Isolation and characterization of polymorphic microsatellites isolated from the spotless starling (Sturnus unicolor) and cross‐species amplification in the European starling (Sturnus vulgaris)

Spotless and European starlings (Sturnus unicolor and Sturnus vulgaris) have attracted attention from researchers interested in sexual selection, evolution of parental care and reproductive strategies. Both species show high levels of intraspecific nest parasitism and extra‐pair paternity, but research in this area is hampered by a lack of molecular markers specific for these species. Here, we describe a set of primers for nine microsatellite loci in spotless starlings, eight of which are highly polymorphic (7.37 alleles in average). These microsatellites are also polymorphic in European starlings (6.75 alleles in average).     

Parent-absent begging: evidence for sibling honesty and cooperation in the spotless starling (Sturnus unicolor)

Begging in avian nestlings is a highly conspicuous behaviorwith important implications for the study of parent–offspringconflict. In some species, nestlings also call for long boutsin the absence of parents, and it has been proposed that thisbehavior is used by nestlings as a means of negotiating accessto food. We studied this phenomenon in the spotless starling(Sturnus unicolor). We found that parent-absent calls were acousticallydistinct from parent-present calls. Observations showed thatthe probability of parent-absent begging increased with nestlingage and brood size, whereas it decreased with increasing bodycondition. This result was confirmed by an experiment that showedthat nestlings produced higher parent-absent begging rates whenfood deprived than when satiated. Finally, we carried out aplayback experiment to test the reaction of nestlings to parent-absentbegging by fellow nestlings. Principle components analyses yielded2 independent components of begging: 1) a general begging componentand 2) a second factor that measures the relative contributionof communicative begging over competitive begging. Nestlingsexposed to playback decreased their general begging levels andsimultaneously increased the relative contribution of communicativeover competitive begging. This behavior may favor needy nestlingsto obtain impending feedings while keeping high levels of foodsolicitation from parents and is consistent with a cooperativestrategy among nestlings. Future research should consider theactual response of parents to these signals.     

The identification of sex in the starling Sturnus vulgaris using a molecular DNA technique

Female birds can be identified through the presence of a W-chromosome. We describe a procedure for amplifying a W-linked DNA marker in the starling (Sturnus vulgaris) by the polymerase chain reaction (PCR) so allowing the diagnosis of sex in this species. The technique is sensitive, allowing even the smallest chicks to be sexed from a blood sample. The method possesses a positive internal control to ensure accuracy. It is also applicable to the spotless starling (S. unicolor) but not to two bird species outside the genus. The nucleotide sequence of the female-specific PCR product is given.     

Invasive species can't cover their tracks: using microsatellites to assist management of starling (Sturnus vulgaris) populations in Western Australia

Invasive species are known to cause environmental and economic damage, requiring management by control agencies worldwide. These species often become well established in new environments long before their detection, resulting in a lack of knowledge regarding their history and dynamics. When new invasions are discovered, information regarding the source and pathway of the invasion, and the degree of connectivity with other populations can greatly benefit management strategies. Here we use invasive common starling ( Sturnus vulgaris ) populations from Australia to demonstrate that genetic techniques can provide this information to aid management, even when applied to highly vagile species over continental scales. Analysis of data from 11 microsatellites in 662 individuals sampled at 17 localities across their introduced range in Australia revealed four populations. One population consisted of all sampling sites from the expansion front in Western Australia, where control efforts are focused. Despite evidence of genetic exchange over both contemporary and historical timescales, gene flow is low between this population and all three more easterly populations. This suggests that localized control of starlings on the expansion front may be an achievable goal and the long-standing practice of targeting select proximal eastern source populations may be ineffective on its own. However, even with low levels of gene flow, successful control of starlings on the expansion front will require vigilance, and genetic monitoring of this population can provide essential information to managers. The techniques used here are broadly applicable to invasive populations worldwide.     

Female presence affects male behavior and testosterone levels in the European starling (Sturnus vulgaris)

In this study, we confronted individually housed male European starlings (Sturnus vulgaris) with a female conspecific for 60 min to study the consequences on behavior and plasma testosterone (T) concentrations. Control males experienced a similar procedure, the only difference being that they were tested in the absence of a female. Female presence significantly affected both behavior and plasma T levels of male starlings. Experimental males spent significantly more time singing in the nest box and flew significantly more into the nest box with green nesting material during female presentations than during control periods. Control males never showed these mate attraction behaviors. In total 5 of the 16 experimental males did not respond behaviorally to the female stimulus bird (NR males). In contrast to T levels of control males, plasma T concentrations of both experimental males that did respond to the female (R males) and of NR males (which only perceived the female stimulus) were positively influenced by female presentation. The time spent singing in the nest box by experimental males (R and NR males combined) during female presence tended to be positively correlated with changes in plasma T levels. Finally, before introduction of a female, plasma T levels of R males were significantly higher than those of NR males indicating that individually housed males respond to the presence of a female conspecific by increasing their mate attraction behaviors only when a threshold plasma T concentration has been reached.     

