Intact Birds Research Articles

GPS tracking technology and re-visiting the relationship between the avian visual Wulst and homing pigeon navigation

Within their familiar areas homing pigeons rely on familiar visual landscape features and landmarks for homing. However, the neural basis of visual landmark-based navigation has been so far investigated mainly in relation to the role of the hippocampal formation. The avian visual Wulst is the telencephalic projection field of the thalamofugal pathway that has been suggested to be involved in processing lateral visual inputs that originate from the far visual field. The Wulst is therefore a good candidate for a neural structure participating in the visual control of familiar visual landmark-based navigation. We repeatedly released and tracked Wulst-lesioned and control homing pigeons from three sites about 10–15 km from the loft. Wulst lesions did not impair the ability of the pigeons to orient homeward during the first release from each of the three sites nor to localise the loft within the home area. In addition, Wulst-lesioned pigeons displayed unimpaired route fidelity acquisition to a repeated homing path compared to the intact birds. However, compared to control birds, Wulst-lesioned pigeons displayed persistent oscillatory flight patterns across releases, diminished attention to linear (leading lines) landscape features, such as roads and wood edges, and less direct flight paths within the home area. Differences and similarities between the effects of Wulst and hippocampal lesions suggest that although the visual Wulst does not seem to play a direct role in the memory representation of a landscape-landmark map, it does seem to participate in influencing the perceptual construction of such a map.

Muscle force-length dynamics during walking over obstacles indicates delayed recovery and a shift towards more 'strut-like' function in birds with proprioceptive deficit.

Recent studies of in vivo muscle function in guinea fowl revealed that distal leg muscles rapidly modulate force and work to stabilize running in uneven terrain. Previous studies focused on running only, and it remains unclear how muscular mechanisms for stability differ between walking and running. Here, we investigated in vivo function of the lateral gastrocnemius (LG) during walking over obstacles. We compared muscle function in birds with intact (iLG) versus self-reinnervated LG (rLG). Self-reinnervation results in proprioceptive feedback deficit due to loss of monosynaptic stretch reflex. We tested the hypothesis that proprioceptive deficit results in decreased modulation of EMG activity in response to obstacle contact, and a delayed obstacle recovery compared with that for iLG. We found that total myoelectric intensity (Etot) of iLG increased by 68% in obstacle strides (S0) compared with level terrain, suggesting a substantial reflex-mediated response. In contrast, Etot of rLG increased by 31% in S0 strides compared with level walking, but also increased by 43% in the first post-obstacle (S+1) stride. In iLG, muscle force and work differed significantly from level walking only in the S0 stride, indicating a single-stride recovery. In rLG, force increased in S0, S+1 and S+2 compared with level walking, indicating three-stride obstacle recovery. Interestingly, rLG showed little variation in work output and shortening velocity in obstacle terrain, indicating a shift towards near-isometric strut-like function. Reinnervated birds also adopted a more crouched posture across level and obstacle terrains compared with intact birds. These findings suggest gait-specific control mechanisms in walking and running.

Hypothalamic molecular correlates of photoperiod-induced spring migration in intact and castrated male redheaded buntings

This study investigated the molecular changes associated with neural plasticity in photoperiodic induction of spring migration in intact and castrated redheaded bunting, Emberiza bruniceps. We measured the hypothalamic mRNA expression of genes in birds that were photostimulated into winter non-migratory and spring (vernal) migratory phenotypes under short and long photoperiods, respectively. These included genes associated with the appetitive phase of reproduction (spring migration drive, th and ddc genes encoding for tyrosine hydroxylase and dopamine decarboxylase enzymes, respectively), sleep/awake state (pmch gene encoding for pro-melanin concentrating hormone; hcrt and hcrtr2 encoding for the hypocretin/orexin and its receptor, respectively) and neurogenesis (dcx and neuN coding for doublecortin and neuronal nuclear proteins, respectively). Higher th mRNA levels suggested an upregulated dopamine synthesis in the hypothalamus of spring migrants. Similarly, elevated hcrt and hcrtr2 mRNA levels suggested an increased wakefulness, and those of dcx and neuN genes suggested an enhanced neurogenesis during the spring migration state. Further, compared to intact birds, the lower th and pmch, and higher hcrtr2 and neuN mRNA levels in castrates suggested a role of testicular steroids in modulation of the appetitive phase of reproduction, sleep and awake states, and neurogenesis during spring migration period. These results provide insights into molecular changes linked with important hypothalamic molecular pathways and steroidal influence in the photoperiodic induction of spring migration in obligate migratory songbirds.

