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The birds and the bees

The birds and the bees 

North America’s birds are dying at a rate that’s alarming ornithologists. Since the 1970s, the continent has lost 3 billion birds, nearly 30% of the total, and even common birds such as sparrows and blackbirds are in decline, U.S. and Canadian researchers report this week online in Science. The findings raise fears that some familiar species could go the way of the passenger pigeon, a species once so abundant that its extinction in the early 1900s seemed unthinkable.

In past decades, researchers have documented the decline of particular bird groups, including migratory songbirds. But more recent studies have been broader: covering 529 bird species, about three-quarters of all species in North America, and accounting for more than 90% of the entire bird population.

Skylark numbers have plummeted

Grassland birds have declined by 53% since 1970—a loss of 700 million adults in the 31 species studied, including meadowlarks and northern bobwhites. Shorebirds such as sanderlings and plovers are down by about one-third, the team says. Habitat loss may be to blame.

The familiar birds that flock by the thousands in suburbs were not exempt. Nineteen common species have each lost more than 50 million birds since 1970. Twelve groups, including sparrows, warblers, finches, and blackbirds, were particularly hard hit. Even introduced species that have thrived in North America, such as starlings and house sparrows, are losing ground. Only waterfowl and raptors seem to be thriving, thanks to habitat restoration and other conservation efforts. But the declines in many other species, particularly those living along shorelines and in grasslands, far exceeded those gains.

Pesticides are very probably a factor. Last week, toxicologists described how low doses of neonicotinoids—a common pesticide—made migrating sparrows lose weight and delay their migration, which hurts their chances of surviving and reproducing. Climate change, habitat loss, shifts in food webs, and even cats may all be adding to the problem, and not just for birds.

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Olduvai IV: Courage
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Olduvai II: Exodus
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