Increased sibling competition does not increase testosterone or corticosterone levels in nestlings of the spotless starling (Sturnus unicolor)

Nestling begging in passerine birds is a complex behaviour that is shaped by a multitude of ecological factors and could be physiologically mediated by varying levels of steroid hormones. Previous research has shown links between sibling competition and testosterone and corticosterone in several bird species. The spotless starling (Sturnus unicolor) is a medium sized passerine in which nestlings compete intensively for resources, often resulting in marked size hierarchies that can have profound effects on their fitness. We tested the hypothesis that an increase in sibling competition levels would result in increases in testosterone and corticosterone in this species. To this end we conducted a brood size manipulation, creating small, medium and large broods. This manipulation had the expected effect on morphology: nestling size and mass decreased with increasing brood size. Androgen levels varied in response to brood size manipulation but, contrary to expectations, the largest concentrations were found in reduced brood sizes. Corticosterone levels increased with increasing brood size, but this effect disappeared when we corrected for the time taken to process nestlings. Cell-mediated immune response was found to decrease with increasing brood size and testosterone levels. The results suggest that the proposed link between testosterone and corticosterone and sibling competition does not hold in this species, and underlines the diversity of species-specific responsiveness to steroids.     

Genetic differentiation of starling (Sturnus vulgaris: Aves) populations in New Zealand and Great Britain

Several hundred starlings (Sturnus vulgaris) were introduced to New Zealand from Great Britain during1860–1880. Allozymic variation at 24 loci was analysed in winter populations sampled at six localities in each country. New Zealand samples had fewer alleles per locus but the same mean heterozygosity (3% per locus) and proportion of polymorphic loci as did British samples. Winter populations in Britain contain European migrants and were genetically homogeneous. Paradoxically, genetic distances among derived New Zealand populations, and between New Zealand and Great Britain were much greater, similar in magnitude to those observed among allopatric populations in other avian species. The geographical pattern of genetic variation in New Zealand suggests that reproductive isolation of populations and random drift have contributed to the development of population differentiation.     

Intraspecific nest parasitism in the grey starling (Sturnus cineraceus)

We studied intraspecific nest parasitism in the grey starling (Sturnus cineraceus) in 1992 and 1993. We used three criteria to detect nest parasitism: (i) the appearance of more than one egg per day while the host was laying; (ii) the appearance of extra eggs after the host completed its clutch; and (iii) the appearance of eggs which were of a different shape, size and color to other eggs in the clutch. There were 290 nests (157 nests in 1992; 133 nests in 1993) in which the clutch was completed early (clutches initiated before May 10). Twenty-nine (1992) and 32 (1993) nests contained at least one parasitic egg. Parasitic eggs hatched if they were laid during the laying period and early in the incubation period of their host, and a few of them fledged. Fledging success of parasitic eggs was not different from that of eggs in non-parasitized nests if parasitic eggs were laid during the host's laying period. However, fledging success of all parasitic eggs was fewer than that of eggs in non-parasitized nests. By comparison, fledging success of parasitized nests was not a great as that of non-parasitized nests.     

Starlings (Sturnus vulgaris) exploiting patches: response to long-term changes in travel time

In this paper we explore the way foraging animals integrateexperience over time. The marginal value theorem shows thatto maximize long-term gain rate, foragers should adjust patchexploitation to theaverage travel time for the habitat, andmany experiments do find a positive relationship between averagepatch exploitation and average interpatch travel time. Thisrelationship implies that animals use experience to determineforaging tactics but, by itself, does not imply that anythingbut the most recent experience (say, the time taken to findthe current patch) has an effect on behavior. We directly testedthe influence of events before the most recently experiencedtravel by examining adjustments in foraging behavior after stepwisechanges between two homogeneous environments, each with a singletravel distance. Using starlings (Sturnus vulgaris) in a closed-economylaboratory simulation of a patchy environment, we found thatduring periods of active foraging, the average number of preyper patch visit is in close agreement with that predicted forrate maximization. After changes in travel time, birds tookapproximately six full cycles of travel and patch use beforereaching a new asymptotic behavior. The pattern of adjustmentdid not vary with successive presentations of the environmentalchange. These results demonstrate that memory for more thanone travel episode is involved in the foraging decisions ofstarlings. We relate our results to apparently conflicting datafrom previous experiments and to models of memory and informationprocessing.     

