Island Syndrome Research Articles

Reproduction in the marsupial dibbler, Parantechinus apicalis; differences between island and mainland populations

Details of the reproductive endocrinology of the dibbler, Parantechinus apicalis, an endangered member of the Family Dasyuridae, are presented from two geographically-separated populations, living either on the mainland or on islands in Jurien Bay, Western Australia. Plasma free cortisol in males measured in the island population during 1998/9 did not differ between the breeding and non-breeding season, but during the March rut in 2000, when males died after breeding, free cortisol levels were significantly raised. Post-mating mortality in dibbler males is facultative, rather than obligatory and the cortisol data implicate the same physiological sequelae described in other dasyurids. In females, a single annual oestrus was recorded during late summer to autumn in both populations with an onset earlier by 12days in the mainland animals. Faecal steroids excreted as progesterone metabolites (PM) and oestradiol-17β were measured during the annual oestrous period and showed significantly higher PM concentrations in island animals. Oestradiol, although raised, was not different between the two populations. A profile of PM levels throughout gestation revealed a small peak at the time of ovulation, followed by slowly rising levels to peak 8days before birth, indicating slow development of the corpora lutea. Using collective data, the presumptive day of ovulation could be identified, allowing the calculation of a presumptive gestation length of 45days in dibblers from mainland populations. This gestation length compares with that of a related species, Pseudantechinus macdonnellensis, reported at 45–55days. A surprising finding is the significantly shorter gestation period of approximately 38days in island animals compared with those from the mainland. This and other differences between reproductive parameters of island and mainland populations are discussed in the context of the ‘island syndrome’.

Demographic aspects of the island syndrome in two Afrotropical Mastomys rodent species

The island syndrome is the name given to the particularities of the behavioural, morphological and demographical characteristics of island populations. As concerns demography, the island syndrome model states that densities and survival are greater in island than in mainland populations. Most previous studies aimed at confirming this prediction for small mammals have addressed species from the North Temperate Zone. Here, we tested the demographic expectations of the island syndrome using data gathered over two years for island and mainland populations of two African rodent species, Mastomys erytholeucus and Mastomys huberti, at two different sites in Senegal. Capture-Mark-Recapture methods allowing for variation in catchability of the individuals were used to yield estimates of both abundance (or density) and probability of survival and seniority (which is a demographic parameter inversely related to recruitment). As predicted from the island syndrome, survival and densities were indeed higher in island populations for the two study sites; however, only for the population with stronger island syndrome was the difference in survival biologically important. Estimates of the probability of seniority were similar for island and mainland populations at the two sites. Our findings provide support for the demographic expectations of the model of island syndrome in an Afrotropical context and thus confirm the general applicability of this syndrome while revealing differences according to particular insular situations.

Reproductive Biology of Insular Reptiles: Marine Subsidies Modulate Expression of the “Island Syndrome”

Differences in ecological conditions can result in the evolution of dramatic inter-population shifts in whole suites of traits. We studied variation in reproductive output in three lizard populations of the Skyros Wall Lizard (Podarcis gaigeae, Lacertidae) endemic to the Skyros Archipelago (Greece), which live under similar climatic conditions but differ in predation pressure and food availability. Based on the ‘‘island syndrome’’ hypothesis, we predicted that females from island populations would produce larger, but fewer offspring. The study populations differ conspicuously in average body size, with males from the satellite Lakonissi and Diavates islets being respectively 20% and 39% larger than males from the main Skyros Island. Lizards from these predator-free islets produced eggs of larger size than the main Skyros population; however, they also produced significantly larger clutches than the Skyros population (2.31±0.83 and 2.73±1.0 vs. 1.97±0.58 eggs). All inter-population differences in clutch size, clutch volume, and egg size were explained by corresponding differences in average body size of the dams, revealing that across all populations, reproductive effort scaled similarly with maternal body size. There was no evidence of trade-offs between egg size and clutch size as generally encountered in many reptile taxa. The occurrence of this unusual pattern of reproductive investment among islet populations of giants is probably best explained by the occurrence of two underlying drivers: first, the substantial marine subsidies by resident seabird colonies and second, the existence of intense cannibalistic behaviors in the form of attacks to the tail and severe intraspecific predation on juveniles. This suggests that subsidies-driven gigantism in island endemics may free species from such trade-offs and allow a population to maximize reproductive output in multiple, normally conflicting dimensions.

