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PubMed1995

The photoperiodic control circuit in euthyroid American tree sparrows (Spizella arborea) is already programmed for photorefractoriness by week 4 under long days.

The aim of this investigation was to determine whether spontaneous testicular regression in male American tree sparrows (Spizella arborea) that were thyroidectomized at week 4 of photostimulation manifests photorefractoriness, as it does in chronically photostimulated euthyroid controls. On the basis of our demonstration that exogenous thyroxine stimulates the gonads only when recipient birds are photosensitive, male tree sparrows were thyroidectomized at week 4 of photostimulation (20 h light:4 h dark) and given thyroxine periodically to assay for photosensitivity. When initiated at weeks 4, 7, 10, 13 and 16 of photostimulation, thyroxine replacement therapy had no effect on testis size until week 16, when most recipient birds showed robust testicular growth. The inductive effect of exogenous thyroxine at week 16 confirms that chronic thyroidectomy dissipates photorefractoriness and simulates the effect of short days. The failure of replacement thyroxine to halt spontaneous testicular regression between week 7 and week 13 establishes that spontaneous testicular regression after thyroidectomy manifests photorefractoriness. Moreover, the failure of replacement thyroxine to induce testicular growth between week 4 and week 7 indicates that by week 4 of photostimulation, at least 3 weeks before photoinduced testicular growth ends, male tree sparrows are programmed for photorefractoriness. This conclusion is strengthened by the finding that thyroidectomy at week 4 of photostimulation does not uncouple photorefractoriness and postnuptial moult, which in euthyroid tree sparrows are tightly linked. In another experiment, photosensitive thyroid-intact tree sparrows were moved from 8 h light:16 h dark to 20 h light:4 h dark and given exogenous thyroxine or vehicle through week 6 of photostimulation. Exogenous thyroxine augmented testicular growth.

Animals↗
PubMed1982

Role of the suprachiasmatic nuclei in the circadian system of the house sparrow, Passer domesticus.

The suprachiasmatic nuclei (SCN) of the hypothalamus are necessary for the persistence of free running circadian activity rhythms in house sparrows. Suprachiasmatic lesions abolish circadian locomotor rhythms in constant darkness. The locomotor activity of lesioned sparrows was analyzed with two different power spectral analysis methods and was found to be arrhythmic. There was a weak correlation between the extent of damage to the SCN and the relative amplitude of the power spectral density in the circadian frequency range. In light-dark cycles (LD 12:12), the locomotor behavior of lesioned sparrows was rhythmic and similar to that of intact birds. However, entrainment was disrupted in SCN-lesioned sparrows exposed to a short photoperiod light cycle (LD 1:24). These results demonstrate that the SCN are crucial for the generation of overt circadian rhythmicity in birds. The fact that SCN lesions abolish circadian rhythms in sparrows and several mammalian species suggests that vertebrate circadian organization may be based on differentially weighted interactions among the pineal, the SCN, and perhaps other brain regions.

Animals↗
PubMed2006

Analysing population numbers of the house sparrow in the Netherlands with a matrix model and suggestions for conservation measures.

The House Sparrow (Passer domesticus), formerly a common bird species, has shown a rapid decline in Western Europe over recent decades. In The Netherlands, its decline is apparent from 1990 onwards. Many causes for this decline have been suggested that all decrease the vital rates, i.e. survival and reproduction, but their actual impact remains unknown. Although the House Sparrow has been dominant in The Netherlands, data on life history characteristics for this bird species are scarce: data on reproduction are non-existent, and here we first present survival estimates based on live encounters and dead recoveries of marked individuals over the period 1976-2003, 14 years before and 14 years during the decline, reported to the Dutch Ringing Centre. We show that there is an indication that both juvenile and adult survival are lower during the period of decline.Secondly, to be able to analyse the relative impact of changes in the vital rates, we formulated a general matrix model based on a range of survival values between zero and one with a step size of 0.01 (both juvenile and adult yearly survival) and a range of realistic reproduction values (one, three or five fledglings per pair per year). With the matrix model, we calculated the finite rate of population change (lambda) and applied elasticity analysis. To diagnose the cause of the decline in the Dutch House Sparrow, we parameterised the model with estimates of survival values before and during the decline and present the resulting lambda. With the survival estimates from the declining period, lambda < 1 only if reproduction is relatively low. We discuss this result within the light of available literature data on survival in the House Sparrow. Finally, we evaluate which of the suggested causes of population decline should be reversed to mitigate the decline and how this can be achieved.