Gap detection in the European starling (Sturnus vulgaris)

Summary Gap-detection thresholds were determined for single units in the cochlear ganglion and in auditory nerve fibres of the starling from responses to two broad-band noise bursts separated by a temporal gap of between 0.4 and 204.8 ms. All 35 units showed a threshold within the range of gap sizes tested. The median minimum-detectable gap was 12.8 ms with the minimum being 1.6 ms. A multiple regression analysis revealed that the size of the minimum-detectable gap was not significantly correlated with the neuron's CF, with its sharpness of tuning as given by its bandwidth 10 dB above threshold, or with its Q_10dB value. Only the level of stimulation above the neuron's threshold showed a significant negative correlation with the size of the minimum-detectable gap. These results are discussed with respect to theoretical considerations of limits posed on temporal resolution by the characteristics of peripheral filters. These findings are also discussed in the context of the coding of gaps at different levels of the starling's auditory system and in relation to psychoacoustic results in the starling on gap detection and time resolution described by temporal modulation transfer functions.     

Metabolic rate and evaporative water loss in the silky starling(Sturnus sericeus)

To better understand the physiological characteristics of the silky starling(Sturnus sericeus), its body temperature(Tb), basal metabolic rate(BMR), evaporative water loss(EWL) and thermal conductance(C) elicited by different ambient temperatures(Ta)(5-30 °C) were determined in the present study. Our results showed that they have a high Tb(41.6±0.1 °C), a wide thermal neutral zone(TNZ)(20-27.5 °C) and a relatively low BMR within the TNZ(3.37±0.17 mL O2/g·h). The EWL was nearly stable below the TNZ(0.91±0.07 mg H2O/g·h) but increased remarkably within and above the TNZ. The C was constant below the TNZ, with a minimum value of 0.14±0.01 mL O2/g·h·°C. These findings indicate that the BMR, Tb and EWL of the silky starling were all affected by Ta, especially when Ta was below 20 °C and the EWL plays an important role in thermal regulation.     

Azimuthal sound localization in the European starling (Sturnus vulgaris)

Summary The physical measurements reported here test whether the European starling (Sturnus vulgaris) evaluates the azimuth direction of a sound source with a peripheral auditory system composed of two acoustically coupled pressure-difference receivers (1) or of two decoupled pressure receivers (2).A directional pattern of sound intensity in the freefield was measured at the entrance of the auditory meatus using a probe microphone, and at the tympanum using laser vibrometry. The maximum differences in the soundpressure level measured with the microphone between various speaker positions and the frontal speaker position were 2.4 dB at 1 and 2 kHz, 7.3 dB at 4 kHz, 9.2 dB at 6 kHz, and 10.9 dB at 8 kHz. The directional amplitude pattern measured by laser vibrometry did not differ from that measured with the microphone. Neither did the directional pattern of travel times to the ear. Measurements of the amplitude and phase transfer function of the starling's interaural pathway using a closed sound system were in accord with the results of the free-field measurements.In conclusion, although some sound transmission via the interaural canal occurred, the present experiments support the hypothesis 2 above that the starling's peripheral auditory system is best described as consisting of two functionally decoupled pressure receivers.Abbreviations CM cochlear microphonics - ITD interaural time difference - IID interaural intensity difference - MRA minimum resolvable angle - dB SPL sound-pressure level (re 0.00002 Pa)     

Azimuthal sound localization in the European starling (Sturnus vulgaris): II. Psychophysical results

Small songbirds have a difficult analysis problem: their head is small compared to the wavelengths of sounds used for communication providing only small interaural time and level differences. Klump and Larsen (1992) measured the physical binaural cues in the European starling (Sturnus vulgaris) that allow the comparison of acoustical cues and perception. We determined the starling’s minimum audible angle (MAA) in an operant Go/NoGo procedure for different spectral and temporal stimulus conditions. The MAA for broadband noise with closed-loop localization reached 17°, while the starling’s MAA for open-loop localization of broadband noise reached 29°. No substantial difference between open-loop and closed-loop localization was found in 2 kHz pure tones. The closed-loop MAA improved from 26° to 19° with an increase in pure tone frequency from 1 to 4 kHz. This finding is in line with the physical cues available. While the starlings can only make use of interaural time difference cues at lower frequencies (e.g., 1 and 2 kHz), additional interaural level difference cues become available at higher frequencies (e.g., 4 kHz or higher, Klump and Larsen 1992). An improvement of the starling’s MAA with an increasing number of standard stimulus presentations prior to the test stimulus has important implications for determining relative (MAA) localization thresholds.     