The island syndrome and population dynamics of introduced rats

The island syndrome predicts directional changes in the morphology and demography of insular vertebrates, due to changes in trophic complexity and migration rates caused by island size and isolation. However, the high rate of human-mediated species introductions to some islands also increases trophic complexity, and this will reduce the perceived insularity on any such island. We test four hypotheses on the role of increased trophic complexity on the island syndrome, using introduced black rats (Rattus rattus) on two isolated coral atolls in the Mozambique Channel. Europa Island has remained relatively pristine and insular, with few species introductions, whereas Juan de Nova Island has had many species introductions, including predators and competitors of rats, anthropogenically increasing its trophic complexity. In the most insular environments, the island syndrome is expected to generate increases in body size and densities of rodents but decreases in the rates of reproduction and population cycling. Morphology and reproduction were compared using linear regression and canonical discriminant analysis, while density and population cycling were compared using spatially explicit capture-recapture analysis. Results were compared to other insular black rat populations in the Mozambique Channel and were consistent with predictions from the island syndrome. The manifestation of an island syndrome in rodents depends upon the trophic composition of a community, and may not relate to island size alone when many species additions, such as invasions, have occurred. The differing patterns of rodent population dynamics on each island provide information for future rodent eradication operations.

Decline and recovery of the Island Fox: a case study for population recovery

Native only to the California Channel Islands, the island fox is the smallest canid in North America. Populations on four of the islands were threatened to extinction in the 1990s due to human-mediated predation and disease. This is the first account of the natural history and ecology of the island fox, illustrating both the vulnerability of island ecosystems and the efficacy of cooperative conservation measures. It explains in detail the intense conservation actions required to recover fox populations, such as captive breeding and reintroduction, and large-scale ecosystem manipulation. These actions were successful due in large part to extraordinary collaboration among the scientists, managers and public advocates involved in the recovery effort. The book also examines the role of some aspects of island fox biology, characteristic of the 'island syndrome', in facilitating their recovery, including high productivity and an apparent adaptation to periodic genetic bottlenecks.

Economic Growth and a Low Carbon Economy―Does the Earth Suffer from an “Easter Island Syndrome”?

The history of the Eastern Islands in the Pacific with an increasing over-utilization of natural resources reminds us of the mistakes modern societies are making and the question is obvious whether the Earth is suffering from an Eastern Islands Syndrome, in other words whether the egoism inherent in humans long-term might have fatal consequences for our species homo sapiens. Climate research identified two important phenomena, which should remind us of the Easter Islands: feedbacks and tipping points, i.e. self-accelerating phenomena of global warming and reaching irreversible points of climate change. Only a quick worldwide return to a low carbon economy is able to stabilize global warming on a bearable level. Both, Annex-I countries and Non-Annex-I countries have to contribute to reaching this goal taking their historical, current and future responsibilities into account. A post Kyoto regime based on cumulative per-capita CO2-emission rights and a international emission trading could provide for incentives to achieve a low carbon economy, especially for newly industrialized countries.

