Various divalent cations protect the isolated perfused pigeon heart against a calcium paradox

The protective effects of various divalent cations against the irreversible damage of myocardium, a phenomenon termed the Ca²⁺-paradox, were examined in the isolated perfused pigeon heart. All cations examined were added at a concentration of 200 mol l^–1 in the calcium-free medium. In hearts perfused with low calcium, upon normal calcium repletion, the maximal recovery of the contractile tension (in the 2nd minute) was approximately 115% and the recovery obtained at the end of reperfusion was 81.5% (compared to the equilibration period value). From the other divalent cations examined, the presence of cobalt, nickel, manganese or barium during calcium depletion powerfully protected the pigeon heart. Upon calcium repletion, the maximal recovery of contractile tension was approximately 60%, 76.5%, 100% and 85%, the recovery estimated at the end of reperfusion was 40%, 12%, 70% and 53%, and the resting tension estimated at the end of reperfusion was 2.69±0.18 g, 6.40±0.50 g, 1.20±0.10 g and 1.90±0.10 g for cobalt, nickel, manganese and barium, respectively. On the contrary, strontium exerted no protective effects. The protective effects were also indicated by reduced total protein and lactate dehydrogenase activity release into the effluent perfusate and maintenance of electrical activity. The effectiveness of the added divalent cations (with the exception of strontium) showed a strong dependence upon their ionic radius. The most potent inhibitors of this phenomenon in the pigeon heart were the divalent cations having an ionic radius closer to the ionic radius of calcium. These results are discussed in terms of the possible mechanisms involved in the protective effects of these cations.Communicated by: G. Heldmaier     

Biochemical properties of pigeon milk and its effect on growth

Summary The avian juvenile food pigeon milk was studied for its chemical composition and effect on growth in vivo and in vitro. Pigeon milk on a wet weight basis consisted of 9–13% protein, 9–11% fat, 0.9–1.5% carbohydrate, 0.8–1.1% ash, 0.10–0.12% non-protein nitrogen, energy content 5.6–6.8 kcal·g^-1. Except for proteins there was little or no decrease in pigeon milk constitutents during the first week of secretion. Pigeon milk proteins consisted of trichloroacetic acid (precipitable), trichloroacetic acid (soluble), and free amino acid components in the ranges 8.4–12.1%, 0.5–0.7% and 1.4–2.5%, respectively; whereas the level of trichloroacetic acid (precipitable) and trichloroacetic acid (soluble) components decreased by about 30%, that of the free amino acids increased by 9% in the first week. About 0.6–1.0% of pigeon milk sugar was found in the trichloroacetic acid (soluble) fraction and increased by 67% in the first week. The remainder was found in the trichloroacetic acid (precipitable) fraction and did not change during this period. Major lipids of pigeon milk were the neutral lipids (7.8–8.4%); the minor lipids were glycolipids (0.9–1.6%), phospholipids (0.5–1.4%) and cholesterol (0.5–0.6%). Squabs fed pigeon milk increased their body weight by 22-fold in the first 3 weeks after hatching, and crude extracts of pigeon milk stimulated the growth of cultured hamster ovary cells. These results reflect the ability of pigeon milk to stimulate growth both in vivo and in vitro.Abbreviations AOAC association of official analytical chemists - BRIT board of radiation and isotope technology - CHO chinese hamster ovary - DNA deoxyribonucleic acid - EDTA ethylenediaminetetra-acetic acid - FCS foetal calf serum - GF growth factor - GS goat serum - MEM minimum essential medium - NPN nonprotein nitrogen - PBS phosphate-buffered saline - PM pigeon milk - TCA(P) trichloroacetic acid precipitable fraction - TCA(S) trichloroacetic acid soluble fraction     

Immunoreactivity to vasoactive intestinal polypeptide (VIP) and thyreotropin-releasing hormone (TRH) in hypothalamic neurons of the domesticated pigeon (Columba livia). Alterations following lactation and exposure to cold

