Sunday, May 7, 2017

Loggerhead Shrike

  Just north of Manistee a Loggerhead Shrike has been hanging out on Bar Lake Rd. for a few days.  On Friday I made the forty minute drive but could not find the bird.  After not seeing any reports of it on Saturday, it was sighted again in the same area by Leonard Graf at 10:45 this morning.   So early this afternoon I finally caught up with the little impaler as it hunted from the power lines right alongside the road.  

   The Red-headed Woodpecker in my yard has not been seen since the 4th which was its fourth straight day of hitting my suet feeders.
    The local Pileated Woodpecker showed up in the yard after almost a one month absence.

    What's remarkable in the unremarkable photo below is that the dark speck near the center is Bald Eagle flying at very high altitude.
Bald Eagle spotted without optical aid and photographed with a 500mm lens and 1.4x converter
  How high you ask?  Well let's do the math.  First we have to figure what its angular size is.  The easiest way to do this is to compare it to an object of a known angular size.   After the sunset on Thursday the waning crescent Moon was high in the evening sky.  So I took a photo of it using the same set up that the eagle photo was taken.  
Moon shot with 500mm lens and 1.4x converter

Cut and pasted Eagle onto Moon while maintaining scale of respective photographs.
  The Moon at that time was 30.807 arcminutes in angular size.  By measuring the Eagles's image and comparing it to the Moon we get an angular size of 2.800 minutes of arc for the bird.  Now we take 1 over the sine of 2.8 arc minutes and find that the raptor was 1227.9 times farther away than its wingspan. The wingspan of a Bald Eagle ranges from 5.9 to 7.5 feet.  You could argue that the Eagle in the photo doesn't have its wings fully extended.  So if you conservatively subtract a foot from the birds full wingspan you get that the birds height is (4.9' to 6.5') x 1227.9 =  6016' to 7981'


  1. Once again, an outstanding analysis. I remember you had done a similar thing years back with migrating Broadwinged Hawks. Simply awesome stuff!


  2. Thanks, I thought about the Broad-winged calculation when that speck circling my neighborhood turned into a Bald Eagle when I put the binoculars on it.