B cells do not play a role in vaccine-mediated immunity against Marek’s disease

BackgroundMarek’s disease virus (MDV), a highly oncogenic α-herpesvirus, is the etiological agent of Marek’s disease (MD) in chickens. The antiviral activity of vaccine-induced immunity against MD reduces the level of early cytolytic infection, production of cell-free virions in the feather follicle epithelial cells (FFE), and lymphoma formation. Despite the success of several vaccines that have greatly reduced the economic losses from MD, the mechanism of vaccine-induced immunity is poorly understood. MethodsTo provide insight into possible role of B cells in vaccine-mediated protection, we bursectomized birds on day of hatch and vaccinated them eight days later. The birds were challenged 10 days post vaccination with or without receiving adoptive lymphocytes from age-matched control birds prior to inoculation. The study also included vaccinated/challenged and non-vaccinated challenged intact birds. Flowcytometric analysis of PBMN cells were conducted twice post bursectomy to confirm B cell depletion and assess the effect of surgery on T cell population. Immunohistochemical analysis and viral genome copy number assessment in the skin samples at termination was performed to measure the replication rate of MDV in the FFE of the skin tissues of the challenged birds. ResultsThe non-vaccinated/challenged birds developed typical clinical signs of MD while the vaccinated/challenged and bursectomized, vaccinated/challenged groups with or without adoptive lymphocyte transfer, were fully protected with no sign of transient paralysis, weight loss, or T cell lymphomas. Immunohistochemical analysis and viral genome copy number evaluation in the skin samples revealed that unlike the vaccinated/challenged birds a significant number of virus particles were produced in the FFE of the non-vaccinated/challenged birds at termination. In the bursectomized, vaccinated/challenged groups, only a few replicating virions were detected in the skin of birds that received adoptive lymphocytes prior to challenge. ConclusionsThe study shows that B cells do not play a critical role in MD vaccine-mediated immunity.

True digestibility of the essential amino acids of high-protein sunflower meals by balanced experiments with intact and caecectomized birds from Gallus species

Abstract. Using adapted methods for balanced experiments with poultry, the true digestibility coefficients of the essential amino acids of two high protein sunflower meals – 40+® and 47® have been established. The true digestibility coefficients by using two methods – with intact and randomized (caecectomized) birds have been compared. Six birds were tube fed and six – feed deprived for both of the fodders. The amino acids were established with amino analyzer AAA-881 after preliminary HCl hydrolysis. The mean digestibility of sunflower meal 40+® is higher in intact (88.11 versus 85.73 of sunflower meal 47®) compared to randomized birds (87.20 versus 85.46 of sunflower meal 47®). The differences by lots are statistically significant only in intact birds. The authors recommend for practical needs to use the average true digestibility coefficients between both meals, established with randomized birds (ileal digestibility).

Morphofunctional condition of the harderian gland of chickens during the post-vaccine immunity to infectious bronchitis

