When the sun never sets: diverse activity rhythms under continuous daylight in free-living arctic-breeding birds

Circadian clocks are centrally involved in the regulation of daily behavioural and physiological processes. These clocks are synchronized to the 24-hour day by external cues (Zeitgeber), the most important of which is the light-dark cycle. In polar environments, however, the strength of the Zeitgeber is greatly reduced around the summer and winter solstices (continuous daylight or continuous darkness). How animals time their behaviour under such conditions has rarely been studied in the wild. Using a radio-telemetry-based system, we investigated daily activity rhythms under continuous daylight in Barrow, Alaska, throughout the breeding season in four bird species that differ in mating system and parental behaviour. We find substantial diversity in daily activity rhythms depending on species, sex and breeding stage. Individuals exhibited either robust, entrained 24-hour activity cycles, were continuously active (arrhythmic), or showed “free-running” activity cycles. In semipalmated sandpipers, a shorebird with biparental incubation, we show that the free-running rhythm is synchronized between pair mates. The diversity of diel time-keeping under continuous daylight emphasizes the plasticity of the circadian system and the importance of the social and life-history context. Our results support the idea that circadian behaviour can be adaptively modified to enable species-specific time-keeping under polar conditions

Is spatial autocorrelation an intrinsic property of territory size?

In animals, competition for space and resources often results in territorial behaviour. The size of a territory is an important correlate of fitness and is primarily determined by the spatial distribution of resources and by interactions between competing individuals. Both of these determinants, alone or in interaction, could lead to spatial non-independence of territory size (i.e. spatial autocorrelation). We investigated the presence and magnitude of spatial autocorrelation (SAC) in territory size using Monte Carlo simulations of the most widely used territory measures. We found significant positive SAC in a wide array of competition-simulated conditions. A meta-analysis of territory size data showed that SAC is also a feature of territories mapped based on behavioural observations. Our results strongly suggest that SAC is an intrinsic trait of any territory measure. Hence, we recommend that appropriate statistical methods should be employed for the analysis of data sets where territory size is either a dependent or an explanatory variable

Jan Kempenaers: the picturesque

At first glance Jan Kempenaers’ photographs may not reflect the traditional ideas we have about an everyday picturesqueness. To better understand the relationship between his compositions and the aesthetic category of the picturesque, we need to look more closely at some of the original eighteenth-century aspects of the picturesque. When we leave aside this popular genre’s legacy – which has been significant though not highly prized, for at one point the picturesque even became synonymous with conventionally beautiful scenery – we will be able to discover its astounding modernity and topicality. The picturesque conceived as such, I will argue, fits perfectly with our contemporary way of looking at and appreciating natural and urban environments, and is also firmly entrenched in contemporary practices of representation. Viewed from this perspective, Kempenaers’ photographs can be understood as an exploration of the continuing relevance of the picturesque in the contemporary visualization of our environment

Evidence for increased olfactory receptor gene repertoire size in two nocturnal bird species with well-developed olfactory ability

<p>Abstract</p> <p>Background</p> <p>In vertebrates, the molecular basis of the sense of smell is encoded by members of a large gene family, namely olfactory receptor (OR) genes. Both the total number of OR genes and the proportion of intact OR genes in a genome may indicate the importance of the sense of smell for an animal. There is behavioral, physiological, and anatomical evidence that some bird species, in particular nocturnal birds, have a well developed sense of smell. Therefore, we hypothesized that nocturnal birds with good olfactory abilities have evolved (i) more OR genes and (ii) more intact OR genes than closely related and presumably less 'olfaction-dependent' day-active avian taxa.</p> <p>Results</p> <p>We used both non-radioactive Southern hybridization and PCR with degenerate primers to investigate whether two nocturnal bird species that are known to rely on olfactory cues, the brown kiwi (<it>Apteryx australis</it>) and the kakapo (<it>Strigops habroptilus</it>), have evolved a larger OR gene repertoire than their day-active, closest living relatives (for kiwi the emu <it>Dromaius novaehollandiae</it>, rhea <it>Rhea americana</it>, and ostrich <it>Struthio camelus </it>and for kakapo the kaka <it>Nestor meridionalis </it>and kea <it>Nestor notabilis</it>). We show that the nocturnal birds did not have a significantly higher proportion of intact OR genes. However, the estimated total number of OR genes was larger in the two nocturnal birds than in their relatives.</p> <p>Conclusion</p> <p>Our results suggest that ecological niche adaptations such as daily activity patterns may have shaped avian OR gene repertoires.</p