Animals↗
PubMed2005

Skeletal muscle fiber composition of the English sparrow (Passer domesticus).

Substrate utilization by English sparrow skeletal muscle has been extensively studied in our lab. However, there are few published studies on the muscle fiber composition of English sparrow wing and gastrocnemius muscles. The objective of the present study was to examine the fiber type composition of a variety of muscles in the English sparrow. The classification of a muscle fiber as fast glycolytic, slow oxidative, or fast oxidative glycolytic provides insight into the physiological function of muscles. Therefore, we completed mATPase and NADH stains on four muscles of the sparrow wing, as well as the gastrocnemius muscle, to characterize these muscle fiber types. Results show that the fibers of extensor digitorum communis, extensor metacarpi ulnaris, and extensor metacarpi radialis are homogeneous fast oxidative. The fibers of the supinator are homogeneous fast oxidative in 62.5% of samples, and heterogeneous (45.2% fast oxidative, 54.8% fast nonoxidative) in 37.5% of samples. Whereas the gastrocnemius muscle fibers are heterogeneous (10% fast oxidative, 64% fast nonoxidative, 26% slow oxidative) in all muscles examined.

Animals↗
PubMed2006

Glucose transporter expression in English sparrows (Passer domesticus).

Patterns of glucose transporter expression have been well-characterized in mammals. However, data for birds is currently restricted to isolated cells, domestic chickens and chicks, and ducklings. Therefore, in the present study, protein and gene expression of various glucose transporters (GLUTs) in English sparrow extensor digitorum communis, gastrocnemius and pectoralis muscles as well as heart, kidney, and brain tissues were examined. The hypothesis is that the expression pattern of avian GLUTs differs from mammals to maintain the high plasma glucose levels of birds and insulin insensitivity. Our studies failed to identify a GLUT4-like insulin responsive transporter in sparrows. GLUT1 gene expression was identified in all tissues examined and shares 88% homology with chicken and 84% homology with human GLUT1. Compared to the rat control, GLUT1 immunostaining of sparrow extensor digitorum communis muscle was weak and appeared to be localized to blood vessels whereas immunostaining of gastrocnemius muscles was comparable to rat muscle controls. Gene expression of GLUT3 was identified in all tissues examined and shares 90% gene sequence homology with chicken embryonic fibroblast and 75% homology with human GLUT3. Protein expression of GLUT3 was not determined as an avian antibody is not available. Moreover, the C-terminus of the mammalian GLUT3 transporter, against which antibodies are typically designed, differs significantly among species. The predominant difference of chicken and sparrow GLUT expression patterns from that of mammals is the lack of an avian GLUT4. The absence of this insulin responsive GLUT in birds may be a contributing factor to the observed high blood glucose levels and insulin insensitivity.

Animals↗
PubMed2006

Seasonal changes in hypothalamic-pituitary-adrenal axis sensitivity in free-living house sparrows (Passer domesticus).

Recent evidence indicates that house sparrows (Passer domesticus) seasonally regulate corticosterone responses to capture, handling, and restraint. Responses during molt and in the fall are lower than responses in the winter and while breeding. This study tested whether changes in either adrenal tissue responsiveness to adrenocorticotropin (ACTH) or pituitary responsiveness to corticotropin releasing factor (CRF) or arginine vasotocin (AVT) could provide the mechanism regulating these seasonal changes. House sparrows were captured at two sites (Massachusetts and New Mexico, USA) and during the above four seasons and injected with exogenous ACTH, CRF, and AVT. ACTH stimulated further corticosterone release in all birds except Massachusetts birds in the winter, suggesting that reduced adrenal sensitivity to ACTH cannot explain reduced corticosterone release during fall and molt. However, exogenous ACTH was less effective during molt at both sites, implying that adrenal sensitivity does change. Pituitary sensitivity also changed seasonally, but these pituitary changes did not match the seasonal changes in corticosterone release. CRF and AVT only succeeded in elevating corticosterone in the spring in Massachusetts birds and in the winter in New Mexico birds, whereas CRF alone also stimulated corticosterone release in New Mexico birds in the fall. Taken together, these data indicate that house sparrows can alter the amount of corticosterone released from adrenal tissue, the amount of ACTH released from the pituitary, and the amount of CRF and AVT released from the hypothalamus, but that none of these changes correlate with seasonal changes in corticosterone release. Consequently, seasonal modulation of corticosterone release in house sparrows appear to result from a complicated mix of adrenal, pituitary, and hypothalamic changes that also vary seasonally.