Aim. To fi nd out the contents and placement of CD4+, CD8+, CD45RA+, CD20+-lymphocyte subpopulations and morphocytochemical architecture of the harderian gland in clinically healthy chickens and for vaccination against infectious bronchitis. Methods. Anatomical, histological, immunohistochemical, optical, morphometric and variational-statistical. Results. The obtained morphometric study results showed that the area of secretory lobules and lymphoid formations was signifi cantly larger in the harderian gland of vaccinated 40-, 90- and 110-day-old chickens. Moreover, the organ size correlates signifi cantly with the development of lymphoid formations, since the area of the secretory lobules in the gland of the experimental group chickens does not differ from that of the control group. Immunohistochemical studies have shown that the number of lymphocytes with CD20+ markers was characterized by a reliable (P < 0.001) increase in B-lymphocytes in the harderian gland of the vaccinated chickens of all ages. Lymphocytes with CD8+ markers were not detected in the gland of vaccinated 8- and 20-day-old chickens. According to cytomorphometric studies, their number in vaccinated 40-, 90- and 110-day-old chickens was signifi cantly (P < 0.001) higher compared to intact birds – 2.11, 2.38 and 2.96 times, respectively. Conclusions. The data on the composition of lymphocytes with CD4+, CD8+, CD45RA+, CD20+ markers in the harderian gland of chickens of different age, on their changes in case of immunization against infectious bronchitis were obtained, and the role of certain clusters at different stages of the immunity formation was determined. The information on the structure, patterns of growth and development of the harderian gland of chickens, which demonstrates the incompleteness of its morphogenesis at the early stages of the postnatal ontogenesis period that should be taken into account during the compilation of vaccine prophylaxis programs, has been supplemented.

Biologically active additives, their effect on the egg production of geese, hatchability, and development of goslings

The prospects of goosewatch development are determined by several factors: goose meat contains 17.5-18.5% protein, 22-23% of fat, 0.9-1.0% of ash. Insufficient reflection of these issues in the husbandry industry, peasant farms determined the direction of our study – the study of the impact of "Pozitron-2 Air 1" artificial ozonizer on the microclimate of the plant growing geese and biologically active additives "Bacell", "Larikarvit" and "Sporobacterin" on the body of geese and gooslings. When performing research work, zoohygienic, hematological, biochemical, zootechnical, veterinary and sanitary, economic research methods using modern methods and instruments were used. The conducted studies had shown that 3-hour sessions of ozonation with the specified device at a dose of 0.02 m3 of ozonated air per 1 m3 of purified air of the room significantly changed the state of the microclimate in it for the better. Thus, the relative humidity in the room for growing gooslings after ozonation significantly decreased from 78.64±0.16 to 71.12±0.14%, that is, on average by 7.52% (P<0.05), ammonia concentration - by 22.73% (P<0.01), hydrogen sulfide – by 32.27% (P<0.01), carbon dioxide – by 18.18% (P<0.01), dust – by 60.56% (P<0.001), microorganisms – by 46.94% (P<0.01) (P < 0.001). These data indicated that the tested artificial ozonizer Pozitron-3 Air-1 improved and normalized the microclimate in the room for growing gooslings. When testing new dietary supplements, geese egg laying, hibernation hatching and hatchability were important indicators. The results of the study showed that egg production in geese of experimental groups, against the background of the use of dietary supplements "Larikarvit", "Bacell", "Sporobacterin", compared with analogues in the control of February – June was higher by an average of 6.44%, 7.49%, 6.64% (P<0.01). Among these experimental groups of birds, in comparison with intact birds, the highest egg production was in the second experimental group of gooslings, where the biologically active additive "Bacell" was used as part of the main diet, within 7.49% (P<0.01). As it is known, the output of young animals in goose breeding is determined by the number of viable, healthy gooslings, expressed as a percentage of the number of eggs laid in the incubator. The results showed that this important indicator in the application of dietary supplements in the diet of geese in experimental batches, compared with the control batch was significantly higher by 7.71, 10.31, 8.85 (P<0.05) percent.

Anosmic migrating songbirds demonstrate a compensatory response following long-distance translocation: a radio-tracking study

