In birds biological clock function pervades all aspects of biology controlling
In birds biological clock function pervades all aspects of biology controlling daily changes in sleep: wake visual function track migratory patterns and orientation as well as seasonal patterns of reproduction track and migration. complex social interactions and their circadian clocks are more sensitive to the hormone melatonin than are those of nocturnal rodents. Each morning and especially in the spring we are greeted by a cacophony of small birds singing a dawn chorus. In eastern North America spring mornings CK-1827452 are sometimes defined by the merry roundelay of the Rabbit Polyclonal to IF2B3. American robin of the white-breasted nuthatch In the backdrop we may hear the doleful of the aptly named mourning dove There is no particular order of who sings or who calls first and the orchestration is usually peripatetic at best seemingly random although many of these garden songsters are reacting to each other’s songs. And yet there is a coordination of the rhythm and timbre of this dawn chorus. These birds all possess an internal biological clock that is coincidentally entrained to the identical environmental signal the rising of the morning sun and in turn these internal clocks are tuned to the expression of clocks by their intraspecific and extra-specific neighbors. While these appear to be the melodious embrace of the warming sun they are in fact a cold war defining territory for breeding and foraging in anticipation of reproductive success [98 151 In no other group of animals are the seasonal changes in reproductive function so obvious to the casual observer. We hear them stake their claims. We see them build their nests incubate the eggs and raise and fledge their young. At certain times of 12 months small songbirds fatten for their annual migrations and at certain times of day dusk usually become increasingly agitated as they gather for CK-1827452 their vernal and autumnal treks to breeding and wintering grounds [67 68 These birds typically eschew their nightly drifts into slumber during this time sleeping little or not at all a phenomenon called as they migrate during the night avoiding the gauntlet of diurnal predators as they cross vast areas of our continent. Each of these processes and more are strictly timed to a time of day and to a time of 12 months . They are not restricted to eastern North America either as these processes are repeated time and time again throughout the world albeit at different times of 12 months depending on the latitude and local environment [89 90 91 The question that arises is usually “Why do birds so strictly time so many of their behavioral and physiological functions and how do they accomplish it?” In essence the child-like question CK-1827452 “Why does the sparrow sing on spring mornings?” is also a scientific question that is beginning to be clarified and CK-1827452 these likely entail an understanding of the biological clock or clocks that underlie all rhythmic processes. Specifically understanding of the molecular physiological and behavioral mechanisms underlying the temporal coordination of these complex processes and actions in birds will tell us more about human chronobiology as well because like humans and unlike the standard laboratory rodent models for biological clocks birds exhibit a complex orchestration of circadian behavior that controls daily patterns of sleep: wake visual sensitivity cognition and interpersonal behavior. Further study of the mechanisms underlying annual cycles of reproduction migration and metabolism in birds will provide clues to anticipated ecological changes due to climatic disruption. In essence birds are images in our own mirrors and we should pay attention to them more than current biomedical science might prefer. Biological Rhythms and the Clocks that Control Them Biological rhythms and the endogenous clocks that control them are fundamental properties of nearly all living organisms ranging from cyanobacteria to humans . As diverse as the organisms that express biological rhythms the formal properties of these rhythms are remarkably conserved . These biological rhythms are functionally tied to environmental cycles they estimate; of these we will concentrate in this review on two-and oscillations that entrain to local time through the process of Rhythmic processes cannot be identified as unless they are experimentally observed to persist for at least 1 or 2 2 cycles preferably more when the organism in question is usually experimentally placed in constant environmental conditions of either constant darkness (DD) or constant dim light (dimLL) (Constant high light LL may have other effects frequently abolishing circadian rhythms altogether and/or damaging.