Long-term trends in first arrival and first egg laying dates of some migrant and resident bird species in northern Italy

Climate change is affecting the phenology of seasonal events in Europe and the Northern Hemisphere, as shown by several studies of birds’ timing of migration and reproduction. Here, we analyse the long-term (1982–2006) trends of first arrival dates of four long-distance migratory birds [swift (Apus apus), nightingale (Luscinia megarhynchos), barn swallow (Hirundo rustica), and house martin (Delichon urbicum)] and first egg laying dates of two migrant (swift, barn swallow) and two resident species [starling (Sturnus vulgaris), Italian sparrow (Passer italiae)] at a study site in northern Italy. We also addressed the effects of local weather (temperature and precipitation) and a climate index (the North Atlantic Oscillation, NAO) on the interannual variability of phenological events. We found that the swift and the barn swallow significantly advanced both arrival and laying dates, whereas all other species did not show any significant temporal trend in either arrival or laying date. The earlier arrival of swifts was explained by increasing local temperatures in April, whereas this was not the case for arrival dates of swallows and first egg laying dates of both species. In addition, arrival dates of house martins were earlier following high NAO winters, while nightingale arrival was earlier when local spring rainfall was greater. Finally, Italian sparrow onset of reproduction was anticipated by greater spring rainfall, but delayed by high spring NAO anomalies, and swift’s onset of reproduction was anticipated by abundant rainfall prior to reproduction. There were no significant temporal trends in the interval between onset of laying and arrival in either the swift or the barn swallow. Our findings therefore indicate that birds may show idiosyncratic responses to climate variability at different spatial scales, though some species may be adjusting their calendar to rapidly changing climatic conditions.     

The Cliff Swallow Bug Oeciacus vicarius (Hemiptera: Cimicidae) in Florida: ectoparasite implications for hole-nesting birds

In May 1988, ten juvenile birds, not yet ready to fledge, jumped to their death from a colony of the purple martin, Progne subis near Okeechobee City, Florida. The martin house and nestlings were found to be infested with ectoparasitic Oeciacus vicarius Horvath, the cliff swallow bug, not previously reported from Florida. This ectoparasite infestation apparently led to early abandonment of two houses by the adult martins. Oeciacus vicarius therefore represents a possible threat to all hole-nesting birds.     

Timing of incorporation of docosahexaenoic acid into brain and muscle phospholipids during precocial and altricial modes of avian development

We investigated the possibilities that the proportion of docosahexaenoic acid (DHA) in phospholipids of brain and skeletal muscle at hatch, and the ontogenetic timing of the DHA accretion spurt in these tissues, might serve as indices of neonatal functional maturity that discriminate between precocial and altricial avian developmental modes. Comparison of the fatty acid profiles of the initial and residual yolks of two free-living altricial species, the swallow (Hirundo rustica) and the sparrow (Passer domesticus), reveals that, in contrast to precocial birds, there is no preferential uptake of DHA from the yolk during embryonic development. At hatch, the proportions of DHA in brain phospholipid (wt.% of fatty acids) of the swallow and sparrow, at 8.1% and 5.0%, respectively, are far lower than the values (16.9-19.6%) reported for non-altricial species. This reflects a marked difference in the timing of the brain DHA accretion spurt, which occurs during the first half of the embryonic period of precocial birds, but is largely delayed until after hatching in the altricial species. By the time of fledging, the proportion of DHA in the swallow brain phospholipid has increased to 14.3%. For non-altricial birds, the brain DHA concentration at hatch shows little interspecies variation, despite major differences in yolk DHA content. The proportions of DHA in leg muscle phospholipid of the newly hatched swallow and sparrow, at 2.9% and 2.5%, respectively, are far lower than the value (6.7%) for the precocial chicken. Again, this relates to differences in developmental timing, with muscle DHA accretion occurring in the first half of the chicken's embryonic period, whereas, in the swallow, this increase is delayed until after hatching. By the time of fledging in the swallow, DHA forms 9.3% of muscle phospholipid fatty acids, equivalent to the level attained in chicken muscle at the mid-embryo stage. The results indicate a clear distinction between altricial and non-altricial avian species in the timing of tissue DHA accretion during development, presumably reflecting differences in neonatal functional maturity.     

