Scruffy

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On Saturday at mid-morning we spotted this Coopers hawk tidying up a bit on a broken old Cottonwood branch. He looked like he has had a bit of a rough time lately with his feathers looking downright scruffy. After a half hour or so of preening his feathers were back in fine order and he was off again hunting in nearby woods.

Hungry Hawk

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Looking like it just finished a meal this Red tailed Hawk was right back at it. Watching the fields intently for a mouse to stir and trying to make the most of the short days this time of year.

Song birds are shrinking

Bergmann’s rule posits that populations and species of larger sizes are found in colder regions while in warmer regions species are smaller.

A study published yesterday in the Journal Ecology Letters reports that over the pervious four decades there has been, on average, a 2.4 percent decrease in the size of the length of the tarsus bone, a standard marker for bird size,  in a sample population of over 70,000 birds from 52 species. The changes in tarsus length were correlated with the increase temperature. The lead authors of the study suggested two explanations for the decrease in body size.

“The first is developmental plasticity, in which individuals that mature in warmer temperatures tend to develop into smaller adults,” Weeks explained. “The second is natural selection, in which smaller birds tend to do better — in survival, reproduction, or both — in warmer temperatures, leading to a shift in the average size of individuals in a population.”

In addition, the study found consistent increases in the wing length of 1.3 percent in 40 of the species. The reason for in increase in wing length is unclear  but the authors hypothesized that increasing wing length may represent a compensatory adaptation to maintain migration as reductions in body size have increased the metabolic cost of flight. Like many of the consequences of climate change, the changes measured in bird size, are not perceptible to the naked eye.

There is a good summary of the study here by the Audubon society.

Click any image for slide show.

 

Beauty

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She’s a beauty don’t you think?

There is just something special, call it perfection if yo will,  about how pronghorn fit in so well with the dry fall grasses in their habitat. A beauty that is laid bare and obvious. A beauty in nature’s design. A beauty we could perhaps call truth.