which is named Isospora neochmiae n. sp. after its host, the red-browed finch (Neochmia temporalis).

Key to Species of the Genus Neocheyletiella (Acariformes: Cheyletidae), With Description of a New Species

A new species of the genus Neocheyletiella Baker, 1949 (Acariformes: Cheyletidae) is described from the zebra finch, Taeniopygia guttata (Viellot, 1817) (Passeriformes: Estrildidae), from a laboratory colony at the Massachusetts Institute of Technology, Cambridge, MA. The setal additions in the ontogeny of the new species, Neocheyletiella parvisetosa Mertins & Bochkov, and the main differential characters of all 17 known species of the genus Neocheyletiella are provided in tabular format. Keys to females and males of Neocheyletiella spp. also are given.

Invasive parasites, habitat change and heavy rainfall reduce breeding success in Darwin's finches

Invasive alien parasites and pathogens are a growing threat to biodiversity worldwide, which can contribute to the extinction of endemic species. On the Galápagos Islands, the invasive parasitic fly Philornis downsi poses a major threat to the endemic avifauna. Here, we investigated the influence of this parasite on the breeding success of two Darwin's finch species, the warbler finch (Certhidea olivacea) and the sympatric small tree finch (Camarhynchus parvulus), on Santa Cruz Island in 2010 and 2012. While the population of the small tree finch appeared to be stable, the warbler finch has experienced a dramatic decline in population size on Santa Cruz Island since 1997. We aimed to identify whether warbler finches are particularly vulnerable during different stages of the breeding cycle. Contrary to our prediction, breeding success was lower in the small tree finch than in the warbler finch. In both species P. downsi had a strong negative impact on breeding success and our data suggest that heavy rain events also lowered the fledging success. On the one hand parents might be less efficient in compensating their chicks' energy loss due to parasitism as they might be less efficient in foraging on days of heavy rain. On the other hand, intense rainfalls might lead to increased humidity and more rapid cooling of the nests. In the case of the warbler finch we found that the control of invasive plant species with herbicides had a significant additive negative impact on the breeding success. It is very likely that the availability of insects (i.e. food abundance)is lower in such controlled areas, as herbicide usage led to the removal of the entire understory. Predation seems to be a minor factor in brood loss.

Diverse wild bird host range of Mycoplasma gallisepticum in eastern North America

Emerging infectious diseases often result from pathogens jumping to novel hosts. Identifying possibilities and constraints on host transfer is therefore an important facet of research in disease ecology. Host transfers can be studied for the bacterium Mycoplasma gallisepticum, predominantly a pathogen of poultry until its 1994 appearance and subsequent epidemic spread in a wild songbird, the house finch Haemorhous mexicanus and some other wild birds. We screened a broad range of potential host species for evidence of infection by M. gallisepticum in order to answer 3 questions: (1) is there a host phylogenetic constraint on the likelihood of host infection (house finches compared to other bird species); (2) does opportunity for close proximity (visiting bird feeders) increase the likelihood of a potential host being infected; and (3) is there seasonal variation in opportunity for host jumping (winter resident versus summer resident species). We tested for pathogen exposure both by using PCR to test for the presence of M. gallisepticum DNA and by rapid plate agglutination to test for the presence of antibodies. We examined 1,941 individual birds of 53 species from 19 avian families. In 27 species (15 families) there was evidence for exposure with M. gallisepticum although conjunctivitis was very rare in non-finches. There was no difference in detection rate between summer and winter residents, nor between feeder birds and species that do not come to feeders. Evidence of M. gallisepticum infection was found in all species for which at least 20 individuals had been sampled. Combining the present results with those of previous studies shows that a diverse range of wild bird species may carry or have been exposed to M. gallisepticum in the USA as well as in Europe and Asia.

