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Biomedical and social scientists are increasingly calling the biological sex into question, arguing that sex is a graded spectrum rather than a binary trait. Leading science journals have been adopting this relativist view, thereby opposing fundamental biological facts. While we fully endorse efforts to create a more inclusive environment for gender‐diverse people, this does not require denying biological sex. On the contrary, the rejection of biological sex seems to be based on a lack of knowledge about evolution and it champions species chauvinism, inasmuch as it imposes human identity notions on millions of other species. We argue that the biological definition of the sexes remains central to recognising the diversity of life. Humans with their unique combination of biological sex and gender are different from non‐human animals and plants in this respect. Denying the concept of biological sex, for whatever cause, ultimately erodes scientific progress and may open the flood gates to "alternative truths." [ABSTRACT FROM AUTHOR]

Vocal amplitude, one of the crucial factors for the exchange of acoustic signals, has been neglected in studies of animal communication, but recent studies on song variation in Common Nightingales Luscinia megarhynchos have revealed new insights into its importance in the singing behavior of territorial birds. In nightingales song amplitude is not maximized per se, but is individually regulated according to the level of masking background noise. Also, birds adjust their vocal intensity according to social variables, as in male-male interactions. Moreover, during such interactions, males exploited the directionality of their songs to broadcast them in the direction of the intended receivers ensuring the most effective signal transmission. Studies of the development of this typical long-range signaling suggest that sound level is highly interrelated with overall developmental progression and learning, and thus should be viewed as an integral part of song ontogeny. I conclude that song amplitude is a dynamic feature of the avian signal system, which is individually regulated according to the ecological demands of signal transmission and the social context of communication.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2009.07.004 Byline: Henrik Brumm (a), Rouven Schmidt (a), Lars Schrader (b) Abstract: Since acoustic communication is considerably constrained by environmental noise, some animals have evolved adaptations to counteract its masking effects. Humans and New World monkeys increase the duration of brief vocalizations (below a few hundred milliseconds) as the background noise level rises, a behaviour that increases the detection probability of signals in noise by temporal summation. We found that domestic fowl, Gallus gallus domesticus, exhibited the Lombard effect, that is, a regulation of vocal amplitude depending on the background noise level. This vocal mechanism for communication in noise is also found in mammals and other bird species. However, in contrast to primates, the chickens did not regulate the duration of their brief call syllables. This evidence for a lack of regulation of syllable duration may hint at limitations in the degrees of freedom for signal coding. Overall, our findings indicate that the common problem of acoustic communication in noise has led to the evolution of a common solution, the Lombard effect, but also to special adaptations in different taxa. Author Affiliation: (a) Max Planck Institute for Ornithology, Communication and Social Behaviour Group, Germany (b) Friedrich-Loeffler-Institut, Institute of Animal Welfare and Animal Husbandry, Germany Article History: Received 16 March 2009; Revised 14 May 2009; Accepted 7 July 2009 Article Note: (miscellaneous) MS. number: 09-00174

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2009.06.016 Byline: Erwin Nemeth (a)(b), Henrik Brumm (a) Abstract: When animals colonize cities they often have to adapt their physiology, life history and behaviour to the novel environment. Songbirds rely on acoustic communication for reproduction, and recent studies indicate that songs vary between urban and nonurban habitats. In cities, birds sing louder or use higher frequencies compared to their conspecifics in forests. These habitat-specific differences in song have been interpreted as an adaptation of the city birds to mitigate acoustic masking by low-frequency traffic noise. We compared the songs of blackbirds, Turdus merula, from the city centre of Vienna and the Vienna Woods and found that forest birds sang at lower frequencies and with longer intervals between songs. This difference in song pitch might reflect an adaptation to urban ambient noise. However, the song divergence could also be the result of more intense vocal interaction in the more densely populated city areas or a side-effect of physiological adaptation to urban habitats. We emphasize the need for experimental studies in blackbirds, but also in other species, to clarify a possible causal link between urban acoustics and song characteristics of city birds. Author Affiliation: (a) Max Planck Institute for Ornithology, Germany (b) Konrad Lorenz Institute for Comparative Ethology, Vienna, Austria Article History: Received 26 January 2009; Revised 26 February 2009; Accepted 3 June 2009 Article Note: (miscellaneous) MS. number: 09-00057