Adrenocorticotropic Hormone↗
PubMed2006

Mass-dependent predation risk as a mechanism for house sparrow declines?

House sparrow (Passer domesticus) numbers have declined rapidly in both rural and urban habitats across Western Europe over the last 30 years, leading to their inclusion on the UK conservation red list. The decline in farmland has been linked to a reduction in winter survival caused by reduced food supply. This reduction in food supply is associated with agricultural intensification that has led to the loss of seed-rich winter stubble and access to spilt grain. However, urban house sparrows have also declined, suggesting that reduced food supply in farmland is not the sole reason for the decline. Here, we show that changes in house sparrow mass and thus fat reserves are not regulated to minimize starvation risk, as would be expected if limited winter food were the only cause of population decline. Instead, the species appears to be responding to mass-dependent predation risk, with starvation risk and predation risk traded-off such that house sparrows may be particularly vulnerable to environmental change that reduces the predictability of the food supply.

Animals↗
PubMed1964

CULTURALLY TRANSMITTED PATTERNS OF VOCAL BEHAVIOR IN SPARROWS.

Male white-crowned sparrows have song "dialects," acquired in about the first 100 days of life by learning from older males. In the laboratory an alien white-crowned sparrow dialect can be taught. Once the song is established further acoustical experience does not change the pattern. White-crowned sparrows do not copy recorded songs of other sparrow species presented under similar conditions.

Animals↗
PubMed2004

Migratory sleeplessness in the white-crowned sparrow (Zonotrichia leucophrys gambelii).

Twice a year, normally diurnal songbirds engage in long-distance nocturnal migrations between their wintering and breeding grounds. If and how songbirds sleep during these periods of increased activity has remained a mystery. We used a combination of electrophysiological recording and neurobehavioral testing to characterize seasonal changes in sleep and cognition in captive white-crowned sparrows (Zonotrichia leucophrys gambelii) across nonmigratory and migratory seasons. Compared to sparrows in a nonmigratory state, migratory sparrows spent approximately two-thirds less time sleeping. Despite reducing sleep during migration, accuracy and responding on a repeated-acquisition task remained at a high level in sparrows in a migratory state. This resistance to sleep loss during the prolonged migratory season is in direct contrast to the decline in accuracy and responding observed following as little as one night of experimenter-induced sleep restriction in the same birds during the nonmigratory season. Our results suggest that despite being adversely affected by sleep loss during the nonmigratory season, songbirds exhibit an unprecedented capacity to reduce sleep during migration for long periods of time without associated deficits in cognitive function. Understanding the mechanisms that mediate migratory sleeplessness may provide insights into the etiology of changes in sleep and behavior in seasonal mood disorders, as well as into the functions of sleep itself.

Animal Migration↗
PubMed1980

Early perceptual selectivity in the swamp sparrow.

The cardiac orienting response to species-specific songs was measured in young swamp sparrows and song sparrows. Swamp sparrows respond with significantly greater deceleration to conspecific songs than to songs of the sympatric song sparrow. This discriminatory ability is operating during the sensitive period for song learning and is evident upon initial exposures to conspecific song. These results are the 1st direct evidence for a sensory component in the process of selective vocal learning in birds.

Aging↗
PubMed2003

Seasonal changes in avian song control circuits do not cause seasonal changes in song discrimination in song sparrows.