A CRANIOMETRIC INVESTIGATION OF THE FIELD VOLE MICROTUS AGRESTIS IN DENMARK - POPULATION SUBSTRUCTURE

A craniometric investigation using univariate and principal component analysis (PCA) was performed on 91 skull traits of 472 field voles, collected on nine islands and from the Jutland peninsula in Denmark in order to reveal possible geographical differences in skull shape and size. Because of missing values in the skulls due to various damages, only 186 individuals were measured for the dorsal side of the skull, 174 individuals for the ventral side and 154 individuals for the mandible. Of these traits, from the dorsal side of the skull 28 traits were measured, from the ventral side 33 traits and from the mandible 30 traits. With few exceptions, differences in skull shape were found between samples collected from the different islands, and also between samples from islands and samples from the Jutland peninsula. It is therefore suggested that field voles have a genetic differentiation between island and island and between island and mainland at the loci determining the shape of the skull. The field voles from some islands and the eastern part of the Jutland peninsula had the largest skulls compared with field voles from other islands and other parts of the Jutland peninsula. The origin of size differences is discussed and attributed to be due to several environmental factors as geographic variation in habitat quality but also as a consequence of the island syndrome.

The blue lizard spandrel and the island syndrome

BackgroundMany small vertebrates on islands grow larger, mature later, lay smaller clutches/litters, and are less sexually dimorphic and aggressive than their mainland relatives. This set of observations is referred to as the 'Island Syndrome'. The syndrome is linked to high population density on islands. We predicted that when population density is low and/or fluctuating insular vertebrates may evolve correlated trait shifts running opposite to the Island Syndrome, which we collectively refer to as the 'reversed island syndrome' (RIS) hypothesis. On the proximate level, we hypothesized that RIS is caused by increased activity levels in melanocortin receptors. Melanocortins are postranslational products of the proopiomelanocortin gene, which controls pleiotropically pigmentation, aggressiveness, sexual activity, and food intake in vertebrates.ResultsWe tested the RIS hypothesis performing a number of behavioral, genetic, and ontogenetic tests on a blue colored insular variant of the Italian Wall lizard Podarcis sicula, living on a small island off the Southern Italian coast. The population density of this blue-colored variant was generally low and highly fluctuating from one year to the next.In keeping with our predictions, insular lizards were more aggressive and sexually dimorphic than their mainland relatives. Insular males had wide, peramorphic heads. The growth rate of insular females was slower than growth rates of mainland individuals of both sexes, and of insular males. Consequently, size and shape dimorphism are higher on the Island. As predicted, melanocortin receptors were much more active in individuals of the insular population. Insular lizards have a higher food intake rate than mainland individuals, which is consistent with the increased activity of melanocortin receptors. This may be adaptive in an unpredictable environment such as Licosa Island. Insular lizards of both sexes spent less time basking than their mainland relatives. We suspect this is a by-product (spandrel) of the positive selection for increased activity of melanocortins receptors.ConclusionsWe contend that when population density is either low or fluctuating annually as a result of environmental unpredictability, it may be advantageous to individuals to behave more aggressively, to raise their rate of food intake, and allocate more energy into reproduction.

Insularity and the evolution of melanism, sexual dichromatism and body size in the worldwide‐distributed barn owl

Island biogeography has provided fundamental hypotheses in population genetics, ecology and evolutionary biology. Insular populations usually face different feeding conditions, predation pressure, intraspecific and interspecific competition than continental populations. This so-called island syndrome can promote the evolution of specific phenotypes like a small (or large) body size and a light (or dark) colouration as well as influence the evolution of sexual dimorphism. To examine whether insularity leads to phenotypic differentiation in a consistent way in a worldwide-distributed nonmigratory species, we compared body size, body shape and colouration between insular and continental barn owl (Tyto alba) populations by controlling indirectly for phylogeny. This species is suitable because it varies in pheomelanin-based colouration from reddish-brown to white, and it displays eumelanic black spots for which the number and size vary between individuals, populations and species. Females are on average darker pheomelanic and display more and larger eumelanic spots than males. Our results show that on islands barn owls exhibited smaller and fewer eumelanic spots and lighter pheomelanic colouration, and shorter wings than on continents. Sexual dimorphism in pheomelanin-based colouration was less pronounced on islands than continents (i.e. on islands males tended to be as pheomelanic as females), and on small islands owls were redder pheomelanic and smaller in size than owls living on larger islands. Sexual dimorphism in the size of eumelanic spots was more pronounced (i.e. females displayed much larger spots than males) in barn owls living on islands located further away from a continent. Our study indicates that insular conditions drive the evolution towards a lower degree of eumelanism, smaller body size and affects the evolution of sexual dichromatism in melanin-based colour traits. The effect of insularity was more pronounced on body size and shape than on melanic traits.