Dominance, competition, and energetic reserves in the European starling, Sturnus vulgaris

We investigated the relationships between social dominance,competition for food, and strategies of body mass and fat regulationin the European starling (Sturnus vulgaris). In birds housedin groups of three, subdominant birds stored more fat than dominants.A removal experiment established a causal link between socialdominance and fat reserves; in groups that had the dominantindividual removed, the remaining birds reduced body mass andfat, relative to control groups that had the subordinate removed.In a second experiment, we investigated the influences of degreeof competition for food and dominance on body mass and fat reserves.Birds under high competition increased fat reserves and tendedto have higher body mass than birds under low competition. Theincrease in fat reserves was higher in the subdominants thanin the dominants. These results are consistent with hypothesesconcerning dominance-dependent access to food; subdominant birds,or birds under increased competition, may store more fat asan insurance against periods when food cannot be obtained. However,relations between dominance, body mass, and fat reserves mayalso arise through other proximate factors relating to dominance-dependentcosts and benefits of fat storage, such as predation risk andenergetic expenditure.     

Immimohistochemical localization of corticotropin-releasing factor in selected brain areas of the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia)

Summary Corticotropin-releasing factor (CRF) was localized in the brains of two passerine species, the European starling (Sturnus vulgaris) and the song sparrow (Melospiza melodia), by means of immunohistochemistry. The hypothalamic distribution of this peptide in these species includes a complex of immunoreactive perikarya observed in the paraventricular nucleus (PVN), in both its medial and lateral divisions. Nerve fibers were also seen running from these areas to the anterior median eminence (AME) where a terminal field is apparent. A wide variety of extra-hypothalamic nuclei containing CRF-immunoreactive cells and fibers were identified. An apparent CRF terminal field can be visualized in the lateral septum. A dense fiber plexus is present in the nucleus accumbens (Ac) and more caudally in the nucleus of the stria terminalis (nST). In colchicinepretreated animals, it was revealed that these areas also contain CRF-stained perikarya. The pattern of CRF immunoreactivity in the Ac-nST complex is continuous, with no distinction apparent between the nuclei. The medial preoptic area (mPOA) and the adjacent diagonal band of Broca contain CRF-fibers, while cells are apparent in the mPOA. In the mesencephalon, cells were visualized in the midbrain central gray; a terminal field and scattered positively stained perikarya were found in areas more ventral to the central grey that are adjacent to the third cranial nerve. Scattered cells were also seen at the border of the nucleus intercollicularis-nucleus mesencephalicus lateralis, pars dorsalis complex. In contrast to mammalian studies, no immunoreactive nerve fibers or perikarya were observed in telencephalic areas homologous to the mammalian neocortex. These studies confirm the presence of a CRF path-way regulating pituitary function and suggest a broad role played by CRF as a neuromodulator or neurotransmitter in autonomic and possibly behavioral activities in these species.     

Criteria for age determination in the Spotless Starling(Sturnus unicolor): cranial pneumatization and tarsal colour

Summary Tarsal coloration inSturnus unicolor becomes progressively lighter with age and is of certain value in ageing adult birds (3Y–4Y). The process of cranial pneumatization lasts about six months from July to December for first clutch birds and from August to January for those of second broads. According to the degree of frontal pneumatization, October and November are the most effective months for the discrimination between adult and juvenile individuals.

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Altersbestimmung beim Einfarbstar(Sturnus unicolor): Pneumatisation des Schädeldachs und Lauffärbung

Zusammenfassung Beim Einfarbstar wird die Lauffärbung mit zunehmendem Alter heller und kann als Hilfe bei der ungefähren Altersgruppierung adulter Vögel verwendet werden. Die Pneumatisation des Schädeldachs dauert etwa 6 Monate (Juli bis Dezember bei Jungen aus Erstbruten, August bis Januar bei Jungen aus Zweitbruten). Nach dem Stand der Pneumatisation des Schädeldachs lassen sich juv. und ad. am besten im Oktober und November unterscheiden.