Summary The distribution of VIP- and TRH-immunoreactivity in neurons and processes within the hypothalamus of the pigeon was investigated with light-microscopic immunocytochemical techniques. Most of the VIP-containing neurons are concentrated in the middle and caudal parts of the hypothalamus, with the greatest concentration of perikarya occurring in the medial and lateral part of the ventromedial hypothalamic nucleus and the infundibular nucleus. These cells give rise to axons that seem to extend into the median eminence. An extensive network of VIP-immunoreactive fibers and varicosities occupy the external layer of the median eminence. The majority of TRH-containing neurons is found in the anterior hypothalamus with the greatest concentration of cells in the magnocellular preoptic, medial preoptic, suprachiasmatic and paraventricular nuclei. TRH-immunoreactive fibers and varicosities form a dense arborization in the external layer of the median eminence. Lactation seems to induce substantial changes in VIP as well as in TRH-immunostaining in the median eminence and other hypothalamic regions as compared to control, sexually active animals. Furthermore, TRH-immunoreactivity decreased in the median eminence following 60-min exposure to cold. These results suggest that VIP- and TRH-containing pathways in the pigeon hypothalamus are involved in the mediation of neuroendocrine responses.     

Drinking behavior and jaw muscle (EMG) activity in the pigeon (Columba livia)

The relation between jaw movements and jaw muscle activity was examined during two different types of drinking in pigeons: tip and rictus drinking. The amplitude and duration of jaw opening is greater for rictus than for tip drinking, but both types involve individual cycles of jaw-opening and closing movements, organized into bouts. Cycle duration increases gradually over the initial portion of the bout and is relatively constant thereafter.Each drinking cycle is composed of an initial rapid jaw-opening component, a sustained opening phase of variable duration and a closing movement. The initial and final phases are related, respectively, to activity in the upper beak levator (protractor) and the jaw closer (adductor, pterygoid) muscles. The amplitude and duration of the sustained phase are correlated with the magnitude and duration of activity in the lower jaw opener (depressor). The kinematic and electromyographic organization of jaw movements during drinking is discussed in relation to the morphology of the jaw apparatus and the functional requirements of the behavior.Abbreviations AMEM adductor mandibulae externus muscle - DM depressor mandibulae muscle - EMG electromyographic - PQP protractor quadrati et pterygoidei muscle - PTP pseudotemporalis profundus muscle - PVL/PVM pterygoideus ventralis muscle, pars lateralis and medialis     

The directionality of the ear of the pigeon (Columba livia)

Summary The directionality of cochlear microphonic potentials in the azimuthal plane was investigated in the pigeon (Columba livia), using acoustic free-field stimulation (pure tones of 0.25–6 kHz).At high frequencies in the pigeon's hearing range (4–6 kHz), changing azimuth resulted in a maximum change of the cochlear microphonic amplitude by about 20 dB (SPL). The directionality decreased clearly with decreasing frequency.Acoustic blocking of the contralateral ear canal could reduce the directional sensitivity of the ipsilateral ear by maximally 8 dB. This indicates a significant sound transmission through the bird's interaural pathways. However, the magnitude of these effects compared to those obtained by sound diffraction (maximum > 15 dB) suggests that pressure gradients at the tympanic membrane are only of subordinate importance for the generation of directional cues.The comparison of interaural intensity differences with previous behavioral results confirms the hypothesis that interaural intensity difference is the primary directional cue of azimuthal sound localization in the high-frequency range (2–6 kHz).Abbreviations CM cochlear microphonic potential - IID interaural intensity difference - IID-MRA minimum resolvable angle calculated from interaural intensity difference - MRA minimum resolvable angle - OTD interaural ongoing time difference - RMS root mean square - SPL sound pressure level     

Protein polymorphism in a feral population of the pigeon Columba livia domestica

Sixteen enzymatic and non-enzymatic proteins of the pigeon Columba livia domestica were examined electrophoretically. These proteins were presumed to be under control by 22 loci. Of the 22 loci, 6 were defined as polymorphic and 15 as monomorphic. Another locus was variable, but the variation was not genetically interpretable. Average heterozygosity calculated over 21 loci was 0.075.     

Age, sexual and seasonal differences of haematological values and antibody status to Chlamydophila sp. in feral and racing pigeons (Columba livia forma domestica) from an urban environment (Zagreb, Croatia)

