American Crows (Corvus brachyrhynchos) aggregate in the thousands on nocturnal roosting sites each night from early autumn through early spring. The impacts of such crow roosts on other wildlife species have not been thoroughly examined. Song Sparrows (Melospiza melodia morphna) hold territories year-round in Washington State, some of which are on crow roosting sites. Here, we tested the hypothesis that Song Sparrows holding territories on crow roosting sites would show season-dependent differences in aggression and vigilance behaviors. We exposed Song Sparrows on territories on crow roost and non-roost sites to playbacks of conspecific songs or distress calls during autumn (non-breeding), winter (non-breeding), and spring (early-breeding). In winter, Song Sparrows showed less territorial aggression on crow roost versus non-roost sites. Specifically, during song playback, they sang fewer songs, approached less closely to, spent less time within 1 m of, and displayed fewer movements toward the playback speaker than non-roost sparrows. Lower territorial aggression by roost sparrows during winter may be due to diminished territory quality when crow numbers are at their seasonal peak. In spring, Song Sparrows showed increased induced vigilance on crow roost versus non-roost sites. Specifically, during distress call playback, they sang fewer songs, spent more time within 5 m of, and made more movements toward the speaker. Increased vigilance by roost sparrows during early breeding may be a response to crows as potential nest predators. Our results suggest that crow roosts are associated with differences in Song Sparrow behaviors linked to survival and reproduction.

This activity will introduce you to the quantitative assessment of bird song. You will examine songs of the white-crowned sparrow, a species that sings a single song type. You will assess phrase duration utilizing a commonly used audio analysis program, Raven Lite (Center for Conservation Bioacoustics, 2016), and using your resultant dataset, you will compare individual and inter-individual variations in this variable.

Crows are highly intelligent and social creatures. Each night during the non-breeding period, they gather on large pre-roost aggregations as they move towards their communal roost where they sleep. Crows make numerous and varied vocalizations on these pre-roost aggregations, but the purpose of these calls, and vocal communication in general, in these pre-roost aggregations is not fully understood. In this paper, an array of four microphones is used as a non-intrusive means to observe crow vocal behavior in pre-roost aggregations in the absence of human observers. By passively localizing animal vocalizations, the location of individuals can be monitored while simultaneously recording the acoustic structure and organization of their calls. Simulations and experiment are undertaken to study the performance of two time difference of arrival-based methods (hyperbolic location estimator and maximum likelihood estimator) for call localization. The effect of signal-to-noise ratio and uncertainty in measurement on the localization error is presented. By describing, modeling, and testing these techniques in this innovative context, the authors hope that researchers will employ the authors' approaches in future empirical studies to more fully understand crow vocal behavior.

Neural vasopressin is a potent modulator of behaviour in vertebrates. It acts at both sensory processing regions and within larger regulatory networks to mediate changes in social recognition, affiliation, aggression, communication and other social behaviours. There are multiple populations of vasopressin neurons within the brain, including groups in olfactory and visual processing regions. Some of these vasopressin neurons, such as those in the main and accessory olfactory bulbs, anterior olfactory nucleus, piriform cortex and retina, were recently identified using an enhanced green fluorescent protein-vasopressin (eGFP-VP) transgenic rat. Based on the interconnectivity of vasopressin-producing and sensitive brain areas and in consideration of autocrine, paracrine and neurohormone-like actions associated with somato-dendritic release, we discuss how these different neuronal populations may interact to impact behaviour.

Biological steroids were traditionally thought to be synthesized exclusively by the adrenal glands and gonads. Recent decades have seen the discovery of neurosteroid production that acts locally within the central nervous system to affect physiology and behavior. These actions include, for example, regulation of aggressive behavior, such as territoriality, and locomotor movement associated with migration. Important questions then arose as to how and why neurosteroid production evolved and why similar steroids of peripheral origin do not always fulfill these central roles? Investigations of free-living vertebrates suggest that synthesis and action of bioactive steroids within the brain may have evolved to regulate expression of specific behavior in different life history stages. Synthesis and secretion of these hormones from peripheral glands is broadcast throughout the organism via the blood stream. While widespread, general actions of steroids released into the blood might be relevant for regulation of morphological, physiological, and behavioral traits in one life history stage, such hormonal release may not be appropriate in other stages. Specific and localized production of bioactive steroids in the brain, but not released into the periphery, could be a way to avoid such conflicts. Two examples are highlighted. First, we compare the control of territorial aggression of songbirds in the breeding season under the influence of gonadal steroids with autumnal (non-breeding) territoriality regulated by sex steroid production in the brain either from circulating precursors such as dehydroepiandrosterone or local central production of sex steroids de novo from cholesterol. Second, we outline the production of 7α-hydroxypregnenolone within the brain that appears to affect locomotor behavior in several contexts. Local production of these steroids in the brain may provide specific regulation of behavioral traits throughout the year and independently of life history stage.

