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PubMed2002

Variation at the major histocompatibility complex in Savannah sparrows.

The class I and class II genes of the major histocompatibility complex (Mhc) encode dimeric glycoproteins responsible for eliciting the adaptive immune response of vertebrates. Recent work with birds suggests that the number, size, and arrangement of these genes can differ markedly across species, although the extent of this variation, and its causes and consequences, are poorly understood. We have used a 157-base-pair (bp) portion of the second exon of a class II B gene to probe the Mhc in a free-living population of Savannah sparrows (Passerculus sandwichensis). Segregation analysis of Mhc bands suggests that class II B genes can be found in two independently assorting clusters, as previously described for domestic chickens (Gallus gallus) and ring-necked pheasants (Phasianus colchicus) but unlike gene organization in mammals. The Mhc in Savannah sparrows appears large (with many class II B genes) and variable; we found 42 unique genotypes among 48 adults breeding on Kent Island, New Brunswick, Canada in 1995. Savannah sparrows are long-distance migrants, and these results support recent predictions that migratory birds should show higher levels of Mhc polymorphism and/or a greater number of genes than sedentary species. Savannah sparrows are also socially polygynous with high levels of extra-pair paternity, suggesting that a history of sexual selection might also influence the size and/or structure of the avian Mhc.

Animals↗
PubMed2003

Inbreeding depresses immune response in song sparrows (Melospiza melodia): direct and inter-generational effects.

A thorough knowledge of relationships between host genotype and immunity to parasitic infection is required to understand parasite-mediated mechanisms of genetic and population change. It has been suggested that immunity may decline with inbreeding. However, the relationship between inbreeding level and a host's response to a novel immune challenge has not been investigated in a natural population. We used the pedigreed population of song sparrows (Melospiza melodia) inhabiting Mandarte Island, Canada, to test the hypothesis that a sparrow's cell-mediated immune response (CMI) to an experimental challenge would decline with individual or parental inbreeding. CMI in 6-day-old chicks declined significantly with their mother's coefficient of inbreeding, demonstrating an inter-generational effect of maternal inbreeding on offspring immunity. In fledged juveniles and adult sparrows, CMI declined markedly with an individual's own coefficient of inbreeding, but not its mother's. This relationship was consistent across seasons, and was not attributable solely to heterosis in offspring of immigrant breeders. CMI also declined with age and increased with body condition in adult sparrows, but inbreeding explained 37% of the total variation. We emphasize the implications of this dramatic inbreeding depression in cell-mediated immunity for theories of parasite-mediated evolution and the susceptibility of small, inbred populations.

Animals↗
PubMed1978

Experimental infection of house sparrows (Passer domesticus) with Rocio virus.

Rocio encephalitis is a new epidemic flaviviral infection of man, first described in São Paulo State, Brazil in 1975. The ecology of the viral transmission cycle remains largely unknown. Experimental studies were undertaken to assess the role of a wild avian species, the House Sparrow, as a maintenance or amplifying host. Approximately two-thirds of nesting and adult sparrows developed 2- to 3-day viremias of low to moderate magnitude (2.0--4.3 log/ml). Rocio-immune birds were not protected against challenge with St. Louis encephalitis (SLE) virus, but prior SLE viral infection prevented detectable viremia in birds challenged with Rocio virus. These studies provide some support for the hypothesis that birds are hosts for Rocio virus, but the House Sparrow probably plays a relatively minor role in viral transmission. Because sparrows are relatively inefficient viremic hosts, they would be expected to play a minor role in transmission should Rocio virus be introduced into the United States.

Animals↗
PubMedDate not supplied

Laboratory infection of house sparrows (Passer domesticus) with Mycoplasma gallisepticum and Mycoplasma synoviae.

House sparrows were infected by aerosol with Mycoplasma gallisepticum (MG) or M. synoviae (MS). MG was reisolated from 5 to 11 sparrows 10 days postinfection, but infection appeared to be temporary. Mycoplasma-free chickens reared in the experimental house became infected with MG during the trial. MS was recovered from only one sparrow. Serological tests were unsatisfactory for diagnosing infected birds. The results suggest that house sparrows may be temporary biological carriers of MG.

Animals↗
PubMed1978

Experimental transmission of Sarcocystis from icterid birds to sparrows and canaries by sporocysts from the opossum.