     

Gender polymorphism in flowers of Silene vulgaris (Moench) Garcke (Caryophyllaceae)

Silene vulgaris occurs in Israel as a stolonifcrous tetraploid which forms mostly sexually polymorphic populations. Fully hermaphrodite and fully male-sterile plants are linked by a range of intermediate forms which are gynomonoecious and bear hermaphrodite, male-sterile, and partially male-sterile flowers. Male-sterile flowers differ from hermaphrodite ones by having a narrower calyx, a shorter corolla, a thicker style, and a considerably larger stigmatic area with longer papillae which are more markedly bulbous basally. In individual anthers of hermaphrodite flowers, diameters of stained pollen grains showed a continuous variation from 36 to 80 μm with a modal value of 56. About 30% of pollen was found to be non-stainable. Reduction in male fertility occurs at different levels, from small or inviable pollen grains through abortion of single anthers, abortion of entire androecia, and through different degrees of gynomonoecy to totally male-sterile individuals. The proportion of stainable pollen to ovules in hermaphrodite flowers alone was found to be less than 100. From the data presented, less than a third of all ovules produced in the different kinds of flower develop into seeds. This may reflect an inadequacy of pollen, which the local population of S. vulgaris can tolerate because of its stoloniferous habit.     

Developmental stress, social rank and song complexity in the European starling (Sturnus vulgaris)

Bird song is a sexually selected trait and females have been shown to prefer males that sing more complex songs. However, for repertoire size to be an honest signal of male quality it must be associated with some form of cost. This experiment investigates the effects of food restriction and social status during development on song complexity in the European starling (Sturnus vulgaris). Birds that experienced an unpredictable food supply early in life produced a significantly smaller repertoire of song phrases than those with a constant food supply. Social status during development was also significantly correlated with repertoire size, with dominant birds producing more phrase types. This study therefore provides novel evidence that social as well as nutritional history may be important in shaping the song signal in this species.     

Sexual dimorphism and bilateral asymmetry of syrinx and vocal tract in the European starling (Sturnus vulgaris)

Sexually dimorphic vocal behavior in zebra finches (Taeniopygia guttata) is associated with a 100% larger syrinx in males and other morphological adaptations of the sound source. The songbird syrinx consists of two independent sound sources, whose specialization for different spectral ranges may be reflected in morphological properties, but the morphology of labia and syringeal skeleton have not been investigated for lateralized specializations. Similarly, little is known whether the morphology of the songbird vocal tract reflects differences in vocal behavior. Here, we tested the hypothesis that different vocal behavior and specialization is reflected in the morphology. We investigated syringeal and upper vocal tract morphology of male and female European starlings (Sturnus vulgaris). Female starlings exhibit smaller vocal repertoires and sing at lower rates than males. In males, the left syrinx produces mostly low frequencies, while the right one is used for higher notes. Macroscopic and histological techniques were used to record nineteen measurements from the syrinx and the vocal tract which were tested for sexual differences in syrinx and vocal tract and for lateral asymmetry within the syrinx. Sexually dimorphic vocal behavior is reflected in the morphology of the starling syrinx. Males have a larger syrinx with the size difference attributable to increased muscle mass and three enlarged elements of the syringeal skeleton. The upper vocal tract, however, does not differ between males and females. Distinct lateralization was found in two elements of the syringeal skeleton of females, and the labia in the left syrinx are larger than those on the right in both sexes. The sexual dimorphism of the syringeal size is smaller in starlings (35%) than in zebra finches (100%), which is consistent with the different vocal behavior of females in both species. The morphological differences between the two sound sources are discussed in relation to their vocal performance. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

A behavioral analysis of prey detection lateralization and unilateral transfer in European starlings (Sturnus vulgaris)

It has been suggested that birds prefer to use a particular eye while learning to detect cryptic prey and that this eye preference enhances foraging performance. European starlings (Sturnus vulgaris) with the left, right, or both eyes available learned to detect inconspicuous cues associated with the presence of hidden prey. Acquisition scores were not significantly different between left and right-eyed birds; however, performance in the binocular condition was significantly higher than in the two monocular conditions. When binocular birds were tested with familiar and unfamiliar cues present simultaneously, the familiar cue was selected significantly more often than the unfamiliar cue, suggesting that the birds were searching for specific cue features. When monocular birds were tested using only the naïve eye, performance dropped significantly. In right-eyed birds using the naïve left eye, performance remained at chance levels over transfer trials. However, left-eyed birds using the naïve right eye had a superior performance compared to the initial acquisition scores of right-eyed birds and also showed a significant improvement in performance over transfer trials. Thus, although there was no direct evidence of lateralization during acquisition, there was unilateral transfer of the prey detection skill from the right to the left hemisphere.