Experimental test of the effect of introduced hematophagous flies on corticosterone levels of breeding Darwin's finches

Parasites can negatively affect the evolutionary fitness of their hosts by eliciting physiological stress responses. Parasite-induced stress can be monitored by measuring changes in the adrenal steroid hormone corticosterone. We examined the effect of an invasive parasite on the corticosterone concentrations of a common species of Darwin's finch, the medium ground finch (Geospiza fortis). Philornis downsi (Diptera: Muscidae) is a parasitic nest fly recently introduced to the Galapagos Islands, where it feeds on the blood of nestlings and breeding adult female finches. Previous work shows that P. downsi significantly reduces the reproductive success of several species of finches. We predicted that the effect of P. downsi on host reproductive success is mediated by stress responses in breeding female finches. High stress levels could reduce the ability of females to invest in offspring, thus decreasing their reproductive success. To test this hypothesis, we experimentally manipulated the abundance of P. downsi in nests, then measured baseline and acute stress-induced corticosterone levels, body condition, and hematocrit (red blood cell content). Acute stress-induced corticosterone levels increased over baseline levels, but this response did not differ significantly with parasite treatment. There was also no significant difference in the body condition or hematocrit of females from parasitized versus non-parasitized nests. Our results suggest that the lower reproductive success of females from parasitized nests is not mediated by a physiological stress response.

The emergence and spread of finch trichomonosis in the British Isles

Finch trichomonosis, caused by the protozoal parasite Trichomonas gallinae, was first recognized as an emerging infectious disease of British passerines in 2005. The first year of seasonal epidemic mortality occurred in 2006 with significant declines of greenfinch Carduelis chloris and chaffinch Fringilla coelebs populations. Here, we demonstrate that large-scale mortality, principally of greenfinch, continued in subsequent years, 2007-2009, with a shifting geographical distribution across the British Isles over time. Consequent to the emergence of finch trichomonosis, the breeding greenfinch population in Great Britain has declined from ca 4.3 million to ca 2.8 million birds and the maximum mean number of greenfinches (a proxy for flock size) visiting gardens has declined by 50 per cent. The annual rate of decline of the breeding greenfinch population within England has exceeded 7 per cent since the initial epidemic. Although initially chaffinch populations were regionally diminished by the disease, this has not continued. Retrospective analyses of disease surveillance data showed a rapid, widespread emergence of finch trichomonosis across Great Britain in 2005 and we hypothesize that the disease emerged by T. gallinae jumping from columbiforms to passeriforms. Further investigation is required to determine the continuing impact of finch trichomonosis and to develop our understanding of how protozoal diseases jump host species.

Evidence of spread of the emerging infectious disease, finch trichomonosis, by migrating birds

Finch trichomonosis emerged in Great Britain in 2005 and led to epidemic mortality and a significant population decline of greenfinches, Carduelis chloris and chaffinches, Fringilla coelebs, in the central and western counties of England and Wales in the autumn of 2006. In this article, we show continued epidemic spread of the disease with a pronounced shift in geographical distribution towards eastern England in 2007. This was followed by international spread to southern Fennoscandia where cases were confirmed at multiple sites in the summer of 2008. Sequence data of the ITS1/5.8S/ITS2 ribosomal region and part of the small subunit (SSU) rRNA gene showed no variation between the British and Fennoscandian parasite strains of Trichomonas gallinae. Epidemiological and historical ring return data support bird migration as a plausible mechanism for the observed pattern of disease spread, and suggest the chaffinch as the most likely primary vector. This finding is novel since, although intuitive, confirmed disease spread by migratory birds is very rare and, when it has been recognised, this has generally been for diseases caused by viral pathogens. We believe this to be the first documented case of the spread of a protozoal emerging infectious disease by migrating birds.

Experimental demonstration of the fitness consequences of an introduced parasite of Darwin's finches

BACKGROUND

Introduced parasites are a particular threat to small populations of hosts living on islands because extinction can occur before hosts have a chance to evolve effective defenses. An experimental approach in which parasite abundance is manipulated in the field can be the most informative means of assessing a parasite's impact on the host. The parasitic fly Philornis downsi, recently introduced to the Galápagos Islands, feeds on nestling Darwin's finches and other land birds. Several correlational studies, and one experimental study of mixed species over several years, reported that the flies reduce host fitness. Here we report the results of a larger scale experimental study of a single species at a single site over a single breeding season.

