Embryonic Calls as Care-soliciting Signals in Budgerigars,Melopsittacus undulatus

Embryonic calls occur 1–3 d before hatching among precocial and some altricial birds. In precocial species, calls may synchronize hatching among siblings or, in semi-precocial species, elicit parental attention to, and often thermoregulation of, the hatching egg. Much less is known about the functional significance of calls in fully altricial species. In this study, naturalistic observations and laboratory experiments were used to document factors affecting calling and the parental responses to calls in one altricial species, the budgerigar Melopsittacus undulatus. Budgerigar chicks hatch asynchronously and vocalize 24–48 h before hatching. Embryonic calling rates increase at higher egg temperatures, and also as embryos near hatching. Parents easily locate a calling egg in their clutch, even among a large brood of much older, vocalizing nestlings. Furthermore, they actively assist in the last stages of hatching by helping to break the shell along the crack in the egg. Both observational and experimental evidence suggests that embryonic vocalizations are distinctive signals that increase parental attention and care, and may stimulate hatching assistance to a calling egg.     

Referential calls signal predator behavior in a group-living bird species

Predation is a powerful agent of natural selection, driving the evolution of antipredator calls [1]. These calls have been shown to communicate predator category [2-4] and/or predator distance to conspecifics [5-7]. However, the risk posed by predators depends also on predator behavior [8], and the ability of prey to communicate predator behavior to conspecifics would be a selective advantage reducing their predation risk. I tested this idea in Siberian jays (Perisoreus infaustus), a group-living bird species. Predation by hawks, and to a lesser extent by owls, is substantial and the sole cause of mortality in adult jays [9]. By using field data and predator-exposure experiments, I show here that jays used antipredator calls for hawks depending on predator behavior. A playback experiment demonstrated that these prey-to-prey calls were specific to hawk behavior (perch, prey search, attack) and elicited distinct, situation-specific escape responses. This is the first study to demonstrate that prey signals convey information about predator behavior to conspecifics. Given that antipredator calls in jays aim at protecting kin group members [10, 11], consequently lowering their mortality [9], kin-selected benefits could be an important factor for the evolution of predator-behavior-specific antipredator calls in such systems.     

Acoustic communication in crocodilians: from behaviour to brain

Crocodilians and birds are the modern representatives of Phylum Archosauria. Although there have been recent advances in our understanding of the phylogeny and ecology of ancient archosaurs like dinosaurs, it still remains a challenge to obtain reliable information about their behaviour. The comparative study of birds and crocodiles represents one approach to this interesting problem. One of their shared behavioural features is the use of acoustic communication, especially in the context of parental care. Although considerable data are available for birds, information concerning crocodilians is limited. The aim of this review is to summarize current knowledge about acoustic communication in crocodilians, from sound production to hearing processes, and to stimulate research in this field. Juvenile crocodilians utter a variety of communication sounds that can be classified into various functional categories: (1) “hatching calls”, solicit the parents at hatching and fine‐tune hatching synchrony among siblings; (2) “contact calls”, thought to maintain cohesion among juveniles; (3) “distress calls”, induce parental protection; and (4) “threat and disturbance calls”, which perhaps function in defence. Adult calls can likewise be classified as follows: (1) “bellows”, emitted by both sexes and believed to function during courtship and territorial defence; (2) “maternal growls”, might maintain cohesion among offspring; and (3) “hisses”, may function in defence. However, further experiments are needed to identify the role of each call more accurately as well as systematic studies concerning the acoustic structure of vocalizations. The mechanism of sound production and its control are also poorly understood. No specialized vocal apparatus has been described in detail and the motor neural circuitry remains to be elucidated. The hearing capabilities of crocodilians appear to be adapted to sound detection in both air and water. The ear functional anatomy and the auditory sensitivity of these reptiles are similar in many respects to those of birds. The crocodilian nervous system likewise shares many features with that of birds, especially regarding the neuroanatomy of the auditory pathways. However, the functional anatomy of the telencephalic auditory areas is less well understood in crocodilians compared to birds.     

