used priors conforming to a scaled non-central F-distribution (Gelman, 2006) with the location parameter equal to zero. The scale parameter for female color elaboration was equal to half of the phenotypic variation in female color elaboration, and for female song the scale parameter was equal to p(1 − p), where p is the mean probability of female song across the dataset. For the residual covariance matrix we assumed an inverse- Wishart distributed prior for female coloration. For female song (which is a binary trait), it is not possible to estimate a residual variance, so we fixed the prior at a value of 1 (Hadfield, 2014). The MCMC chain had 20,600,000 iterations, with a burn- in of 600,000 and a thinning interval of 20,000, resulting in ∼ 1000 samples of the posterior distribution of the parameters. Model fit was confirmed by ensuring that autocorrelation was low and the trait means lay within the 95% highest posterior density (HPD) intervals of the posterior predictive distribution of each trait. To incorporate some of the uncertainty in the phylogenetic relationships among bird species, we applied the statistical model described above to 10 different phylogenetic trees randomly selected from http://birdtree.org (Jetz et al., 2012). Finally, we examined the convergence of the phylogenetic variances and covariances estimated from the 10 models (each using different trees, and therefore with different numerator relationship matrices for the phylogenetic effects), with the Gelman and Rubin (1992) diagnostic, R. For these 10 trees, the point estimate was R = 1.2 indicating moderate convergence. This phylogenetic uncertainly is incorporated in all the estimates of the posterior means and the HPD intervals we present.
Bird song is commonly regarded as a male trait that has evolved through sexual selection. However, recent research has prompted a re-evaluation of this view by demonstrating that female song is an ancestral and phylogenetically widespread trait. Species with female song provide opportunities to study selective pressures and mechanisms specific to females within the wider context of social competition. We investigated the relationship between reproductive success and female song performance in the New Zealand bellbird (Anthornis melanura), a passerine resident year round in New Zealand temperate forests. We monitored breeding behavior and song over 3 years on Tiritiri Matangi Island. Female bellbirds contributed significantly more toward parental care than males (solely incubating young and provisioning chicks at more than twice the rate of males). Female song rate in the vicinity of the nest was higher than that of males during incubation and chick-rearing stages but similar during early-nesting and post-breeding stages. Using GLMs, we found that female song rates during both incubation and chick-rearing stages strongly predicted the number of fledged chicks. However, male song rate and male and female chick provisioning rates had no effect on fledging success. Two measures of female song complexity (number of syllable types and the number of transitions between different syllable types) were also good predictors of breeding success (GLM on PC scores). In contrast, song duration, the total number of syllables, and the number of “stutter” syllables per song were not correlated with fledging success. It is unclear why male song rate was not associated with reproductive success and we speculate that extra-pair paternity might play a role. While we have previously demonstrated that female bellbird song is important in intrasexual interactions, we clearly demonstrate here that female song predicts reproductive success. These results, with others, highlight the need for a change in how we view the significance of female secondary sexual traits; traits long underestimated due to a focus on male song.
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When presented with a model of duetting A. nigrovittata comprising a 16 kHz, 60 dB SPL male song and a 28 kHz, 60 dB SPL female reply 35 ms after the male ‘trigger syllable’, AN5 responded preferentially or exclusively to the female reply (Fig. 2A). The intensities were chosen assuming that the female is at a distance of 0.5–1 m and that the male has a reduced sensitivity during song production (see Brush et al., 1985; Wolf and von Helversen, 1986; Hedwig et al., 1988). The response was usually a burst of several spikes on top of an EPSP. In addition, inhibitory postsynaptic potentials (IPSPs) were observed in some of the recordings during the 16 kHz syllables of the male song. Inhibition became very obvious after signal-averaging or in peristimulus time histograms (PSTHs) and appeared as a suppression of spontaneous spiking during the male song (Fig. 2A). Often the first syllable of the male song elicited some excitation (seen as a small EPSP in the averaged recording shown in Fig. 2A); this EPSP was sometimes large enough to trigger spiking. In Fig. 2A, both the PSTH and the averaged recording include all stimuli of a test series (in which the male song model was always the same, while the female song model was varied in frequency). It becomes obvious that the only prominent excitation takes place immediately after the ‘female reply’. Fig.
