Geographic Variation of Color in the Synanthropic Blue Rock Pigeon

Variation in plumage color was studied in 211 populations of the blue rock pigeon (Columbia livia) from various geographic zones. The frequency distribution of three common and three rare phenotypes and an interspecific hybridization zone ofC. liviaand C. rupestriswere described. Different conditions of the origin of the urban populations of blue rock pigeon and consequent high genetic heterogeneity of this species were revealed. The key aspect of color polymorphism in blue rock pigeon is synanthropization, i.e., anthropogenic evolution.     

Polymorphism and phene geography of the blue rock pigeon in Europe

The variation of blue rock pigeon plumage color has been studied in 192 settlements of Europe. As in earlier studies, six color phenotypes have been distinguished, the main of which are blue, intermediate and melanistic. The phenotype frequency distribution patterns in urban and rural landscapes have been determined. Pigeon populations with increased density are the most melanistic. Rural populations are less melanistic than urban ones. The frequency of birds with aberrant plumage colors varies randomly and is increased in some localities. The phenotypic structure of synanthropic populations of the blue rock pigeon in Europe displays a latitudinal gradient.     

Polymorphism and phene geography of the blue rock pigeon in Europe

The variation of blue rock pigeon plumage color has been studied in 192 settlements of Europe. As in earlier studies, six color phenotypes have been distinguished, the main of which are blue, intermediate and melanistic. The phenotype frequency distribution patterns in urban and rural landscapes have been determined. Pigeon populations with increased density are the most melanistic. Rural populations are less melanistic than urban ones. The frequency of birds with aberrant plumage colors varies randomly and is increased in some localities. The phenotypic structure of synanthropic populations of the blue rock pigeon in Europe displays a latitudinal gradient.     

Effect of some autonomic drugs on heat defence in the pigeon.

As compared to the time of median control death (i.e. the time inducing 50% death in untreated birds at 50 degrees C), exogenous noradrenaline afforded 100% survival in the blue rock pigeon, Columba livia. The survival percentages with the other autonomic drugs were: chlorpromazine 70%; reserpine 60%; adrenaline 60%; pentolinium 50% and dihydroergotamine 30%. The time of median control death at 50 degrees C was found to be 3.5 hours in the pigeon. During 10-day exposure at 45 degrees C all the birds pre-treated with noradrenaline survived, and 47% of those treated with adrenaline and 42% of the untreated birds survived the stress. It is concluded that noradrenaline acts definitely as a "heat protective" hormone in the pigeon.     

Dynamics of balanced polymorphism morphs in blue rock pigeon (Columba livia) from Moscow

Analysis of the 30-year dynamics (from 1978 to 2008) of phenotype frequencies in the Moscow blue rock pigeon population revealed changes in the frequency distribution of several plumage color phenotypes. The frequency of the melanistic phenotype decreased as a result of the decrease in the total population size and, consequently, population density in colonies. This decrease in the pressure of the melanistic phenotype led to increased proportions of wild-type and aberrantly colored birds throughout the town and an increased frequency of transitory phenotypes in the central region. A predominance of one phenotype suppressed genetic diversity of plumage color phenotypes. The changes in the phenotype distribution in populations were associated with changes in the social structure of the human population. As the feeding resources grew poorer because of social anthropogenic factors, the pigeon population size decreased. This decrease in population size changed the phenotype frequencies, which was considered to be an adaptive response of the population to environmental changes.     

Dynamics of balanced polymorphism morphs in blue rock pigeon <Emphasis Type="Italic">Columbia livia</Emphasis>

Analysis of the 30-year dynamics (from 1978 to 2008) of phenotype frequencies in the Moscow blue rock pigeon population revealed changes in the frequency distribution of several plumage color phenotypes. The frequency of the melanistic phenotype decreased as a result of the decrease in the total population size and, consequently, population density in colonies. This decrease in the pressure of the melanistic phenotype led to increased proportions of wild-type and aberrantly colored birds throughout the town and an increased frequency of transitory phenotypes in the central region. A predominance of one phenotype suppressed genetic diversity of plumage color phenotypes. The changes in the phenotype distribution in populations were associated with changes in the social structure of the human population. As the feeding resources grew poorer because of social anthropogenic factors, the pigeon population size decreased. This decrease in population size changed the phenotype frequencies, which was considered to be an adaptive response of the population to environmental changes.     