A note on an interaction between Rhinopithecus bieti and a buzzard at Baima Snow Moutain

Predation avoidance relies primarily on behavioural mechanisms [van Schaik and van Hooff, 1983]. Primates alarm call at predators, including most birds and mammals [Cheney and Wrangham, 1987]. Alarm calls could be used to signal to the predator that it has been spotted [Zuberbühler et al., 1999], thereby probably decreasing the likelihood of an attack [Schultz, 2001], and they also inform prey of the presence of the predator, thereby increasing overall attention levels [Schülke, 2001]. Although eagles are reported to be one of the predators of Rhinopithecus bieti [Bai et al., 1987], few interactions between these monkeys and raptors have been documented to date. Here I document an interaction witnessed between R. bieti and a buzzard [Buteo sp., Yang X-J, pers. comm.].     

Distress call alternation in hand-reared goslings (Anser indicus): vocal co-operation between siblings?

Hand-reared bar-headed goslings (Anser indicus) isolated in pairs tend to alternate their distress calling. This phenomenon has earlier been reported for ducklings by other authors, who suggested a co-operative function in attracting the parent(s). In this paper six possible functions are considered: co-operation between siblings; non-interference (not calling when other sounds interfere with the signal); orientation response (listening to other sounds); calm down response (reducing arousal when sounds are heard); approach response (approach instead of calling when parent calls); and fear response (inhibition of calling when fear-provoking stimuli are heard). Playback experiments showed that the goslings alternated more with some low-frequency sounds (electric buzzer, adult excitement calls) than with the much higher distress calls of siblings or other goslings, which were the most attractive for parent geese. When silent, the subjects increased locomotion and did not show listening behaviour. The results seem most compatible with a fear response function, and it is suggested that alternation with siblings might be an artifact. Difficulties in measuring the alternation tendency are discussed.     

Retinal asymmetry in birds

Vertebrate sensory systems are generally based on bilaterally symmetrical sense organs. It is evident, nevertheless, that birds preferentially use either their left or right eye for viewing novel or familiar stimuli [1], and perform visual discrimination tasks under monocular viewing conditions better with one eye than with the other [2] [3]. Because of the nearly complete contralateral decussation of the optic nerves in birds [4], it has been assumed that this division of labour is due solely to cerebral hemispheric specialisation, generated as a result of uneven photostimulation of the eyes of the developing embryo during the last three or four days before hatching [5] [6]. Here, however, we present evidence that in the European starling, Sturnus vulgaris, even the retinae are morphologically asymmetrical in terms of photoreceptor distribution. This is the first evidence for such asymmetry in any bird and suggests that retinal photoreceptor composition should be assessed during studies involving the lateralisation of visually mediated behaviours.     

Prestin's role in cochlear frequency tuning and transmission of mechanical responses to neural excitation

The remarkable power amplifier [1] of the cochlea boosts low-level and compresses high-level vibrations of the basilar membrane (BM) [2]. By contributing maximally at the characteristic frequency (CF) of each point along its length, the amplifier ensures the exquisite sensitivity, narrow frequency tuning, and enormous dynamic range of the mammalian cochlea. The motor protein prestin in the outer hair cell (OHC) lateral membrane is a prime candidate for the cochlear power amplifier [3]. The other contender for this role is the ubiquitous calcium-mediated motility of the hair cell stereocilia, which has been demonstrated in vitro and is based on fast adaptation of the mechanoelectrical transduction channels [4, 5]. Absence of prestin [6] from OHCs results in a 40-60 dB reduction in cochlear neural sensitivity [7]. Here we show that sound-evoked BM vibrations in the high-frequency region of prestin(-/-) mice cochleae are, surprisingly, as sensitive as those of their prestin(+/+) siblings. The BM vibrations of prestin(-/-) mice are, however, broadly tuned to a frequency approximately a half octave below the CF of prestin(+/+) mice at similar BM locations. The peak sensitivity of prestin(+/+) BM tuning curves matches the neural thresholds. In contrast, prestin(-/-) BM tuning curves at their best frequency are >50 dB more sensitive than the neural responses. We propose that the absence of prestin from OHCs, and consequent reduction in stiffness of the cochlea partition, changes the passive impedance of the BM at high frequencies, including the CF. We conclude that prestin influences the cochlear partition's dynamic properties that permit transmission of its vibrations into neural excitation. Prestin is crucial for defining sharp and sensitive cochlear frequency tuning by reducing the sensitivity of the low-frequency tail of the tuning curve, although this necessitates a cochlear amplifier to determine the narrowly tuned tip.     

