Re-run: Why don't the eyasses fall off the edge of the nest?

This is a re-run from last year (May 20, 2011).  Though the images are of last year's eyasses, 

the information is completely relevant as we watch and worry about how close they are to 

the edge of the nest.

Why don't the eyasses fall off the edge of the nest?  As the eyasses become increasingly curious about the world out there... 

... nervous nest watchers worry as they see the eyasses move closer to the edge of the nest.

Each day, there is more wingercising...

... and scary losses of balance right at the edge of the nest, four floors up from the concrete sidewalk of Winter Street.

Experienced Franklin Institute nest watchers have lived through this twice already, and know that the eyasses manage to stay safe.  I asked John Blakeman why this is, and he shared this fascinating information:

"Actually, the little eyasses have a pretty developed and strong impulse to stay down in the bowl of the nest. They don’t rationally know that they sit precariously at height in a tree or on a ledge. But instinct and natural selection have left them with good instincts regarding the hazards of getting too close to the edge of the nest.

However, Red-tail eyasses do sometimes fall out of the nest, but almost always during defecation. It goes like this - unlike passerine birds (“song birds”), Red-tails and other similar raptors do not excrete fecal sacs. These little bags of feces are lifted out of the nest and carried away by the parents. This keeps the nest clean, and reduces the discovery of the nest by marauding predators such as raccoons who would prey upon the nestlings if discovered by olfactory hints.  But in Red-tails, the little eyasses have an instinct to, as falconers and raptor biologists say, “slice.” Watchers of the eyasses in The Franklin Institute nest have seen this. The little eyass stands and backs its tail out toward the perimeter of the nest. Then, in an instantaneous spurt, the eyass squirts the “slicings” out over the edge of the nest.

            Scott Kemper (2012)

But very infrequently, the little eyass backs up too close to the edge of the nest, and simply falls out backwards, all in the good attempt to direct its slicings away from the nest. Frankly, I’ve never encountered this, but it has been reported. I think that when an eyass falls from the nest during slicing, it may have some neuromuscular difficulties. It happens, but rather rarely. We needn’t concern ourselves with it. 

A word about the “slicings.” In defecation, hawks and eagles are said to “slice.” The feces are “slicings,” and the remnants in the FI case are seen as the white stains on the lower edge of the window. Our three eyasses have nicely sliced on that surface.

 They have also sliced on the wall alongside their nest.

But things are a bit different in true falcons. Falcons don’t slice, they “mute.” Falcons are unable to powerfully project their feces (called “mutes”). Instead, a defecating (“muting”) falcon merely drops her mutes beneath her. This has significant results at falcon aeries [nests], which are almost always on a ledge or cliff. 

Falcons are known to occupy aeries for literally centuries. There are Peregrine Falcon aeries in the UK that have been occupied since the Middle Ages. Actually, they have probably been occupied for millennia, since the ending of the Ice Age. 

How do we know this? Well, there is the historical record of falconry, where British and Scottish falconers have been taking eyasses from these nests as long as falconry has been in the British Isles, probably from the ninth century or earlier.  But these piles of falcon mutes tell their own story. The same phenomenon occurs in American Prairie Falcons, in the West. Out there, raptor biologists have bored down through many feet of ancient Prairie Falcon mutes and have counted the layers (a new layer each year). Some of these aeries are centuries old. 

A falcon can get away with this, as mammalian predators of eyasses such as raccoons, weasels, badgers, and the like, can’t climb around on steep, high cliffs. The eyasses are safe, even though their aeries can be easily spotted from afar. Falconers and raptor biologists scan the long streaks and thick deposits of falcon mutes, the “hawk chalk.” I’ve spent five summers in the West studying raptors out there, and finding a Prairie Falcon nest was not very hard. Just scan a long cliff face with a pair of binoculars and look for the white hawk chalk. Very obvious. (And obvious, too, to the falcons. New aeries have been created by merely painting white hawk chalk-like streaks on an empty cliff ledge. Within a year a pair of Prairie Falcons will often take up residence, subsequently creating their own hawk chalk.) 

About raptor feces. Hawk slicings and falcon mutes are predominantly white, with a central blob of darker, more consolidated material. The white, liquidy portion is primarily uric acid, a concentrated form of the liquid, dissolved urea found in mammalian urine, including us. We, like most mammals, both urinate and defecate. Not so with birds, especially our hawks and falcons. Instead of clearing waste proteins and other nitrogenous materials with water and dissolved urea (from the kidneys), birds can’t be carrying around ample amounts of water to make urine. Instead, they further process the urea their livers create into concentrated white crystals of insoluble uric acid. That’s the white part of the bird’s splat on a windshield. It’s concentrated, so as to use very little water. 