Equal frequencies of recombination nodules in both sexes of the pigeon suggest a basic difference with eutherian mammals.

The total number of recombination nodules (RNs) in the autosomal synaptonemal complexes (SCs) is statistically equivalent in oocytes and spermatocytes from the domestic pigeon Columba livia. The distribution on RNs along the three longest autosomes is also equivalent in oocytes and spermatocytes. The numbers of RNs show a linear relationship when plotted against SC length both in oocytes and spermatocytes. On the other hand, the ZW pair shows a single and strictly localized RN near the synaptic termini, but the ZZ pair shows unrestricted location of RNs (average 3.8). The ZW and ZZ pairs of the pigeon are euchromatic and do not show specific chromatin packing at pachytene in either sex. The lack of sex-specific differences in the number and location of RNs in the autosomal bivalents of C. livia and previous data on the chicken, suggest that the regulation of crossing-over is basically different in birds and mammals.     

Predator fitness increases with selectivity for odd prey

The fundamental currency of normative models of animal decision making is Darwinian fitness. In foraging ecology, empirical studies typically assess foraging strategies by recording energy intake rates rather than realized reproductive performance. This study provides a rare empirical link, in a vertebrate predator-prey system, between a predator's foraging behavior and direct measures of its reproductive fitness. Goshawks Accipiter gentilis selectively kill rare color variants of their principal prey, the feral pigeon Columba livia, presumably because targeting odd-looking birds in large uniform flocks helps them overcome confusion effects and enhances attack success. Reproductive performance of individual hawks increases significantly with their selectivity for odd-colored pigeons, even after controlling for confounding age effects. Older hawks exhibit more pronounced dietary preferences, suggesting that hunting performance improves with experience. Intriguingly, although negative frequency-dependent predation by hawks exerts strong selection against rare pigeon phenotypes, pigeon color polymorphism is maintained through negative assortative mating.     

Cutaneous water evaporation--I. Its significance in heat-stressed birds

In a comparative study on avian cutaneous evaporation, two species of Phasianidae, Japanese quail Coturnix coturnix japonica and chukar partridge Alectoris chukar, and three species of Columbidae, palm dove Streptopelia senegalensis, collared turtle dove Streptopelia decaocto and rock pigeon Columbia livia, were investigated. The skin resistance to vapor diffusion (rs) and cutaneous water loss (CWL) were studied in these birds exposed to air temperatures (Ta) between 20 and 52 degrees C. The skin resistance was measured with Lambda instrument diffusive resistance meter. Skin resistance within the thermo-neutral zone varied between a minimum of 62 sec/cm in the palm dove exposed to 20 degrees C and a maximum of 309.1 sec/cm in the partridge exposed to 36 degrees C. The CWL values were 2.5 mg H2O/cm2.hr and 0.51 mg H2O/cm2.hr respectively. Maximum CWL of the quail and partridge was 1.9-2.1 mg H2O/cm2.hr, equivalent to a cooling capacity of about 17% of metabolic heat production at 45 degrees C Ta. In the palm dove, collared dove and pigeon CWL reached 6.8, 13.1 and 20.9 mg H2O/cm2.hr and rs values reached 31.2, 16.2 and 9.4 sec/cm respectively. The cooling capacity amounted to 51.5, 86.1 and 96.5% of metabolic heat during heat stress (52 degrees C). The significance of skin evaporation in body temperature regulation of heat-stressed birds is discussed.     

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.     

Semen characteristics, cryopreservation, and successful artificial insemination in the Blue rock pigeon (Columba livia)