Immune Responses of a Native and an Invasive Bird to Buggy Creek Virus (Togaviridae: Alphavirus) and Its Arthropod Vector,the Swallow Bug (Oeciacus vicarius)

Invasive species often display different patterns of parasite burden and virulence compared to their native counterparts. These differences may be the result of variability in host-parasite co-evolutionary relationships, the occurrence of novel host-parasite encounters, or possibly innate differences in physiological responses to infection between invasive and native hosts. Here we examine the adaptive, humoral immune responses of a resistant, native bird and a susceptible, invasive bird to an arbovirus (Buggy Creek virus; Togaviridae: Alphavirus) and its ectoparasitic arthropod vector (the swallow bug; Oeciacus vicarius). Swallow bugs parasitize the native, colonially nesting cliff swallow (Petrochelidon pyrrhonota) and the introduced house sparrow (Passer domesticus) that occupies nests in cliff swallow colonies. We measured levels of BCRV-specific and swallow bug-specific IgY levels before nesting (prior to swallow bug exposure) and after nesting (after swallow bug exposure) in house sparrows and cliff swallows in western Nebraska. Levels of BCRV-specific IgY increased significantly following nesting in the house sparrow but not in the cliff swallow. Additionally, house sparrows displayed consistently higher levels of swallow bug-specific antibodies both before and after nesting compared to cliff swallows. The higher levels of BCRV and swallow bug specific antibodies detected in house sparrows may be reflective of significant differences in both antiviral and anti-ectoparasite immune responses that exist between these two avian species. To our knowledge, this is the first study to compare the macro- and microparasite-specific immune responses of an invasive and a native avian host exposed to the same parasites.     

Group size and nest spacing affect Buggy Creek virus (Togaviridae: Alphavirus) infection in nestling house sparrows

The transmission of parasites and pathogens among vertebrates often depends on host population size, host species diversity, and the extent of crowding among potential hosts, but little is known about how these variables apply to most vector-borne pathogens such as the arboviruses (arthropod-borne viruses). Buggy Creek virus (BCRV; Togaviridae: Alphavirus) is an RNA arbovirus transmitted by the swallow bug (Oeciacus vicarius) to the cliff swallow (Petrochelidon pyrrhonota) and the introduced house sparrow (Passer domesticus) that has recently invaded swallow nesting colonies. The virus has little impact on cliff swallows, but house sparrows are seriously affected by BCRV. For house sparrows occupying swallow nesting colonies in western Nebraska, USA, the prevalence of BCRV in nestling sparrows increased with sparrow colony size at a site but decreased with the number of cliff swallows present. If one nestling in a nest was infected with the virus, there was a greater likelihood that one or more of its nest-mates would also be infected than nestlings chosen at random. The closer a nest was to another nest containing infected nestlings, the greater the likelihood that some of the nestlings in the focal nest would be BCRV-positive. These results illustrate that BCRV represents a cost of coloniality for a vertebrate host (the house sparrow), perhaps the first such demonstration for an arbovirus, and that virus infection is spatially clustered within nests and within colonies. The decreased incidence of BCRV in sparrows as cliff swallows at a site increased reflects the "dilution effect," in which virus transmission is reduced when a vector switches to feeding on a less competent vertebrate host.     

Development of parameters influencing blood oxygen carrying capacity in the welcome swallow and fairy martin

Welcome swallow (Hirundo neoxena) and fairy martin (Petrochelidon ariel) nestlings develop relatively slowly. They exceed adult mass early in development, then lose weight and fledge at about adult mass, i.e. have a mass-overshoot-recession (Mor) growth profile. Development of parameters influencing blood oxygen carrying capacity (O2Cap) was documented to determine if O2Cap also reached a plateau substantially before fledging or increased continuously throughout nestling development. Hematocrit (Hct), erythrocyte count (RBC) and whole blood haemoglobin (Hb) increased 1.8- to 2.8-fold, so that O2Cap doubled during development in both species. Increase in Hct, Hb and RBC was not continuous, peak values occurring well before fledging, in contrast to passerines with standard growth profiles in which the increase occurs throughout nestling development and peak values occur at fledging. However, the timing of O2Cap increase differed from that in some other Mor species (e.g. shearwaters). Mean erythrocyte volume (MCV) decreased linearly throughout development by 30-41%, but mean erythrocyte haemoglobin content (MCH) remained constant, so that mean erythrocyte haemoglobin concentration (MCHC) increased linearly 1.3- to 1.5-fold. Possible reasons for the apparent differences in the timing of O2Cap increase between rapidly and slowly growing altricial species and among MOR species are discussed.     

