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<\/p>\nI don’t have any beautiful photos today but I do have some interesting behavior.<\/p>\n
Yesterday morning, I came across this female American Kestrel sitting in the middle of a large, isolated, gravel parking lot\/camping area\u00a0on Antelope Island.\u00a0 I thought it was an unusual resting place for a kestrel\u00a0and as I approached her in my pickup I was even more intrigued when she didn’t immediately fly off, as this species typically does.<\/p>\n
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She repeatedly took a couple of wingbeats and\u00a0flew a few feet, but never far.\u00a0 She was, for some reason, reluctant to leave\u00a0and at first I couldn’t figure out why.<\/p>\n
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![\"american](\"http:\/\/featheredphotography.com\/blog\/wp-content\/uploads\/2012\/11\/american-kestrel-2799-ron-dudley.jpg\" "\\"american")
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I was eventually able to work my way close enough to her to see that she was\u00a0swallowing small stones from the gravel\u00a0parking lot.<\/p>\n
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![\"american](\"http:\/\/featheredphotography.com\/blog\/wp-content\/uploads\/2012\/11\/american-kestrel-2798-ron-dudley.jpg\" "\\"american")
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This was a behavior that I’d never seen before in a raptor, though I’ve often seen it in other birds.\u00a0 As a biologist, I’m aware of the general function of the gizzard in birds – that seed eating birds swallow “grit” to act as teeth (birds have no true teeth, presumably\u00a0a weight saving adaptation for flight) within the grinding gizzard so they can physically break down their hard food and prepare it for chemical digestion.\u00a0 And it had been my understanding that raptors don’t consume grit because they don’t eat seeds.\u00a0\u00a0The flesh they\u00a0consume is easily digested and doesn’t need to be physically broken down first.<\/p>\n
So why is this little falcon swallowing small stones?\u00a0 I decided to ask Mark Runnels, an extremely knowledgeable\u00a0master falconer from Oklahoma and an all around nice guy.\u00a0 I’ll try to summarize his detailed response below.<\/p>\n
Hawks, falcons and eagles do not eat grit or small stones\u00a0to digest their food like most other birds do.\u00a0\u00a0 The flesh they consume is\u00a0turned to liquid in the crop by strong acids and indigestible materials\u00a0(teeth, fur, feathers etc) are regurgitated as pellets.\u00a0 So grit is not needed by\u00a0these birds as a digestive aid.<\/p>\n
But these raptors still consume\u00a0stones and there’s a very good reason why.\u00a0\u00a0 The diet of these\u00a0birds (plump rodents, grasshoppers etc)\u00a0is very fatty and eventually a thick layer\u00a0of greasy fat builds up in the lining of the crop, which becomes a hindrance to the proper functioning of that organ.\u00a0\u00a0So they swallow\u00a0small stones, which scour out the greasy lining of the crop and eventually they will be cast out, just like pellets.\u00a0 And when they are, they’re covered in heavy grease.<\/p>\n
Mark goes on to say that old-time falconers\u00a0used to gently force small stones (called\u00a0“rangle”)\u00a0into\u00a0their falconry birds until their crops were about half full.\u00a0 The indigestible stones were later cast out, covered with a heavy layer of grease\u00a0(called “gleam”).\u00a0\u00a0 Modern falconers\u00a0have mostly abandoned this practice and focus on “whole body nutrition”, where the bird is allowed to eat food with lots of casting material (bones, feathers, etc) which, when cast out, carries with it much of the fat from within the crop.\u00a0 Falconers also occasionally\u00a0provide their captive birds with small, smooth, round stones.<\/p>\n
Anyway, I find this kind of stuff fascinating and hope at least a few of you share that interest.<\/p>\n
And thank you, Mark Runnels.\u00a0 Once again!<\/p>\n","protected":false},"excerpt":{"rendered":"
I don’t have any beautiful photos today but I do have some interesting behavior. Yesterday morning, I came across this female American Kestrel sitting in the middle of a large, isolated, gravel parking lot\/camping area\u00a0on Antelope Island.\u00a0 I thought it was an unusual resting place for a kestrel\u00a0and as I approached her in my pickup I was even more intrigued when she didn’t immediately fly off, as this species typically does. She repeatedly took a couple of wingbeats and\u00a0flew a few feet, but never far.\u00a0 She was, for some reason, reluctant to leave\u00a0and at first I couldn’t figure out why. I was eventually able to work my way close enough to her to see that she was\u00a0swallowing small stones from the gravel\u00a0parking lot. This was a behavior that I’d never seen before in a raptor, though I’ve often seen it in other birds.\u00a0 As a biologist, I’m aware of the general function of the gizzard in birds – that seed eating birds swallow “grit” to act as teeth (birds have no true teeth, presumably\u00a0a weight saving adaptation for flight) within the grinding gizzard so they can physically break down their hard food and prepare it for chemical digestion.\u00a0 And it had been my understanding that raptors don’t consume grit because they don’t eat seeds.\u00a0\u00a0The flesh they\u00a0consume is easily digested and doesn’t need to be physically broken down first. So why is this little falcon swallowing small stones?\u00a0 I decided to ask Mark Runnels, an extremely knowledgeable\u00a0master falconer from Oklahoma and…<\/p>\n