Variation in fine-scale genetic structure and local dispersal patterns between peripheral populations of a South American passerine bird

Indexación: Scopus.The distribution of suitable habitat influences natal and breeding dispersal at small spatial scales, resulting in strong microgeographic genetic structure. Although environmental variation can promote interpopulation differences in dispersal behavior and local spatial patterns, the effects of distinct ecological conditions on within-species variation in dispersal strategies and in fine-scale genetic structure remain poorly understood. We studied local dispersal and fine-scale genetic structure in the thorn-tailed rayadito (Aphrastura spinicauda), a South American bird that breeds along a wide latitudinal gradient. We combine capture-mark-recapture data from eight breeding seasons and molecular genetics to compare two peripheral populations with contrasting environments in Chile: Navarino Island, a continuous and low density habitat, and Fray Jorge National Park, a fragmented, densely populated and more stressful environment. Natal dispersal showed no sex bias in Navarino but was female-biased in the more dense population in Fray Jorge. In the latter, male movements were restricted, and some birds seemed to skip breeding in their first year, suggesting habitat saturation. Breeding dispersal was limited in both populations, with males being more philopatric than females. Spatial genetic autocorrelation analyzes using 13 polymorphic microsatellite loci confirmed the observed dispersal patterns: a fine-scale genetic structure was only detectable for males in Fray Jorge for distances up to 450 m. Furthermore, two-dimensional autocorrelation analyzes and estimates of genetic relatedness indicated that related males tended to be spatially clustered in this population. Our study shows evidence for context-dependent variation in natal dispersal and corresponding local genetic structure in peripheral populations of this bird. It seems likely that the costs of dispersal are higher in the fragmented and higher density environment in Fray Jorge, particularly for males. The observed differences in microgeographic genetic structure for rayaditos might reflect the genetic consequences of population-specific responses to contrasting environmental pressures near the range limits of its distribution.http://onlinelibrary.wiley.com/doi/10.1002/ece3.3342/epd

Playback of predator calls inhibits and delays dawn singing in a songbird community

Recent studies have demonstrated that experimental increases in perceived predation risk can substantially impair breeding behavior and reduce reproductive success. Perceived predation risk may also occur in the context of sexual signaling, with potential consequences for sexual selection. In songbirds, singing at dawn is an important sexual signal but may also attract predators. Here, we report on 2 experiments designed to test whether perceived predation risk affects the occurrence and timing of dawn singing in a songbird community. In a pilot experiment, we broadcast predator playbacks intermittently across half a forest plot and nonpredator playbacks across the other half throughout early spring. In the second experiment, we repeated the treatments in 16 independent but smaller plots (8 with predator calls and 8 with nonpredator calls). In the predator treatment, most species were less likely to sing at dawn (small, nonsignificant effects) and started later if they did sing (significant for 2 species). Meta-analyses combining the data from both experiments showed an overall significant effect of the treatment on both the likelihood and timing of singing. Species that were less likely to sing also sang later if they did sing, corroborating that an increase in perceived predation risk was the common cause of the effects on both measures

Paternity in mallards: effects of sperm quality and female sperm selection for inbreeding avoidance

Postcopulatory processes might play an important role in sexual selection. In theory, fertilization success could be controlled by females via selection of particular sperm within their reproductive tract, or it could be determined by sperm competition per se. In practice, these two mechanisms are difficult to disentangle. To assess the relative importance of both mechanisms we used artificial insemination in combination with measurements of sperm quality (swimming speed and motility) in mallards. In this species, females often lack behavioral control over copulations and hence may use postcopulatory mechanisms to optimize their reproductive output. One important factor affecting female fitness may be selection of genetically compatible males. To investigate the influence of sperm quality and parental relatedness on paternity we inseminated 12 groups of related females with a sperm mixture containing equal numbers of sperm from a brother and from an unrelated male. Paternity was independent of the relatedness of the siring male to the female but was significantly affected by long-term sperm swimming speed and motility. No interaction between relatedness and sperm quality on paternity was observed. These results suggest that female mallards are not able to select sperm on a purely genetic basis and emphasize the importance of sperm quality in gaining paternit

