How many golden eagles are there?

Date:  October 18, 2017

Source:  American Ornithological Society Publications Office

Summary:

For conservation to be effective, wildlife managers need to know how many individuals of a species are out there. When species are spread out over large areas and occur at low densities, this can be tricky. However, a new study applies an old technique called 'mark-recapture' in a novel way to count golden eagles, eliminating the need to actually capture and mark eagles with math that allows scientists to turn individual observations into population estimates.

Continued  

Adelie Penguin population in east Antarctica double previous estimate

Almost six million Adelie Penguins are living in East Antarctica, more than double the number previously thought, scientists have announced, in findings that have implications for conservation.

 

Research by an Australian, French and Japanese team used aerial and ground surveys, tagging and resighting data and automated camera images over several breeding seasons, which allowed them to come up with the new figure. 

They focused on a 5,000 kilometre (3,100 mile) stretch of coastline, estimating it was home to 5.9 million birds - some 3.6 million more than previously thought. On this basis, they estimate a likely global population of 14 to 16 million. 

Before, population estimates only took into account breeding pairs, said Australian Antarctic Division seabird ecologist Louise Emmerson. 

"Non-breeding birds are harder to count because they are out foraging at sea, rather than nesting in colonies on land," she said. 

"However, our study in East Antarctica has shown that non-breeding Adelie Penguins may be as, or more, abundant than the breeders. 

"These birds are an important reservoir of future breeders and estimating their numbers ensures we better understand the entire population's foraging needs." 

Adelie Penguins, slick and efficient swimmers, live on the Antarctic continent and on many small, surrounding coastal islands. They spend the winter offshore in the seas surrounding the pack ice. 

Continued 

Rise and fall of prehistoric penguin populations charted

Study shows correlation between declines and climate change

A study of how penguin populations have changed over the last 30,000 years has shown that between the last ice age and up to around 1,000 years ago penguin populations benefitted from climate warming and retreating ice. This suggests that recent declines in penguins may be because ice is now retreating too far or too fast.

An international team, led by scientists from the Universities of Southampton and Oxford, has used a genetic technique to estimate when current genetic diversity arose in penguins and to recreate past population sizes. Looking at the 30,000 years before human activity impacted the climate, as Antarctica gradually warmed, they found that three species of penguin; Chinstrap, Adélie and southern populations of Gentoo penguins increased in numbers. In contrast, Gentoo penguins on the Falkland Islands were relatively stable, as they were not affected by large changes in ice extent. 

A report of the research is published in the journal Scientific Reports.

Continued

Climate change not effecting Great tit populations - More hatchlings die - More juveniles survive

Wild populations of great tits and earlier springs - Courtesy of The Norwegian University of Science and Technology (NTNU) 

May 2013. What happens when climate change makes for a food timing problem for great tit populations? Norwegian, French, American and Dutch researchers have explained (In Science magazine) that while more hatchlings may die, greater juvenile survival and immigration have surprisingly kept populations stable. 

Earlier springs

One of the many changes that results from global warming is a shift to earlier springs - something that has led many biologists to worry what will happen to populations that have adapted to specific events with precise timing when that timing shifts. 

Caterpillars hatching earlier

Earlier springs have caused caterpillars to hatch and grow earlier than they used to. But great tits, which catch caterpillars to feed their young, have not been able to advance their timing of egg-laying to keep pace with the caterpillars. This has caused an increasing mismatch between the peak availability of caterpillars and the hatching of baby great tits, which has caused early offspring survival in great tits to decline. 

Continued: http://www.wildlifeextra.com/go/news/climate-change-birds.html