From “On the Wing” February 6, 2015
Rain Birds – Birds don’t like getting rain-soaked but they like the way the rain softens the ground so they can get a bite to eat. Thrushes especially like to poke in the soft soil and eat buggy things. Varied Thrushes, those colourful robin-sized winter birds, need more nutrients than seeds can provide although they will eat them when the ground is frozen.
American Robins, also members of the thrush family, will be coming through soon. They usually show up in big numbers around the third week in February. They appear suddenly on golf courses and meadows on island to munch on those nutrient packed invertebrates to get them further north. Although we don’t seem to expect robins to migrate as they seem to be here all year, they do. Those that nest here have migrated in from somewhere else.
Rain softens the ground for sparrows as well. Our small cement walkway to the house kept getting covered with leaves a few days after being swept. I thought perhaps that the wind must have kicked something up so swept it again, Next day, all along the edge, small patches of soil and litter darkened the path again. Song Sparrows! As they scrabbled in the flower-bed for bugs they spread their diggings over the walkway.
If you’ve walked through the forest on a quiet day and heard strange rustlings in the dead leaves, it could be a Fox Sparrow. They dig industriously with their long toes through the leaves and soft earth. It is their métier. Pacific Wrens too, those small dark, perky, ground-dwellers need soft earth to get at their food even in the chilliest times. Most birds suffer in the cold, but wrens seem particularly vulnerable.
Many of the forest birds here are darker than those in the interior. When colour change relates to environmental factors, “Gloger’s Rule” applies. He was a zoologist in the 1800’s and he found that birds in more humid habitats tended to be darker than their relatives in more arid regions. Recent studies have shown that this might happen because “feather-degrading bacteria from the plumage of sparrows (i.e. Song Sparrows) in the humid Northwest degraded feathers more rapidly and more completely than feather-degrading bacteria from sparrows of the arid Southwest. Dark feathers are more resistant than light feathers to bacterial degradation (Burtt and Ichida 2004).” It is buggy country here, and the island sparrows have evolved so that they are darker and not so vulnerable to all that stuff out there in the forest that eats away at their feathers. We’re back to rain, bugs, soft soil and the good green earth. firstname.lastname@example.org