Comparison of life‐history characteristics of island and mainland populations of the swamp antechinus

AbstractThe reproductive ecology of the swamp antechinus Antechinus minimus, a small dasyurid (Dasyuridae) marsupial with obligate male semelparity, was investigated in populations inhabiting the mainland coast and on a nearby offshore island in south‐eastern Australia. The size and sex ratios of litters, individual body mass and size, timing of births and female longevity were determined from live‐trapped animals. The island population had significantly smaller litter sizes and greater adult body mass in comparison with the mainland population. This is consistent with features of the ‘island syndrome’, which predicts directional selection for these traits in high‐density populations with reduced extrinsic mortality. However, inter‐annual variability in litter sizes in the island population suggests that litter size is more responsive to fluctuating local conditions, such as population density, which is likely to affect food availability, rather than directional genetic changes. In contrast with other antechinus species, biased sex ratios were not evident. In addition, large variations of the timing of births were estimated at both sites and these appear to be related to seasonal conditions such as autumn rainfall and female body mass before mating.

Reproduction and Growth of a Rare, Island-Endemic Cavy (Cavia intermedia) from Southern Brazil

Cavia intermedia is a rare cavy, endemic to the 10-ha Moleques do Sul Island, southern Brazil. We conducted the 1st study of reproductive and growth patterns for this species in its natural environment. Based on 17 months of monthly population monitoring using capture–mark–recapture methods, females were reproductively active throughout the year. Litter size was small (1 or 2 young per litter), with well-developed offspring that weighed approximately 19% of the mass of an adult female. Sexual maturity was reached later than in other species of this genus, at around 59 days of age or 70% of adult body size. There was no evidence that longevity was longer than for congeneric species. Other than longevity, these characteristics are consistent with the island syndrome, which may contribute to the persistence of this species.

Circulating corticosterone levels in breeding blue tits Parus caeruleus differ between island and mainland populations and between habitats

Little is known about whether adaptations to an insular life also involve adaptations in basal corticosterone levels or in the adrenocortical stress response, thus being part of a genetically based island syndrome. However, differences in corticosterone between island and mainland may also be a direct phenotypic response to differences in environmental conditions or may depend on individual characteristics of the animal such as body condition or parental investment. In this paper, we investigated whether insular (Island of Corsica) and mainland (nearby Southern France) blue tits Parus caeruleus populations differed in baseline and handling-stress induced corticosterone levels during the breeding season as a response to biological changes of insular biota. We also examined whether corticosterone levels of both mainland and insular blue tits differed between birds living in two different habitats (summergreen and evergreen oak woods) that differ in food availability and whether individual characteristics affected corticosterone levels. We found (a) differences in baseline corticosterone plasma levels between Corsica and the mainland, independent of regional differences in fat scores, (b) a regional difference in the relationship between corticosterone levels and brood size, (c) a difference in the rapidity of onset of the stress response to handling between habitats, independent of region, and (d) a negative relationship between body fat stores and baseline corticosterone levels independent of region. Reduced baseline corticosterone levels on Corsica may be a component of the insular syndrome, allowing birds to be less aggressive and to enhance parental investment despite higher breeding densities. We suggest that baseline corticosterone levels are only elevated if food availability affects directly the parents. However, when conditions deteriorate unexpectedly (as mimicked by handling stress), food allocation between parents and offspring needs to be re-adjusted in favor of the parents, possibly by increased circulating corticosterone levels. The switch to self-maintenance seems to be modified by the amount of body energy stores.