Cowbirds (Molothrus ater) and grackles (Cassidix mexicanus) infected with muscle cysts of Sarcocystis were fed to opposums (Didelphis virginiana) and fecal sporocysts from the latter were given to sparrows (Passer domesticus, Family Ploceidae), canaries (Serinus canarius, Family Fringillidae) and ducks (Anas platyrhynchos, Family Anatidae). Asexual parasites were found in the endothelium of sparrows and canaries but not in ducks. When birds were kept 10 weeks or more after infection, muscle cysts were found grossly and microscopically in the majority of sparrows, and in 1 canary, but not in ducks. Muscle zoites were found in digests of all sparrows and canaries but not in that of ducks. Metrocytes and forms dividing by endodyogeny also were found in the digest. Thus, avian Sarcocystis was transmitted experimentally from 2 genera of 1 family (Icteridae) to 2 different families of passerine intermediate hosts by sporocysts from the definitive host. This is the broadest intermediate host spectrum known for a species of Sarcocystis.

Animals↗
PubMed2005

Stable isotope and band-encounter analyses delineate migratory patterns and catchment areas of white-throated sparrows at a migration monitoring station.

The Canadian Migration Monitoring Network consists of several fixed migration monitoring stations (MMS) that apply constant-effort protocols to track changes in the abundance of migratory birds. Such monitoring will be important for tracking long-term population trends of songbirds, especially for species breeding in remote areas such as the North American boreal forest. The geographical catchment sampled by individual MMS, however, remains largely unknown. Here, we used hydrogen isotope measurements (deltaD) of feathers of white-throated sparrows (Zonotrichia albicollis) moving through Delta Marsh MMS in Manitoba, Canada, to determine both wintering and breeding ground catchment areas monitored by this station. The deltaD of tail feathers, collected from spring and fall migrants delineated previous breeding or natal latitudes, ranging from the northern to the southern extremes of the western boreal forest. The deltaD values of head feathers grown on the wintering grounds and collected during spring migration revealed that individuals wintered in a broad region of the southeastern United States. The isotope data showed no relationship between estimated breeding/natal and wintering latitudes of white-throated sparrow populations. Stable isotope data provided little information on longitude. Band-encounter analyses, however, indicated a clear east-west segregation of these sparrows across Canada, supporting connectivity among breeding/natal and wintering longitudes over the entire scale of this species' range. Isotope analyses of multiple feather types representing different periods and geographic regions of the annual cycle can provide key information on migratory connectivity for species moving through dedicated MMS.

Animal Migration↗
PubMed2006

Water and energy economy of an omnivorous bird: population differences in the Rufous-collared Sparrow (Zonotrichia capensis).

We investigated the intraspecific variation in basal metabolic rate (BMR) and total evaporative water loss (TEWL) in the omnivorous passerine Zonotrichia capensis from two populations inhabiting regions with different precipitation regimes and aridity indices. Values of TEWL in birds from the semi-arid region were significantly lower than those found in sparrows from the mesic region. TEWL in birds from the semi-arid site was 74% of the expectation based on body mass for passerines from mesic areas and similar to the allometric expectation for passerines from arid environments. In sparrows from the mesic area, TEWL was higher than predicted by their body mass for passerines from arid environments (133%), but very close (97%) to the expectation for passerines from mesic areas. BMR values were 25% lower in sparrows from the semi-arid region. The lower TEWL and BMR of birds from the semi-arid region may be a physiological adjustment that allows them to cope with fewer resources and/or water. We propose that the lower endogenous heat production in birds from the semi-arid environment may decrease their water requirements.

Animals↗
PubMed2006

Corticosterone responses change seasonally in free-living house sparrows (Passer domesticus).

Avian corticosterone (CORT) concentrations vary seasonally for many species, but most studies examined species from extreme environments or from only a few times of the year. It is unclear how general a phenomenon this is. We examined both baseline and stress-induced CORT from house sparrows (Passer domesticus) in two habitats-Massachusetts, similar to their ancestral habitat; and New Mexico, a semi-arid desert where the house sparrow only thrives as an obligate human commensal. We captured both males and females during four times of the year-Spring (when the male cloacal protuberance indicated birds were in breeding condition), Fall, Winter, and in the late summer when birds were undergoing a prebasic molt. Birds were heaviest and had the longest wing chord lengths in the Fall at both sites and Massachusetts birds were approximately 10% heavier than New Mexico birds. House sparrows also showed a seasonal variation in the amount of fat stores, but the seasonal pattern differed. Massachusetts birds were fatter overall and showed the most fat during Fall and Winter, whereas New Mexico birds showed the most fat in the Spring. Both baseline and stress-induced total CORT did not differ between sexes or sites, with the exceptions of baseline CORT in the Fall and stress-induced CORT in the Spring being elevated in Massachusetts males. There was a distinct seasonal pattern at both sites, however, with total CORT being highest in the Spring and Winter and lowest during Fall and molt. This seasonal pattern was mirrored in corticosterone binding globulin (CBG) capacities, and when free CORT was estimated, the seasonal pattern disappeared. Stress-induced free CORT, however, was higher in Massachusetts males and females during the Fall and Winter, suggesting a potential differential response to stress associated with commensalism.