The dark part of a mute or slicing is actual intestinal feces. Because raptors very thoroughly digest their food, and there is no “fiber” content, there isn’t much left coming out of the intestines after digestion. Most of what raptors eat is bone and protein. Hawks and falcons (unlike owls) thoroughly digest all bone material, so there is no solid bone waste in the mutes or slicings. The proteins of the prey are completely digested and eventually end up as the white uric acid — except for feathers or fur, which is not digested but vomited up each day as a “casting,” or “pellet.” Castings are the balls of fur or feathers from the previous day’s meals, expelled through the mouth.

Well, I guess I’ve pretty much sliced up all of that. I’ll now go mute.

–John Blakeman

 While John is mute, here are some pictures from this week at our nest.

The eyasses still take long naps, sometimes spread out ....
 

... and sometimes in a cosy clump.

When they are awake, they are on full alert.  Here, the tiercel (dad) has just flown off the nest, and they are intently watching him as he flies across the Parkway.

John Blakeman tells us that "honing visual acuity is one of the very important maturation processes that the eyasses are learning while "just sitting around on the nest." This ability to follow distant objects moving in the landscapes these hawks live in is a crucial survival lesson. The FI eyasses are learning those ocular and neuromuscular skills now. They are learning to visually follow food, something that will allow them to follow rats and mice when they start to hunt."

The following are pictures I took through the Board Room window with a point-and-shoot camera, so the quality is nowhere near that of Kay's pictures, but it gives a sense of their growth, and also of the surrounding landscape.

Here's the formel looking out across Winter Street and the Parkway with the Vine Street Expressway running underneath.

She sees everything, and here she is keeping a very close watch on a passing dog walker.  You can see how huge the eyasses' feet are.  They have to keep them arranged out in front so as not to tangle in the nest sticks!

The formel is a very intimidating bird up close.  I was glad the window glass is thick.....

The eyasses' wing feathers are starting to grow through their fluff...

... and the characteristic chestnut and black banded tail feathers are apparent.  The red tail feathers do not appear for the first two years.

That bobblehead has a serious beak!  Their eyes are currently jet black, but by the time the eyasses fledge from the nest, their eyes will be a lovely gold in color.  The eyes turn back to black when they are mature hawks.  Golden eyes are a clear indication of an immature hawk.

The eyasses line up nicely while mom picks off tasty morsels for them...

... and there is no squabbling as she feeds each one.

After eating, they settle down for the afternoon, but it is not long before this eyass decides to play tug-o-war with a rat carcass, yanking on its tail.

They are intensely curious about what is going on behind the window, showing no fear whatsoever.

The tiercel flew in and joined the family for a quick visit.  He is noticeably smaller than his mate, and though he is a stone-cold killer, he has a gentler face than the formel.

He brought a nestling - looked like a young robin - pulled it apart, and enthusiastically fed the eyasses.

The nest now has three year's worth of sticks and towers above the wooden frame that the Franklin Institute installed after the haggards' first few attempts at a nest kept blowing off the ledge.

And so ends another great week for the eyasses and their parents.  Let's fasten our seat belts and have the valium on hand for when they start hopping and "catching air" and heading out to the ledge!

Why does T2 keep taking the rats away?

While it has been thrilling to see how well the new tiercel - T2 - is adapting to his role as step-dad, hawkcam watchers have been frustrated that he keeps removing the white rats that are put out as food drops.

Typically, when the rat is put out the window onto the ledge, the formel grabs it and plops it down at the front of the nest, much to the excitement of the eyasses who now clearly recognize an imminent meal.

T2 almost immediately arrives on the nest, if he's not already there...

... grabs the rat with his talons, and flies to a nearby roof, ledge or monument where he starts eating the rat - usually the head and neck.  After 5-10 minutes, he returns the rat to the nest.

Sometimes he stays to feed the eyasses...

... but he often drops and runs, leaving the eyasses to figure out what to do next.

I asked John Blakeman what this behavior meant, and whether T2 was an opportunistic freeloader.  It turns out that T2 deserves credit rather than criticism.  John Blakeman also comments on the miraculous adaptation that T2 has made in feeding the eyasses:

"The biological mystery of T2's astonishing fulfillment of normal tiercel duties at the FI nest continues. It's progressing just as I might have written it in some fictional story about modern urban Red-tails.

But I don't write fiction. This is real biology, not of the imagination of some author.

