I have nothing to base this on other then theory based on things I have read and observed. We have seen Robins that appeared to be drunk that stumbled around after eating fermented apples. Could the rotten parts of the apples be fermented and contain alcohol? If they do, it might explain why it doesn't freeze as hard.

I have read that our bodies will use any sugar alcohol in our system for fuel before it will use other sources. Could this be the same with birds. Maybe the alcohol sugar is easier for them to assimilate and may not be frozen. Both would be a plus for the birds.

I will be interested to see answers to your question and to my answer.
----- Original Message -----
From: Kelly Cassidy
To: Tweeters
Sent: Tuesday, January 25, 2005 9:25 PM
Subject: [Tweeters] Postscript on apples and thrushes.


I previously posted about the physics of eating frozen apples. I concluded that a bird eating frozen apples would spend more energy to melt the ice in the apple than the bird would gain from the sugar in the apple.



A cold front hit the Palouse about two weeks ago. Highs were in the 20s and lows in the teens for many days. I was particularly concerned about the male (?) Varied Thrush overwintering in the yard. He appeared to be eating mostly apples supplemented with invertebrates. As the cold air was starting to move in, an aggressive Robin staked out the best apple area and did his best to drive all other birds away.



I confess that, despite my usual philosophy of non-intervention, I moved a few of the apples to another area in the yard under conifer trees. The Varied Thrush moved right into the new apple foraging area.



As the temperature got colder, and with snow on the ground, more and more birds began relying on the apples. In the best apple area where the Robin was standing guard, there was a steady stream of magpies, flickers, quails, and starlings pecking at the apples on the ground. The Robin would lurk in the junipers above the apples and swoop down at all these intruders who would bounce away from him and then go back to eating apples.



Now, all this seems to contradict the physics of the situation. How could all these birds be surviving on frozen apples? I examined the apples. Most were frozen hard into apple rocks. Rotten spots on the apples stayed unfrozen for longer than non-rotting parts. Apples that had been pecked at also tended to be softer. The birds seemed to show a preference for the rotting apples and the ones that had already been pecked at, but I didn't set up an experiment to test that impression.



A succession of birds would hollow out an apple, leaving the peel and working their way around the core. Possibly the pecking ruptured cell walls and allowed water to evaporate or sublimate, which would increase the sugar to ice ratio in the apple. Or maybe the birds chose softer apples with less water. Whatever the explanation, the apples were the mainstay of many birds when the invertebrates were inaccessible under cover of light snow and frozen leaves.



A warm mass of air moved in about 10 days ago. The wind and rain melted the snow almost overnight and the ground quickly defrosted. The Varied Thrush survived the cold spell. I saw him morning of the first day of warmer weather. Now, it's been many days since the temperature was below freezing, even at night. I've seen flying insects.



The birds abandoned the apples almost as soon as the weather warmed., probably to gorge on the sudden, unseasonable availability of bugs. Or maybe they were getting nervous about being so concentrated in a small area for so long. Or maybe they were just plain sick of apples.



Yesterday morning I heard the Varied Thrush singing creakily but incessantly from the direction of the creek. Later in the day, he was under the trees kicking leaves around (but not eating many apples). I'm assuming he was the same thrush that has been here all winter, but maybe not. He had a companion. Female? To me, the difference between male and female Varied Thrushes are rarely as apparent in the field as they are in the field guides, but the new thrush was a shade drabber than the first.



On a different note, there's been a flock of about 8 Red Crossbills in the yard for the past 4 or 5 days. They're a little unusual this far out into the fields. They are ripping through spruce cones like factory workers with a quota. This morning, I saw only one crossbill, a female, chirping and chirping from the top of a spruce. She had apparently gotten separated from the flock and wasn't happy about it. I could stay long enough to see if she was reunited with her little tribe.





Kelly Cassidy
Pullman, WA
mailto:lostriver at completebbs.com


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