Posted by: atowhee | January 16, 2014

THE DROUGHT AND THE BIRDS

It’s official, California and much of Oregon are having the driest year on record. Click here to read more gruesome details on the current drought.
How bad? There is a serious forest fire burning in Southern California right now, in the middle of the “rainy season.” The drought will stress living organisms of all types and make them more susceptible to disease and death.
This will certainly affect the bird populations in both states. It will make some seeds and insects much harder to find. Fish eating birds from Osprey to Common Merganser will surely suffer, not to mention the fish themselves. Shorebirds and waterfowl on migration will be compressed into smaller wetlands leading to avian cholera, starvation and other pleasantries of severe drought. Some species may forego breeding this spring if food is hard to find. Seabirds are noted for not breeding when El Nino reduces the fish supply in the nearshore Pacific.

SO MANY ROBINS
Recently a friend asked me why I thought there were so many Robins in the Ashland area this winter. The Ashland Christmas Bird Count (Jan 4) recorded more than 10 times as many Robins as we found on any of the three previous counts.
Here is my speculation:
With some southward migrating birds in fall, the regional food supplies affect how far they go and where they stop…migration in birds is largely triggered by changes in day length coupled with genetically-programmed hormonal changes that say “fly, fly, fly”…if birds in midst of southward migration find a good food supply, they may halt…as the Robins did this year with our huge madrone berry crop…there are few Robins in northern Oregon right now as two different Portland area birders confirmed for me recently…they have no madrones there and thus no madrone berry crop (which varies from year to year)…at some point in the fall the migrational impulses driven by biochemistry and day-length change abate…and I think this year the Robins ended up here because the madrone berries held out well into December and by that time there was no biological drive to migrate further…however, if the food supply runs out or it snows heavily and Robins can’t feed on the ground, I suspect many of the Robins will held out to the south or the coast. Lack of food here may also drive many to leave.
robins field
About three years ago the same thing happened here with Waxwings, based on huge mistletoe and madrone berry crops…by February the mistletoe and madrone were stripped clean… the Waxwings were so desperate they were on the ground feeding with Robins (which can go after a lot wider array of food than Waxwings who fly-catch and eat largely in trees)…within a couple days nearly all the Waxwings had left the Rogue Valley for warmer, more nutritious pastures.

Varied Thrush are similar to Robins, Snowy Owls and other irruptive species: they go where the food supply that fall or winter promises to be the best or move south until they find enough to eat…and Varied Thrush like wet and shady…this year’s drought alone may be enough to deter most Varied Thrush from our area, somewhere they are having a great Varied Thrush incursion, perhaps where it is wetter…I’ll bet there are many on the Olympic Peninsula right now.

Now I wonder if the drought in California hasn’t had some effect. Perhaps some of these Robins went further south in late summer and then circled back north. The large Robin concentration was certainly not obvious even as recently as October after most migration is over in a typical year. The population here this fall and winter seemingly increased through November and December. Robins could have been coming from either north or south. And this almost-snowless winter finds many Robins at a very high elevation (4000′ +) for winter. The lack of snow-covered land is cleasrly a direct result of the continuing and severe drought here. Short-term help for ground-feeders like Robin and Junco.


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