The North Creek Wetlands Restoration on the University of Washington Bothell campus is home to a large nocturnal American crow (Corvus brachyrhynchos) roost. Each day from Autumn to Spring, crows form pre- and post-roost aggregations, which consist of tens to hundreds of crows. Crows on these aggregations are often highly vocal, but the functions of their vocalizations are not well understood. Identifying any context-dependent patterns in these vocalizations is critical to fully understand communication in this highly social and intelligent species. Previous studies have shown the presence of human observers near large groups of crows may disrupt natural vocal and non-vocal behavior. In this study, the potential confound of these observer effects are eliminated by recording crow vocalizations using a remotely activated, time-synched microphone array. Simulations are undertaken to study the performance of the Time Difference of Arrival (TDOA) method to localize individual callers. A parametric study is used to analyze the effects of number of receivers, signal frequency and duration, and crow location on the performance of TDOA. In addition to the simulation, different types of recorded crow vocalizations are used to design robust playback experiments to fine-tune our localization technique for use in actual crow aggregations in future.

Dehydroepiandrosterone (DHEA) is a testosterone/oestrogen precursor and known modulator of vertebrate aggression. Male song sparrows (Melospiza melodia morphna) show high aggression during breeding and nonbreeding life‐history stages when circulating DHEA levels are high, and low aggression during molt when DHEA levels are low. We previously showed that androgen receptor and aromatase mRNA expression are higher during breeding and/or nonbreeding in brain regions associated with reproductive and aggressive behaviour, although the potential role of DHEA in mediating these seasonal changes remained unclear. In the present study, nonbreeding male song sparrows were captured and held in the laboratory under short days (8 : 16 h light/dark cycle) and implanted with s.c. DHEA‐filled or empty (control) implants for 14 days. DHEA implants increased aggression in a laboratory‐based simulated territorial intrusion. Brains of DHEA‐implanted birds showed higher aromatase mRNA expression in the preoptic area (POA) and higher androgen receptor mRNA expression in the periventricular nucleus of the medial striatum (pvMSt) and ventromedial nucleus of the hypothalamus. The DHEA‐induced increases in aromatase expression in the POA and androgen receptor expression in the pvMSt are consistent with previously reported seasonal increases in these markers associated with naturally elevated DHEA levels. This suggests that DHEA facilitates seasonal increases in aggression in nonbreeding male song sparrows by up‐regulating steroid signalling/synthesis machinery in a brain region‐specific fashion.

Central vasopressin and oxytocin, and their homologues, modulate a multitude of social behaviors in a variety of animal taxa. All social behavior requires some level of social (re)cognition, and these neuropeptides exert powerful effects on an animal's ability to recognize and appropriately respond to a conspecific. Social cognition for many mammals, including rodents, begins at the main and accessory olfactory systems. We recently identified vasopressin expressing neurons in the main and accessory olfactory bulb and in the anterior olfactory nucleus, a region of olfactory cortex that transmits and processes information in the main olfactory system. We review this and other work demonstrating that both vasopressin and oxytocin modulate conspecific social recognition at the level of the olfactory system. We also outline recent work on the somato-dendritic release of vasopressin and oxytocin, and propose a model by which the somato-dendritic priming of these neuropeptides in main olfactory regions may facilitate the formation of short-term social odor memories. This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior.

Central vasopressin facilitates social recognition and modulates numerous complex social behaviors in mammals, including parental behavior, aggression, affiliation, and pair-bonding. In rodents, social interactions are primarily mediated by the exchange of olfactory information, and there is evidence that vasopressin signaling is important in brain areas where olfactory information is processed. We recently discovered populations of vasopressin neurons in the main and accessory olfactory bulbs and anterior olfactory nucleus that are involved in the processing of social odor cues. In this review, we propose a model of how vasopressin release in these regions, potentially from the dendrites, may act to filter social odor information to facilitate odor-based social recognition. Finally, we discuss recent human research linked to vasopressin signaling and suggest that our model of priming-facilitated vasopressin signaling would be a rewarding target for further studies, as a failure of priming may underlie pathological changes in complex behaviors.

Central vasopressin facilitates social recognition and modulates numerous complex social behaviors in mammals, including parental behavior, aggression, affiliation, and pair‐bonding. In rodents, social interactions are primarily mediated by the exchange of olfactory information, and there is evidence that vasopressin signaling is important in brain areas where olfactory information is processed. We recently discovered populations of vasopressin neurons in the main and accessory olfactory bulbs and anterior olfactory nucleus that are involved in the processing of social odor cues. In this review, we propose a model of how vasopressin release in these regions, potentially from the dendrites, may act to filter social odor information to facilitate odor‐based social recognition. Finally, we discuss recent human research linked to vasopressin signaling and suggest that our model of priming‐facilitated vasopressin signaling would be a rewarding target for further studies, as a failure of priming may underlie pathological changes in complex behaviors.

