Readers’ wildlife photos

Once again we have a nice science-and-photo post by biology professor Bruce Lyon from the University of California at Santa Cruz. His notes are indented, and the subject is owls, also known as Honorary Cats™.

A second batch of owl photos and natural history to follow on the Northern Pygmy Owl post (here) from a couple of weeks ago. To contrast with the pygmy owl, here are some photos of a very large species, the Great Gray Owl (Strix nebulas), the tallest North American owl. Their height is deceptive thought because under all those feathers is a puny body—despite being five inches longer than Great Horned Owls (see post about them here), Great Grays Owls are 15% lighter than great horneds.

Below: a comparison of the heads of great grays (left) and great horns (right) reveals another important size difference—great grays have very small eyes. I do not know if this is just a consequence of great grays having smaller heads when the feathers are removed (i.e., skull size), or whether, relative to skull size, they have smaller eyes. I suspect they do. They often hunt during the day, so diurnal hunting might not require large eyes. And the fact that they can find prey based on sound may make the eyes less important for hunting than for great horns. I do not know if great horneds can hunt by sound alone but I suspect not. Their facial disc is not as well developed as the great gray and they also have bilaterally symmetric ear openings.

Great Gray Owls are one of my favorite birds, period! They seem mystical with their huge heads and facial discs, and they have a slow flapping flight that is almost butterfly like. They also live in beautiful wild areas that have a mix of coniferous forest and meadows for hunting. Small rodents (voles, mice, lemmings) comprise the bulk of their diet (90-95% depending on location). It’s amusing to think that tiny pygmy owls often take larger prey.

Below: A great gray owl hunting in a burned-out forest not too far from Yosemite National Park this spring. Hunting involves sitting on a perch for a long period of time and then gliding down and pouncing on prey.

Below: When the owls are sitting still next to the trunks of large trees they can be remarkably cryptic. Another owl near Yosemite.

Below: The same bird hunting in a meadow. It is much more conspicuous than in the above photo but they can still be surprisingly easy to miss even when out in meadows.

These owls can hunt entirely by hearing, and the big facial disk apparently serves as a parabola to focus sound on the asymmetric ears used to triangulate and pinpoint the location of a sound source. In winter, the owls can locate mice hidden under the snow and then glide to the area and punch down hard through the snow to snatch the rodent. They are deadly accurate. A friend who watches gray grays in winter in Canada has several times had an owl glide in from a perch a hundred meters away and then punch through the snow and grab a mouse a mere couple of feet from where he was standing. These birds can be extremely tame and apparently can hear mice from a long distance away. Below is video clip from National Geographic showing a bird hunting in winter.

These owls breed in the forest near the wetlands where I do my coot research in central British Columbia but it took me many years to find a nest. Great gray nests can be found by following an adult returning to the nest with prey.  I found my owl nest by watching a great gray catch a mouse in a meadow and then fly off into the woods. I knew it was going to its nest so I sprinted after it for about 400 meters but then lost sight of it as it disappeared in the fairly dense forest.  On whim, I continued on in the same trajectory the bird had been going and after 300 more meters I encountered the bird now flying back towards me in the opposite direction. I went another 200 meters to where the bird had flown from and heard the faint calls of a female calling from the nest and her calls led me to the nest (she was probably telling the male to keep hunting). Unfortunately, the nest was in the worst possible location for observing or taking photos: it was in an old raven nest very well hidden at the top of a tall spruce. However, once the chicks fledged I was able to get great views of the family hanging out—this pair of birds was completely oblivious to people.

Below: Look at the massive head on this bird! I think it hears a mouse.

Below: The same bird. This bird has heard something rustle in the underbrush and has gone into what I call ‘mouse mode’. They often have a relaxed posture but when they hear something that could be rodent, their comportment changes—they stare intensely at the source of the sound and their entire posture changes and they often cock their head back and forth, presumably to pinpoint the location of the sound.

Below: The same bird hunting in the forest in the early evening when the light was quite nice.

Below. Something suspicious has been detected and the bird launches for a pounce.

Below: One of the three chicks out of the nest. Owl chicks often leave the nest before they can fully fly. They scramble around the branches and are sometimes called ‘branchers’ at this stage.