In seasonally breeding songbirds, brain nuclei of the song control system that act in song perception change in size between seasons. It has been hypothesized that seasonal regression of song nuclei may impair song discrimination. We tested this hypothesis in song sparrows (Melospiza melodia), a species in which males share song types with neighbors and must discriminate between similar songs in territorial interactions. We predicted that song sparrows with regressed song systems would have greater difficulty in discriminating between similar songs. Sparrows were housed either on short days (SD) and had regressed song circuits, or were exposed to long days and implanted with testosterone (LD+T) to induce full growth of the song circuits. We conducted two experiments using a GO/NO-GO operant conditioning paradigm to measure song discrimination ability of each group. Birds learned four (experiment 1) or three (experiment 2) pairs of song types sequentially, with each pair more similar in the number of shared song elements and thus more difficult to discriminate. Circulating T levels differed between the SD and LD+T groups. The telencephalic song nuclei HVc, RA, and area X were larger in the LD+T birds. The two groups of sparrows did not differ, however, in their ability to learn to discriminate between shared song types, regardless of the songs' similarity. These results suggest that seasonal changes in the song control system do not affect birds' ability to make difficult song discriminations.

Animals↗
PubMed2000

Female song sparrow, Melospiza melodia, response to simulated conspecific and heterospecific intrusion across three seasons.

To investigate female responses to territorial intrusion I presented female song sparrows with either a simulated female song sparrow intrusion or a simulated spotted towhee, Pipilo maculatus, intrusion as a control during either the prebreeding, breeding or postmoult seasons. Aggressive and nonaggressive behaviours and vocalizations were compared between intrusion types and across seasons. Principle components analysis suggested that female responses fell into three categories: (1) responses directed towards the intruder, mostly aggressive; (2) responses directed towards the mate; and (3) lack of response to the intruder. In every season, females responded more aggressively to simulated female song sparrow intrusion than simulated towhee intrusion. Responses directed towards female song sparrow intruders dropped across the three seasons and were significantly higher in the prebreeding season than in the breeding or postmoult seasons. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1993

Control of testicular cycles in the song sparrow, Melospiza melodia melodia: interaction of photoperiod and an endogenous program?

Adult male song sparrows, Melospiza melodia melodia, underwent testicular development accompanied by increases in plasma levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) regardless of photoperiods tested. Although gonadal development progressed rapidly in birds exposed to long days, males subjected to short day lengths also showed testicular growth between 90 and 200 days. Onset of photorefractoriness during exposure to continual long days was highly variable among individuals. Short days were not required to regain photosensitivity, and thus spontaneous testicular recrudescence occurred in birds held on long days for prolonged periods. However, cycles of testicular mass, length of cloacal protuberance, and prebasic-type molt in birds held on continuous long days became dissociated and were erratic. It males held on short days were exposed to 1 long day (18L 6D) and then returned to short days, a rapid increase in testicular mass and plasma levels of LH and FSH followed. The effect of 1 long day was greater if males had been exposed to short days for 2 months or longer. Thus, although short days were not absolutely required for dissipating photorefractoriness, they apparently accelerate the process. Female song sparrows showed a similar response to 1 long day. Input from changing day length was also important for triggering testicular regression. Male song sparrows held on 16L 8D for 10 months showed no signs of prebasic molt or testicular regression. When half of the males in this group were then exposed to 14L 10D (a shorter day length but still photostimulatory in spring), there were rapid declines in testis mass and FSH levels. These results are consistent with the phenomenon of "relative photorefractoriness," in which decreased day length results in gonadal regression despite the fact that similar day lengths would have been photostimulatory earlier in spring. It is suggested that song sparrows have "programs" of gonadal activity and molt that are not usually expressed in captivity as part of a complete cycle. The annual change in day length may act to drive the cycle, as continual environmental input for entraining endogenous programs to exactly 1 year and for scheduling the correct temporal sequence of events. Such a combination of continual environmental input and endogenous rhythms may be widespread.

Animals↗
PubMed1996

The timing of thyroid-dependent programming in seasonally breeding male American tree sparrows (Spizella arborea).