Role of peridomestic birds in the transmission of St. Louis encephalitis virus in southern California

In response to the 1984 St. Louis encephalitis (SLE) epidemic in the Los Angeles Basin of southern California (USA), an investigative program was initiated to evaluate the interactive components of the SLE virus transmission cycle. From 1987 through 1996 (10 yr), 52,589 birds were bled and their sera tested for SLE and western equine encephalomyelitis (WEE) virus antibodies by the hemagglutination inhibition (HAI) test. Eighty-three percent of the birds tested were house finches (Carpodacus mexicanus) (48.7%) and house sparrows (Passer domesticus) (34.6%); 1.1% of these birds were positive for SLE antibodies. Prevalence of WEE antibodies was negligible. The analysis of 5,481 sera from rock doves (Columbia livia) yielded 3.6% SLE positives and 0.4% WEE positives. Collection sites were maintained as study sites when identified as positive bird, mosquito, and SLE virus activity localities; others were abandoned. Serial serum samples from 7,749 banded house sparrows and 9,428 banded house finches from these selected sites demonstrated year-round SLE virus transmission. One location exhibited significant numbers of house finches undergoing annual SLE seroconversion and a number of seroconversion-reversion-reconversion sequences suggesting either viral reinfection from mosquitoes or recrudescence by latent virus. A proportion of both bird species also lived for longer than 1 yr, thus, increasing the possibility of virus carry-over from autumn to spring. Assessment of concurrently collected mosquitoes indicated no correlative association between mosquito populations and SLE seroconversion and reconversion. European house sparrows introduced in the 1800's may have provided a supplemental link to the existing SLE virus enzootic cycle involving endemic house finches. Meteorological factors are reviewed as possible important correlates of SLE epidemics. The house finch/house sparrow serosurveillance system is also evaluated for use as an "Early Warning" indicator of SLE virus activity.     

Hybrid speciation in sparrows I: phenotypic intermediacy,genetic admixture and barriers to gene flow

Homoploid hybrid speciation is thought to require unusual circumstances to yield reproductive isolation from the parental species, and few examples are known from nature. Here, we present genetic evidence for this mode of speciation in birds. Using Bayesian assignment analyses of 751 individuals genotyped for 14 unlinked, nuclear microsatellite loci, we show that the phenotypically intermediate Italian sparrow (Passer italiae) does not form a cluster of its own, but instead exhibits clear admixture (over its entire breeding range) between its putative parental species, the house sparrow (P. domesticus) and the Spanish sparrow (P. hispaniolensis). Further, the Italian sparrow possesses mitochondrial (mt) DNA haplotypes identical to both putative parental species (although mostly of house sparrow type), indicating a recent hybrid origin. Today, the Italian sparrow has a largely allopatric distribution on the Italian peninsula and some Mediterranean islands separated from its suggested parental species by the Alps and the Mediterranean Sea, but co‐occurs with the Spanish sparrow on the Gargano peninsula in southeast Italy. No evidence of interbreeding was found in this sympatric population. However, the Italian sparrow hybridizes with the house sparrow in a sparsely populated contact zone in the Alps. Yet, the contact zone is characterized by steep clines in species‐specific male plumage traits, suggesting that partial reproductive isolation may also have developed between these two taxa. Thus, geographic and reproductive barriers restrict gene flow into the nascent hybrid species. We propose that an origin of hybrid species where the hybrid lineage gets geographically isolated from its parental species, as seems to have happened in this system, might be more common in nature than previously assumed.     

Extrapair paternity and hybridization in birds

Hybridization in birds is a widely acknowledged phenomenon. It often occurs when one species is absent or rare which leads to mixed pairings between different species (Hubb's principle). However, Hubb's principle cannot explain hybridization in one of the most common Passeriform hybrids, barn swallow Hirundo rustica ×house martin Delichon urbica , since these hybrids usually occurred in areas where both species were common. Such hybrids were often found as singletons between true barn swallows siblings suggesting that extrapair copulations, and not mixed breeding pairs, might be the reason for the existence of these hybrids. Extrapair copulations are common in both these species. Here, I tested the idea, that EPP and hybridization may be linked on a macro-evolutionary scale across species. I used data on EPP from review studies and assigned each species a dichotomous variable whether it has produced hybrids or not. Hybridizing species did not show a higher percentage of extrapair copulations compared to non-hybridizing species. However, while these data did not show any influence on the macro-ecological scale, these factors could, nevertheless, facilitate hybridization in some species pairs as in the example of the swallows.     