The present study was undertaken in the Blue rock pigeon (Columba livia) to evaluate the annual semen characteristics, to identify a suitable extender for semen short-term storage, to determine a protocol for cryopreservation of semen and finally to check whether intracloacal insemination would lead to the birth of a chick. Semen characteristics such as semen volume, sperm concentration, sperm motility, and percentage of normal spermatozoa were maximum during the monsoon season. TALP was observed to be the most suitable semen extender and the sperm survived best at 37 degrees C at a dilution of 1:100 in TALP. Further, cryopreservation studies on pigeon semen indicated that 8% DMSO with or without egg yolk (20%) proved to be a better cryoprotectant compared to glycerol and polyethylene glycol. In addition, the slow freezing protocol was better than the fast-freezing protocol and about 40% of the cryopreserved spermatozoa were motile following thawing. Computer-aided semen analysis indicated that pigeon spermatozoa were extremely active immediately after dilution in TALP and exhibited linear trajectories persisting up to 9h. But, with time there was a time-dependent decrease in the velocity parameters (VAP, VSL, and VCL). Cryopreserved spermatozoa following thawing also exhibited linear trajectories but had reduced velocity as evident from the significant decrease in VAP, VSL, and VCL. Further, artificial inseminations using fresh semen resulted in 45% fertilization and birth of a live chick.     

The molecular genetics of red and green color vision in mammals.

To elucidate the molecular mechanisms of red-green color vision in mammals, we have cloned and sequenced the red and green opsin cDNAs of cat (Felis catus), horse (Equus caballus), gray squirrel (Sciurus carolinensis), white-tailed deer (Odocoileus virginianus), and guinea pig (Cavia porcellus). These opsins were expressed in COS1 cells and reconstituted with 11-cis-retinal. The purified visual pigments of the cat, horse, squirrel, deer, and guinea pig have lambdamax values at 553, 545, 532, 531, and 516 nm, respectively, which are precise to within +/-1 nm. We also regenerated the "true" red pigment of goldfish (Carassius auratus), which has a lambdamax value at 559 +/- 4 nm. Multiple linear regression analyses show that S180A, H197Y, Y277F, T285A, and A308S shift the lambdamax values of the red and green pigments in mammals toward blue by 7, 28, 7, 15, and 16 nm, respectively, and the reverse amino acid changes toward red by the same extents. The additive effects of these amino acid changes fully explain the red-green color vision in a wide range of mammalian species, goldfish, American chameleon (Anolis carolinensis), and pigeon (Columba livia).     

Tracing of sensory neurones and spinal motoneurones of the pigeon by injection of fluorescent dyes into peripheral nerves

The projection of peripheral sensory and motor nerves was investigated in the pigeon (Columba livia) by means of retrogradely transported fluorescent dyes. Two combinations of fluorescent tracers were used that could be identified within the same cell when excited by light of 405 nm: 1) Propidium iodide and Bisbenzimide, which label the cytoplasm orange and the nucleus blue, respectively; 2) Fast Blue, which labels the cytoplasm blue, and Nuclear Yellow, which labels the nucleus (especially the nucleolar ring) yellow. The presence of the tracers in a given cell was confirmed microspectrophotometrically. Following injection of the tracers into peripheral nerves, labelled sensory neurones were seen in the dorsal root ganglia and motoneurones of the spinal cord. The peroneal and tibial nerves projected to L2-L5 and L2-L7, respectively, whereas the median and ulnar nerves projected to C12-Th2 and C13-Th1. Double-labelled sensory neurones were observed when both peroneal and tibial, or median and ulnar nerves were injected with different tracers. This indicates that some sensory neurones possess peripheral processes that dichotomize to pass down two different peripheral nerves. Double labelling was never seen in motoneurones, or in sensory neurones after tracer injection into the sciatic and femoral nerves.     

Effect of virulent Trichomonas gallinae on the band-tailed pigeon.

Nine Trichomonas-free band-tailed pigeons (Columba fasciata fasciata) trapped in Colorado died from experimental infection with Jones' Barn Trichomonas gallinae 7.1 days (av.) post-inoculation. Three experimentally infected domestic pigeons (C. livia) used as controls died 5.7 days (av.) post-inoculation. Three band-tailed pigeons from Colorado naturally infected with avirulent T. gallinae. Trichomonads obtained from a fatal case of trichomoniasis in a band-tailed pigeon from California killed a band-tailed pigeon from Colorado; they did not kill five domestic pigeons but did induce severe oral caseation.     

Effect of LH, FSH, LH + FSH and homoplastic pituitary extract on developing testis and epididymis of pigeon Columba livia

Ovine LH is needed for differentiation of juvenile Leydig cells and for their maintenance and steroidogenic potential, while FSH is necessary for Sertoli cell activity and spermatogonial multiplication suggesting that LH is steroidogenic hormone and FSH is gametogenic in the developing pigeon, C. livia. Homoplastic pituitary extract is more potent than ovine LH + FSH in stimulating gametogenic and endocrine components of the developing testis.     