There is convincing evidence that euthyroid male American tree sparrows are already programmed for seasonal reproduction and postnuptial molt by Week 4 of photostimulation. To explore more precisely when, during early photostimulation, thyroid-dependent programming of seasonal events occurs, photosensitive male tree sparrows were radiothyroidectomized or sham thyroidectomized on the first day of photostimulation (Week 0) or at Weeks 1 or 3 thereafter. Birds were monitored for testicular growth and regression over 8 or 12 weeks and then tested for photosensitivity or photorefractoriness by exposing them to constant light and exogenous L-thyroxine for 4 weeks. Molt of the primary flight feathers was scored periodically, and at the end of the experiment, hypothalami were saved for cGnRH-I (chicken gonadotropin-releasing hormone I) assay. Because (1) the thyroid is already dysfunctional by Day 4 after radiothyroidectomy, (2) thyroid-dependent photoinduced gonadal growth is programmed growth, and as demonstrated here, (3) testis length at Week 6 on long days (i.e., maximum or near-maximum testis size) is independent of the time of thyroidectomy at or after the onset of photostimulation, we conclude that male American tree sparrows were programmed for photoperiodic testicular growth during the first week of photostimulation. Based on measurements of testis length and hypothalamic cGnRH-I content, only 2 of 11 birds thyroidectomized at Week 1 were already programmed for photorefractoriness by Week 1, whereas all birds thyroidectomized at Week 3 were so programmed by Week 3. Marked differences in molt scores between photorefractory (thyroidectomized and euthyroid) and photosensitive (thyroidectomized) birds argue that postnuptial molt also was programmed roughly between Weeks 1 and 3. To explain these results, we ascribe organizational-like actions directly or indirectly to endogenous thyroid hormones and argue that the onset of photostimulation opens a window, during which time euthyroid male American tree sparrows are programmed for seasonality. A clear dissociation of photorefractoriness from photoperiodic testicular growth in birds thyroidectomized at Week 1 suggests that separate control circuits mediate these two annually periodic events.

Animals↗
PubMed1999

Long days and thyroxine program american tree sparrows for seasonality: evidence for temporal flexibility of the breeding season of euthyroid females.

To explore the role of the thyroid in the control of seasonality, photosensitive female American tree sparrows (Spizella arborea) were thyroidectomized (THX), moved to long days, and given daily injections of thyroxine (T4) for 3 weeks; THX and thyroid-intact (THI) controls received daily injections of alkaline vehicle. Birds were retained on long days 4 additional weeks and then moved to constant light and given T4 in drinking water for 5 weeks in order to test for photorefractoriness. Endpoints were ovarian mass, molt score, and hypothalamic cGnRH-I (chicken gonadotropin-releasing hormone I) content; data were collected as independent measures at intervals of 1 to 5 weeks. THX females given T4 replacement therapy (THXT4 females) exhibited all components of seasonality (i.e., photoperiodic ovarian growth, photorefractoriness, and postnuptial molt), as did THI females. THX females not given replacement T4 were aseasonal: They showed only minor thyroid-independent photoperiodic ovarian growth; they remained photosensitive, despite chronic photostimulation; and they did not initiate postnuptial molt. Collectively, these observations support, and extend to female tree sparrows, our model of seasonality in male tree sparrows, wherein control circuits are programmed for gonadal growth, photorefractoriness, and postnuptial molt by interactive effects of long days and thyroid hormone during the first 3 weeks of photostimulation. The unexpected finding that constant light and/or exogenous T4 extended the simulated breeding seasons of some THI females prompted us to investigate the nature and expression of photorefractoriness. Our approach was to evaluate the same endpoints as before in chronically photostimulated THI females either retained on long days, with or without T4 in drinking water, or moved to constant light, with or without T4. The results showed that exposure to constant light (not T4) near the end of a simulated breeding season can-though usually it does not-temporarily extend the breeding season and prevent the onset of postnuptial molt. It remains unclear whether these perturbations caused by constant light reflect a transitional relative photorefractoriness or merely a delay in the onset of absolute photorefractoriness. In either case, the thyroid- and daylength-dependent programs controlling seasonality in female American tree sparrows have a heretofore undemonstrated potential for limited temporal flexibility.