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2008.09.009 Byline: Henrik Brumm (a)(b), Robert F. Lachlan (a)(c), Katharina Riebel (a)(d), Peter J.B. Slater (a) Abstract: Why some bird species have evolved elaborate song repertoires has puzzled biologists for a long time. According to the antiexhaustion hypothesis avian song type repertoires have evolved because switching between different songs, involving different patterns of muscle contractions, causes less exhaustion in the singer and thus allows a higher song rate to be maintained. Although it is a classic explanation referred to in many textbooks, this hypothesis is still the subject of debate. We investigated the antiexhaustion idea in the chaffinch, Fringilla coelebs, a species in which males may have only one song type or a repertoire of up to six types. We analysed the song delivery rates of 101 male chaffinches, taking into account various seasonal, ecological and social variables. We found that males with a repertoire of several song types did not sing at a higher rate than males with only one song type, even though single song type males produced longer songs on average. Also, repertoire birds singing at high rates did not switch song types more often. These findings indicate that song type switching is not necessary for the maintenance of high song rates in this species. We conclude that preventing motor fatigue was not important in the evolution of chaffinch song type repertoires. Thus other factors, such as direct sexual selection of repertoire size or the use of song type repertoires for vocal interactions, are much more likely to explain why many bird species have evolved a repertoire of several song types. Author Affiliation: (a) School of Biology, University of St Andrews, U.K. (b) Communication and Social Behaviour Group, Max Planck Institute for Ornithology, Germany (c) Department of Biology, Duke University, U.S.A. (d) Institute of Biology, Leiden University, The Netherlands Article History: Received 2 March 2008; Revised 13 May 2008; Accepted 8 September 2008 Article Note: (miscellaneous) MS. number: 08-00145R

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2006.01.020 Byline: Henrik Brumm, Peter J.B. Slater Abstract: Acoustic signals attenuate with the distance over which they travel, but a vocalizing animal might maintain signal transmission by increasing vocal amplitude when addressing a distant receiver. Such behaviour is well known in humans as speakers vary vocal amplitude with changing distance from an audience, a phenomenon that has been interpreted as resulting from our higher cognitive abilities. However, whether nonhuman animals are capable of this form of vocal adjustment appears to be unknown. We investigated whether birds are also able to regulate the amplitude of their vocal signals depending on receiver distance. Male zebra finches, Taeniopygia guttata, increased their song amplitude with increasing distance to addressed females, indicating that songbirds, like humans, respond to differences in communication distance and that they adjust vocal amplitude accordingly. Our findings show that animal communication is flexible in a previously unsuspected way, and that human speech and bird song share a basic mechanism for ensuring signal transmission. We suggest that this behaviour can be accounted for by simple proximate mechanisms rather than by the cognitive abilities that have been thought necessary in humans. Author Affiliation: Centre for Social Learning and Cognitive Evolution, School of Biology, University of St Andrews, U.K. Article History: Received 26 September 2005; Revised 25 October 2005; Accepted 13 January 2006 Article Note: (miscellaneous) MS. number: 8687R

Research is presented concerning the importance of song intensity in the development of song in oscine birds such as nightingales. The ontogenetic trajectory in the singing of nightingales which were hand-reared is discussed.

Animals use acoustic signals for communication, implying that the properties of these signals can be under strong selection. The acoustic adaptation hypothesis predicts that species in dense habitats emit lower‐frequency sounds than those in open areas because low‐frequency sounds propagate further in dense vegetation than high‐frequency sounds. Signal frequency may also be under sexual selection because it correlates with body size and lower‐frequency sounds are perceived as more intimidating. Here, we evaluate these hypotheses by analysing variation in peak song frequency across 5,085 passerine species (Passeriformes). A phylogenetically informed analysis revealed that song frequency decreases with increasing body mass and with male‐biased sexual size dimorphism. However, we found no support for the predicted relationship between frequency and habitat. Our results suggest that the global variation in passerine song frequency is mostly driven by natural and sexual selection causing evolutionary shifts in body size rather than by habitat‐related selection on sound propagation. [ABSTRACT FROM AUTHOR]