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However, the move to playing the “adult woman” on her next album, In the Zone (2003), is seen by the critics as one in which she “equates maturity with transparent sexuality and the pounding sounds of nightclubs” (Erlewine, “Review of In the Zone”). In this adult world, there is precious little room for love and romance, which are invariably qualified by critics as “teen”, hence discursively inappropriate for “adult women”. Instead, the “invitation” song comes to predominate on this and Britney‟s 2007, “comeback” release, Blackout, as an indication of sexual independence. If in the early years, the invitation was one primarily to dance, with sex as a double entendre, on these two albums the invitations become more and more literally sexual, with numbers such as “Freakshow” and “Get Naked (I Got a Plan)” incurring critical scorn as “strip-club anthems” (Erlewine, “Review of Blackout”). Indeed, Britney‟s online fans take up this issue in relation to the video of “Gimme More”, where many of the comments are critical, and the words “stripper” and “slut” occur quite frequently. 8
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Syllable diversity is the number of unique syllables produced in a standardised sample of 10 songs. Versatility was calculated by dividing the number of unique syllables found within one song by the total number of syllables found in that song, then averaging across each of an individual’s 10 songs. Average syllables per second was calculated by dividing the number of syllables found in each song by song length and then averaging over the 10 songs. Song rate was calculated using the number of complete songs produced within a single 30-minute period of observation for each individual during which the bird sang at least once, starting at the time when the bird was first observed singing.
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The evolutionary conservation of neural mechanisms for forming and maintaining pair bonds is unclear. Oxytocin, vasopressin and dopamine (DA) transmitter systems have been shown to be important in pair-bond formation and maintenance in several vertebrate species. We examined the role of dopamine in formation of song preference in zebra finches, a monogamous bird. Male courtship song is an honest signal of sexual fitness; thus, we measured female song preference to evaluate the role of DA in mate selection and pair- bond formation, using an operant conditioning paradigm. We found that DA acting through the D2 receptor, but not the D1 receptor, can induce a song preference in unpaired female finches and that blocking the D2 receptor abolished song preference in paired females. These results suggest that similar neural mechanisms for pair-bond formation are evolutionarily conserved in rodents and birds.
processed as described above. To determine the appropriate dose of GnRH to inject, I conducted a pilot study using adult male song sparrows that were caught in the spring of 2010 (Fig. 4-2). Birds were brought into captivity and housed on a long day photoperiod in individual cages. The pilot study was conducted one month after birds had been in captivity. I took an initial blood sample within 3 min of disturbance. Subjects then received an injection of either a low (0.05 µg/g, n=4) or a high (0.10 µg/g, n=4) dose of chicken GnRH-I (54-8-23, The American Peptide Company, Inc., Sunnyvale, CA, U.S.A.) into the pectoralis muscle. Additional blood samples were collected 30, 60 and 120 min post-injection. I collected no more than a total of 200 µ L of blood from each bird. Similar doses and time points were used in a study of dark-eyed juncos (Junco hyemalis; Jawor et al., 2006). Testosterone levels peaked 30 min after injection and decreased to near baseline levels by 60 min (see Results Section). Peak testosterone levels were similar for the low and the high dose. Thus, I used the low dose of GnRH for the experiment and collected blood samples prior to and 30 and 60 min post-injection. Although I did not conduct pilot studies in female song sparrows, I chose the same dose and time points to use in females. Initial blood samples were collected between 10:00 AM - 12:00 PM. Samples collected 30 min post-injection represent maximum
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Abstract: New Zealand’s managed offshore islands provide sanctuary to endangered and rare fauna but also benefit common native species. These productive islands may facilitate the expansion of mobile species back to the mainland. In northern New Zealand, many mainland protected sites are located on coastal headlands within short distances of these offshore islands. Bellbirds (Anthornis melanura), locally extinct on the mainland of this region for >100 years, are capable of dispersing these distances and are occasionally sighted along the coast. Nonetheless, it was unknown whether they had established breeding populations. Natural dispersal events are difficult to assess in terms of their source, structure and likelihood of succeeding. Females are generally more difficult to detect but when present provide conservation practitioners with confidence that a population may establish. Here we test a non-invasive monitoring method for a self-reintroduced population of bellbirds at Tawharanui, a managed coastal headland situated equal distances (20 km) from two potential source populations, Little Barrier and Tiritiri Mātangi islands (LBI and Tiri, respectively). Bellbird song playbacks effectively confirmed the presence of both male and female bellbirds. The male and female song types recorded at Tawharanui were not found on Tiri but matched those of LBI and we propose this as the source population. We tested our playback protocol at other coastal parks and advocate annual playback surveys for detecting new populations at potential mainland sites.