Collapse of Easter Island

The collapse of Easter Island is one of the world's major archeological and anthropological mysteries. Small islands are closed systems, and they represent a microcosm of the planet Earth, which is also a closed system on a planetary scale. Observing and comprehending interconnected economic, social and ecological changes taking place in small islands is relatively straightforward. This article contends that we have been witnessing ‘Easter Island Syndrome’ signals; yet, we continue to ignore them at our peril. Under the dynamics of globalization, we have been liquidating finite natural capital at an unprecedented rate. If the current trends continue unchecked, many countries, particularly small islands, are likely to get caught in ‘Easter Island traps’.

Threatened Pollination Systems in Native Flora of the Ogasawara (Bonin) Islands

Various alien species have been introduced to the Ogasawara Islands (Japan). A survey was made investigating whether the native pollination systems fit an 'island syndrome' (biasing the flora to dioecy, with subdued, inconspicuous flowers) and whether alien species have disrupted the native pollination network. Flower visitors and floral traits were determined in the field (12 islands) and from the literature. Associations among floral traits such as sexual expression, flower colour and flower shape were tested. Among the 269 native flowering plants, 74.7 % are hermaphroditic, 13.0 % are dioecious and 7.1 % are monoecious. Classification by flower colour revealed that 36.0 % were white, 21.6 % green and 13.8 % yellow. Woody species (trees and shrubs) comprised 36.5 % of the flora and were associated with dioecy and white flowers. Solitary, endemic small bees were the dominant flower visitors and visited 66.7 % of the observed species on satellite islands where the native pollination networks are preserved. In contrast to the situation on the satellite islands, introduced honeybees were the most dominant pollinator (visiting 60.1 % of observed species) on the two main islands, Chichi-jima and Haha-jima, and had spread to satellite islands near Chichi-jima Island. The island syndrome for pollination systems in the Ogasawara Islands was evident in a high percentage of dioecious species, the subdued colour of the native flora and solitary flower visitors on satellite islands. The shape and colour adaptations of several flowers suggested native pollination niches for long-proboscis moths and carpenter bees. However, the domination and expansion of introduced honeybees have the potential for disruption of the native pollination network in the two main, and several satellite, islands of the Ogasawara Islands.

Are there differences in immune function between continental and insular birds?

Generally, immune system architecture varies with different environments, which presumably reflect different pathogen pressures. Specifically, populations from relatively disease-free, oceanic islands are expected to exhibit reorganized immune systems, which might be characterized by attenuated responses, given the costs of immune function. Some insular animals exhibit an 'island syndrome,' including increased susceptibility to disease, and some insular populations have declined when they failed to resist infection by introduced pathogens. I measured eight indices of immune function (haemolysis, haemagglutination, concentration of haptoglobin and concentration of five leukocyte types) in 15 phylogenetically matched pairs of bird populations from North America and from the islands of Hawaii, Bermuda and the Galápagos. Immune responses were not attenuated in insular birds, and several indices, including the concentration of plasma haptoglobin, were elevated. Thus, I find no support for the specific hypothesis that depauperate parasite communities and the costs of immune defences select for reduced immune function. Instead, I suggest that life on islands leads to an apparent reorganization of immune function, which is defined by increases in defences that are innate and inducible. These increases might signal that systems of acquired humoral immunity and immunological memory are less important or dysfunctional in island populations.

