Dawn song of male blue tits as a predictor of competitiveness in midmorning singing interactions

During the dawn chorus, territorial male songbirds vocalise intensively within signalling range of several conspecific males and can therefore be considered members of a busy communication network. The more or less continuous singing over a long period of time under standardised stimulus conditions makes the dawn song a potentially important information source both for simple receivers and for eavesdroppers. Male blue tits (Parus caeruleus) vary in features of their dawn song, e.g. older males sing longer strophes, and females choose males that sing longer strophes as extra-pair partners. However, so far, dawn song in the blue tit has been investigated separately from other singing behaviour of the same males. In this study, we investigate aspects of blue tit male quality, reflected in dawn song characteristics, and their predictive value for how males behave during singing interactions later in the morning. We acted as simple receivers by recording the singing activity of one male at a time at dawn and compared features of its dawn song, such as onset before sunrise, repertoire size, mean bout length, strophe length and percentage performance time to responses of the same male to a territory intrusion simulated by playback of synthesised songs later during the same morning. We assume that an aggressive response towards an intruder will involve a fast approach to the loudspeaker broadcasting strophes of blue tit song, searching for the intruder (flying around), and a high amount of counter singing and overlapping of the intruders songs. Aspects of vigour of response to the simulated intrusion could be predicted from all five investigated dawn song parameters as well as male age. This is, to our knowledge, the first indication that a simple receiver could extract reliable information from a males dawn singing behaviour about its competitiveness later in the day.Communicated by P.K. McGregor     

西黑冠长臂猿雄性取代前后鸣叫行为的变化

本文通过长时间的野外监测,首次报道了西黑冠长臂猿的一次雄性取代行为。一个研究群体(G3)中的1 只亚成年雄性长臂猿在10 岁左右取代了相邻群体(G2)中的成年雄性。整个取代过程持续了15 d时间。雄性取代发生前,G2 中雌雄的配对关系已经不稳固,这为雄性取代提供了机会。而G2 与G3 群的一次长时间冲突可能消耗了G2 中成年雄性大量体能,这为G3 中的亚成年雄性打败并取代G2 中的成年雄性创造了机会。本研究在取代发生后,对新形成群体的鸣叫行为进行了连续4 个月的监测。结果表明与处于稳定时期的G2 群相比,新形成群体的鸣叫频次更高,但每次二重唱中雌性的平均激动鸣叫次数降低。这证明了Geissmann (1986)提出的假说,新配对的群体应该在尽量短的时间内多练习二重唱,这样导致新配对群体的鸣叫频率明显升高。虽然经历了4 个月的合唱练习,新形成群体的激动鸣叫次数仍然偏低,并且两只雌性同时激动鸣叫的频次也比较低。这说明新形成的配对之间配合依然不默契,或者说明配对之间的关系还不稳定。     

Directionality of the tympanal vibrations in a cicada: a biophysical analysis

1. Laser vibrometry and acoustic measurements were used to study the biophysics of directional hearing in males and females of a cicada, in which most of the male tympanum is covered by thick, water filled tissue “pads”. 2. In females, the tympanal vibrations are very dependent on the direction of sound incidence in the entire frequency range 1–20 kHz, and especially at the main frequencies of the calling song (3–7 kHz). At frequencies up to 10 kHz, the directionality disappears if the contralateral tympanum, metathoracic spiracle, and folded membrane are blocked with Vaseline. This suggests some pressure-difference receiver properties in the ear. 3. In males, the tympanal vibrations depend on the direction of sound incidence only within narrow frequency bands (around 1.8 kHz and at 6–7 kHz). At frequencies above 10–12 kHz, the directionality appears to be determined by diffraction, and the ear seems to work as a pressure receiver. The peak in directionality at 6–7 kHz disappears when the contralateral timbal, but not the tympanum, is covered. Covering the thin ventral abdominal wall causes the peak around 1.8 kHz to disappear. 4. Most observed tympanal directionalities, except around 1.8 kHz in males, are well predicted from measured transmissions of sound through the body and measured values of sound amplitude and phase at the ears at various directions of sound incidence. Accepted: 18 October 1996     

Implications of conspecific background noise for features of blue tit, Cyanistes caeruleus , communication networks at dawn

Communication among animals often comprises several signallers and receivers within the signal’s transmission range. In such communication networks, individuals can extract information about differences in relative performance of conspecifics by eavesdropping on their signalling interactions. In songbirds, information can be encoded in the timing of signals, which either alternate or overlap, and both male and female receivers may utilise this information when engaging in territorial interactions or making reproductive decisions, respectively. We investigated how conspecific background noise at dawn may overlay and possibly constrain the perception of such singing patterns. We simulated a small communication network of blue tits, Cyanistes caeruleus, at dawn in spring. Two loudspeakers simulated a singing interaction which was recorded from four different receiver positions simulating potential eavesdroppers. During the recordings, resident blue tit males were vocalising and created natural conspecific background noise. Levels of conspecific background noise were high and varied among positions of potential eavesdroppers. We conclude that conspecific background vocalisations may potentially constrain the perception of singing patterns and may constitute costs for eavesdroppers. On the other hand, signallers may position themselves strategically and privatise their interactions.     