attraction, resource defense, and group cohesion (Bradbury & Vehrencamp 2011). Birds have been at the forefront of vocal communication research given the complexity of their vocal signals and the similarity of their vocal development to that of humans (Doupe & Kuhl 1999). Until recently, however, published research has been largely ignorant of female bird song. Once thought to be rare, female song is now estimated to be present in more than half of all surveyed songbird species (Odom et al. 2014; Webb et al. 2016). Furthermore, phylogenetic reconstruction demonstrates that both sexes sang in the ancestor of modern songbirds (Odom et al. 2014). Consequently, most of what we know about birdsong is biased by the fact that we have overwhelmingly focused on male songbirds(Odom & Benedict 2018). Through a long-term study of Rufous-and-white Wrens in Costa Rica, Dan Mennill and his students have collected 15 years of song recording data that includes both male and female singers. For my
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Much of what we know about sender–receiver matching in acoustic communication is from the temporal domain of song. Most of the insects and anurans investigated so far use the temperature coupling strategy (Gerhardt, 1978; Gerhardt and Doherty, 1988; Pires and Hoy, 1992b; Gerhardt and Huber, 2002), with the notable exception of the grasshopper Chorthippus biguttulus, which uses a ‘broad-tuning’ strategy (von Helversen and von Helversen, 1981). At the level of spectral tuning, much less is known, especially about the behaviour of the tympanum in response to different temperatures. In anurans, female preference for call spectral characters is temperature dependent, as is the tuning of auditory receptors (Stiebler and Narins, 1990; Smotherman and Narins, 1998; Gerhardt and Huber, 2002), even though the spectral characters of their calls are not (Gerhardt and Mudry, 1980). In tree crickets, where such spectral change is observed, little is known about the temperature dependence of either the behaviour, the neurobiology of the female preference or the biophysics of the tympanal membrane (but see Mhatre et al., 2009).
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Two important empirical findings in evolutionary biology, Haldane’s rule and the large X effect, are so consistent that they have been likened to “rules” (Coyne & Orr, 1989; Coyne & Orr, 2004). Both suggest that X chromosomes play a key role in the establishment of post-zygotic barriers between species (Coyne & Orr, 1989; Masly & Presgraves, 2007; Presgraves, 2010). However, most research on the genetic basis of reproductive isolation has focused on male sterility and on male heterogametic species, as opposed to female fertility (though see Orr & Coyne, 1989; Hollocher & Wu, 1996; Watson & Demuth, 2012; Suzuki & Nachman, 2015). Rare cases in which homogametic females suffer disproportionate effects of hybridization provide an important opportunity to investigate the genetic basis of female sterility and processes that may counter Haldane’s rule. Crosses between T. oceanicus and T. commodus provide one such remarkably rare exception to Haldane’s rule – female hybrids were almost uniformly sterile in this experiment, out of 80 backcrosses with reciprocal hybrid females only a single offspring hatched. A considerable number of hybrid females, amongst the different cross types, produced eggs which indicates that not all ovaries are degenerate (Figure 4-2Bi). This suggests a complex genetic basis for hybrid female sterility, in which certain hybrid genic combinations may occasionally result in fertile hybrid females in natural populations (Virdee & Hewitt, 1994).