Within- and between-year variation in the presence of individually marked Ruff <i>Calidris pugnax</i> at a stopover site during northward migration

Ruffs Calidris pugnax migrate from wintering areas in West-Africa and Europe tobreeding grounds in northern Eurasia, using stopover sites along the way. At onesuch stopover site in southwest Friesland (53°N, The Netherlands), we studiedvariation in the timing of individual stopover based on 6474 Ruffs colour-ringedin 2004–2012. 43% of males and 22% of females were recorded in the studyarea in March–May the years following marking. Minimal stopover duration ofreturning individuals showed substantial within-year heterogeneity. We distinguishedtwo classes: (1) ‘transient’ individuals were observed only on a singleday in the study area within a season (51% of observed males and 79% offemales), and (2) ‘staging’ individuals were observed on multiple days. Weobserved two seasonal peaks in the presence of transient Ruffs, typically coincidingwith the peak of arrival and departure of staging birds. Males known towinter in Europe were more likely to be observed in the study area and arrivedearlier than males of unknown winter origin (3.1 days and 3.7 days earlier fortransient and staging males, respectively), but departure was unrelated to winterorigin. Staging and transient females arrived later than males. Between-yearrepeatability of individual behaviour was low, and individuals did not significantlyadvance their arrival date over the course of years, in contrast with a pattern ofshifting arrival dates at the population level. The observation that a large proportionof Ruffs visit southwest Friesland for only a short stop suggests that manyindividuals rely on other sites for moulting and refuelling during spring migration.Resightings of marked individuals elsewhere in western Europe indicated thatthese sites are largely located between 51° and 54°N. Thus, during springmigration, Ruffs marked in southwest Friesland displayed high between- andwithin-individual variation in minimal stopover duration

Sources of individual variation in plasma testosterone levels

The steroid hormone testosterone (T) plays a central role in the regulation of breeding in males, because many physiological, morphological and behavioural traits related to reproduction are T dependent. Moreover, in many seasonally breeding vertebrates, male plasma T levels typically show a pronounced peak during the breeding season. While such population-level patterns are fairly well worked out, the sources and the implications of the large variability in individual T levels within the seasonal cycle remain surprisingly little understood. Understanding the potential sources of individual variation in T levels is important for behavioural and evolutionary ecologists, for at least two reasons. First, in ‘honest signalling’ theory, T is hypothesized to play a critical role as the assumed factor that enforces honesty of the expression of sexually selected quality indicators. Second, T is often considered a key mediator of central life-history trade-offs, such as investment in survival versus reproduction or in mating versus parental care. Here, we discuss the patterns of within- and between-individual variation in male plasma T levels in free-living populations of birds. We argue that it is unclear whether this variability mainly reflects differences in underlying individual quality (intrinsic factors such as genetic or maternal effects) or in the environment (extrinsic factors including time of day, individual territorial status and past experience). Research in avian behavioural endocrinology has mainly focused on the effects of extrinsic factors, while other sources of variance are often ignored. We suggest that studies that use an integrative approach and investigate the relative importance of all potential sources of variation are essential for the interpretation of data on individual plasma T levels

Genetic Correlates of Individual Differences in Sleep Behavior of Free-Living Great Tits (Parus major)

Within populations, free-living birds display considerable variation in observable sleep behaviors, reflecting dynamic interactions between individuals and their environment. Genes are expected to contribute to repeatable between-individual differences in sleep behaviors, which may be associated with individual fitness. We identified and genotyped polymorphisms in nine candidate genes for sleep, and measured five repeatable sleep behaviors in free-living great tits (Parus major), partly replicating a previous study in blue tits (Cyanistes caeruleus). Microsatellites in the CLOCK and NPAS2 clock genes exhibited an association with sleep duration relative to night length, and morning latency to exit the nest box, respectively. Furthermore, microsatellites in the NPSR1 and PCSK2 genes associated with relative sleep duration and proportion of time spent awake at night, respectively. Given the detection rate of associations in the same models run with random markers instead of candidate genes, we expected two associations to arise by chance. The detection of four associations between candidate genes and sleep, however, suggests that clock genes, a clock-related gene, or a gene involved in the melanocortin system, could play key roles in maintaining phenotypic variation in sleep behavior in avian populations. Knowledge of the genetic architecture underlying sleep behavior in the wild is important because it will enable ecologists to assess the evolution of sleep in response to selection