About 2 billion birds cross the Gulf of Mexico during the spring migration season, according to a new study that combined data from 11 weather radar stations and observations from citizen scientists.
Researcher Kyle Horton of Cornell University’s Lab of Ornithology said that before he and his colleagues looked at the data from 1995 to 2015, “we could only guess at the overall numbers from surveys done along small portions of the shoreline.”
Horton says that while climate change has caused the earliest seasonal migrations to begin 1.5 days earlier per decade, the peak has remained at the same period between April 19 and May 7.
Quieter Spring Skies over North America
The skies across much of North America have become increasingly more quiet over recent decades as the bird populations plummeted by 1.6 billion, according to a new study.
Scientists say that of the 86 species studied, 22 have lost at least half of their population since 1970.
“We’re really getting down to the dregs of some of these populations,” said study co-author Judith Kennedy of Environment Canada.
Domestic cats are believed to kill more than 2 billion birds each year, while farming disrupts habitats of grassland birds and adulterates the landscape with pesticides.
Logging has also thinned the forests used by many migrating birds as resting and refuelling stops.
Finland study tracks global warming impacts on bird populations.
Researchers in Finland say they’ve documented bird populations trends that are at least partly linked with global warming. Comparing data from extensive bird counts conducted between 1981 to 1999, and 2000 to 2009, the biologists said that, in general, northern species have decreased and southern species increased.
Mean temperatures in Finland rose between the two periods, with April to June mean temperatures climbing by 0.7 degrees Celsius. According to the study, population densities of common forest habitat generalists remained the same between the two periods, while species preferring old-growth or mature forests increased, but those living on mires and wetlands, and species of Arctic mountains decreased.
The trends suggest that climate change impacts on species in natural boreal and Arctic habitats most probably are habitat-specific with large differences in response times and susceptibility. Open mires and mountain heaths change more rapidly in consequence of climate warming than old-growth forests, for which reason populations on mires and mountain heaths may also be more affected by climate change.