A number of studies have shown that migrating birds can navigate to their destinations even when displaced to unfamiliar territory. It has been demonstrated that adult Eurasian Reed Warblers (Acrocephalus scirpaceus) captured in spring in the Eastern Baltic, displaced 1000 km eastward to the Moscow region and tested in orientation cages, show a clear orientation tendency towards their breeding grounds. This response requires the ability to determine a new geographic position relative to the goal. The natural cues that are used as coordinates for this behaviour remain controversial. Among other natural cues, both magnetic and olfactory sources of information have received the most experimental attention. More recently, virtual displacement experiments have shown that the geomagnetic information alone is sufficient for Reed Warblers to find their geographic position. However, the role of olfaction was not explicitly examined. In the present study, we displaced anosmic Reed Warblers together with untreated controls between the same capture and displacement sites where the Emlen funnel tests were previously performed. Following release, we radio-tracked birds for the first few kilometres using an array of automated radio-tracking towers. The results strongly suggest a navigational response of both anosmic and intact birds (anticlockwise re-orientation), unlike some other experiments showing impaired navigational abilities of anosmic migrating birds. This data supports the hypothesis that, at least in this songbird species, the olfactory system is not crucial for determining geographic position, and that the zinc sulfate anosmia treatment is unlikely to have any non-specific effects on navigational abilities.

Beyond Critical Period Learning: Striatal FoxP2 Affects the Active Maintenance of Learned Vocalizations in Adulthood.

In humans, mutations in the transcription factor forkhead box P2 (FOXP2) result in language disorders associated with altered striatal structure. Like speech, birdsong is learned through social interactions during maturational critical periods, and it relies on auditory feedback during initial learning and on-going maintenance. Hearing loss causes learned vocalizations to deteriorate in adult humans and songbirds. In the adult songbird brain, most FoxP2-enriched regions (e.g., cortex, thalamus) show a static expression level, but in the striatal song control nucleus, area X, FoxP2 is regulated by singing and social context: when juveniles and adults sing alone, its levels drop, and songs are more variable. When males sing to females, FoxP2 levels remain high, and songs are relatively stable: this “on-line” regulation implicates FoxP2 in ongoing vocal processes, but its role in the auditory-based maintenance of learned vocalization has not been examined. To test this, we overexpressed FoxP2 in both hearing and deafened adult zebra finches and assessed effects on song sung alone versus songs directed to females. In intact birds singing alone, no changes were detected between songs of males expressing FoxP2 or a GFP construct in area X, consistent with the marked stability of mature song in this species. In contrast, songs of males overexpressing FoxP2 became more variable and were less preferable to females, unlike responses to songs of GFP-expressing control males. In deafened birds, song deteriorated more rapidly following FoxP2 overexpression relative to GFP controls. Together, these experiments suggest that behavior-driven FoxP2 expression and auditory feedback interact to precisely maintain learned vocalizations.

The causative effects of corticosterone on innate immunity during the stress response in the House Sparrow, Passer domesticus

Stress-induced inhibition of innate immune activity has been observed in a variety of wild birds and may increase chances of infection because this activity constitutes the first line of defense against pathogens. We previously reported that the transient elevation of plasma corticosterone (CORT; the primary avian glucocorticoid) that occurs during stress is necessary for stress-induced suppression of natural antibody-mediated, complement-mediated, and bactericidal activity. Here, we further investigated the regulatory role of CORT during this suppression. To this end, we treated House Sparrows (Passer domesticus) with mitotane to block endogenous CORT production, administered CORT at one of three doses (HI: 1.34 mg/kg; LO: 1.00 mg/kg; CON: vehicle), and assessed natural antibody-mediated, complement-mediated, and bactericidal activity during acute stress induced by handling and restraint. Mitotane administration eliminated the endogenous plasma CORT increase that normally takes place during stress, and corticosterone treatment increased plasma CORT to levels similar to those measured in intact birds during acute stress. As predicted, mitotane-treated birds receiving CON injections did not exhibit stress-induced suppression of complement-mediated and bactericidal activity, and CORT administration at both LO and HI doses restored this suppression. Contrary to expectations, mitotane-treated birds receiving CON injections demonstrated stress-induced suppression of natural antibody-mediated activity. Furthermore, CORT administration did not influence this parameter. These results suggest that stress inhibits innate immune activity through both CORT-dependent and CORT-independent mechanisms, but the contribution of these mechanisms can vary. This variation may result from effects of environmental factors, the identity and role of which warrant further research.