Animals↗
PubMed2006

Control of luteinizing hormone and testosterone secretion in a flexibly breeding male passerine, the Rufous-winged Sparrow, Aimophila carpalis.

Rufous-winged Sparrows, Aimophila carpalis, reside in the Sonoran desert and although testicular development is initiated in the spring under the influence of increasing day length, breeding occurs opportunistically in summer in association with heavy rainfall or "monsoon". The aim of this study in free-living male Rufous-winged Sparrows was to establish the relationship between concentrations of plasma luteinizing hormone (LH) and testosterone (T), and breeding associated with heavy rainfall, and to investigate whether breeding is mediated by changes in pituitary gland sensitivity to gonadotropin releasing hormone-I (GnRH) and the recently discovered avian gonadotropin-inhibitory hormone (GnIH). Concentrations of plasma LH and T were relatively low until mid-summer, but increased rapidly and transiently immediately prior to the monsoon which occurred after the summer solstice, when day lengths were decreasing. At this time the birds came into full breeding condition. An injection of chicken GnRH (10 ng) increased plasma LH within 2 min when given before or during the monsoon. An injection of GnIH (1 microg) did not affect plasma LH within 2 min during the monsoon and did not decrease GnRH-elicited LH secretion before or during the monsoon. No experimental treatment affected plasma T concentrations. The data suggest in male Rufous-winged Sparrows that the seasonal increase in plasma LH associated with summer monsoon results from increased stimulation of the pituitary gland by GnRH, rather than from a change in the responsiveness of the gland to GnRH, and that GnIH does not play an acute role in this mechanism. However, a possible chronic role for GnIH in the seasonal control of LH synthesis and secretion through an inhibitory effect on the hypothalamic GnRH system remains to be investigated.

Animals↗
PubMed2004

Plasma corticosterone increases during migratory restlessness in the captive white-crowned sparrow Zonotrichia leucophrys gambelli.

Plasma corticosterone increases during the period of spring migration in a variety of bird species. Long-distance migrants show elevations in corticosterone specifically in association with the stage of flight, suggesting that corticosterone may support flight-related processes, for example, locomotor activity and/or energy mobilization. The pattern of corticosterone secretion as it relates to migratory flight has hitherto not been clearly described in migrants that frequently interrupt flight to refuel, for example, the Gambel's white-crowned sparrow (Zonotrichia leucophrys gambelii). The Gambel's white-crowned sparrow fuels by day and expresses peak migratory activity during the first few hours of night. To determine if plasma corticosterone increases in association with the stage of migratory flight also in this short-bout migrant, we induced captive white-crowned sparrows to enter into the migratory condition by placing photosensitive birds on long days (16L:8D) and then evaluated birds for plasma corticosterone and locomotor activity during four time points of the day. Patterns found in long-day birds were compared to those observed in short-day controls (8L:16D). Differences in energy metabolism as determined from plasma metabolites were also evaluated. We found that locomotor activity and corticosterone were significantly elevated at the onset of the dark period, but only in long-day birds. Plasma beta-hydroxybutyrate (a ketone body) was also elevated. Thus, findings suggest that plasma corticosterone and ketogenesis increase in association with migratory restlessness in a short-bout migrant. In fact, corticosterone may play a regulatory role, because it shows a trend to increase already before night-time activity.

Adaptation, Physiological↗
PubMed2006

Cutaneous immune activity varies with physiological state in female house sparrows (Passer domesticus).

Many vertebrates show seasonality in immune defenses, perhaps because of trade-offs with other physiological processes. Trade-offs between reproduction and immune function have been well studied, but how other life cycle events such as molt affect immune function remains unclear. Here, we hypothesize that one possible explanation is that accumulative dissociated processes (e.g., resource deficits generated over the long term by physiological processes) can have delayed effects on immune activity. To test this hypothesis, we compared cutaneous immune responses in groups of captive female house sparrows (Passer domesticus) photoperiodically induced into six different life cycle stages. We predicted that if delayed trade-offs occur, immune activity would be reduced after a mature life state was reached (e.g., postmolt) and not just compromised when other tissues were actively growing (instantaneous trade-off). We found evidence for both types of trade-offs: immune responses were weakest in sparrows that had just completed postnuptial molt, but they were also weak in birds growing reproductive tissues or feathers. Birds in mature reproductive states or light molt had strong immune responses comparable with birds in a nonbreeding/nonmolting state. Altogether, our results indicate that immune activity in female house sparrows can be influenced by both instantaneous and delayed trade-offs.