鼠类超声波通讯的社会原因和功能

鼠类的超声通讯已有报道,并且在实验室深入研究了小鼠和大鼠接受和释放这些叫声的能力。由于对不同刺激的反应和出自不同的目的,幼鼠和成年鼠都释放超声。发出者的年龄/性/品系以及自然和社会环境的不同,导致这些超声的频率和持续时间也不同。在社会隔离和操作处理时,未成年个体可释放超声波。作为成熟程度以及对环境信号和药物处理时反应的指标,这些叫声得到了广泛研究,表明超声在调节出生后早期的母幼联系中起相应的作用。随着幼鼠的长大及体温调节和感觉能力的增强,发生的数量大大减少。然而,成年小鼠和大鼠在不同的社会条件下,释放出的超声有种间差异:大鼠的超声与正面和负面的社会作用有关,而在小鼠中,这些叫声主要与领域有关.     

A homologue of cysteine-rich secretory proteins induces premature degradation of vitelline envelopes and hatching of Xenopus laevis embryos

We cloned Xenopus laevis CRISP, XCRISP, a homologue of the mammalian family of cysteine-rich secretory proteins (CRISPs), which has been previously identified as a Wnt3a/noggin responsive gene in an expression screen [Mech. Dev. 87 (1999) 21]. We detected XCRISP expression exclusively in the hatching gland. XCRISP enters the secretory pathway and accumulates on the surface of presumptive hatching gland cells. Overexpression studies of XCRISP and XCRISP-mutants show that XCRISP induces premature hatching of embryos preceded by degradation of the vitelline envelope. A deletion mutant that lacks a 35 amino acid domain even accelerates hatching, while further deletion of the carboxy-terminus reverses these effects. From our studies, we conclude that XCRISP is sufficient to induce degradation of vitelline envelopes and that this activity maps to the most C-terminal amino acids, while the adjacent domain regulates XCRISP activity.     

Increased lifetime reproductive success of first‐hatched siblings in Common Kestrels Falco tinnunculus

Order of birth has profound consequences on offspring across taxa during development and can have effects on individuals later in life. In birds, differential maternal allocation and investment in their progeny lead to variance in the environmental conditions that offspring experience during growth within the brood. In particular, laying and hatching order have been proposed to influence individual quality during the growing period, but little is known about the fitness consequences that these two factors have for offspring from a lifetime perspective. We explored the effect of laying and hatching order on post‐fledgling survival (measured as recruitment probability) and lifetime reproductive success (LRS) in Common Kestrels Falco tinnunculus, using a long‐term and individual‐based dataset. First‐hatched chicks showed higher survival probability and LRS than their siblings. This effect was not due to body condition of the individuals at adulthood, the quality of their mates or the reproductive outcome compared with later‐hatched individuals. Instead, first‐hatched chicks had a higher recruitment probability. This could be explained by the higher body condition attained by first‐hatched chicks at the end of the nesting period, perhaps due to an enhanced competitive advantage for food over their siblings at the time of hatching. Laying order, in contrast to hatching order, appeared to have little or no effect on LRS. Our results suggest that hatching order within siblings predicts fitness, and that better early‐life conditions during growth experienced by first‐hatched chicks improve first survival and then recruitment, resulting in an enhanced LRS.     