Recurrent development of song idiosyncrasy without auditory inputs in the canary, an open-ended vocal learner

Complex learned behaviors, like bird song and human speech, develop under the influence of both genetic and environmental factors. Accordingly, learned behaviors comprise species specificity and individual variability. Auditory information plays a critical role in vocal learning by songbirds, both to memorize tutor songs and to monitor own vocalizations. Nevertheless, audition-deprived songbirds develop structured, species-specific song patterns. It remains to be elucidated how the auditory input contributes to the development of individual variability of song characteristics. Here we show that an open-ended vocal learner, the canary, annually recapitulates individually unique songs without audition. Although the total number of syllable types was reduced by auditory deprivation, other vocal phenotypes examined in the syllable, phrase, and syntax of songs were conserved between the 1st and 2nd years, both in deafened and intact birds. In deafened canaries, approximately 60% of the syllables were yearly reproduced with consistent acoustic features, whereas the remaining syllables were replaced with new ones in an annual cycle of song development. These results indicate that the open-ended vocal learning of canaries involves an audition-independent mechanism for the development of recurrent song idiosyncrasy.

Changes in the content of edible and non-edible components and distribution of tissue components in cockerels and capons

The aim of this study was to determine the effects of castration and age on the content of edible and non-edible components, and the distribution of tissue components in the carcasses of cockerels and capons. The study was conducted on 200 birds (Green-legged Partridge), divided into two sex categories (with 5 replications per group and 20 birds per replication), raised to 28 wk of age. At 8 wk of age, 100 birds were surgically castrated and afterwards at 12 wk of age and at four-wk intervals, 10 intact cockerels and 10 capons were selected randomly and slaughtered. Cockerels, compared with capons, were characterized by a higher proportion of edible components at 24 and 28 wk of age, and a more desirable carcass tissue composition due to a higher content of lean meat in total body weight (BW). Capons had higher abdominal fat content than cockerels, which resulted in a higher percentage of non-edible components in their BW at 24 and 28 wk of age. Differences in the distribution of lean meat in the carcass were noted from 20 wk of age in both castrated and intact birds. The content of breast muscles increased in capons, and the content of leg muscles (thigh and drumstick) increased in cockerels. The results of this study indicate that in view of the optimal lean meat content of the carcass and the optimal distribution of major tissue components, Green-legged Partridge capons should be fattened for a maximum period of 24 wk.

Experienced migratory songbirds do not display goal-ward orientation after release following a cross-continental displacement: an automated telemetry study.

The ability to navigate implies that animals have the capability to compensate for geographical displacement and return to their initial goal or target. Although some species are capable of adjusting their direction after displacement, the environmental cues used to achieve this remain elusive. Two possible cues are geomagnetic parameters (magnetic map hypothesis) or atmospheric odour-forming gradients (olfactory map hypothesis). In this study, we examined both of these hypotheses by surgically deactivating either the magnetic or olfactory sensory systems in experienced white-throated sparrows (Zonotrichia albicollis) captured in southern Ontario, Canada, during spring migration. Treated, sham-treated, and intact birds were then displaced 2,200 km west to Saskatchewan, Canada. Tracking their initial post-displacement migration using an array of automated VHF receiving towers, we found no evidence in any of the groups for compensatory directional response towards their expected breeding grounds. Our results suggest that white-throated sparrows may fall back to a simple constant-vector orientation strategy instead of performing true navigation after they have been geographically displaced to an unfamiliar area during spring migration. Such a basic strategy may be more common than currently thought in experienced migratory birds and its occurrence could be determined by habitat preferences or range size.

Đánh giá các phương pháp xác định tỷ lệ tiêu hóa biểu kiến acid amin và các dưỡng chất ở gà Sao tăng trưởng

A comparative study was conducted to evaluate the apparent digestibility methods of amino acids and nutrients on growing Guinea fowls at 10 weeks of age. The experiment was a completely randomized design with three treatments and five replications. The treatments were total tract, caecetomised, and ileal digestibilities. The results showed that the apparent EE digestibility and nitrogen retention of intact birds were resemble with those of caecetomised birds (p>0.05). However, the apparent digestibility coefficients of CF, NDF and ADF were higher for the intact birds as compaired to those of the caecetomised birds (p0.05). The amino acid digestibility values obtained of the intact birds were significantly higher (p

True navigation in migrating gulls requires intact olfactory nerves.

