Mar 23 2010

Heron Rookery

Published by at 9:01 am under Nesting & Courtship,Water and Shore


Have you ever seen a tree that looks like this?  With a lot of big nests in it?  Surrounded by trees with similar nests?  If you’re in southwestern Pennsylvania, you’ve found a great blue heron rookery.

Great blue herons nest colonially near creeks, rivers, lakes and wetlands.  Their group of nests is called a rookery after the colonial nests of the Eurasian rook, a common bird like our crow that’s called a “rook” because of the sound he makes.

Great blue heron rookeries are large, often containing several hundred nests that are used year after year.  In Pennsylvania they’re usually located in sycamores in an isolated place on an island or in a wooded swamp.  The location is chosen for its access to food and isolation from predators, but food doesn’t need to be right there.  Adult herons will commute nine miles on foraging missions, so the heron you see hunting koi in your backyard pond may well have flown a long distance to get food for his kids.

In March the great blue herons return to Pennsylvania to set up housekeeping.  Even from a distance you can see them standing on the old nests making home improvements, a twig here, a stick there. They also do elaborate courtship displays on the nest including stretching, bill snapping and a crest raising display.  They look too large to use the nests, but I’ll show you how they do it in tomorrow’s blog.

If you have the chance now’s the time to notice heron rookeries, for in six short weeks they’ll be hidden.  The trees will be covered in leaves by May.

And remember, if you find a rookery don’t disturb the birds.  They’ve chosen the site because it’s isolated from predators, including humans.  Herons will abandon a rookery where the disturbance becomes too great.

(photo of great blue heron rookery in a sycamore tree by Tim Vechter)

8 responses so far

8 Responses to “Heron Rookery”

  1. Cory DeSteinon 23 Mar 2010 at 2:42 pm

    And not always will it be just herons in the rookery as I learned!!!

  2. maryon 23 Mar 2010 at 2:46 pm

    Those of us in northern California are treated to eucalyptus trees, too tall and too dense to reveal the GBH nests. But they are there. It is quite a sight to see a heron slowly glide in, circling the nest, and then disappearing among the upper branches and leaves of the trees. First time I saw it, I couldn’t quite believe it.
    First time I saw a GBH stalking small rodents in the parking lot next to the ocean beach I also thought I was mistaken. But no, every Spring they return to open fields, sometimes standing for hours, patiently waiting for amphibians and rodents to make a move. Their best hunting hours appear to be between morning and early afternoon. They then return to the nests later in the afternoon. What a delightful experience to behold!

  3. Kate St. Johnon 23 Mar 2010 at 2:54 pm

    Cory, your story of finding a red-tailed hawk nest in a heron rookery partly inspired me to write about them.

  4. Cory DeSteinon 23 Mar 2010 at 4:39 pm

    Cool! I did some research on my own, and found one rookery, that was a good bit larger, but it also had a red tail nest, but in a far end of the rookery, a great horned owl nest.
    Herons nested right next to and around the hawk, but all nearby nests to the owl were abandoned! I dont blame the herons. Also reports of a bald eagle nest in a heron rookery, although in that scenario i dont know if the herons returned, or left for another site? Eagles would be much more of a threat.

  5. Becky Grimeson 24 Nov 2010 at 5:05 am

    Here in the Sheridan, WY area we saw an eagle that had set up housekeeping in the middle of a rookery. The GBH didn’t seem to mind and were certainly not going to say NIMBY to the eagle.

  6. Patrickon 23 Jun 2012 at 11:08 am

    I know the location of a rookery that has close to 20 Great Blue Heron nesting in it. It is hard to see the babies in the nests and hard to judge their ages, but if i had to guess they may be anywhere from 1-2 months old. I watched them for hours last evening with my brother and our friend from 2pm to midnight. I was absolutely amazed and stunned by how vocal they are. At times they sound like Tasmanian Devils fighting to the death. They scream, bark, hiss, quack, and make other horrific noises. I can’t describe the feelings that rush through your body when you hear them screaming and barking at each other at night time. I would love to record them for an hour and use it for a haunted house soundtrack. They are Heron during the day but at night they turn into Pterodactyls hah! I need to acquire some high quality filming equipment soon so i can record them. I’d love to make a documentary about them and the surrounding area.

  7. Cindyon 01 Mar 2013 at 3:44 pm

    Hi,
    My family and I have driven up toward Franklin a few times in March in years gone past to see the Great Blue Heron rookery there. Today’s Post Gazette showed pictures of herons at Bell Acres on Big Sewickley Creek. This reminded me that I had heard there was a visible rookery much closer to Pittsburgh than Franklin. I’m wondering if you can give me directions or at least guidance so we can check on these magnificent birds and their nests.
    Thank you,
    Cindy

  8. Kate St. Johnon 02 Mar 2013 at 2:39 am

    Cindy, I’m not familiar with the rookery in Bell Acres but I do know of one on an island in the Allegheny River near Lock & Dam #3. You can drive to within a mile of it but must walk the last mile on Barking Road (off Coxscomb Hill Rd). Barking Road is the road to the dam. Perhaps the heron rookery is visible from Freeport Road on the Cheswick side of the river. I can’t say as I’ve never looked from that side.

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