Family dynamics through time: brood reduction followed by parental compensation with aggression and favouritism

Parental food allocation in birds has long been a focal point for life history and parent–offspring conflict theories. In asynchronously hatching species, parents are thought to either adjust brood size through death of marginal offspring (brood reduction), or feed the disadvantaged chicks to reduce the competitive hierarchy (parental compensation). Here, we show that parent American coots (Fulica americana) practice both strategies by switching from brood reduction to compensation across time. Late‐hatching chicks suffer higher mortality only for the first few days after hatching. Later, parents begin to exhibit parental aggression towards older chicks and each parent favours a single chick, both of which are typically the youngest of the surviving offspring. The late‐hatched survivors can equal or exceed their older siblings in size prior to independence. A mixed allocation strategy allows parents to compensate for the costs of competitive hierarchies while gaining the benefits of hatching asynchrony.     

Larval sensory abilities and mechanisms of habitat selection of a coral reef fish during settlement

In most animals, siblings from a given reproductive event emerge over a very short period of time. In contrast, many species of birds hatch their young asynchronously over a period of days or weeks, handicapping last-hatched chicks with an age and size disadvantage. Numerous studies have examined the adaptive significance of this atypical hatching pattern, but few have attempted to explain the considerable intrapopulation variation that exists in hatching asynchrony. I explored proximate determinants of hatching asynchrony by monitoring 112 Burrowing Owl (Athene cunicularia) nests in the grasslands of southern Saskatchewan, Canada, over 4 years. Age disparities between first- and last-hatched siblings (i.e., hatching spans) varied considerably, ranging between 1 and 7 days (mode = 4 days). These hatching spans increased with increased hatching success. Hatching spans also increased with larger clutches, but the increase was less than predicted given the increased time required to lay more eggs. Hatching span was unrelated to number of prey cached in the nest during egg laying (an index of food availability), and was unaltered by a year of super-abundant prey. Furthermore, pairs given extra food during laying had hatching spans equal to those of unsupplemented control pairs. These results were inconsistent with both the energy constraint and facultative manipulation hypotheses, which predict that hatching asynchrony should vary with the level of food during laying, when incubation onset is determined. Burrowing Owls were apparently free of food limitation early in breeding, yet may not have been able to optimize hatching spans because food conditions during laying were largely unrelated to food conditions during brooding. Thus, one of the premises for facultative manipulation of hatching asynchrony—that laying females are able to forecast post-hatch food conditions—may not have been met for this population of Burrowing Owls.     

Vocal-tract resonances as indexical cues in rhesus monkeys

Vocal-tract resonances (or formants) are acoustic signatures in the voice and are related to the shape and length of the vocal tract. Formants play an important role in human communication, helping us not only to distinguish several different speech sounds [1], but also to extract important information related to the physical characteristics of the speaker, so-called indexical cues. How did formants come to play such an important role in human vocal communication? One hypothesis suggests that the ancestral role of formant perception--a role that might be present in extant nonhuman primates--was to provide indexical cues [2-5]. Although formants are present in the acoustic structure of vowel-like calls of monkeys [3-8] and implicated in the discrimination of call types [8-10], it is not known whether they use this feature to extract indexical cues. Here, we investigate whether rhesus monkeys can use the formant structure in their "coo" calls to assess the age-related body size of conspecifics. Using a preferential-looking paradigm [11, 12] and synthetic coo calls in which formant structure simulated an adult/large- or juvenile/small-sounding individual, we demonstrate that untrained monkeys attend to formant cues and link large-sounding coos to large faces and small-sounding coos to small faces-in essence, they can, like humans [13], use formants as indicators of age-related body size.     