Regarding T2's prompt removal of the rats. I don't see this as stealing of any sort; rather, it's the pro forma, ritualistic performance of instinctive tiercel behaviors. T2 sees the new rat on the ledge, accurately, as new prey that he must "capture," fly off with, and then - very importantly - prepare for the eyasses by decapitating or otherwise rendering the rat both completely "dead," and opened up for easy feeding to the eyasses, either by himself or the formel. 

The real astonishment, however, is T2's deliberate, effective, and frequent feeding of the eyasses.  Tiercel haggards at many nests do little of this, leaving most feedings to the formel. But T2 has taken up this duty with gusto and efficacy. He's ever more into the entire tiercel haggard role at the nest. 

There isn't much more a resident tiercel parent could do at this stage. The only question will be if T2 assists in defending the summer territory and guides (as best this can be done) the fledged eyasses into appropriate hunting areas. Will he, for example, drop captured prey so that the free-flying eyasses (fledglings) can then spot the prey and decide to hunt such prey for themselves? Right now, there is little doubt T2 will do all of this--and who knows what more.

T2 wins the Red-tailed Hawk Tiercel of the Year Award.

And The Franklin Institute, by the provision of both the nest cam and chat room, and the (formerly) essential provision of sustaining prey on the ledge, wins the Red-tailed Hawk Human Assistance and Appreciation Award.

--John Blakeman

Speaking of appreciation, Andria Ayer, Assistant Director of Annual Giving at The Franklin Institute, sent me this exciting information:

"I am pleased to share that we have received 125 gifts totaling $5,210 - the hawk fans are an exceptionally generous group and everyone at the Institute is deeply appreciative.

I also think it’s worth noting that gifts have been received from all across the country and even the world! As of today, people from 19 states (including Texas, Washington, California, Ohio, Oklahoma, Florida, North and South Carolina, Tennessee, Indiana) and Poland have made contributions for the hawks. The contributions range from “In memory of Dad/Tiercel/Papa Hawk” to “for continuing care and feeding of the eyasses” and “with thanks to The Franklin Institute for four years of sharing the hawkcam.” The emails and phone calls are always accompanied by stories of the amazing connections viewers have made with these hawks and fun stories of watching them over the years."

Here is the information previously posted about how to make a donation to the Franklin Institute:

"Please know that all contributions to the Institute’s Annual Fund in honor of the hawks, or in memory of the tiercel will be directed to the care and feeding of the hawks (as human intervention is deemed appropriate), maintenance of the hawkcam, and related activities and staff assistance. Any funds raised beyond the needs of the hawks will be channeled into ongoing science and technology education initiatives, which include environmental programs, online curriculum, community outreach, and much more.

To donate in support of the hawks, please visit this Annual Fund link and, when prompted, either write a note in the comment section regarding the intention of the gift, or select the in honor of/in memory of option. Donations can also be made by credit card over the phone by calling Andria Ayer at (215) 448-1339 or Daniel Chermak at (215) 448-1130, or by sending a check to The Franklin Institute, c/o Development Department, 222 North 20^th Street, Philadelphia, PA 19103. If you are sending a check, please be sure to note in the memo section that the gift is intended to support the hawks.

All gifts to the Institute in support of the hawks will be recognized in a special section of the Institute’s 2012 Annual Report. Please note if you would prefer your gift to remain anonymous."   -- Andria Ayer

Happy Mother's Day to the Franklin Institute formel

What a joy it was to salute the magnificent Franklin Institute formel on Mother's Day - definitely the front-runner for Hawk Mother of the Year.

       Kay Meng

      Kay Meng

She has done an amazing job of recovering from the loss of her mate - Dad - two weeks ago almost to the day.  Here she sat anxiously that Saturday morning waiting for him to return, with possibly the last greenery he brought to the nest surrounding the week-old eyasses.

As soon as the Franklin Institute started to drop food on the ledge, she figured out that this was the only way she could sustain herself and the baby hawks in the absence of Dad's formidable hunting skills.

Almost as soon as the food items (mice or white rats) are put through the window onto the ledge, she pounces towards them... 

      Scott Kemper

 ... and brings them efficiently back to the nest...

       Scott Kemper


... and feeds her eyasses.

       Kay Meng

How could anyone have predicted her miraculous acceptance of a new mate (T2) within a few days of Dad's disappearance? 

       Ari Rosenthal

And a mate who seems willing to make some huge adaptations and do his best to learn his role and responsibilities.

       Kay Meng

And two weeks after she lost the tiercel, her three fluffball eyasses have flourished and grown, and are now stretching their wings and showing off the beginnings of their powerful flight feathers.