METHODOLOGY/PRINCIPAL FINDINGS

We manipulated the abundance of flies in the nests of medium ground finches (Geospiza fortis) and quantified the impact of the parasites on nestling growth and fledging success. We used nylon nest liners to reduce the number of parasites in 24 nests, leaving another 24 nests as controls. A significant reduction in mean parasite abundance led to a significant increase in the number of nests that successfully fledged young. Nestlings in parasite-reduced nests also tended to be larger prior to fledging.

CONCLUSIONS/SIGNIFICANCE

Our results confirm that P. downsi has significant negative effects on the fitness of medium ground finches, and they may pose a serious threat to other species of Darwin's finches. These data can help in the design of management plans for controlling P. downsi in Darwin's finch breeding populations.

A new species of Brueelia Kéler (Phthiraptera: Philopteridae) parasitic on the Common Diuca-Finch, Diuca diuca diuca (Aves: Emberizidae) in Chile

A new species of the genus Brueelia Kéler is described as parasitic on the Common Diuca-Finch, Diuca diuca diuca, based on specimens from three localities in Chile: Punitaqui (Coquimbo Province), La Rinconada (Colchagua Province) and Chillán (Nuble Province). The species is fully described and illustrated, and brief comments on its morphological affinities with allied species are also made.

Mycoplasma gallisepticum infection in house finches (Carpodacus mexicanus) affects mosquito blood feeding patterns

Disease-induced lethargy can diminish host capacity to repel or kill biting mosquitoes. We exposed house finches (Carpodacus mexicanus) to mosquitoes (Culex pipiens pipiens), repeated the experiment after inoculating finches with Mycoplasma gallisepticum, and then repeated the experiment with the same birds after curing their infections. We videotaped avian behaviors before and during mosquito exposure, identifying hosts through blood meal DNA fingerprinting. Results revealed heterogeneity in mosquito preference regardless of infection. Mosquitoes choosing between two healthy finches were more likely to feed upon the same individual bird consistently. When one bird was sick, mosquitoes exhibited no preference. Sick birds made fewer total defensive behaviors than healthy birds, but only foot stomps were associated with reduced mosquito feeding success. Our results suggest that Mycoplasma and other avian infections that alter bird defensive behavior may influence mosquito feeding patterns and transmission of arthropod-borne pathogens such as West Nile virus.

Three new species of Isospora Schneider, 1881 (Apicomplexa: Eimeriidae) from the lesser seed-finch, Oryzoborus angolensis (Passeriformes: Emberizidae) from Brazil

Three new coccidian (Apicomplexa: Eimeriidae) species are reported from the lesser seed-finch, Oryzoborus angolensis from Brazil. Sporulated oocysts of Isospora curio n. sp. are spherical to subspherical; 24.6 x 23.6 (22-26 x 22-25) microm, shape-index (SI, length/width) of 1.04 (1.00-1.15). Oocyst wall is bilayerd, approximately 1.5 microm thick, smooth and colourless. Micropyle and oocyst residuum are absent. The sporocysts are ovoid, 13.2 x 10.9 (15-17 x 10-13) microm, SI = 1.56 (1.42-1.71), with a small Stieda body and residuum composed of numerous granules scattered among the sporozoites. Sporozoites are elongated and posses a smooth surface and two distinct refractile bodies. Oocysts of Isospora braziliensis n. sp. are spherical to subspherical, 17.8 x 16.9 (16-19 x 16-18) microm, with a shape-index of 1.06 (1.00-1.12) and a smooth, single-layered wall approximately 1 microm thick. A micropyle, oocyst residuum and polar granules are absent. Sporocysts are ellipsoid and slightly asymmetric, 13.2 x 10.8 (12-14 x 9-12) microm, SI = 1.48 (1.34-1.61). Each sporocyst contains a barely visible Stieda body and a residuum composed numerous of granules. Sporozoites are elongated and each of them contains two distinct refractile bodies. Oocysts of Isospora paranaensis n. sp. are subspherical to broadly ellipsoid 24.3 x 19.8 (22-26 x 18-22) microm, SI = 1.22 (1.15-1.38) with smooth single-layered wall approximately 1.5 microm thick. A micropyle and oocyst residuum are absent, but one distinct ellipsoid polar granule (2.5-3.5 x 1.5-2.5 microm) is present. Sporocyst are ovoid, 15.7 x 10.1 (14-18 x 8-12) microm, SI = 1.46 (1.31-1.72), with distinct Stieda and sub-Stieda bodies. Each sporocyst contains a spherical sporocyst residuum, 4 microm in diameter All described isosporan species represent a possible cause of acute coccidiosis for O. angolensis in captivity.