Significance of Mother and Sibling Experience for Mating Preferences in the Mallard (Anas platyrhynchos)

Social attachment seems necessary for sexual imprinting. In mallards the likely period of social attachment is from hatching until the broods disperse. The potential imprinting objects are mother and siblings. Four combinations of mother-sibling groups of same and different colour were used (N = 131). The groups were kept together from hatching until the young were 12 weeks old. When sexually mature, the birds' choices of mate were recorded. Colouration is an important cue in mate selection. Both mother and siblings are of importance. The effect of experimental factors cannot be attributed to any particular sex.     

一种泡蟾的配偶识别:脑、行为和进化研究

综述了对泡蟾(Physalaemuspus pustulosus)的性通讯所进行的各种研究。本文作者研究了通讯系统的功能重要性、通讯的神经机制以及通讯进化的格局,特别研究了雌蛙如何使用简单和复杂的叫声来识别可以交配的物种,以及如何识别同种的不同雄性个体。本文确定了复杂叫声的反选择力、一种食蛙蝠——缨唇蝠(Trachops cirrhosus)以及叫声的能量消耗,并阐述了引起雌性反应的重要特征。作者的比较研究表明,对复杂叫声的偏好在复杂叫声进化前就有了,这支持感官开发假说(Hypothesis of sensory exploitation,雄性特征进化的结果是开发雌性预先存在的对雄性的偏好)。结合比较研究和人工神经网络的模拟,作者认为雌蛙用来识别雄性简单叫声的解码策略受其祖先解码策略的影响[动物学报49(6)：713～726,2003]。     

Maternal manipulation of hatching asynchrony limits sibling cannibalism in the predatory mite Phytoseiulus persimilis

1. Sibling cannibalism is a common phenomenon in the animal kingdom but entails a high risk of direct and inclusive fitness loss for the mother and her offspring. Therefore, mechanisms limiting sibling cannibalism are expected to be selected for. One way of maternal manipulation of sibling cannibalism is to influence hatching asynchrony between nearby laid eggs. This has rarely been tested experimentally. 2. We examined the ability of ovipositing females of the cannibalistic predatory mite Phytoseiulus persimilis to influence the occurrence of sibling cannibalism among offspring by manipulating hatching asynchrony of nearby laid eggs. 3. In the first experiment, we assessed the occurrence of sibling cannibalism in relation to the hatching interval (24 h and 48 h) between nearby laid eggs. In the second experiment, we tested whether ovipositing females discriminate sites containing young (24-h old) and old (48-h old) eggs, fresh and old traces (metabolic waste products and possibly pheromones) left by the same female (24 h and 48 h ago), or young eggs plus fresh female traces and old eggs plus old female traces. Both experiments were conducted with and without prey. 4. Without prey, siblings were more likely to cannibalize each other if the hatching interval between nearby laid eggs was short (24 h). Cannibalism occurred less often when senior siblings (protonymphs) experienced a delay in the opportunity to cannibalize junior siblings (larvae). 5. Independent of prey availability, females preferentially added new eggs to sites containing old eggs plus old female traces but did neither distinguish between young and old eggs presented without own traces nor between fresh and old traces presented without eggs. 6. We discuss cue perception and use by P. persimilis females and contrast the outcome of our experiments and theoretical predictions of sibling cannibalism. We conclude that P. persimilis mothers increase hatching asynchrony of nearby laid eggs to prevent sibling cannibalism on the last produced offspring. Such a behaviour may be considered a simple form of maternal care increasing the survival prospects of offspring.     

Social rank governs the effective environment of siblings

Siblings within the same family often differ dramatically in phenotype. Some differences are attributable to initial maternal handicaps (birth or hatching asynchrony, differences in egg or neonate size and hormonal or antioxidant titre); but differences among siblings may also arise from differences in the brood-rearing environment that offspring experience. Here, I use a model system--a long-term study of nestlings in an altricial bird--to study how an initial maternal handicap, hatching asynchrony, regulates the effective social environment of siblings in the same family as measured by offspring survival. The interaction of family size and structure generated wide differences in the effective environments of siblings living in the same physical space (a nest), and reared by the same parents, in the same family structure. Social rank was the key component of the unshared environment of contemporary siblings, and was alone sufficient to generate near-maximal differences in offspring performance. Nestlings sitting side-by-side effectively lived in different worlds.     