Free‐living male song sparrows experience three annually repeating life history stages associated with differential expression of sex steroid‐dependent reproductive and aggressive behavior. In the breeding stage, they display reproductive and aggressive behavior and have elevated circulating testosterone levels. During molt, males show little or no aggression and no reproductive behavior, and have basal levels of circulating testosterone. In the non‐breeding stage, they display high levels of aggression and no reproductive behavior, and have basal levels of circulating testosterone. In order to understand more fully the neural regulation of seasonal aggressive and reproductive behavior, birds were collected during all three life history stages, and levels of neural aromatase, androgen receptor (AR), and estrogen receptor α (ERα) and β (ERβ) mRNA expression were measured. Breeding males had the highest levels of aromatase expression in both the preoptic area (POA) and medial preoptic area/medial bed nucleus of the stria terminalis (mPOA/BSTm), and the highest AR expression levels in the POA, consistent with the well‐established role these regions play in the regulation of male reproductive behavior. Aromatase expression in the ventromedial nucleus of the hypothalamus (VMH) was higher during breeding and non‐breeding compared with molt, suggesting that the VMH may play a role in the estrogen‐dependent regulation of aggression in this species. AR expression also varied in medial HVC and pvMSt, a newly described periventricular region in the medial striatum. ERα and ERβ mRNA expression did not vary seasonally in any brain region examined, suggesting that estrogen‐dependent changes in behavior are mediated by differences in neural estrogen synthesis. J. Comp. Neurol. 518:3819–3835, 2010. © 2010 Wiley‐Liss, Inc.

This paper examines the role that androgen receptors (ARs) play in modulating aggressive behavior in male song sparrows, Melospiza melodia morphna. Song sparrows are seasonally breeding, territorial birds that maintain year-round territories with male–female pair bonds formed during the spring breeding season. Plasma testosterone levels peak as territories are established and mates acquired. In late summer, testosterone levels fall and remain basal during the non-breeding season. We examined the role of ARs in regulating territorial aggression in captive song sparrows under short- and long-day conditions as well as just prior to, and at the start of the breading season in freely living birds using the nonsteroidal antiandrogen flutamide to block AR function. Birds were implanted with either empty or drug filled silastic implants for 18 to 42 days and then challenged with a novel male decoy to assess the individual birds level of male–male aggression. Freely living birds remained on their home territory and underwent a simulated territorial intrusion, whereas laboratory-held birds were assessed using a laboratory simulated territorial intrusion and remained in their home cage. Experimental treatment of male song sparrows decreased aggressive behavior during the pre-breeding life history substage (March–April) in freely living birds as well as in laboratory-held birds under long-day (16L:8D) conditions. During the early breeding substage (April–May) there was no measurable effect of flutamide treatment on aggressive behavior, nor was there a difference in behavior in the (8L:16D) laboratory birds. This demonstrates that ARs are an important component of the neuroendocrine control of aggressive behavior. Given that flutamide only affected aggression during the pre-breeding substage and in LD birds, the results suggest that AR dependent control of aggressive behavior changes as song sparrow life history states change.

Peptide hormones, like oxytocin or vasopressin, are well known to influence social behaviour in various mammalian species. While oxytocin is thought to be prosocial and enhance cooperation, vasopressin may function to trigger aggressive behavioural responses. In most mammals, the olfactory system is key to social recognition, and now a population of vasopressin-expressing interneurons in the olfactory bulb has been identified as being required for proper social recognition in rodents. The activity of these neurons, in response to vasopressin signalling, is linked directly to the modulation of information processing by the olfactory system. Although vasopressin itself may not play an identical role in humans, such an experience-dependent mechanism of hormone release underlying social recognition may be common. Peptide hormones such as oxytocin and vasopressin influence social behaviour in several mammalian species. Here it is shown that a population of interneurons in the rat olfactory bulb releases vasopressin, and that vasopressin signalling is required in the olfactory system for proper social recognition in rats. Although vasopressin may not work in exactly the same way in humans, social recognition mediated by experience-dependent vasopressin release may be common. Many peptides, when released as chemical messengers within the brain, have powerful influences on complex behaviours. Most strikingly, vasopressin and oxytocin, once thought of as circulating hormones whose actions were confined to peripheral organs, are now known to be released in the brain, where they have fundamentally important roles in social behaviours1. In humans, disruptions of these peptide systems have been linked to several neurobehavioural disorders, including Prader–Willi syndrome, affective disorders and obsessive–compulsive disorder, and polymorphisms of V1a vasopressin receptor have been linked to autism2,3. Here we report that the rat olfactory bulb contains a large population of interneurons which express vasopressin, that blocking the actions of vasopressin in the olfactory bulb impairs the social recognition abilities of rats and that vasopressin agonists and antagonists can modulate the processing of information by olfactory bulb neurons. The findings indicate that social information is processed in part by a vasopressin system intrinsic to the olfactory system.