During migratory journeys, birds may become displaced from their normal migratory route. Experimental evidence has shown that adult birds can correct for such displacements and return to their goal. However, the nature of the cues used by migratory birds to perform long distance navigation is still debated. In this experiment we subjected adult lesser black-backed gulls migrating from their Finnish/Russian breeding grounds (from >60°N) to Africa (to < 5°N) to sensory manipulation, to determine the sensory systems required for navigation. We translocated birds westward (1080 km) or eastward (885 km) to simulate natural navigational challenges. When translocated westwards and outside their migratory corridor birds with olfactory nerve section kept a clear directional preference (southerly) but were unable to compensate for the displacement, while intact birds and gulls with the ophthalmic branch of the trigeminal nerve sectioned oriented towards their population-specific migratory corridor. Thus, air-borne olfactory information seems to be important for migrating gulls to navigate successfully in some circumstances.

Duration of melatonin regulates seasonal plasticity in subtropical Indian weaver bird, Ploceus philippinus

Day length regulates seasonal plasticity connected with reproduction in birds. Rhythmic pineal melatonin secretion is a reliable indicator of the night length, hence day length. Removal of rhythmic melatonin secretion by exposure to constant bright light (LLbright) or by pinealectomy renders several species of songbirds including Indian weaver bird (Ploceus philippinus) arrhythmic. Present study investigated whether rhythmic melatonin is involved in the regulation of key reproductive neuropeptides (GnRH I and GnIH) and reproduction linked neural changes, viz. song control nuclei, in Indian weaver birds. Two experiments were performed using birds in an arrhythmic condition with low (under LLbright) or no (in the absence of pineal gland) endogenous melatonin. In experiment I, three groups of birds (n=5 each) entrained to 12L:12D were exposed to LLbright (25lux) for two weeks. Beginning on day 15 of LLbright, a control group received vehicle for 16h and two treatment groups were given melatonin in drinking water for 8h or 16h. In experiment II, one group of sham-operated and three groups of pinealectomized birds (n=5 each) entrained to 12L:12D were exposed to constant dim light (LLdim, 0.5lux). Beginning on day 15 of LLdim, three groups received similar treatment as in experiment I. Birds were perfused after thirty cycles of the melatonin treatment, and brain sections were immunohistochemically double-labeled for GnRH I and GnIH or Nissl stained. Activity was recorded throughout the experiments, while body mass and testes were measured at the beginning and end of the experiment. Birds were synchronized with melatonin cycles and measured the duration of melatonin as “night”. Pinealectomized birds that received 16h of melatonin had significantly higher GnIH-ir cells than those received 8h melatonin; there was no difference in the GnRH I immunoreactivity between two treatment groups however. Intact birds that received long duration melatonin cycles exhibited small song control nuclei, specifically the high vocal center (HVC) and the robust nucleus of the arcopallium (RA), while birds that received short duration melatonin or no melatonin exhibited large HVC and RA. Thus, melatonin possibly regulates seasonal reproduction via GnIH secretion, and also controls seasonal neuroplasticity in the song control system in songbirds.

The Bird Circadian Clock: Insights from a Computational Model

The circadian timekeeping system appears more complex in birds than in mammals. In mammals, the main pacemaker is centralized in the suprachiasmatic nuclei, whereas in birds, the pacemaker involves the interplay between the pineal and hypothalamic oscillators. In order to investigate the consequence of this complex mechanism, we propose here a mathematical model for the bird circadian clock. The model is based on the internal resonance between the pineal and hypothalamic oscillators, each described by Goodwin-like equations. We show that, consistently with experimental observations, self-sustained oscillations can be generated by mutual inhibitory coupling of the 2 clocks, even if individual oscillators present damped oscillations. We study the effect of constant and periodic administrations of melatonin, which, in intact birds, acts as the coupling variable between the pineal and the hypothalamus, and compare the prediction of the model with the experiments performed in pinealectomized birds. We also assess the entrainment properties when the system is subject to light-dark cycles. Analyses of the entrainment range, resynchronization time after jet lag, and entrainment phase with respect to the photoperiod lead us to formulate hypotheses about the physiological advantage of the particular architecture of the avian circadian clock. Although minimal, our model opens promising perspectives in modeling and understanding the bird circadian clock.