      Scott Kemper

Her new mate, T2, has had to climb an extremely steep learning curve since he first arrived at the nest last Monday.  Normally, the tiercel initiates nest building in the fall and early winter, and will bring numerous sticks and twigs to the nest.  T2 is doing this well, but because it is May, the sticks and twigs are covered in leaves, and it seems to us that all he brings is greenery when food is needed.

Mom, however, seems happy to receive his gifts.

He is hunting and bringing prey back to the nest - usually small creatures like voles and sparrows.  His confusion with the speeded-up process of learning how to be a mated tiercel with a family - most of which he missed - shows in his tendency to remove food from the nest for his own eating.  He appears to be opportunistic, bringing in a vole, and racing out with a rat!  Cries of "Freeloader!" have been heard from outraged hawkaholics as he pulled this move several times in his first days on the nest.

This young hawk has landed in a kind of time-warp where he's supposed to do all the polite "getting to know you as my new mate" stuff and at the same time fast-forward past all the "we have one egg/we have two eggs/we have three eggs and now we're incubating."  He also missed the part where he brings her food on the nest while she's incubating.

He is much smaller and thinner than the formel and is probably several years younger.  It looks as if he has only ever hunted for himself, and it is taking a while for those instincts to be overridden by those of hunting for his new family.  But he is making progress, and although he still cannot seem to resist the urge to grab-and-go with the rat, he always reappears with it a few minutes later, though it is often missing some body parts when it is returned.

He is doing a fine job of feeding the eyasses under the formel's watchful eye.  He knows how to tear off small enough morsels...

 ... and then carefully reach forward...

...and feed it to the eyass.

John Blakeman made this assessment of T2:

"The twigs he's bringing to the nest are just the sorts of things usually brought in January and February, before eggs are laid. He's entered this whole process without going through the winter twigs-to-the-nest period; nor has he watched his mate sit and incubate in March and April, when he would then go into the serious hunting mode.

He's just a bit behind in the sequence of tiercel nesting behaviors. He's at least bringing voles to the nest, so he is fulfilling a good portion of his duties. I would hope that he will progress now to full hunting mode, giving up the stick thing. His taking away an uneaten or partially eaten prey means that he still doesn't have his duties (instinctual, but not fully developed) yet in place.

It's nonetheless remarkable that he's able and willing to do any of this.

And his provision of "mere" voles just indicates where he's hunting (in a meadow) and the lack of larger prey there. Voles can easily provide all the food Red-tails need, when provided in sufficient quantities.  Right now, it's probably good for the FI to continue set out rats or mice, as make-up prey for the entire family.

    --John Blakeman

We knew the formel's trust in him was complete when she allowed him to feed the eyasses by himself.  These images are from Mother's Day!  How appropriate that he seems to be giving Mom a break from nest duties.

T2 is such an enthusiastic eyass feeder that sometimes he doesn't seem to notice that his clients have started to keel over into their customary postprandial food coma, and he keeps trying to feed them.  Eventually, of course, he can't help but notice that no-one is awake...

... and off he goes.  When T2 leaves the nest...

        Kay Meng


... he can often be seen sitting close by, somewhere on the facade of the Franklin Institute.

        Ari Rosenthal

When Mom is away from the nest, she usually heads for her favorite tree across the expressway about 75 yards from the nest over on the Parkway.  

        Scott Kemper

She sits in the topmost branches where she can keep the nest in clear view.

        Scott Kemper

Once she relaxes, she will start to preen...

                                        Scott Kemper

... all the while watched from the nest by her eyasses who now are intensely curious about everything in their environment.

               Scott Kemper

The eyasses' rate of growth is simply astonishing.  When you see a bobblehead over the edge of the nest...

          Scott Kemper

... you don't realize how large the body beneath has become.

                           Scott Kemper

The eyasses can now stand up, and have started "wingercizing" - flapping their wings to strengthen the muscles that will soon be needed for flying.

        Scott Kemper

The flight feathers are erupting along the edges of their wings.

       Scott Kemper

        Kay Meng

They are starting to make grabs at the food instead of waiting to be fed.

         Kay Meng


If the Cute-O-Meter is still not in the red zone, these images should do the trick...

        Scott Kemper

        Kay Meng

How incredibly fortunate we are that this beautiful young tiercel has been accepted by the formel.

                   Ari Rosenthal

                     Kay Meng

On Mother's Day morning, as they sat side by side on a ledge at the Franklin Institute calmly watching the Race for The Cure roll beneath them...

       Karen McCunney


... it feels that the sadness of the past two weeks has been replaced by hope for the future of this pair of Red-tails and the three eyasses they are raising. 

Many thanks, as always, to the wonderful photographers who generously allow me to use their images that grace this post: Kay Meng, Scott Kemper, Ari Rosenthal and Karen McCunney.