Development of vocal behaviour in Peking ducklings

Vocal communication appears to play an important role in maintaining group cohesion in broods of Peking ducklings (Anas platyrhynchos). In order to describe the development of the vocal repertoire of the young, the present study examined the vocalizations of six ducklings from several hours before hatching through 48 h posthatching. Vocalizations were recorded in standardized situations in the laboratory, including the presence of conspecific peers, exposure to maternal calls, and social isolation. A major methodological aim of the present study was to determine whether the vocal repertoire of the ducklings would sort itself on objectively measured acoustic features without the necessity of experimenter preclassification (as has been relied upon in the past). This objective procedure produced two acoustically distinct (and conventional) types: (a) contentment calls, which have short note durations, fast repetition rates, and low pitch, and are elicited by the presence of peers and/or the maternal call; (b) distress calls, with longer note durations, slower repetition rates, and higher pitch, which are uttered in social isolation and emerge in mature form only after hatching. A simple physiological model based on respiratory activity is proposed to account for the acoustic variation between the two vocalization types.     

Body condition of Little Egret Egretta garzetta nestlings in relation to hatching order in a southern Tunisian breeding colony

The effect of asynchronous hatching on nestling health and condition in ardeids is still in need of empirical evidence from populations living in different environmental conditions. Using morphometric and hematologic data from Little Egret Egretta garzetta nestlings in a Tunisian breeding colony, we assessed the relationship between hatching order and nestling condition, while accounting for the effects of brood size, age and hatching date. Our results showed that the youngest nestlings had lower values of hematocrit and body condition index but higher levels of fluctuating asymmetry compared with their older siblings. These trends seem to stem from increased nutritional stress experienced by younger nestlings who would have received less food from their parents than their siblings due to their less competitive nature. Additional constraints during the rearing period, such as possible injuries resulting from conflicts with siblings and the energy cost of thermoregulation, may also have contributed to the deterioration of the condition of last nestlings. Overall, our findings provide empirical evidence of the short-term repercussions of asynchronous hatching in a North African population of Little Egrets. They also highlight the great complexity of mechanisms by which asynchronous hatching may affect body condition and health of bird nestlings.     

Pre-hatching maternal effects inhibit nestling humoral immune response in the tawny owl Strix aluco

Although evidence is accumulating that mothers can transfer antibodies to their offspring, little is known about the consequences of such a transfer to the offspring immune system. Because maternal antibodies are effective only during a short period of time after their transfer to offspring, one hypothesis is that maternal antibodies provides a transitory antigen-specific protection to offspring, thus lessening the need for offspring to mount their own humoral immune response towards these specific antigens. In birds, this scenario predicts that offspring immune response towards a specific antigen is inhibited to a larger extent in hatchlings than in older nestlings. We tested this hypothesis in tawny owls Strix aluco by cross-fostering clutches between nests and then challenging siblings with a vaccine either two times (at 4- and 11-d-old) or only one time at 11-d-old to compare the strength of the humoral response between nestlings born from mothers with naturally high and low levels of antibodies against this vaccine. Because maternal antibodies are expected to be effective only during a short period of time after hatching, we predict that maternal antibodies should inhibit the immune response of nestlings vaccinated from the fourth day after hatching more than in nestlings vaccinated only at a later age. As expected, the inhibitory effect of maternal antibodies was stronger in nestlings vaccinated soon after hatching than in siblings injected at a later age. Therefore, in wild avian populations pre-hatching maternal effects may confer offspring with a transitory immune protection in the first days following hatching.