Animals↗
PubMed2006

Hypothalamic pro-GnRH-GAP, GnRH-I and GnRH-II during the onset of photorefractoriness in the white-crowned sparrow (Zonotrichia leucophrys gambelii).

Gambel's white-crowned sparrow is a long distance migrant that undergoes spontaneous gonadal regression as a result of long day exposure. This termination of breeding is caused by the development of photorefractoriness and the birds become insensitive to long days, including continuous light. The present study investigated its possible mechanisms by examining the activity of the gonadotrophin-releasing hormone (GnRH) system under different photoperiodic regimes. We investigated the localisation and distribution of GnRH-I, its precursor pro-GnRH-GAP and GnRH-II in Gambel's white-crowned sparrow brain using immunocytochemistry with specific antibodies during photostimulation and the development of photorefractoriness. The study revealed that photoperiodic treatment, including the onset of photorefractoriness, had no significant effect on the size or number of GnRH-I, pro-GnRH-GAP or GnRH II immunoreactive cells, or the density of the GnRH-I, pro-GnRH-GAP immunoreactive fibres at the median eminence. GnRH-II was not found in the median eminence, suggesting that it does not regulate pituitary gonadotrophin secretion. GnRH-I measurement in hypothalamic extracts by radioimmunoassay did not reveal any significant difference between birds that were photostimulated or in the early stages of photorefractoriness. Furthermore, the action of the excitatory amino acid glutamate agonist N-methyl-D-aspartate on GnRH neurones in photorefractory birds was demonstrated by the significant blockade of luteinising hormone release with a specific GnRH antagonist. Taken together, these results suggest that, in Gambel's white-crowned sparrow, a decrease in GnRH-I secretion is the initial step for the onset of photorefractoriness and not a decrease in GnRH-I biosynthesis.

Animal Migration↗
PubMed2005

Gizzard spirurid nematode Acuaria skrjabini in Japanese tree sparrows and a gray starling from Tokyo.

Gastrointestinal helminths were collected from 49 Japanese tree sparrows (Passer montanus saturatus) in Tokyo, Japan. In 16 sparrows, 1-9 (average, 3.5) gizzard spirurid nematodes (Acuaria skrjabini Ozerskaya, 1926) were found embedded in the mucosa of the gizzard. In addition, Capillaria sp., Platynosomum passeri Yamashita et Tsumura, 1962, and a hymenolepidid cestode were collected from 1, 2, and 1 sparrows, respectively. A sexually mature A. skrjabini female and 3 males were found also in a young gray starling (Sturnus cineraceus) that was found dead in the same area after failure to leave the nest. Starlings are a new host record for this spirurid species. Until this study, this gizzard spirurid species has not been recorded in this country or the Far East region.

Animals↗
PubMed2005

A biogeographic pattern in sparrow bill morphology: parallel adaptation to tidal marshes.

The study of ecological convergence, the evolution of similar traits on multiple occasions in response to similar conditions, is a powerful method for developing and testing adaptive hypotheses. However, despite the great attention paid to geographic variation and the foraging ecology of birds, surprisingly few cases of convergent or parallel feeding adaptations have been adequately documented. In this study, we document a biogeographic pattern of parallel bill morphology across 10 sparrow taxa endemic to tidal marshes. All North American tidal marsh sparrows display parallel differentiation from close relatives in other habitats, suggesting that selection on bill morphology is strong. Relative to their body mass, tidal marsh sparrows have longer, thinner bills than their non-tidal marsh counterparts, which is likely an adaptation for consuming more invertebrates and fewer seeds, as well as for probing in sediment crevices to capture prey. Published data on tidal marsh food resources and diet of the relevant taxa support this hypothesis. This morphological differentiation is most pronounced between sister taxa with the greatest estimated divergence times, but is found even in taxa that show little or no structure in molecular genetic markers. We, therefore, speculate that tidal marsh ecosystems are likely settings for ecological speciation.

Adaptation, Biological↗
PubMed2005

Interspecific differences in hematozoan infection in Sonoran desert Aimophila sparrows.

