Category Archives: Cooper’s Hawks

Beware of rodent poisons: Cooper’s Hawk killers

A story in the latest online edition of the Berkeley Daily Planet reminds us of the dangers of the stuff we use without thinking to rid ourselves of pests.

Joe Eaton writes that someone in Berkeley trying to rid themselves of rats has caused the death of esnl‘s favorite flying critter, the Cooper’s Hawk:

It’s the worst kind of déjà vu. Last month a juvenile Cooper’s hawk was found dead in a pool of blood on a west Berkeley sidewalk, not far from where three other hawks succumbed four years ago. This year’s victim tested positive for the anticoagulant rodenticide brodifacoum, with a trace amount of another rodenticide, diphacinone. Brodifacoum was also implicated in at least two of the 2007 deaths.

Some rodenticide users, homeowners and professionals alike, seem oblivious to the collateral damage the stuff can cause. Even if the bait is placed indoors, a poisoned rat or mouse can wander outside where it can be picked off or scavenged by a predator or pet. Although Cooper’s hawks are primarily bird-hunters, rats may be “starter” prey for younger individuals, easier to catch than pigeons or starlings. Hard-pressed parents may also bring rodents home for their hungry nestlings.

Death by brodifacoum is particularly nasty. It kills by internal bleeding, which results in intense thirst. (The 2008 hawks were found in a backyard wading pool.) Like other “second-generation anticoagulants,” brodifacoum was introduced in the 1970s after rodents developed resistance to older products. The risk of secondary poisoning of non-target species like hawks is increased by the fact that the poison is not immediately fatal: a rat may keep coming back to the bait for several days as the brodifacoum in its body builds up to several times the lethal amount.

According to the American Bird Conservancy (, brodifacoum has killed hundreds of birds of prey: red-tailed and Cooper’s hawks, great horned owls, eastern screech-owls, golden eagles. Even mountain lions and endangered kit foxes have fallen victim. In New Zealand, populations of both raptors and insect-eating birds decreased following a brodifacoum-baiting program.

The second chemical found in the hawks’ tissues, diphacinone, is one of the first-generation anticoagulants. Previous tests on mallard ducks and bobwhite quail had been used to claim that it was only minimally harmful to birds. However, a more recent US Geological Survey study found that small amounts of diphacinone were lethal to American kestrels. As little as 3 grams of liver from a poisoned rodent could kill one of these small falcons.

Read the rest.

Sunday afternoon, Cooper’s Hawks at leisure

First, some Cooper’s Hawk factoids, thanks to Cornell University’s All About Birds page on the critter. Lots of interesting things thing, including recordings of the critter’s call.

To the ornithologically minded, the hawk is known by its formal handle, Accipiter cooperii.

Some other hawk lore:

  • A Cooper’s Hawk captures a bird with its feet and kills it by repeated squeezing. Falcons tend to kill their prey by biting it, but Cooper’s Hawks hold their catch away from the body until it dies. They’ve even been known to drown their prey, holding a bird underwater until it stopped moving.
  • Once thought averse to towns and cities, Cooper’s Hawks are now fairly common urban and suburban birds. Some studies show their numbers are actually higher in towns than in their natural habitat, forests. Cities provide plenty of Rock Pigeon and Mourning Dove prey. Though one study in Arizona found a downside to the high-dove diet: Cooper’s Hawk nestlings suffered from a parasitic disease they acquired from eating dove meat.
  • Life is tricky for male Cooper’s Hawks. As in most hawks, males are significantly smaller than their mates. The danger is that female Cooper’s Hawks specialize in eating medium-sized birds. Males tend to be submissive to females and to listen out for reassuring call notes the females make when they’re willing to be approached. Males build the nest, then provide nearly all the food to females and young over the next 90 days before the young fledge.
  • The oldest known Cooper’s Hawk was 20 years, 4 months old.

This afternoon, one of the hawks lit in a favorite perch two trees west of its nesting tree. The branches are thinner, making it easy to catch a glimpse of possible prey. This fellow was in the midst of grooming when a pigeon passed by, and the lens snapped at the instant he [?] turned to catch a glimpse of possible prey. But an ongoing itch proved the more compelling draw, so at least one Rock Dove [the true name of our pretend pigeons] was able to escape the raptor hug of death — at least for the moment.

