Onshore east winds will spread some moisture to the coast from the Atlantic this weekend so expect a few showers from I-95 to the beaches, especially Sat. Temps. will continue to moderate with highs near 70 inland, 60s at the beaches Sat. & near 70 at the coast Sun. but mid to upper 70s inland.
The next front is due into the area Mon. with a band of showers & possibly an isolated t'storm late Mon. through early Tue. A stronger system will move into the area late in the week, & we might see some frost next weekend.
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Earth Gauge: Annual Christmas Bird Count
December 14 marks the beginning of Audubon’s annual Christmas Bird Count. The Count runs through January 5, 2013. The first Christmas Bird Count (CBC) took place on December 25, 1900 when 27 participants counted and identified about 18,500 birds, mostly in the northeastern U.S. Today, volunteers brave snow and chilly temperatures to identify and count birds throughout the 50 states and in Canada. Last year, over 2200 counts were completed and 64 million birds were reported! CBC data helps scientists understand how bird populations have changed over the past century.
Forty years’ worth of observation data from the CBC show that 58 percent of North American bird species seen in the first few weeks of winter have shifted their ranges north. Sixty species have moved over 100 miles north – the wild turkey has moved a whopping 400 miles! (Learn more about range shifts of finches in the Western-click here, Midwestern-click here, and Eastern United States-click here.)
Tip: Anyone can participate in the Christmas Bird Count. CBC takes place in “count circles” that focus on specific geographic areas. Every circle has a leader, so even if you are a beginner birdwatcher, you’ll be able to count birds with an experienced birder and contribute data to the longest-running wildlife census. If your home happens to be within the boundaries of a count circle, you can count the birds that visit your backyard feeder.
Visit ** here ** for more information.
Audubon press releases and photos available here.
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Climate Fact: Eastern United States Winter Bird Trends
In Brief: In the eastern United States, the recent warming trend and the pause in minimum winter temperature rise since 1995 are causing diverse responses among bird species, with an overall increase in bird diversity and a decline in body size being two observed effects.
Because they are highly mobile, birds’ ranges are often suggested as an effective proxy for tracking temperature changes. Each bird species is highly idiosyncratic, however, which leads to a variety of different responses to climate change. Moreover, because each species responds differently, communities of birds that have traditionally operated as part of the same ecosystem may become significantly altered as different species move into a particular area and others move out. In the eastern United States, the average annual winter temperature is over one degree Fahrenheit warmer than it was in 1960. This warming has been accompanied by several observed trends the region’s winter assemblages of birds:
· Considered all together, there was a general movement of winter bird ranges north as winter minimum temperatures rose between 1975 and 1995 and a general move south as this rise halted or even reversed slightly from about 1995 to 2010. However, unlike what you would expect from mobile birds, this overall range shift lagged the climate shift considerably, highlighting the importance of other factors besides climate relevant to bird survival. Turkey vultures and Ruby-throated hummingbirds most closely track the minimum winter temperature. One outlier is the Black vulture which is now a common winter sight as far north as Massachusetts, whereas several decades ago it was rare there.
· An increase since the 1960s in the number of different species wintering in the East has been observed. A rise in the number of short-distance Nearctic migrants – or birds that winter outside of the tropics – is the primary driver behind this trend, as opposed to an influx of long-distance migrants from the tropics. The rise in minimum winter temperatures allows more southerly bird species to winter closer to their northern nesting grounds, likely giving them an earlier start on spring feeding, nesting and reproduction. Birds used to wintering in the tropics do not benefit like Nearctic migrants do from wintering closer to nesting grounds.
· Birds wintering across North America, including the East, are smaller than they were in the 1960s. Berman’s Rule states that, all other things being equal, a member of a species living in a warmer climate will be smaller than a member of the same species in a colder climate. A precise mechanism for Bergman’s rule has yet to be established, but it is likely that natural selection has favored the survival of smaller birds during the recent warming period.
(Sources: Buskirk, JV et al. “Declining body sizes in North American birds associated with climate change.” Oikos 119 (2010): 1047-1055 and McDonald, KW et al. “Diversity of birds in eastern North America shifts north with global warming.” Ecology and Evolution 2012 and La Sorte, FA and Jetz, W. “Tracking of climatic niche boundaries under recent climate change.” Journal of Animal Ecology 81 (2012): 914-925 and La Sorte, FA et al. “Disparities between observed and predicted impacts of climate change on winter bird assemblages.” Proceedings of the Royal Society B 276 (2009): 3167-3174.)
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Climate in the News: “Mighty Old Trees Are Perishing Fast, Study Warms.” – The New York Times, Green Blog, December 7, 2012 – Earth’s oldest and biggest trees, the largest organisms on the planet and crucial features of forest ecosystems, are experiencing increased mortality rates due to logging and a suite of factors related to climate change.
Have a great & safe weekend!