The aim of this study was to determine the basic haematological parameters in feral and racing pigeons and to compare these parameters according to age, sex and season in healthy feral pigeons as well as between Chlamydophila-serologically positive and negative feral pigeons. Red blood cells (RBC), packed cell volume (PCV), haemoglobin (Hb), mean cell volume (MCV), mean corpuscular haemoglobin (MCH), mean corpuscular haemoglobin concentration (MCHC), white blood count (WBC), thrombocyte count and differential WBC, were determined in 366 pigeons (Columba livia forma domestica) captured in the City of Zagreb between 1999 and 2002. Of these, 232 feral (179 adult and 53 juvenile, 104 male and 75 female) and 57 racing pigeons (25 male and 32 female) were clinically healthy and bacteriologically and serologically negative, but 77 birds had antibody titres against Chlamydophila sp. Significantly lower values of RBC, PCV, Hb, MCH, WBC and thrombocyte (P<0.05) were observed in young compared to adult pigeons, while the differences in MCV and MCH were not significant between age classes. In differential WBC of young pigeons, a significantly higher percentage of heterophils, eosinophils, basophils and monocytes and a significantly smaller percentage of lymphocytes (P<0.01) was found than in adult pigeons. Significant sex-related differences were seen only in MCV values and in the percentage of lymphocytes (higher in females) and neutrophils (higher in males). PCV, Hb, MCV and MCH increased, while WBC decreased during wintertime (P<0.05). In differential WBC, percentage of heterophils was low in summer and autumn. At the same time, a higher percentage of basophils was found. Low numbers of monocytes were found in summer and low values of eosinophils in winter. In racing pigeons, values of eosinophils and basophils were significantly lower than in feral pigeons. Pigeons which had antibodies against Chlamydophila sp. possessed a higher percentage of monocytes and less lymphocytes than sero-negative animals, while WBC was significant lower than in sero-negative feral pigeons.     

Jaw movement kinematics and jaw muscle (EMG) activity during drinking in the pigeon (Columba livia)

Summary Movements of the maxilla and mandible were recorded during drinking in the head-fixed pigeon and correlated with electromyographic activity in representative jaw muscle groups. During drinking, each jaw exhibits opening and closing movements along both the dorso-ventral and rostro-caudal axes which may be linked with or independent of each other. All subjects showed small but systematic increases in cycle duration over the course of individual drinking bouts. Cyclic jaw movements during drinking were correlated with nearly synchronous activity in the protractor (levator) of the upper jaw and in several jaw closer muscles, as well as with alternating activity in tongue protractor and retractor muscles. No EMG activity was ever recorded in the lower jaw opener muscle, suggesting that lower jaw opening in this preparation is produced, indirectly, by the contraction of other muscles. The results clarify the contribution of the individual jaws to the generation of gape variations during drinking in this species.Abbreviations AMEM adductor mandibulae externus muscle - DM depressor mandibulae muscle - EMG electromyographic - GENIO geniohyoideus muscle - LB lower beak - LED light-emitting diode - PQP protractor quadrati et pterygoidei muscle - PVL pterygoideus ventralis muscle, pars lateralis - SeH/StH serpihyoideus or stylohyoideus muscle - UB upper beak     

Jaw muscle (EMG) activity and amplitude scaling of jaw movements during eating in pigeon (Columba livia)

During each phase of the pigeon's eating sequence, jaw opening amplitude (gape) is adjusted to the size of the food object; first prior to contact (Grasping), again in positioning the food (Stationing), and finally, during its movement through the oral cavity (Intraoral Transport). Part I of this study examined jaw movement kinematics during ingestion of different size food pellets to determine the relative contribution of velocity and rise time variables. Part II specified the muscle activity patterns mediating each phase of the eating sequence, and determined how these patterns are modulated to produce adjustments of gape size.The relative contribution of velocity and rise time variables to the control of gape differs in each phase of the eating sequence. However, for any pellet size, variations in opening rise time may function in a compensatory manner to minimize gape undershooting. Each phase of the eating sequence is mediated by a characteristic muscle activity pattern. The adjustment of gape size to pellet size involves systematic modulation of this pattern, and the parameters modulated differ in the different phases in a manner which may reflect the functional requirements of each phase.Abbreviations AMEM adductor mandibulae externus muscle - DM depressor mandibulae muscle - EMG electromyographic - PDC/PDR pterygoideus muscle, pars dorsalis caudalis and rostralis - PQP protractor quadrati et pterygoidei muscle - PTP pseudotemporalis profundus muscle - PVL/PVM pterygoideus ventralis muscle, pars lateralis and medialis     

Environmental variation and quantitative genetic prameters in the feral pigeon, Columba livia

The estimation of quantitative genetic parameters and modes of selection in natural populations can provide critical information concerning both past and current evolution of mean phenotypes. We examine the influence of environmental variation on the genetic variance-covariance matrix ( G ) of external morphological traits in feral pigeons, and the degree of correspondence between phenotypic (r_p) and genetic correlations (r_g) of these characters. Our results suggest that adverse environmental conditions affect heritability, and that the correspondence between seasonal estimates of G based on midparent scores is low. There is, however, a strong correspondence between r_p and r_g. We suggest that, if environmental variation is relatively common, estimates of quantitative genetic parameters for prospective selection studies must be undertaken at each selection episode.     

