Wild bird populations threatened by...

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Wild bird populations threatened by...

Mortality cost of sex-specific parasitism in wild bird populations, published on the Scientific reports, is a study that offers a very interesting retrospective on wild bird populations and the relationship they have with sex parasitism and mortality.

This is a really interesting article, which offers a 360 degree overview on the subject. We can read: "Sex-specific mortality is frequent in animals although the causes of different male versus female mortalities remain poorly understood.

Parasitism is ubiquitous in nature with widespread detrimental effects to hosts, making parasitism a likely cause of sex-specific mortalities. Using sex-specific blood and gastrointestinal parasite prevalence from 96 and 54 avian host species, respectively, we test the implications of parasites for annual mortality in wild bird populations using phylogenetic comparative methods.

First, we show that parasite prevalence is not different between adult males and females, although Nematodes showed a statistically significant but small male-biased parasite prevalence. Second, we found no correlation between sex-biased host mortalities and sex-biased parasite prevalence.

These results were consistent in both blood and gastrointestinal parasites. Taken together, our results show little evidence for sex-dependent parasite prevalence in adults in w ild bird populations, and suggest that parasite prevalence is an unlikely predictor of sex difference in adult mortalities, not withstanding sampling limitations.

We propose that to understand causes of sex-biased mortalities, more complex analyzes are needed that incorporate various ecological and life history components of animals life that may include sex differences in exposure to predators, immune capacity and cost of reproduction."

Global warming is destroying Arctic summer sea ice

Global warming refers to an increase in the average temperatures of the Earth's surface not attributable to natural causes and found since the beginning of the twentieth century.

According to the fourth report of the Intergovernmental Panel on Climate Change (IPCC) of 2007, the average temperature of the earth's surface increased by 0.7 ± 0.2 ° C during the 20th century. Data from the historical thermal series in possession of scientists indicate that warming is not uniform across the globe: it is greater on land than in the oceans.

Furthermore, due to the greater distribution of emerged lands and relative anthropization, it is more accentuated in the northern hemisphere than in the southern one and higher in northern latitudes rather than in medium and low latitudes, the Arctic areas of Siberia and Canada are in strong warming, on the other hand the area of ​​Antarctica is cooling.

Rising temperatures are causing major ice losses and rising sea levels. Impacts on rainfall structures and intensity are also visible, resulting in changes in the location and size of subtropical deserts. The global darkening, caused by the increase in the concentration of aerosols in the atmosphere, detected between the 1960s and 1980s, blocking the sun's rays, would at least partially mitigate the effects of global warming.

A new alarm is launched by the study published in Nature communications, entitled: Global warming due to loss of large ice masses and Arctic summer sea ice. In the article we can read how "several large-scale cryosphere elements such as the Arctic summer sea ice, the mountain glaciers, the Greenland and West Antarctic Ice Sheet have changed substantially during the last century due to anthropogenic global warming.

of their possible future disintegration on global mean temperature (GMT) and climate feedbacks have not yet been comprehensively evaluated. Here, we quantify this response using an Earth system model of intermediate complexity.

Overall, we find a median additional global warming of 0.43 ° C (interquartile range: 0.39-0.46 ° C) at a CO2 concentration of 400 ppm. Most of this response (55%) is caused by albedo changes, but lapse rate together with water vapor (30%) and cloud feedbacks (15%) also contribute significantly.

While a decay of the ice sheets would occur on centennial to millennial time scales, the Arctic might become ice-free during summer within the 21st century. Our findings imply an additional incre ase of the GMT on intermediate to long time scales."