11 July 2010, 600mm, f6.3

Seconds later, another avian arrived, this one a sibling. The bird perched higher up the tree in one of the few areas heavily shaded by the branches above.

11 July 2010, 600mm, 1/1250 sec, f5.3

Young Cooper’s Hawk takes a shady breather

All three of the young birds were perched a couple of trees south of the nest, but two had flown by the time the camera was in range, leaving this critter as the sole candidate for today’s hawk post.

10 July 2010, 600mm, 1/500 sec, f6.3

Cooper’s Hawk gives in to that urge to scratch

Chin-scratching is quite a feat for a young Cooper’s Hawk, since it requires standing on one foot while keeping balance from atop a branch.

8 July 2010, 600mm, 1/500 sec, f5.3

Cooper’s Hawks in the late afternoon sun

A pair of the young were ought to catch the rays today.

8 July 2010, 440mm, 1/1000 sec, f5.6

Here a sibling comes in for a landing, just a bit too fast for the camera to grab the sharpest possible image. Still. . .

8 July 2010, 440mm, 1/800 sec, f6.3

Young Cooper’s Hawk sneaks a jealous peek

While a nestmate dines on birdie de jour, a sibling looks on hungrily moments after being driven off with by the well fed erstwhile comrade.

3 July 2010, 600mm,

Finally, the shot you’ve been waiting for

At least esnl was. Shooting a bird flying with a long lens is tricky, but this worked out perfectly. One of the young taking wing. . .

6 July 2010, 600mm, 1/8000 sec, f5.6

Monday afternoon, raptors and their prey

The daily raptor hunt found one of the adults sitting on a branch two trees west of the nest.

5 July 2010, 600mm, 1/2000 sec, f5.6

One the ground below were evidence of two types of prey. The mouse had been rejected after a couple of bites. T’would be interesting to see if the critter were infected with sometime, since it’s the first discarded prey esnl‘s found. Nothing was left of the feathers’ source. . .

5 July 2010, 120mm, 1/6000 sec, f5.6

5 July 2010, 120mm, 1/1600 sec, f5.6

Click to enlarge the images. . .

Raptors celebrate their own independence

The Prince Street Cooper’s Hawks are growing fast, and while they may display a bit of birdling rivalry — especially when one has food and the other two don’t — they seem to get along well otherwise. A morning stroller along Prince Street in Berkeley found a pair of the critters perched together, first on a branch of one of the lower trees on the block, with one of the critters making a high-pitched squawk, perhaps calling for the missing third.

4 July 2010, 390mm, 1/2000 sec, f5.6

A few minutes later they departed their perch to find a higher branch across the street, a dozen feet or so below their nest.

4 July 2010, 420mm, 1/600 sec, f5.6

And one final shot, just because. . .

4 July 2010, 600mm, 1/2000 sec, f5.64 July 2010, 600mm, 1/2000 sec, f5.6

Note to Prince Street Cooper’s Hawks fans

There’s a new entry in the Categories sidebar. Just click on “Cooper’s Hawks” and you find the full slate of avian entries going back to the first shots on 13 March.

Junior Cooper’s Hawk grabs a bite of lunch

Once in a great while fortune smiles on a photographer, as it did today when he came upon one of the trio of young Prince Street Cooper’s Hawks sooner after the critter had caught caught another bird and was sitting down for lunch. First, he plucked his prey of feathers, stopping as the photographer sidled up to shooting range.

3 July 2010, 600mm, 1/200 sec, f5.6

Then, his lunch defeathered, the young hawk got down to business, his two siblings squawking in protest from a pair of nearby trees, upset that no sharing was happening.

3 July 2010, 600mm, w/500 sec, f5.6

The three little hawks, a Prince Street tale

While folks have been telling esnl they thought the raptors’ nest in the 2300 block of Prince Street in Berkeley had produced three young, the most he’d ever seen at one time was two.

Until today, that is.

While they’ve only be able to fly for a few days now, at least one of the triplet Cooper’s Hawks has proven to be a resourceful hunter, and this morning the critter brought back some prey to one of the lower branches of the home tree.

2 July 2010, 600mm, 1/800 sec, f5.6

As the victor zealously chowed down on a feathery Friday morning brunch, a brother/sister perched on a limb in the shadows a few feet away, looking rather wistful.