The effect of alpha2-adrenergic receptors on cutaneous water evaporation in the rock pigeon (Columba livia)

The role of beta-adrenergic receptors in regulating cutaneous water evaporation (CWE) in the rock pigeon (Columba livia) is well documented. Here, we studied the involvement of the alpha2-adrenergic receptors in this cooling mechanism of the heat-acclimated (HAc) pigeon. Systemic alpha2-adrenergic activation [clonidine, 50 microg kg(-1), intramuscular (i.m.)] was found to increase CWE in heat-acclimated pigeons at an ambient temperature (T(a)) of 25 degrees C. Subcutaneous administration of the drug had no significant effect. Preinjection of an alpha2-adrenergic antagonist (yohimbine, 10 mg kg(-1), i.m.) completely prevented clonidine-induced CWE and attenuated propranolol-induced CWE by 53%. Pretreatment with a beta-adrenergic agonist (isoproterenol, 4 mg kg(-1), i.m.) abolished the effect of clonidine. None of the above treatments was found to elicit significant CWE in nonacclimated (NAc) pigeons. These findings, in addition to previously reported data, indicate a complex regulatory pathway of CWE in the heat-acclimated pigeon consisting of alpha2- and beta2-adrenergic receptors. The possible hierarchical pattern of these receptors is discussed.     

家鸽Caveolin-1基因全长cDNA的克隆、序列和组织表达分析

窖蛋白(Caveolin)是一类构成细胞膜上胞膜窖主要结构的标志蛋白,由Caveolin基因家族编码而成。Caveolin-1基因是Caveolin基因家族的成员之一。该实验采用RT-PCR与RACE(rapid amplification of cDNA ends)技术成功地克隆了家鸽Caveolin-1基因的全长cDNA。该cDNA全长2605bp,包含537bp的完整编码区,编码178个氨基酸;分析发现家鸽Caveolin-1基因编码区与牛、家犬、鸡、褐家鼠等核苷酸同源性为80.1%～93.4%,氨基酸同源性高达85.4%～97.2%;半定量RT-PCR分析表明该基因在家鸽各种组织广泛表达,脂肪中表达量最高,各种肌肉中表达量次之,肝脏中表达量最低。此结果说明家鸽Caveolin-1基因可能与脂肪、肌肉中的某些代谢途径有关。     

Distribution and genetic structure of the Japanese wood pigeon (Columba janthina) endemic to the islands of East Asia

The Japanese wood pigeon (Columba janthina) is endemic to the islands of East Asia and it is included in the Japanese and Asian Red Lists because of its narrow habitat range that is restricted to mature forests on small islands and because of the destruction of these habitats. We examined the genetic structure of Columba janthina by studying 463 base pairs of the mitochondrial control region sequences. We analyzed 154 samples from eight populations and identified 27 haplotypes. Three population groups were identified based on the pairwise Φ_ST values. A substantial gene flow, as reflected by the low and non-significant Φ_ST values, is maintained among the northern group that includes six populations found on the Okinawa, Tokara, Goto, Setouchi, Oki, and Izu islands. In contrast, the southeastern group found on the Ogasawara Islands had large Φ_ST values with every population from other regions (0.910 < Φ_ST < 0.962). The southwestern group found on the Sakishima Islands also had significant but small Φ_ST values with every population from the northern group (0.081 < Φ_ST < 0.205). The Mantel test showed a highly significant correlation between the Φ_ST values and the route length of the habitat network, as well as the linear distance with correction of the habitat gap effect, indicating the importance of the closely connected structure of the habitats. The three groups mentioned above could be considered as independent management units, and the southeastern group has the highest conservation priority due to its narrow distribution range and small population size. Electronic Supplementary Material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

Molecular cloning and characterization of pigeon (Columba liva) ubiquitin and ubiquitin-conjugating enzyme genes from pituitary gland library