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However, as indicated above, the predicted response probability to the mean song of O. indicus is high when compared with the behaviour. The model is, however, useful because it indicates which combinations of the temporal features found in the heterospecific songs elicit relatively high response probabilities and hence need to be tested. Testing females on combinations of features, which were not included for the model generation, would also serve to externally validate this model and this is planned to be done in future experiments. This model, moreover, can be used more generally and is not restricted to the reported pair of sympatric species. The response of O. henryi to various combinations of chirp period, chirp duration and syllable period can be evaluated, in effect testing the response to other heterospecific signals. This approach could also be used to test and construct similar multivariate response spaces of other cricket species. It would be very interesting indeed to construct the same for the females of the sympatric heterospecific O. indicus, and compare the response spaces between the two sympatrics. In O. indicus where the signal variability is more than that in O. henryi, one could expect the space for the high response probabilities to be broader.
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A tonal reading implies that the narrator has not successfully borne the burden; a modal reading enables the song to close. A tertium quid presents both possibilities simultaneously. One might imagine Heine occasionally wondering whether discomfort will further cripple him while simultaneously marveling that he has trudged thus far. A tertium-quid synthesis thus does not merely present a third alternative: “Characteristic for the song, I believe, is a certain rhythm or progression, from one unambiguous hearing to the other—or at least the possibility of the other” (166). Thereupon ensues the most extensive elaboration of the tertium quid that Lewin ever provides:
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Pharmacological inhibition of cricket song patterns The early lesion experiments, which elicited long-lasting stridulation, and the finding that electrical brain stimulation blocked ongoing stridulation indicated the existence of inhibitory mechanisms within the brain controlling stridulation (Huber, 1955, 1964; Otto, 1971). Our data from GABA and picrotoxin injections support this evidence. GABA is a common inhibitory transmitter within the CNS that binds to ionotropic receptors. It elicits a rapid transient opening of Cl − channels and thereby a hyperpolarization of the affected neuron (Sattelle, 1990; Hosie et al., 1997). GABAergic neurons are widely distributed within the CNS of insects (Homberg, 1994), where there is some evidence for different subtypes of GABA receptors (Sattelle, 1990; Hue, 1991; Anthony et al., 1993), although their spatial distribution within the CNS has not yet been mapped. The effects of GABA injections on singing behaviour indicate that the control system for stridulation in the brain of crickets is sensitive to this transmitter. These data are supported by the effects of picrotoxin, an alkaloid that is known to stabilize activated insect GABA receptors in an agonist-bound closed formation (Hosie et al., 1997), thus blocking GABA-mediated inhibitory postsynaptic potentials (Sattelle, 1990; Anthony et al., 1993). Since picrotoxin elicited motor activity combined with singing behaviour, we assume that picrotoxin caused a general disinhibition of descending motor commands that also allowed the song patterns to occur. Thus, either the descending command neurons for stridulation and/or their presynaptic neurons seem to be under constant inhibition from GABAergic neurons.
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devised in which the female cricket can change neither her heading angle nor her distance with respect to the sound source (Hedwig and Poulet, 2004). Both open-loop and compensated phonotaxis paradigms are better suited to dissecting the neural mechanisms underlying pattern recognition and sound localization than arena phonotaxis. Female phonotaxis in the field, however, occurs under closed-loop conditions and female locomotor behaviour has direct consequences on the subsequent stimuli perceived. Open-loop and compensated walking paradigms are thus unlikely to be sufficient to understand natural phonotactic walking behaviour. There have been only a few previous studies quantifying the phonotactic trajectories of crickets walking in arenas (Bailey and Thompson, 1977; Murphey and Zaretsky, 1972; Oldfield, 1980; Stout et al., 1983; Stout and McGhee, 1988).
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Alternatively, these initial pulses may be disregarded by the female because the low intensity may indicate that the male is relatively far away. In either case, the female response is activated towards the end of the natural song of the male. Conversely, the results suggest that the distance between the male and the female will have a significant effect on the timing of the female response. Latency will decrease with shorter range because of the shorter time taken for the song to travel and the intensity/latency correlation (Zimmermann et al., 1989); if the male and the female are relatively close, she will be more likely to respond to the early pulses of the male’s song. There is a difference between males and females with respect to the time reference for the female response; in another study, we used the latency from the termination of the chirp (E. Tauber, D. Cohen, M. D. Greenfield and M. P. Pener, in preparation) because this interval dictates whether the response falls within the male’s putative sensitive time window. However, the female response is initiated by the first detectable pulses of the chirp.