Animals↗
PubMed2000

Photoperiodic regulation of the male house sparrow song control system: gonadal dependent and independent mechanisms.

The primary and secondary sexual characteristics of many species of passerine birds undergo dramatic seasonal variation in response to the change in the length of photoperiod. Among the many physiological processes that undergo seasonal changes, bird song and the song control system underlying it undergo similar seasonal variation in size and function. The mechanisms of this seasonal variation are largely unknown but are at least partially due to steroidal action from the gonads. The present study determined the relative roles played by the gonads and the photoperiodic timing system that controls gonadal development on song control nuclei in the brain of the male house sparrow, Passer domesticus. Sparrows maintained in short photoperiods (SD) possessed small regressed testes. Transfer to long photoperiods (LD) for 6 weeks evoked a dramatic increase in testes size, but, after 20 weeks under the same conditions (LDLD), testes completely collapsed. Song control nuclei HVC and RA were smaller in SD than in LD but regressed only moderately in LDLD. Castration of sparrows in SD reduced the amplitude of the seasonal variation but did not completely abolish it. The data support the view that the song control system of the house sparrow is regulated by the photoperiodic timing system independently of gonadal influence, but that the gonads augment seasonal regulation of song, presumably via steroidal hormone secretion.

Animals↗
PubMed2004

Diversity of Mhc class I and IIB genes in house sparrows (Passer domesticus).

In order to understand the expression and evolution of host resistance to pathogens, we need to examine the links between genetic variability at the major histocompatibility complex ( Mhc), phenotypic expression of the immune response and parasite resistance in natural populations. To do so, we characterized the Mhc class I and IIB genes of house sparrows with the goal of designing a PCR-based genotyping method for the Mhc genes using denaturing gradient gel electrophoresis (DGGE). The incredible success of house sparrows in colonizing habitats worldwide allows us to assess the importance of the variability of Mhc genes in the face of various pathogenic pressures. Isolation and sequencing of Mhc class I and IIB alleles revealed that house sparrows have fewer loci and fewer alleles than great reed warblers. In addition, the Mhc class I genes divided in two distinct lineages with different levels of polymorphism, possibly indicating different functional roles for each gene family. This organization is reminiscent of the chicken B complex and Rfp-Y system. The house sparrow Mhc hence appears to be intermediate between the great reed warbler and the chicken Mhc, both in terms of numbers of alleles and existence of within-class lineages. We specifically amplified one Mhc class I gene family and ran the PCR products on DGGE gels. The individuals screened displayed between one and ten DGGE bands, indicating that this method can be used in future studies to explore the ecological impacts of Mhc diversity.

Alleles↗
PubMed2005

Leucocytozoonosis in the Israeli sparrow, Passer domesticus biblicus Hartert 1904.

Among the 91 house sparrows (Passer domesticus biblicus Hartert, 1904) examined and caught in the Jordan valley, Israel, 79% were found to be infected with Leucocytozoon fringillinarum Woodcock 1910. In the coastal plain of Israel (South of Tel Aviv), Leucocytozoon infection was found in only 3 out of 43 examined sparrows. In the birds examined, Leucocytozoon gametocytes were present, often in large numbers, in the circulating blood of the visceral organs, whereas they were only sporadic or even absent in the peripheral blood. Gametocytes were seen in the brain capillaries in only a few birds. Only one of the heavily infected sparrows was anemic. Leucocytozoon merozoites were present in the liver and kidneys in only a few infected birds. Merogonic infections did not induce any severe pathological changes, while the gametocyte congestion caused dilation of the blood vessels and sinuses. Tissue damage by the gametocyte parasitemia was most evident in the liver and kidneys. Leucocyte infiltration developed alongside the affected vessels; diffuse necrosis developed in the infiltrated areas. In the kidneys, many tubules were degenerated. Leucocytozoon gametocyte infection in sparrows is unique in that it appears to be confined, for most of its duration, to the visceral circulation, resulting in clinical consequences. Geographically, it is confined to habitats presumably supporting vectors.

Animals↗