In the study of the regulation of incubation, broodiness and laying performance in pigeons (Columba liva), a cDNA library, which was enriched with full-length brooding-related genes, was constructed by SMART LD-PCR techniques using the pituitary glands of incubating White King pigeons. The titers of optimal primary libraries were 1.54×10⁶ pfu/mL and 1.80×10⁶ pfu/mL and the titers of amplified libraries were 1.89×10⁸ pfu/mL and 2.32×10⁹ pfu/mL. The percentages of recombinant clones of primary libraries and amplified libraries were all over 90%. A positive clone was sequenced and named ubiquitin based on the highly similar from other species. The fragment has the four initial codons of ATG, a termination codon of TAA and a signal sequence of AATAAA for adding the poly-A tail. The open reading frame of 918bp encodes 305 amino acids (NCBI accession number is {"type":"entrez-nucleotide","attrs":{"text":"EU981283","term_id":"197693971","term_text":"EU981283"}}EU981283). Recombinant pigeon ubiquitin protein was efficiently expressed with the form of insoluble inclusion bodies in E. coli BL21 transformed with a pET28a⁺ expression vector containing the DNA sequence encoding mature pigeon ubiquitin. The molecular weight of expressed protein is the same as predicted size of approximately 35kD. To improve the efficiency of cloning full-length cDNA, strategies of RACE combined with cDNA library were used. The length of pigeons ubiquitin-conjugating enzyme gene obtained was 1263 bp containing a complete open reading frame of 435 bp that encodes 144 aa (NCBI accession number is {"type":"entrez-nucleotide","attrs":{"text":"EU914824","term_id":"197130954","term_text":"EU914824"}}EU914824). The results of this study not only provide a starting point for further study of ubiquitin function in pigeon species, but also provide a starting point for investigating the brooding mechanisms of pigeons.     

Humoral immunoresponse of pigeons toAspergillus fumigatus antigens

The aim of this study was to develop an immunological model of avian Aspergillosis by studying the humoral response of pigeons toAspergillus fumigatus antigens. Immunization was performed by administering weekly injections ofA. fumigatus extracts for 70 days (10 weeks). A new booster injection was given 270 days (9 months) following the last immunization. Results showed an earlyAspergillus-specific humoral immunoresponse which reached a maximum level at 42–63 days (6–9 weeks) post-immunization. Using the ELISA method, it could be observed thatA. fumigatus-specific IgG became elevated in the 2nd week and reached a maximum titre at 63rd day (9th week). In contrast,A. fumigatus-specific IgM levels appeared early showing maximum levels at the 2nd week, after which they declined despite the maintenance of antigenic stimulation. Termination of immunization resulted in the decrease of specific humoral immunoresponse with minimal levels of specific antibodies detectable 210 days (7 months) later. A booster injection given at 270 days (9 months) induced a very fastAspergillus-specific IgM and IgG immunoresponse, reaching levels of antibodies similar to those observed during the immunization period.     

Patterns of mobilization of calcium,magnesium, and phosphorus by embryonic yellow-headed blackbirds(Xanthocephalus xanthocephalus)

Summary Embryonic blackbirds(Xanthocephalus xanthocephalus) obtain most of their calcium from the eggshell (85 90%), but all of their phosphorus comes from reserves in the yolk (80–85%) and albumen (15–20%). Approximately equal amounts of magnesium are supplied by the eggshell, the yolk, and the albumen. Yolk is depleted of magnesium and phosphorus during embryogenesis, but excess calcium absorbed from the eggeshell is stored in the yolk. Consequently reserves of calcium in the yolk actually increase 8-fold during embryonic development. Our results reveal that altricial birds manifest patterns of mobilization and deposition of calcium and other elements similar to those described for precocial species. Evolution of altriciality from precocity evidently did not entail major changes in how embryonic birds meet the challenge of obtaining the calcium, magnesium, and phosphorus required for development.     

Histological and electrophysiological investigations on the vibration-sensitive receptors (Herbst corpuscles) in the wing of the pigeon (Columba livia)

