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Why Are Birds of Prey Harassed or Mobbed?

Golden Eagle

Golden Eagle juvenile photo by Hans Nydahl

I was driving home this afternoon in northern California and saw a large bird soaring fairly low over a very large grassy field off the road. I thought at first it was a Turkey Vulture, as they are abundant in our area, but I noticed it had a definite white tail with a wide black band. I had to pull off the side of the road and watch it for awhile to make sure I could identify it once I got home.

Well, I kept watching as this beautiful large bird rode the air currents, never flapping a wing, until as it soared higher and neared the upper elevations over a wooded area, a Red-Tailed Hawk began harassing the much larger bird. I had seen Bald Eagles previously in this same area but this was not a Bald Eagle. Once I returned home, I identified it as a juvenile Golden Eagle (the photo above shows a juvenile Golden Eagle being harassed by a gull, but the incident I witnessed was a young eagle being harassed by a Red-Tailed Hawk).

Now it is way past breeding time in our area for Red-Tails so I don’t think this hawk was defending a nest but perhaps just defending it’s hunting grounds and trying to run off the young eagle.

I’ve seen this behavior many times with crows or other small birds harassing much larger birds of prey.  This usually is an attempt to drive off birds of prey to protect nesting grounds, feeding territory or young offspring.

There is another behavior known as “mobbing” described here by the Royal Society for Protection of Birds (RSPB):  “Mobbing is a noisy, obvious form of behavior that birds engage in to defend themselves or their offspring from predators.  When a predator is discovered, the birds start to emit alarm calls and fly at the predator, diverting its attention and harassing it.  Sometimes they make physical contact.

Mobbing usually starts with just one or two birds, but may attract a large number of birds, often of many species.  For example, a chorus of different alarm calls coming from the same tree is often a good sign of a roosting owl or cat.  Mobbing behavior has been recorded in a wide range of species, but it is particularly well developed in gulls and terns, while crows are amongst the most frequent mobbers.”

The hawk and the eagle went at it a few times before the young eagle soared off toward my property but it was a very interesting interaction to watch.  Below is a photo of a mature Golden Eagle along with information on this beautiful bird of prey.

Glden Eagle

Golden Eagle (Aquila chrysaetos) photo by Walter Ammann

Size: 30-40 inches; Wingspread: 7 1/2 feet.  Adult; dark brown above with golden brown nape and white at base of tail.  Immature; seen in flight from below show well-defined white patches at base of primaries, white tail with distinct dark terminal band.  Inhabits mountainous or hilly terrain, hunting over open country for small mammals, snakes, and birds, also eats carrion.  In flight, tips of flight feathers are outspread and upcurved; soars high then dives for prey; occasionally hovers.  Nest is bulky stick mass on tree or high cliff.  Lays 1-3 white, blotched with red-brown eggs.  Resident from Alaska to Mexico, rare in the east, fairly common in the west.

If you have any information on birds of prey being harassed by smaller birds or other birds of prey, please share your experience with the rest of us so that we may all be better informed.

Thanks to Hans Nydahl and Walter Ammann for their super photos of these magnificent birds!  You can view more of their great photos by clicking on the Bird Forum link in the blogroll.

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  • Breeze December 26, 2007, 9:49 am

    Most smaller birds will mob a bird of prey to protect their young and other family members. Hawks, etc. will mob larger birds of prey to defend territory, protect their young, and ensure the safety of their food supply. Crows however, are somewhat full of mischief and seem to mob larger birds for fun in addition to the previous reasons. What a wonderful thing to be blessed to witness.

  • sarah August 1, 2008, 6:55 pm

    I live outside washington dc. The other day I woke to a chorus of frantic crows. they were “mobbing” and chasing a peregrine falcon! It was something to see. I have seen peregrine’s up high on tall trees along the interstate but not in my wooded subdivision before

  • Larry August 3, 2008, 4:50 pm

    Hi Sarah,

    That must have been a site to see! I would love to see a Peregrine in my neighborhood but I have not as yet. We have plenty of one of their favorite foods though, doves. I was lucky enough years ago to go with a wildlife biologist friend of mine to a Peregrine’s nest site near Lake Shasta in Redding California.

    They were studying the local Peregrine population to help bring their numbers back up from their road to extinction due to the use of DDT. I was able to watch, first hand and close up, their incredible speed and diving manuevers. What an incredibly beautiful bird.

  • F J October 7, 2009, 6:36 pm

    I saw a golden eagle being harassed by two hawks (one of which was definitely a red-tailed hawk) over Rose Canyon, in San Diego, this past weekend. It was harassed out of the area, which was apparently the territory of the hawks.
    .-= F J´s last blog ..Close Encounter =-.

  • Larry October 7, 2009, 9:22 pm

    @FJ this kind of behavior is pretty common amongst birds of prey, especially if they are breeding, which neither of these species would be at this time of year. Like you said, probably simply a case of being the hawk’s territory

  • veronica June 4, 2010, 9:02 am

    I have two red tailed Hawks in a tall tree in my backyard. The other day I noticed a hawk was on the grund near the wood pile. It began walking the perimeter of the yard, as the parents made alot of noise and swooped around if anybody went into the yard. The baby was friendly and appeared not to fear. I was able to feed it a chicken leg which it took from my hand and began eating as if I wasn’t there. It slept on the rail of my trailer all night and noticed today it is hiding, perhaps it came out yesterday because it was hungry. Most beautiful thing I have ever experienced.

  • Andy June 15, 2010, 2:49 pm

    There is currently a story going around the Web about a bald eagle being harassed by three crows when his mate (?) shows up and the two eagles attack and possibly kill the crows. I have never witnessed nor heard of this happening when a raptor is being harassed by “lesser” birds, and am suspicious that the Web story is fiction. Does anyone know of a substantiated account of raptors turning the tables on their tormentors like this?

  • Larry June 15, 2010, 8:46 pm

    @Veronica Wow, what a great experience, hand feeding a Red-tailed Hawk chick! Were the parents watching the whole thing with concern? I would love to have been there. We have had hawks come down into our bird feeding area but never a Red-tailed Hawk, even though they nested close by for years.

    The RTs nesting in the power lines are about 5 miles away and their nestlings have just recently fledged.

    Magnificent creatures!