Circannual rhythms in birds

Gwinner, Eberhard

doi:10.1016/j.conb.2003.10.010

Cited by 196 publications

(175 citation statements)

References 38 publications

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“…At and around the equator, changes in photoperiod are minimal at best, and other environmental cues may not occur at the correct time with respect to ultimate factors. For example, rainfall may occur too close to the (Gorman et al 2001;Zucker 2001;Gwinner 2003). However, the functional role of photoperiod differs for the two mechanisms.…”

Section: (C) Timers Versus Clocksmentioning

confidence: 99%

Tracking the seasons: the internal calendars of vertebrates

Paul

Zucker

Schwartz

2007

Phil. Trans. R. Soc. B

175

152

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Animals have evolved many season-specific behavioural and physiological adaptations that allow them to both cope with and exploit the cyclic annual environment. Two classes of endogenous annual timekeeping mechanisms enable animals to track, anticipate and prepare for the seasons: a timer that measures an interval of several months and a clock that oscillates with a period of approximately a year. Here, we discuss the basic properties and biological substrates of these timekeeping mechanisms, as well as their reliance on, and encoding of environmental cues to accurately time seasonal events. While the separate classification of interval timers and circannual clocks has elucidated important differences in their underlying properties, comparative physiological investigations, especially those regarding seasonal prolactin secretions, hint at the possibility of common substrates.Keywords: seasonality; photoperiodism; circannual; interval timers While the Earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease.Genesis 8: 22, King James Version (1611) As the Earth makes its yearly orbit around the Sun, the planet's 23.58 axial tilt leads to the cyclical environmental changes that we call the seasons. Recurrent challenges to the survival of organisms and their offspring arise with the dawning of each new season, and animals have evolved seasonally induced changes in phenotype that adapt them to these predictable events. For example, in many temperate environments, winter is generally characterized by severe decreases in ambient temperature and food availability, leading to increased energetic demands at a time when resources are diminished. Because energy requirements of female mammals typically increase markedly during lactation (Bronson 1989) and newly weaned offspring are particularly vulnerable to environmental perturbations (Hill 1992), raising offspring during this time of year is often futile. Thus, many temperate species have evolved winter-specific behaviours and physiology to conserve energy (e.g. hibernation, a more insulative pelage, huddling) or provide for escape (e.g. migration). Many species also increase the chances of offspring survival by timing their mating behaviours so that parturition occurs during energetically favourable times of year.

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Section: (C) Timers Versus Clocksmentioning

confidence: 99%

Tracking the seasons: the internal calendars of vertebrates

Paul

Zucker

Schwartz

2007

Phil. Trans. R. Soc. B

175

152

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“…While the core of the circadian molecular clock has been defined in mammals, the knowledge in the regulation of the circannual (annual) clock is very poor (Davis, 1976;Gwinner, 2003). A recent study on sheep suggests an anatomical substrate of circannual clock based in the pituitary gland in which melatonin-receptor-containing cells may operate as key calendar cells, transmitting seasonal temporal information to the endocrine system (Lincoln et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Seasonal variations in daily rhythms of activity in athletic horses

Bertolucci

Giannetto

Fazio

et al. 2008

Animal

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Circadian rhythms reflect extensive programming of biological activity that meets and exploits the challenges and opportunities offered by the periodic nature of the environment. In the present investigation, we recorded the total activity of athletic horses kept at four different times of the year (vernal equinox, summer solstice, autumn equinox and winter solstice), to evaluate the presence of seasonal variations of daily activity rhythms. Athletic Thoroughbred horses were kept in individual boxes with paddock. Digitally integrated measure of total activity of each mare was continuously recorded by actigraphy-based data loggers. Horse total activities were not evenly distributed over the day, but they were mainly diurnal during the year. Daily activity rhythms showed clear seasonal variations, with the highest daily amount of activity during the vernal equinox and the lowest during the winter solstice. Interestingly, the amount of activity during either photophase or scotophase changed significantly throughout the year. Circadian analysis of horse activities showed that the acrophase, the estimated time at which the peak of the rhythm occurs, did not change during the year, it always occurred in the middle of the photoperiod. Analysing the time structure of long-term and continuously measured activity and feeding could be a useful method to critically evaluate athletic horse management systems in which spontaneous locomotor activity and feeding are severely limited. Circadian rhythms are present in several elements of sensory motor and psychomotor functions and these would be taken into consideration to plan the training schedules and competitions in athletic horses.

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“…In a similar way, circannual rhythms represent the endogenous organization of annual cycles (Gwinner 1986 ). Birds have been very important models for the study of circannual rhythmicity, and although the proximate mechanisms that regulate these cycles are still very elusive, birds offer some of the best examples of circannual rhythms studied so far (Gwinner 2003 ). These endogenously produced rhythms mean little if they are not synchronized, or entrained, to the external environment.…”

Section: Light and Circadian Rhythmsmentioning

confidence: 99%

The effects of light pollution on biological rhythms of birds: an integrated, mechanistic perspective

Dominoni

2015

J Ornithol

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Light pollution is considered a threat for biodiversity given the extent to which it can affect a vast number of behavioral and physiological processes in several species. This comes as no surprise as light is a fundamental, environmental cue through which organisms time their daily and seasonal activities, and alterations in the light environment have been found to affect profoundly the synchronization of the circadian clock, the endogenous mechanism that tracks and predicts variation in the external light/dark cycles. In this context, birds have been one of the most studied animal taxa, but our understanding of the effects of light pollution on the biological rhythms of avian species is mostly limited to behavioral responses. In order to understand which proximate mechanisms may be affected by artificial lights, we need an integrated perspective that focuses on light as a physiological signal, and especially on how photic information is perceived, decoded, and transmitted through the whole body. The aim of this review is to summarize the effects of light pollution on physiological and biochemical mechanisms that underlie changes in birds' behavior, highlighting the current gaps in our knowledge and proposing future research avenues.

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Circannual rhythms in birds

Cited by 196 publications

References 38 publications

Tracking the seasons: the internal calendars of vertebrates

Tracking the seasons: the internal calendars of vertebrates

Seasonal variations in daily rhythms of activity in athletic horses

The effects of light pollution on biological rhythms of birds: an integrated, mechanistic perspective

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