Summary The Herbst corpuscles (HCs) of the pigeon's wing were investigated both histologically and electrophysiologically. All HCs found in the wing were lamellated, basic type corpuscles without any specialized structures. Their lengths ranged from 67 to 853 m (mean = 310 m). Unexpected findings were their large number (about 1000 in the manual part of the wing), their irregular distribution and their preferred orientation (approximately parallel or at right angles to the primary feather follicles). The HCs were highly sensitive to vibrational stimuli applied to wing feathers. Their electrophysiological behaviour has the following characteristics: no spontaneous activity, phase-locked nerve impulses, a 11 stimulus-response relation up to at least 660 Hz at sufficiently high stimulus amplitudes, and a sensitivity to stimulus frequencies up to 1800 Hz. The best frequencies of 52 receptive units for which complete threshold curves were obtained lay between 100 and 900 Hz, 67% of the best frequencies were between 200 and 400 Hz. The threshold amplitudes at best frequency ranged from 0.5 to 150 m. Two virtually non-overlapping mechanosensitive areas on the wing were identified. One is a very narrow band along the frontal edge and the other covers a large area of the remaining wing. They correspond with the two branches of the radial nerve. The histological and electrophysiological findings suggest that the HCs are part of a vibrational sensory system that is principally involved in flight control. The actual aerodynamic state during flight could be detected by the frontal receptive area, and flight behaviour could be adjusted accordingly. The effectiveness of these corrective reactions would then be assessed on the basis of air current changes along the caudal wing edge by the caudal receptive area. Despite some physiological differences considerable similarities between HCs and Pacinian corpuscles support the hypothesis that they evolved from a unique ancestral lamellar receptor.Abbreviations HC(s) Herbst corpuscle(s) - PC(s) Pacinian corpuscle(s) All experiments were carried out at the Ruhr-Universität Bochum, Lehrstuhl für Allgemeine Zoologie     

Spatial response properties of homing pigeon hippocampal neurons: correlations with goal locations,movement between goals,and environmental context in a radial-arm arena

The amniote hippocampal formation plays an evolutionarily-conserved role in the neural representation of environmental space. However, species differences in spatial ecology nurture the expectation of species differences in how hippocampal neurons represent space. To determine the spatial response properties of homing pigeon (Columba livia) HFneurons, we recorded from isolated units in birds freely navigating a radial arena in search of food present at four goal locations. Fifty of 76 neurons displayed firing rate variations that could be placed into three response categories. Location cells (n=25) displayed higher firing rates at restricted locations in the arena space, often in proximity to goal locations. Path cells (n=13) displayed higher firing rates as a pigeon moved between a subset of goal locations. Arena-off cells (n=12) were more active when a pigeon was in a baseline holding space compared to inside the arena. Overall, reliability and coherence scores of the recorded neurons were lower compared to rat place cells. The differences in the spatial response profiles of pigeon hippocampal formation neurons, when compared to rats, provide a departure point for better understanding the relationship between spatial behavior and how hippocampal formation neurons participate in the representation of space.     

Metabolic responses of homing pigeons to flight and subsequent recovery

This study examines metabolic changes occurring during short to endurance flights and during subsequent recovery in free-flying pigeons, in particular the change towards lipid utilization with increasing flight duration, lipid supply to the flight muscles, protein utilization and the time needed to metabolically recover. Eight plasma metabolite concentrations were measured in homing pigeons released from sites 20–200 km from the loft (0.3–4.8 h flight duration) just after landing and after keeping birds fasting at rest for 30 and 60 min, respectively, after their return. Birds kept in the loft fasting at rest were used as controls. Plasma free fatty acid and glycerol concentrations increased rapidly with flight duration and leveled off after about 1.5 h. This indicates a marked change towards a high and stable lipid utilization from adipose tissues within 1–2 h of flight. Plasma triglyceride levels and very-low-density lipoproteins were decreased after short flights, but subsequently regained or surpassed fasting levels at rest. This indicates that re-esterification of free fatty acids and delivery as very-low-density lipoproteins to the flight muscles to circumvent constraints of fatty acid supply, as described previously for small passerines, is not as significant in the pigeon which has a much lower mass-specific energy rate. An initial increase in plasma glucose levels and a transient decrease to fasting levels at rest was observed and may reflect the initial use and subsequent exhaustion of glycogen stores. Contrary to other birds and mammals, -hydroxy-butyrate levels increased markedly with flight duration. This may suggest a more important sparing of carbohydrates and protein as gluconeogenic precursors in the pigeon than in other species. Plasma uric acid levels increased linearly up to about 4 h flight duration. This indicates an accelerated protein breakdown during flight which may primarily serve to deliver amino acids as glucogenic precursors and citrate cycle intermediates. With increasing flight duration, the energy sources change from an initial phase based primarily on carbohydrates to a lipid-based endurance phase. It is discussed whether this metabolic change depends on the level of power output or the performed work (energy spent) since the start of flight. During the first hour of recovery, most metabolites reached or approached fasting levels at rest, indicating a marked reduction in lipolysis and protein breakdown. -hydroxy-butyrate levels remained at flight levels and glucose levels increased slightly, indicating a restoration of glycogen stores.Abbreviations VLDL very-low-density lipoproteins - FFA free fatty acids