Keratinophilic fungi from Orissa, India, II: Isolations from feathers of wild birds and domestic fowls

Feather samples from 117 birds, representing 11 species, were examined for keratinophilic fungi. Of these, 63 (53.8%) were found to be positive. Nine species of fungi classified in 6 genera were isolated: Aphanoascus terreus (1.7%), Chrysosporium indicum (26.4%), Chrys. tropicum (11.1%) the Chrysosporium state of Aphanoascus spp. (2.5%), the Chrysosporium state of Arthroderma tuberculatum (3.4%), Ctenomyces serratus (0.8%), Gymnoascoideus petalosporus (7.6%), Malbranchea spp. (6.8%), Rollandina hyalinospora (6.8%). Passer domesticus (the house sparrow) harboured the largest varieties of keratinophilic fungi: the Chrysosporium state of Arthroderma tuberculatum was found to be associated with it selectively. The associations of these keratinophilic fungi with birds were non-clinical in nature.     

North‐African house martins endure greater haemosporidian infection than their European counterparts

Afro‐Palearctic migrant species are exposed to parasites at both breeding and over‐wintering grounds. The house martin Delichon urbicum is one such migratory species facing high instances of blood parasite infection. In an attempt to determine whether breeding European house martins harbour similar blood parasite communities to populations breeding in North Africa, birds were sampled at their breeding grounds in Switzerland and Algeria. Moreover, haemosporidian prevalence and parasite communities were compared to published data sets on Spanish and Dutch breeding populations. This study furthermore wanted to establish whether co‐infection with multiple genera or lineages of parasites had negative e?ects on host body condition. Breeding house martins caught in Algeria showed a higher prevalence of avian haemosporidian parasites than did European populations. Swiss house martins showed a prevalence comparable to that of Spanish and Dutch populations. There were slight differences in the haemosporidian community between European and North‐African populations in terms of composition and abundance of each lineage. Similar to the Dutch house martins, but in contrast to the Spanish population, infection status and number of genera of parasites infecting single hosts did not in?uence Swiss house martin body condition.     

Proportions of mammalian-type and reptilian-type nephrons in the kidneys of two passerine birds

We compared the proportions of mammalian-type and reptilian-type nephrons in the kidneys of two species of passerine birds. The desert house sparrow (Passer domesticus) is relatively well adapted for water conservation, whereas the white-crowned sparrow (Zonotrichia leucophrys) is more mesic adapted. The two species do not differ in body mass, but the kidneys of P. domesticus are significantly smaller than those of Z. leucophrys. Associated with its smaller size, the house sparrow kidney has significantly fewer glomeruli (35,700 per kidney) than does the white-crowned sparrow kidney (53,000 per kidney). The medullary cones, which contain the loops of Henle of the mammalian-type nephrons, are significantly longer in house sparrows than in white-crowned sparrows (2.2 vs. 1.9 mm). The number of medullary cones, the number of nephrons per medullary cone, and, hence, the number of mammalian-type nephrons do not differ between the two species. The smaller number of nephrons in the kidney of the house sparrow therefore represents a smaller number of reptilian-type nephrons. Desert house sparrows have 18% mammalian-type nephrons, whereas white-crowned sparrows have 10% mammaliantype nephrons. The relative reduction of reptilian-type nephrons in P. domesticus may reduce the flow of dilute urine through the collecting ducts, thereby permitting a greater concentration gradient to be established along the length of the medullary cones.     

An enzootic vector-borne virus is amplified at epizootic levels by an invasive avian host

Determining the effect of an invasive species on enzootic pathogen dynamics is critical for understanding both human epidemics and wildlife epizootics. Theoretical models suggest that when a naive species enters an established host–parasite system, the new host may either reduce (‘dilute’) or increase (‘spillback’) pathogen transmission to native hosts. There are few empirical data to evaluate these possibilities, especially for animal pathogens. Buggy Creek virus (BCRV) is an arthropod-borne alphavirus that is enzootically transmitted by the swallow bug (Oeciacus vicarius) to colonially nesting cliff swallows (Petrochelidon pyrrhonota). In western Nebraska, introduced house sparrows (Passer domesticus) invaded cliff swallow colonies approximately 40 years ago and were exposed to BCRV. We evaluated how the addition of house sparrows to this host–parasite system affected the prevalence and amplification of a bird-associated BCRV lineage. The infection prevalence in house sparrows was eight times that of cliff swallows. Nestling house sparrows in mixed-species colonies were significantly less likely to be infected than sparrows in single-species colonies. Infected house sparrows circulated BCRV at higher viraemia titres than cliff swallows. BCRV detected in bug vectors at a site was positively associated with virus prevalence in house sparrows but not with virus prevalence in cliff swallows. The addition of a highly susceptible invasive host species has led to perennial BCRV epizootics at cliff swallow colony sites. The native cliff swallow host confers a dilution advantage to invasive sparrow hosts in mixed colonies, while at the same sites house sparrows may increase the likelihood that swallows become infected.     