短翅树莺的繁殖习性

短翅树莺是森林益鸟。本文着重记述了其种群的分布和数量及迁徙动态,并对其歌唱声和惊叫声作了录音分析及文字描述。文内较全面地记述了繁殖习性和食性。并对其繁殖力和雏鸟(257只)生长曲线方程作了较深入的探讨。     

Seasonal and diel budgets of song: a study of Savi’s warbler (Locustella luscinioides)

Seasonal and diel patterns of singing activity of Savis warblers (Locustella luscinioides) were studied in two areas of Central Europe 300 km apart, over a period of 18 years. We assess about 4,600 records of individuals singing. Males were found to exhibit similar singing activity in both study sites. They started to sing after arrival at the beginning of April and peaked from the end of April to the beginning of May. Thereafter, their singing activity was lower but more stable for a relatively long period from mid-May to mid-July. At the end of July, males sang only sporadically and singing activity ceased at the beginning of August. At the beginning and towards the end of the song-period males sang sporadically whereas in the period of the highest singing activity they sang over the entire 24-h period. During the whole song-period, there was a significant difference in singing activity between daylight and the dark (67.2 and 32.8%, respectively). However, the period of daylight was longer. Average singing activity showed similar levels in daylight and the dark with mean numbers of 5.9 and 6.6 males per hour, respectively. Major changes in singing activity were related to the twilight periods. There were distinctive dawn and dusk choruses. In the morning, Savis warblers exhibited similar levels of singing activity over 3 h of the dark before twilight, singing reached its highest level at twilight and 1 h after twilight. During the evening, singing activity reached its highest-level 1 h before twilight, while during twilight it was decreasing, with a considerable decline 1 h after nightfall.     

Androgens modulate song effort and aggression in Neotropical singing mice

Androgens are an important class of steroid hormones involved in modulating the expression and evolution of male secondary sex characters. Vocalizations used in the context of aggression and mate attraction are among the most elaborate and diverse androgen-dependent animal displays as reflected in a rich tradition of studies on bird song and anuran calls. Male Alston's singing mice (Scotinomys teguina) commonly emit trilled songs that appear to function in male-male aggression. In this study, we experimentally manipulated androgens in singing mice to assess their role in modulating aggression and song effort. Testosterone- and DHT-treated animals retained aggressive and song attributes similarly. However, castrated mice administered empty implants showed more subordinate behavior and sang fewer songs that were shorter, lower in power, higher in frequency, and less stereotyped. The extensive effects of androgens on a suite of phenotypes highlight their role in linking gonadal status with decisions about investment in reproductive behaviors.     

Plasticity of the Rufous-winged Sparrow, Aimophila carpalis, song control regions during the monsoon-associated summer breeding period

In most temperate zone songbirds, exposure to increasing photoperiod in the spring stimulates the reproductive system and induces reproductive behaviors. Additionally, the brain regions that control singing (song control regions; SCRs) are larger during the breeding season, thus paralleling changes in the activity of the reproductive system. However, in some birds, environmental factors other than photoperiod initiate breeding. For example, free-living male Rufous-winged Sparrows develop their testes in March due to increasing photoperiod, but have relatively low plasma T until after they begin to breed, usually in July, during the monsoon period when day length is declining. We tested the hypothesis that SCRs grow and singing behavior increases after the monsoon rains begin. We captured adult male Rufous-winged Sparrows in July 2002, 7 days before and 20 days after the monsoon rains began, euthanized birds in the field, collected their brains, and measured SCR volumes from sections immunostained for the neuronal marker NeuN. In June and July 2006, we measured song rates in the field before and after the monsoon rains. SCR volumes were larger and singing behavior increased after the onset of the monsoon rains, coinciding with the initiation of breeding. Unlike in other species studied so far, SCR volumes grew as day length was decreasing. Comparative studies utilizing species that do not breed when day length is increasing may provide information on the relative contributions of various environmental factors to SCR neuroplasticity.     

Testosterone and social context affect singing behavior but not song control region volumes in adult male songbirds in the fall

Testosterone (T) induces singing behavior and mediates changes in the sizes and neuroanatomical characteristics of brain regions controlling singing behavior (song control regions, SCRs) in songbirds. These effects may require the enzymatic conversion of T into androgenic and estrogenic metabolites by brain tissues and can be modulated by factors such as season and social context. Testosterone administration to adult male House Finches, Carpodacus mexicanus, in the spring increases the size of their SCRs. Here, we used males of this species to investigate effects of T and T metabolism on brain morphology and singing behavior in the fall. Birds received Silastic capsules containing androgens, estrogens, and/or inhibitors of androgenic action or estrogen synthesis to determine effects of these hormones on song rates and SCR volumes. We also manipulated the social environment by changing the number of birds in visual contact with each other. Testosterone treatment stimulated singing behavior in finches held in small, visually isolated groups and exposed to song playbacks. However, administration of T or T metabolites did not increase SCR sizes. The data suggest that photoperiodic condition and social context may modulate the effects of steroids on SCRs and singing behavior.     

鸟类学习记忆研究进展

在学习记忆研究中,需根据不同的实验目的选用不同的实验动物和模型。鸟类在生物进化上具有独特的地位,由此决定了其在认知科学研究中的价值。现已建立了呜禽呜唱学习、鸟类空间学习及视觉分辨学习等重要实验模型,并开展了一系列的学习记忆机制研究。文章对近年来鸟类学习记忆研究的进展,从鸟类鸣唱行为、海马功能以及神经递质作用等方面做了回顾。