Parasites and the island syndrome: the colonization of the western Mediterranean islands by Heligmosomoides polygyrus (Dujardin, 1845)

AbstractAim Populations of free‐living vertebrates on islands frequently differ from their mainland counterparts by a series of changes in morphometric, life‐history, behavioural, physiological and genetic traits, collectively referred to as the ‘island syndrome’. It is not known, however, whether the ‘island syndrome’ also affects parasitic organisms. The present study establishes the colonization pattern of the Mediterranean islands by the nematode Heligmosomoides polygyrus, a direct and specific parasite of rodent hosts of the Apodemus genus, and evaluates the effects of island colonization by this species on two components of the island syndrome: the loss of genetic diversity and the enlargement of the ecological niche.Location Heligmosomoides polygyrus was sampled on seven western Mediterranean islands − Corsica, Crete, Elba, Majorca, Minorca, Sardinia and Sicily − as well as in 20 continental locations covering the Mediterranean basin.Methods The mitochondrial cytochrome b gene (690 base pairs) was sequenced in 166 adult H. polygyrus individuals sampled in the 27 continental and island locations. Phylogenetic reconstructions in distance, parsimony, maximum likelihood and Bayesian posterior probabilities were carried out on the whole cytochrome b gene data set. The levels of nucleotide, haplotype and genetic divergence (Kimura two‐parameter distance estimator) diversities were estimated in each island population and in the various continental lineages.Results Phylogenetic reconstructions show that the mainland origins of H. polygyrus were continental Spain for the Balearic Islands (Majorca, Minorca), northern Italy for the Tyrrhenian Islands (Corsica, Sardinia, Elba), southern Italy for Sicily, and the Balkan region for Crete. A comparison of island H. polygyrus populations with their mainland source populations revealed two characteristic components of the island syndrome in this parasite. First, island H. polygyrus populations display a significant loss of genetic diversity, which is related (r2 = 0.73) to the distance separating the island from the mainland source region. Second, H. polygyrus exhibits a niche enlargement following insularization. Indeed, H. polygyrus in Corsica is present in both A. sylvaticus and Mus musculus domesticus, while mainland H. polygyrus populations are present exclusively in Apodemus hosts.Main conclusions Our results show that H. polygyrus has undergone a loss of genetic diversity and a niche (host) enlargement following colonization of the western Mediterranean islands. To our knowledge, this study provides the first evidence for components of the ‘island syndrome’ in a parasitic nematode species.

‘Island syndrome’ in a population of Arctic foxes (Alopex lagopus) from Mednyi Island

AbstractComparative analysis of the biology of insular and mainland populations has demonstrated a number of differences in characteristics of insular populations, termed the ‘island syndrome’. A subspecies of Arctic fox on the Commander Islands (Alopex lagopus semenovi on Mednyi Island) has been isolated for an evolutionarily significant time in small territories at the periphery of the species' range. The number of foxes on Mednyi had been observed to be very high since the islands were discovered in 1741, but a drastic decline in population density in the late 1970s, owing to mange, has left the population low. The aim of the study was to determine whether the Mednyi Arctic fox population exhibited the features expected in an isolated insular population, such as difference in body size, increased population density, larger social groups, lower tendency to disperse and lower fertility, and whether any behavioural changes were evolutionarily reinforced or were a temporal response to current ecological factors on the island. Eight predictions were identified based on the island syndrome, of which the Mednyi Arctic foxes conformed to seven. We suggest a new prediction, namely that the tendency for increased sex dimorphism in dispersal may also be a distinguishing feature of insular populations. All the features displayed by the insular population on Mednyi – conservative use of space, increased tendency to form complex groups, decreased fertility and dispersal – seemed to be preserved regardless of the currently comparatively low populations. Thus, although foxes have been below carrying capacity for at least 10 generations, island syndrome characteristics have persisted.

The island syndrome in isolated populations of a tropical forest rodent.