2 July 2010, 600mm, 1/400sec, f5.6

Whilst the third sib perched in a tree across the street, vocalizing a presumably jealous lament [that presumption coming from a blogger's own experience with his offspring].

2 July 2010, 600mm, 1/800 sec, f5.6

Young raptor spreading his [her?] wings

If there’s one maxim in photographing wild critters, it’s this: You never have the right the lens for that exceptional shot. esnl was loaded up with his long lens when he went out looking for raptors this afternoon, and some nice shots resulted, especially of this young bird flexing his gorgeous plumage.

1 July 2010, 600mm, 1/125 sec, f5.6

Here’s another with the young raptor engaged in a tail feather display. One thing that struck esnl was the role of the tail feathers as a sexual signaling device, forming rings like a target directed at what Victorians once called “the organs of generation.”

1 July 2010, 600mm, 1/125 sec, f5.6

Then there’s the photo he didn’t get. A few seconds later, both parents and the second sibling arrived amidst a great deal of clamor and all four took wing — the first time the whole brood has been aloft at once — but that required a shorter lens, so, alas, you’ll just have to take our word that a marvelous sight ensured.

Sometimes a photograph just captions itself

As when esnl received the full-on glare of Papa Cooper’s Hawk early Wednesday evening. . .

Click on the image to embiggen.

30 June 2010, 600mm, 1/800 sec, f5.6

In Berkeley, Wednesday is raptor FLY-day

Well, today’s the big day! esnl was sitting before his computer when a knock on the door got him off his posterior. Alan Cartwright, who runs the car repair shop across the street, had come to announce that one of the young raptors had flown from the nest and was now across the street on a power line. Grabbing his camera, esnl was rewarded when the young critter flew across the street and landed on a limb outside his door.

So without further ado, the first Prince Street Cooper’s Hawk to fly!

30 June 2010, 600mm, 1/250 sec, f5.6

And because just one picture simply isn’t enough. . .

30 June 2010, 600mm, 1/250 sec, f5.6

Hawk chronicles: Nestling ventures out on a limb

Having watched over a few nestlings of his own, esnl has been thoroughly delighted with the opportunity to see other critters going through the same process. Today’s reward was a chance to watch one of the nestlings make an excursion outside the nest. Two pix here, two more after the jump.

First came the urge, apparent in the raptor focus as the branch catches the young bird’s attention. . .

29 June 2010, 600mm, 1/125 sec, f5.6

Next comes the leap, captured here at the landing end, with wings and tail feathers deployed.

29 June 2010, 600mm, 1/160 sec, f5.6


Cooper’s Hawk watching the nest at sunrise

What else to say?

28 June 2010, 600mm, 1/640 sec, f6.3

And a final Cooper’s Hawk shot of the day

Sitting there so pretty at the approach of the Golden Hour and with a deep blue sky behind, how could a hapless neighborhood picture-taker resist?

26 June 2010, 600mm, 1/800 sec, f6.3

Young hawks preparing to leave the nest

Things have been busy high above Prince Street these days. The young Coopers Hawks are getting ready to leave the nest. Shooting the nestlings is hard, since there are only two small places a photographer can stand and catch a glimpse of the birds, and the wind-caused movement of the branches often makes use of a tripod impossible.

In this first shot, we see one of the young flexing wings, getting used to all those muscles that will soon take him [or her] aloft.

26 June 2010, 600mm, 1/800 sec, f6.3

In many ways this second shot is more interesting, since it’s the first time esnl has spotted one of the young outside the nest [which is hidden by the leaves to the right]. One of these days they’ll not be sitting away from the nest but flying, a time anticipated with both joy and sorrow.

26 June 2010, 600mm, 1/100 sec, f6.3

Big babies’ days in the nest are numbered

Just a few weeks ago, the Prince Street Cooper’s Hawk nestlings were small, fuzzy, blue-eyed critters. Now they’re almost as big as mom and pop, the blue eyes have turned to brown, and only their beaks lack that deadly raptor curl that would identify them as full-grown adults.

When I took this shot, I wasn’t sure if it was mom or a kid, but the final image let me know I was getting what may be one of the last shots we’ll see of the young.

25 June 2010, 600mm, 1/250 sec, f6.3