Reproduction of rock pigeon exposed to extreme ambient temperatures

1. The breeding biology of rock pigeon (Columba livia) exposed to ambient temperatures (Ta) between 50 and 60 degrees C was investigated. 2. Four families accomplished three complete life cycles after long term daily exposure to extreme Ta, with about 100% success. 3. The steady state temperatures in the nest were 60, 58, 53 and 44.6 degrees C in the air, substrate surface, underwing, and in the egg's microenvironment, respectively. 4. At thermal conditions between 30 and 60 degrees C, egg temperature (Tegg) was regulated between 36.8 +/- 0.8 (S.D.) and 41.7 +/- 0.4 (S.D.). Tegg increases by 0.163 degrees C/1 degree C rise in Ta. 5. Mean Tb of the nonincubating parent exposed to 30-60 degrees C is 41.6 +/- 0.6 degrees C (S.D.). Under the same conditions the incubating parent regulated a significantly (P less than 0.01) lower Tb (38.8 degrees C) at 45 degrees C Ta and about 1 degree C lower Tb at 30 and 60 degrees C Ta, respectively. 6. By comparing the differences between fast (5 min) cooling of hot egg (44.8 degrees C) to slow heating (60-90 min), we could demonstrate the high sensitivity of the incubating parent to the danger of embryo overheating. 7. The significance of the adaptive behavioral and physiological mechanisms in breeding under extreme thermal conditions are discussed.     

The heat-acclimated pigeon: an ideal physiological model for a desert bird

Acclimation of rock pigeon (Columba livia) to high ambient temperature (Ta) 50 degrees C from the time of hatching resulted in a well-developed cutaneous evaporative cooling mechanism (CECM), which became the dominant mechanism for heat dissipation. After the age of 15 days and in adults, acclimated pigeons exposed to 48-60 degrees C Ta could regulate normal body temperature (Tb) without employing either panting or gular fluttering. Respiration rate varied between 36 +/- 12 (SD) and 35 +/- 14 breaths/min at moderate and at extreme high Ta's, respectively. During thermal stress (42, 45, and 47 degrees C) imposed in a metabolic chamber, nonpanting pigeons' heat balance was achieved by adjusting low-level heat production (46.2 +/- 6.8 W/m2) and by use of an efficient CECM that dissipated 145% of the metabolic heat. Tb was regulated between 40.7 +/- 0.5 and 41.8 +/- 0.4 degrees C over a wide range of Ta's (20-56 degrees C). The respiratory evaporative cooling mechanism (RECM) was effective since hatching. The CECM developed approximately 24 h later during the ontogeny of the altricial nestling pigeon. This trait, which exists in many bird species and may be a recent development, possibly evolved as an adaptation to hot environments. In the present study we have brought evidence for a multitrait physiological adaptation that takes preeminence in adjusting the processes involved in maintaining heat balance. This integrative complex creates a powerful, efficient tool for contending with the most extreme thermal conditions.     

Characterization of heterochromatin by sequential counterstain-enhanced fluorescence in three domestic bird species: Meleagris gallopavo, Columba livia domestica, and Anser anser L

The karyotypes of three avian species--Meleagris gallopavo, Anser anser L., and Columba livia domestica--were investigated by means of counterstain-enhanced fluorescence techniques (chromomycin A3/distamycin A/DAPI followed by DAPI/actinomycin D staining). A heterochromatin characterization of macro- and microchromosomes was performed. CMA3-positive (GC-rich) regions in the turkey included the telomeres of chromosomes 1, 3, 4, and Z. In the goose, the chromosome 2 was also CMA3-bright at the telomeres. The W chromosome possessed large amounts of CMA3-bright material on the short arm in both the turkey and the goose. Two types of centromeric heterochromatin were distinguished on acro- to telocentric chromosomes 6 to 14 in the pigeon. The microchromosomal heterochromation of the turkey and goose was GC-rich but had a high degree of variation. In the pigeon, several microchromosomes possessed predominantly AT-rich heterochromatin.     

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.