I examined population traits of eight isolated populations of a tropical forest rodent (Proechimys semispinosus, the Central American spiny rat) for 1 year in central Panamá. Populations were sampled by monthly live-trapping, and seven traits (density, population growth rate, adult survival, reproductive effort, age structure, sex ratio, and body mass) were compared among populations. I also compared results with published data from nearby mainland populations. Each isolated population showed characteristics typical of island populations when compared with mainland populations, including higher and more stable densities, reduced reproductive effort, and greater body mass. Densities were the highest yet recorded for this species, and biomass of these island populations was among the highest of any tropical rodent yet studied. Population traits varied not only between island and mainland populations but also among island populations. P. semispinosus have traits that allow individuals in a population to rapidly respond to temporal changes in habitat quality or resource abundance. These traits include a high reproductive rate and an ability to adjust reproductive effort to changes in density. P. semispinosus are therefore able to quickly reach and maintain high densities under favorable conditions, thereby allowing close tracking of temporally and spatially varying resources. This flexibility is predicted for habitat generalists and presumably promotes abundance and persistence in temporally and spatially heterogeneous environments. P. semispinosus, often the most abundant and widely distributed species of rodent in forests throughout their geographic range, therefore have traits that are similar to those of generalist rodents in temperate forests.

The island syndrome in rodent populations.

Populations of rodents isolated on islands often show systematic differences in demography, reproduction, behavior, and morphology when compared to mainland populations. These differences, termed the island syndrome, include higher and more stable densities, better survival, increased body mass, and reduced aggressiveness, reproductive output, and dispersal. We synthesize information in the literature on island rodent populations and construct a conceptual model to explain the island syndrome. Population density and other manifestations of the island syndrome are predicted to increase with island isolation and to decrease with island area. The effect of isolation is direct by limiting dispersal, while the effect of area is less direct. As area increases, predators, competitors, and habitat structure increase in diversity. We suggest that the intensity or absence of density-depressing factors (primarily predation in communities comprised of only a few morphologically and trophically divergent species) is primarily responsible for the area effect and serves as a principal factor differentiating island from mainland populations of rodents. Other characteristics associated with the island syndrome may be the result of both short-term and long-term processes or responses. Short-term responses include reproductive, body size, and behavioral changes that may be phenotypic reaction norms in response to higher island densities. Thus, higher densities lead to reduced reproductive output, which then leads to greater body size. Initial behavioral differences may be owing to better survival and reduced dispersal, which result in less population turnover, greater neighbor familiarity, and less aggression. Long-term changes may be due to directional selection for reduced dispersal, increased body size in response to increased intraspecific competition, reduced reproductive output (smaller litters and delayed maturation) in response to reduced mortality schedules, and reduced aggressiveness. While the model is specific to rodent populations, the conclusions may be applicable to other systems if characteristics such as body size, vagility, and community composition are considered.

Do birds use biological control against nest parasites?

Hippoboscid flies, also known as louse flies, are obligate blood-feeders ectoparasites of birds and mammals. By studying louse fly parasites of four Passeriformes species, Eurasian blackbird (Turdus merula), Eurasian blackcap (Sylvia atricapilla), common chaffinch (Fringilla coelebs) and European robin (Erithacus rubecula), with dissimilar time of colonization of Azores islands, we tested whether: (i) island host populations have lower parasite richness than the mainland one; (ii) island host populations undergo higher parasite prevalence, mean intensities and mean abundance than the mainland one; (iii) island parasite diversity are composed exclusively by specific parasites and (iv) parasite richness is positively correlated with the island area and proximity to the continent. For these purposes, 775 birds were sampled for presence of louse flies, by modified fumigation chamber method, from Azores Islands (São Miguel, Terceira and Flores) and Portugal mainland. Insular and mainland parasite assemblages were statistically compared. We record for the first time to Azores, Ornithomya fringillina and Icosta minor from Portugal mainland. Louse flies had highest prevalence and abundance from Azores Islands compared to those observed in mainland birds, especially blackbirds. The insular parasite diversity of Azores blackbirds, blackcaps and chaffinches was richer than the one observed in mainland population. None of the hippoboscid flies observed on the islands and mainland were host-specific. Thus, our findings provide an upgrade of parasite island syndromes knowledge, in the context of the ectoparasites, namely to the hippoboscid flies case.