Extrapair paternity and hybridization in birds

Hybridization in birds is a widely acknowledged phenomenon. It often occurs when one species is absent or rare which leads to mixed pairings between different species (Hubb's principle). However, Hubb's principle cannot explain hybridization in one of the most common Passeriform hybrids, barn swallow Hirundo rustica×house martin Delichon urbica, since these hybrids usually occurred in areas where both species were common. Such hybrids were often found as singletons between true barn swallows siblings suggesting that extrapair copulations, and not mixed breeding pairs, might be the reason for the existence of these hybrids. Extrapair copulations are common in both these species. Here, I tested the idea, that EPP and hybridization may be linked on a macro‐evolutionary scale across species. I used data on EPP from review studies and assigned each species a dichotomous variable whether it has produced hybrids or not. Hybridizing species did not show a higher percentage of extrapair copulations compared to non‐hybridizing species. However, while these data did not show any influence on the macro‐ecological scale, these factors could, nevertheless, facilitate hybridization in some species pairs as in the example of the swallows.     

The characteristics of the relationships of arthropods of the refuge complex with the causative agents of transmissible viral infections in bird rookeries

The isolation of viruses of tick-borne encephalitis, West Nile fever, and Omsk hemorrhagic fever from arthropods of nests of colonial birds (rook, sand martin, tree sparrow, Laridae) in different zones of West Siberia (from tundra to steppe) has been analyzed. The role of gamasid mites, hematophages and saprophages, characteristic inhabitants of nests of colonial birds, and of the tick Ixodes lividus in connection with their biology, coadaptation with hosts, microclimatic nest conditions, etc. has been evaluated. It has been concluded that the whole nest community of arthropods in a nest rather than one infected individual has to be regarded as an infective unit in colonies.     

Broad-scale latitudinal patterns of genetic diversity among native European and introduced house sparrow (Passer domesticus) populations

Introduced species offer unique opportunities to study evolution in new environments, and some provide opportunities for understanding the mechanisms underlying macroecological patterns. We sought to determine how introduction history impacted genetic diversity and differentiation of the house sparrow (Passer domesticus), one of the most broadly distributed bird species. We screened eight microsatellite loci in 316 individuals from 16 locations in the native and introduced ranges. Significant population structure occurred between native than introduced house sparrows. Introduced house sparrows were distinguished into one North American group and a highly differentiated Kenyan group. Genetic differentiation estimates identified a high magnitude of differentiation between Kenya and all other populations, but demonstrated that European and North American samples were differentiated too. Our results support previous claims that introduced North American populations likely had few source populations, and indicate house sparrows established populations after introduction. Genetic diversity also differed among native, introduced North American, and Kenyan populations with Kenyan birds being least diverse. In some cases, house sparrow populations appeared to maintain or recover genetic diversity relatively rapidly after range expansion (<50 years; Mexico and Panama), but in others (Kenya) the effect of introduction persisted over the same period. In both native and introduced populations, genetic diversity exhibited large-scale geographic patterns, increasing towards the equator. Such patterns of genetic diversity are concordant with two previously described models of genetic diversity, the latitudinal model and the species diversity model.     

The role of a synanthropic bird in the nest niche expansion of a secondary cavity nester to man‐made structures

Species with similar ecological characters often compete with each other; however, a species may also facilitate the survival or reproduction of another ecologically similar species, although such interaction is rarely documented in birds. Here, we reported a facilitative species interaction between Asian house martins (Delichon dasypus) and russet sparrows (Passer cinnamomeus), both passerines using closed nests, in a montane farming area of Taiwan. We found that Asian house martins constructed dome‐shaped nests in human houses that provided additional nest sites for russet sparrows, secondary cavity nesters with greatly declining populations in Taiwan. Russet sparrows that used house martin nests had reproductive success comparable to those that used artificial nest boxes. However, Asian house martins avoided reclaiming sparrow‐used nests, which reduced their available nest sites. Interestingly, our results imply that man‐made structures may be used as a conservation tool to improve the breeding of the endangered russet sparrows via this facilitative interaction.