Although IPI does not seem to be having a major influence on mating speed in the selected females, it may still influence ancestral female preference. Pietrastomina females showed no difference in mating speed between Short and Pietrastomina males, suggesting that sexual selection for (or against) a shorter mean IPI is unlikely to be strong. However the difference in mating speed between the Pietrastomina line and the Long line is indicative of stronger discrimination. As the difference in IPI between the Pietrastomina and Long line is less than that between the Short and Pietrastomina line, female preference of the Pietrastomina line may be asymmetrical (figure 4.23). This agrees with the asymmetry of response to selection seen between the two selection regimes, indicating that the directional selection against longer IPI may have been effective in reducing heritability for IPI over a long period of evolutionary time. In evolutionary terms, males may have little to gain in temis of increased female matings by increasing the pulse rate, given the possible energetic cost, but much to lose by possessing a longer IPI. It may be that males with a longer IPI include some males whose longer IPI is due to lower viability.
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a larger mass in comparably short time by using more energy i.e. stronger muscles. An increase of selected muscles has already been demonstrated for columbid species: among the jaw muscles, M. pterygoideus plays a profound role in closing the beak. In species that peck seeds and grains from the ground, this muscle is of comparatively simpler structure than it is in species who pluck off large-sized fruits from the lofty tree-branches and grasp them with considerable force before swallowing. The force produced by the muscle during closure of the beak is much greater in the latter than in the former species (Bhattacharyya 1997). In birds with prizing movements (Lorenz 1949; Beecher 1951; Wickler 1961; Neweklowsky 1972) however I would suggest that muscles for jaw opening may be particularly strong (see also Stresemann 1934). Podos (2001) who studied Darwin finches, however suggests an intrinsic trade-off in jaw biomechanics between maximal force and velocity. But whether this intrinsic trade-off also holds true for comparisons between less closely related species, like canaries and house sparrows, remains an open question. Whether house sparrows, having significantly larger bodies than canaries (see Fig. 6.4), also might posses generally stronger jaw muscles, which may eliminate differences in song performance based on different beak dimensions, is not known. This, however, asks for a comparative analysis of sparrow and canary jaw muscles in relation to beak dimension.
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22 individually housed females were randomly divided into two groups, one in each of two experimental rooms, where they were in auditory but not visual contact with members of the same group. Each group received playback treatment in a different order (attractive–control or control–attractive). Nesting material was provided from the commencement of playback. Eggs were removed and replaced with dummy eggs on the day that they were laid, and yolks were frozen for later analysis. Nests were removed 3·days after the last egg was laid, and the female was moved to the other room, where she was exposed to playback of the alternate treatment immediately. Nest cups were returned after 3·days in the new room. 13 of the 22 females laid one clutch in each treatment, and the analysis of yolk hormones presented here is limited to these clutches. Since no males were present, the eggs were unfertilized.
Subtle random deviations from perfect symmetry in bilateral traits are suggested to signal reduced phenotypic and genetic quality of a sender, but little is known about the related receiver mechanisms for discriminating symmetrical from asymmetrical traits. Here, we investigated these mechanisms in behavioural and neurophysiological experiments in the Mediterranean field cricket, Gryllus bimaculatus. A downward frequency modulation at the end of each syllable in the calling song has been suggested to indicate morphological asymmetry in sound radiating structures between left and right forewings. Even under ideal laboratory conditions on a trackball system, female crickets only discriminated between songs of symmetrical and asymmetrical males in two-choice experiments at carrier frequencies of 4.4 kHz and a large modulation depth of 600 and 800 Hz. Under these conditions they preferred the pure-tone calling songs over the modulated (asymmetrical) alternative, whereas no preference was observed at carrier frequencies of 4.9 and 5.2 kHz. These preferences correlate well with the responses of a pair of identified auditory interneurons (AN1), known for their importance in female phonotaxis. The AN1 interneuron is tuned to an average frequency of 4.9 kHz, and the roll-off towards lower and higher frequencies determines the magnitude of responses to pure-tone and frequency- modulated calling songs. The difference in response magnitude between the two neurons appears to drive the decision of females towards the song alternatives. We discuss the relevance of song differences based on asymmetry in the morphology of song- producing structures under natural conditions.