Variation in enkephalin immunoreactivity in the social behavior network and song control system of male European starlings (Sturnus vulgaris) is dependent on breeding state and gonadal condition

Many temperate zone songbird species exhibit marked seasonal variation in song quality as well as in the motivation to sing. Two brain systems are known to mediate such annual variation in song quality and motivation: (1) the song control system (SCS), and (2) the social behavior network (SBN), respectively. How these two circuits interact to produce changes in singing behavior is not well understood. The opioid enkephalin is expressed in both the SCS and SBN and may function to modulate song quality in a socially relevant manner. Using immunocytochemistry, we examined variation in enkephalin immunoreactivity (ENK-ir) in male European starlings (Sturnus vulgaris) that were in breeding conditions (i.e. photostimulated) or non-breeding conditions (i.e. photorefractory). We also included a group of castrated photostimulated males to investigate the relationship between gonadal steroids and ENK-ir. ENK-ir in the preoptic area (POA) and lateral septum (LS) was greater in photostimulated intact birds as compared to photorefractory males, but not in other regions within the SBN. There was a significant difference in ENK-ir in two forebrain song nuclei, HVC and the lateral nucleus of the anterior medial nidopallium (lMAN), with lower expression in photostimulated intact as compared to photorefractory birds. ENK-ir did not change across breeding conditions in the Nucleus Interface (NIf). After accounting for the volumetric change in HVC and lMAN, the pattern of ENK-ir remained greater in photorefractory compared to intact photostimulated starlings. We propose that the observed regulation of ENK-ir in the POA and LS may be related to seasonal changes in the motivation to engage in singing behavior, while the change in ENK-ir in the song system are associated with the quality of the song produced. Thus seasonal changes in a single neuromodulatory system can have very different functional effects based on the neuroanatomical specificity of its expression.

Effect of Caponization on Muscle Composition, Shear Value, ATP Related Compounds and Taste Appraisal in Taiwan Country Chicken Cockerels

An experiment was conducted to determine the effects of caponization on the muscle composition, ATP-related compounds, the shear values, the taste panel scores and the muscle fiber areas of Taiwan country chicken cockerels. At 10 wks of age, cockerels were divided into two groups: caponized and untreated. Birds were fed grower and finisher diets ad libitum in an eighteen-week experimental period. Results showed that capons contained significantly greater muscle fat content, less breast and thigh muscle moisture content, shear value and muscle fiber area (p0.05) in breast and thigh muscle protein content. Compared with the intact birds, the capons contained significantly (p0.05) in thigh muscle ash content. The breast muscle IMP and ATP+ADP+AMP+IMP contents in the intact birds were significantly (p

Does testosterone determine dominance in the house sparrow Passer domesticus? An experimental test

Badges of status function in many birds within a social context to establish dominance hierarchies and reduce antagonistic encounters. In order to maintain the honesty of the signalling system, such badges must be costly to produce or to maintain. The chest bib of the house sparrow functions as a badge of status and changes in size are known to be controlled by testosterone levels. We sought to test the relative importance of testosterone as opposed to bib size in determining dominance within a group of male house sparrows. We did this by manipulating testosterone levels independently during both breeding and post‐breeding seasons in experimental birds and examining the effect of testosterone titre, as well as corticosterone titre relative to bib size on dominance levels. Dominance hierarchies within the groups were tested during both the breeding and post‐breeding phases. We compared the results of these tests with dominance among intact (unmanipulated) birds. Results suggested that the breeding season dominance levels were largely determined by testosterone levels as well as bib size, whereas the post‐breeding dominance levels were determined by post‐breeding testosterone titre and previous breeding season dominance level. Within unmanipulated birds, basal corticosterone levels were significantly, negatively correlated with dominance level, but only during the breeding season. The influence of breeding season dominance on post‐breeding dominance suggests social history is important in determining dominance interactions as well as current testosterone levels and bib size.