Phylogeographic structuring of Plasmodium lineages across the North American range of the house finch (Carpodacus Mexicanus)

The determinants of the geographic distribution of avian hematozoa are poorly understood. Sampling parasites from one avian host species across a wide geographic range is an accepted approach to separate the potential influence of host species distribution from geographic effects not directly related to host species biology. We used polymerase chain reaction to screen samples for hematozoan infection from 490 house finches (Carpodacus mexicanus) collected at 8 sites spanning continental North America. To explore geographic patterns of parasite lineage distributions, we sequenced a portion of the mitochondrial cytochrome b gene of Plasmodium species infecting 77 house finches. We identified 5 distinct Plasmodium haplotypes representing 3 lineages that likely represent 3 species. One lineage was common at all sites where we detected Plasmodium species. The second lineage contained 3 haplotypes that showed phylogeographic structuring on a continent-wide scale, with 1 haplotype common in eastern North America and 2 common in western North America. The third divergent lineage was recovered from 1 individual host. Considered together, the partial phylogeographic structuring of Plasmodium cytochrome b lineages over the range of the house finch suggests that parasite lineage distribution is not solely dependent on host species distribution, and other factors such as arthropod vector competence and distribution may be important.

Dispersal ecology versus host specialization as determinants of ectoparasite distribution in brood parasitic indigobirds and their estrildid finch hosts

Brood parasitic birds offer a unique opportunity to examine the ecological and evolutionary determinants of host associations in avian feather lice (Phthiraptera). Brood parasitic behaviour effectively eliminates vertical transfer of lice between parasitic parents and offspring at the nest, while at the same time providing an opportunity for lice associated with the hosts of brood parasites to colonize the brood parasites as well. Thus, the biology of brood parasitism allows a test of the relative roles of host specialization and dispersal ecology in determining the host-parasite associations of birds and lice. If the opportunity for dispersal is the primary determinant of louse distributions, then brood parasites and their hosts should have similar louse faunas. In contrast, if host-specific adaptations limit colonization ability, lice associated with the hosts of brood parasites may be unable to persist on the brood parasites despite having an opportunity for colonization. We surveyed lice on four brood parasitic finch species (genus Vidua), their estrildid finch host species, and a few ploceid finches. While Brueelia lice were found on both parasitic and estrildid finches, a molecular phylogeny showed that lice infesting the two avian groups belong to two distinct clades within Brueelia. Likewise, distinct louse lineages within the amblyceran genus Myrsidea were found on estrildid finches and the parasitic pin-tailed whydah (Vidua macroura), respectively. Although common on estrildid finches, Myrsidea lice were entirely absent from the brood parasitic indigobirds. The distribution and relationships of louse species on brood parasitic finches and their hosts suggest that host-specific adaptations constrain the ability of lice to colonize new hosts, at least those that are distantly related.