Below: One of the fledgling next to the trunk of a very large Douglas fir. Although the birds nested in a tall spindly spruce, there were lots of large Douglas fir nearby. This nice patch of woods has since been logged.

 

24 Comments

  1. ThyroidPlanet
    Posted July 30, 2018 at 7:36 am | Permalink

    Beautiful!

    The one against the tree background – very clear, very strong photo!

  2. Posted July 30, 2018 at 7:49 am | Permalink

    Wonderful Bruce! Thanks for sharing all this!

  3. busterggi
    Posted July 30, 2018 at 8:09 am | Permalink

    This is the only way I’ll ever see a Great Grey so it’s much appreciated.

    • Glenda Palmer
      Posted July 30, 2018 at 2:16 pm | Permalink

      +1

  4. Posted July 30, 2018 at 8:34 am | Permalink

    What wonderful pictures and commentary. Fantastic.

  5. Lee Beringsmith
    Posted July 30, 2018 at 9:24 am | Permalink

    These photos are wonderful, what a great way to start out my Monday morning with such beauty, thanks for sharing.

  6. Posted July 30, 2018 at 10:03 am | Permalink

    Are the owls cryptic to avoid being prey or so their prey don’t see them and go into hiding? I’m guessing the latter.

    • busterggi
      Posted July 30, 2018 at 10:38 am | Permalink

      My guess is that its so they can slep peacefully rather than hide from prey. Most small mammals have poor vision.

    • Bruce Lyon
      Posted July 30, 2018 at 11:01 am | Permalink

      Perhaps to avoid being mobbed by crows, owls and other things. More on this in the next post!

      • Posted July 30, 2018 at 11:24 am | Permalink

        Looking forward to it! It’s an interesting subject.

  7. W.T. Effingham
    Posted July 30, 2018 at 10:30 am | Permalink

    My daughter’s cat frequently behaves as if she wants to be an honorary owl. My son’s dog often behaves like an honorary warthog.

  8. BJ
    Posted July 30, 2018 at 10:53 am | Permalink

    What wonderful photographs! Owls are some of the coolest animals in the kingdom.

  9. DTaylor
    Posted July 30, 2018 at 11:26 am | Permalink

    Such interesting information and great photographs! I especially liked “hearing a mouse” and the fluffy chick.
    Thanks for sharing!

  10. Terry Sheldon
    Posted July 30, 2018 at 12:10 pm | Permalink

    Thank you so much for the marvelous images and commentary!

  11. Mark R.
    Posted July 30, 2018 at 4:28 pm | Permalink

    Thanks for this wonderful post. Such a majestic bird. I was glad to learn so many fun and interesting facts about this species. But I did have a let down at the end, learning that those Douglas Firs were logged.

  12. Posted July 30, 2018 at 7:12 pm | Permalink

    These are simply breathtaking, Bruce. Thanks!

  13. Cruzrad
    Posted July 30, 2018 at 11:35 pm | Permalink

    Oh my, what exquisite photo. Thank you so much!

  14. Posted July 31, 2018 at 2:48 am | Permalink

    Gray owls creep me out.

  15. Posted July 31, 2018 at 3:15 am | Permalink

    Great photos of an exceptionally beautiful species. Sadly we don’t get Great Grey Owls in the UK where I live but I’d love to see one one day – another good reason to make a trip to Yosemite! Meanwhile the owls we do get here are pretty cool too and always a pleasure to see!

    • Bruce Lyon
      Posted July 31, 2018 at 10:42 am | Permalink

      This bird does occur in Europe—it just has a different name (Lapp Owl). Closest area to you with Lapp Owls would be Sweden. A little closer than Yosemite!

  16. Diane G
    Posted July 31, 2018 at 3:16 am | Permalink

    Fantastic photos of a spectacular bird! I particularly love the one of the bird in “mouse mode,” as I’ve never seen such a pose before!

    Thanks for posting, and keep ’em coming! 🙂

  17. Posted July 31, 2018 at 7:32 pm | Permalink

    That was excellent owl watching…. the grey is a surperb bird.

  18. Andrea Kenner
    Posted August 1, 2018 at 5:33 am | Permalink

    Beautiful photos of a beautiful bird!

  19. Posted August 9, 2018 at 4:14 pm | Permalink

    The cryptic photo is amazing!


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