Differential temperature effects on photoperiodism in female voles:A possible explanation for declines in vole populations

Many mammalian species use photoperiod as a predictive cue to time seasonal reproduction. In addition, metabolic effects on the reproductive axis may also influence seasonal timing, especially in female small, short-lived mammals. To get a better understanding of how annual cycling environmental cues impact reproductive function and plasticity in small, short-lived herbivores with different geographic origins, we investigated the mechanisms underlying integration of temperature in the photoperiodic-axis regulating female reproduction in a Northern vole species (tundra vole, Microtus oeconomus) and in a Southern vole species (common vole, Microtus arvalis). We show that photoperiod and temperature interact to determine appropriate physiological responses; there is species-dependent annual variation in the sensitivity to temperature for reproductive organ development. In common voles, temperature can overrule photoperiodical spring-programmed responses, with reproductive organ mass being higher at 10°C than at 21°C, whereas in autumn they are less sensitive to temperature. These findings are in line with our census data, showing an earlier onset of spring reproduction in cold springs, while reproductive offset in autumn is synchronized to photoperiod. The reproductive organs of tundra voles were relatively insensitive to temperature, whereas hypothalamic gene expression was generally upregulated at 10°C. Thus, both vole species use photoperiod, whereas only common voles use temperature as a cue to control spring reproduction, which indicates species-specific reproductive strategies. Due to global warming, spring reproduction in common voles will be delayed, perhaps resulting in shorter breeding seasons and thus declining populations, as observed throughout Europe

Early successional stages of reed Phragmites australis vegetations and its importance for the Bearded Reedling Panurus biarmicus in Oostvaardersplassen, The Netherlands

A study on Bearded Reed ling Panurus biarmicus feeding habits in combination with a sample-wise breeding bird survey of the marshland zones of the Dutch wetland Oostvaardersplassen shows clear-cut spatial differences in densities and habitat use. The more mature stands of Reed Phragmites australis constitute the main nesting area, while the more open, younger stands, particularly when inundated and grazed by moulting Greylag Geese, provide the main feeding areas. Arthropod, and especially Chironomid, densities were generally higher in grazed Reed stands and frequent feeding flights were carried out by parent birds between grazed and ungrazed parts of the area during chick raising. Chironomids also proved to constitute the main prey items brought to the nests. Apart from higher prey densities in grazed stands, better detectability as well as better accessibility of the lower vegetation layers are also likely to contribute to the habitat preference of insect-feeding Bearded Reedlings. When in winter the birds shift to Reed seeds, patches with higher seed index hold higher densities of feeding birds. When seed index drops below a certain level, density of birds is low and independent of seed index. The highest seed production is associated with rejuvenated Reed stands, recovering from previous grazing. Bearded Reedlings thus highly depend on the early successional stages of Reed stands. Temporal and spatial habitat diversification is mediated by changing water levels and rejuvenation caused by grazing geese. A number of other marshland bird species depend on this type of vegetation, and wetland management should therefore aim at favouring the natural processes governing Reed succession