Numerous studies have identified factors that control avian hematozoan infections, but the mechanisms that account for host differences in parasitemia remain largely speculative. To address this issue, we compared the prevalence of these parasites in stained blood smears from four conspecific Sonoran desert Aimophila sparrow species sampled during their breeding season: rufous-winged (Aimophila carpalis; RWSP), rufous-crowned (Aimophila ruficeps; RCSP), Cassin's (Aimophila cassinii, CASP), and Botteri's (Aimophila botterii; BOSP) sparrows. Blood smears contained Haemoproteus fringillae (RWSP), Trypanosoma everetti (RWSP, RCSP, BOSP), Trypanosoma avium (CASP), and microfilariae (all species). Most (92.5%) RWSP (n=40) were infected with Haemoproteus, but this parasite was not detected in RCSP (n=20) or BOSP (n=20) and was found only in one (2.5%) CASP (n=40). Trypanosoma spp. and microfilariae were detected in all species, but prevalence differed between these four sparrow species. Species differences in parasite prevalence were not due to difference in sex, age, adult body mass, incubation period, breeding habitat, or plumage colorfulness. However, differences in Haemoproteus sp. prevalence correlated with preferred nesting height, as RWSP generally nest above ground, whereas the other species nest on or close to the ground. Elevated H. fringillae prevalence in breeding-condition RWSP presumably does not result from a seasonal relapse associated with breeding or require new infection because 1) this prevalence did not differ in males sampled during and outside (n=21) the breeding season, and 2) all male RWSP (n=25) that we held in captivity and shielded from new infections and influence of natural photoperiod for 1 yr had viable blood H. fringillae gametocytes. H. fringillae prevalence in fall-sampled hatch-year male RWSP (n=11) was 63.6%, demonstrating that this parasite can be transmitted on the breeding grounds and during the first months of life. T. everetti prevalence in RWSP was lower in winter than in summer and also in long-term captive than in free-ranging adults. Presence of this parasite in the blood of breeding males may depend on recrudescence of existing infections or new infections.

Animals↗
PubMed2005

Variation in virulence of West Nile virus strains for house sparrows (Passer domesticus).

The observation of avian mortality associated with West Nile virus (WNV) infection has become a hallmark epidemiologic feature in the recent emergence of this pathogen in Israel and North America. To determine if phenotypic differences exist among different WNV isolates, we exposed house sparrows (Passer domesticus) to low passage, lineage 1 WNV strains from North America (NY99), Kenya (KEN), and Australia (KUN; also known as Kunjin virus). House sparrows inoculated with the NY99 and KEN strains experienced similar mortality rates and viremia profiles. The KUN strain elicited significantly lower-titered viremia when compared with the other strains and induced no mortality. This study suggests that natural mortality in house sparrows due to Old World strains of WNV may be occurring where the KEN strain occurs.

Animals↗
PubMed1989

Addition of song-related neurons in swamp sparrows coincides with memorization, not production, of learned songs.

During song learning in birds, neurons are added to some song nuclei and lost from others. Previous studies have been unable to distinguish whether these neural changes are uniquely associated with memorizing a song model (sensory acquisition) or vocal practice (sensorimotor learning). In this study we measured changes in neuron number within song nuclei of swamp sparrows, a species in which the two phases of song learning are nonoverlapping. Male swamp sparrows were collected as hatchlings and tape-tutored from approximately 22 to 62 days of age. Swamp sparrows memorize about 60% of their song material during this period, but do not begin practicing this learned material until approximately 275 days of age. Birds were sacrificed at 23, 41, 61, 71, 274, or 340 days of age. During sensory acquisition, neuron number increased drastically in both the caudal nucleus of the ventral hyperstriatum (HVc) and Area X. The period of sensorimotor learning was not associated with any further changes in neuron number within these regions. We were unable to detect any significant changes in neuron number within the magnocellular nucleus of the neostriatum or the robust nucleus of the archistriatum during either stage of song learning. These results raise the possibility that ongoing addition of HVc and Area X neurons may encourage, and thereby temporally restrict, song acquisition.

Aging↗
PubMed1995

Seasonal changes in song nuclei and song behavior in Gambel's white-crowned sparrows.

In males of several songbird species, the morphology of forebrain nuclei that control song changes seasonally. The only seasonally breeding songbird in which seasonal changes in the structure of song control nuclei have been reported not to occur is the nonmigratory Nuttall's subspecies of white-crowned sparrow. In the present study, we manipulated photoperiod and plasma testosterone concentrations in captive male white-crowned sparrows of the migratory Gambel's subspecies. Males exposed to photoperiods and plasma testosterone concentrations typical of those experienced by wild breeding males had larger song control nuclei than males held on a winter photoperiod. We also found seasonal changes in stereotype of spectral and temporal parameters of song in wild Gambel's white-crowned sparrows. We hypothesize that seasonal changes in the song control nuclei may correlate with seasonal changes in song stereotypy.

Animals↗