Sex-biased maternal effects reduce ectoparasite-induced mortality in a passerine bird

Duration of developmental stages in animals evolves under contrasting selection pressures of age-specific mortality and growth requirements. When relative importance of these effects varies across environments, evolution of developmental periods is expected to be slow. In birds, maternal effects on egg-laying order and offspring growth, two proximate determinants of nestling period, should enable rapid adjustment of developmental periods to even widely fluctuating mortality rates. We test this hypothesis in a population of house finches (Carpodacus mexicanus) breeding under two contrasting mortality risks: (i) a nest mite-free condition when selection on offspring survival favors a longer time in the nest; and (ii) a mite infestation when selection favors a shorter nest tenure. Mites affected survival of sons more than daughters, and females breeding under mite infestation laid male eggs last and female eggs first in the clutch, thereby reducing sons' exposure to mites and associated mortality. Strong sex bias in laying order and growth patterns enabled mite-infested offspring to achieve similar fledging size, despite a shorter nest tenure, compared with mite-free conditions. In mite-infested nests, male nestlings hatched at larger sizes, completed growth earlier, and had faster initial growth compared with mite-free nests, whereas mite-infested females grew more slowly but for a longer period of time. A combination of heavily sex-biased laying order and sex differences in growth patterns lowered mite-induced mortality by >10% in both sexes. Thus, strong maternal effects can account for frequently observed, but theoretically unexpected, concordance of mortality risks and growth patterns, especially under fluctuating ecological conditions.

The life-cycle of Philornis downsi (Diptera: Muscidae) parasitizing Darwin's finches and its impacts on nestling survival

The fly, Philornis downsi Dodge & Aitken, was first collected in 1964 on the Galápagos Islands and is now widespread across the archipelago. Virtually nothing is known about the behaviour and ecology of the fly as well as for the genus in general. Here, we describe all larval instars for the first time, and discuss infection intensity and impacts of parasitism on nestling survival of Darwin's finches. Adult P. downsi are non-parasitic free-living flies, whereas the larvae are obligate blood-feeding parasites on nestling birds. The larvae show a marked shift in their host site specificity--a novel finding for the genus Philornis: the first and early second larval instars live as agents of myiasis in finch nostrils and other tissues, while the older second and third instar larvae reside in the nest material and feed externally on the blood of nestlings, leading to blood losses in nestlings of 18-55%. Pupation occurs in the bottom layer of the nest. The combined effects of tissue damage by the endoparasitic instar larvae and anaemia by nest-dwelling haematophagous instar larvae account for the high nestling mortality (76%) due to Philornis parasitism. This represents the highest mortality by Philornis reported in the literature and emphasizes the extremely serious threat this parasite poses for the endemic passerine fauna of the Galápagos Islands.

Mites associated with the small ground finch, Geospiza fuliginosa (Passeriformes: Emberizidae), from the Galápagos Islands

In collections of ectoparasites from 368 small ground finches, Geospiza fuliginosa, in populations from the islands of Isabela, Santa Cruz, San Cristóbal, and Santa Fé, in the Galápagos Archipelago, Ecuador, we found 8 species of mites. Four mite species were common on all islands sampled, i.e., Mesalgoides geospizae Mironov and Pérez (Psoroptoididae), Xolalges palmai Mironov and Pérez (Xolalgidae), and 2 new species, Trouessartia geospiza n. sp. (Trouessartiidae) and Proctophyllodes darwini n. sp. (Proctophyllodidae). Four other species were represented by single collections from G. fuliginosa, i.e., Pterodectes atyeoi n. sp. (Proctophyllodidae), Strelkoviacarus sp. (Analgidae), Dermoglyphus sp. (Dermoglyphidae), and Dermanyssus sp. (Dermanyssidae). Authorship of new species names is attributed to the 3 authors who prepared the descriptions (B.M.O.C., J.F., D.L.). Trouessartia geospiza and P. atyeoi were also found on previously collected specimens of other Geospiza species in museum collections. For the 4 common species, we found no differences in prevalence among the 4 island populations, but infection prevalence differed among the 4 species. The mean infection prevalence was high for T. geospizae (89%), moderate for M. geospizae (58%) and X. palmai (44%), and low for P. darwini (26%) in all populations. The feather mite fauna of G. fuliginosa was similar to that of other Geospiza species, and generally related to communities found on other emberizid finches.