Wednesday, March 21, 2012

More on Egg #3 and will there be a fourth egg?

Tuesday was the day that our regular-as-clockwork formel was due to lay her third egg.  As the morning fog lifted over the city, she was sitting comfortably on her two eggs.

Every so often she stood up and stretched, allowing the camera viewers to do a quick count, but only two eggs each time.

At around 10:00 AM there was a changing of the guard and the tiercel settled in on the eggs.

He does not have the staying power of the formel, and soon got restless and started to preen.

He stood up, climbed to the front of the nest and appeared to be looking for his mate.

She was nowhere in sight, so he stepped back into the nest bowl and rolled the eggs

Finally the formel returned, settled back onto the eggs...

... and now seemed ready to lay that third egg.

Right around 11:30 AM, she appeared to rise up a little, looked tense and uncomfortable, and over the course of the next few minutes looked as if she might be laying her egg.

At this point, the camera watchers were in a frenzy waiting for her to move to the side a little to see if there were indeed a third egg.  But she sat right back down, and there followed a most frustrating hour when she would stand, stretch and move, but never enough to allow a clear confirmation of the third egg.

We needed dad to fly back in with food or an offer to spell her on the eggs, and finally he did.  She stood up and slowly moved, and tantalizingly the eggs came into view... one... two ...

... and then the glorious moment...THREE!

Mom wasted no time and was outta there after her arduous morning, leaving dad to inspect the latest addition to his family...

... and then get them covered up.

The formel eventually returned, ready to resume her nesting responsibilities, but the tiercel was not about to give up his spot.

He stolidly sat there as if he did not notice her looming over him!

Finally, he got up and we saw those gorgeous eggs again.

He took off, and left her gazing down at the eggs, perhaps with her three years' previous experience realizing that she was now about to settle in for the long haul of incubation.

She moved down to cover them up...

... and this final view of her early this afternoon is almost a mirror image of where she was first thing this morning, but now with three eggs safely underneath her.

There has been much speculation from Franklin Institute hawk fans about whether there could be a fourth egg, given this pair's experience and the incredibly mild winter.

Here's John Blakeman's take on that question:

The possibility of a fourth egg, at either The Franklin Institute or the New York University nests, would have been entirely dismissed by me, until last year. An experienced formel nesting at Fordham University in New York, incongruously laid, hatched, and fledged four progeny last spring. I was astonished.
Here are the cogent factors.
Much of the literature on red-tails states, with authentication, that this species can produce between one and five eggs and fledglings. Those of us who study red-tails in the Midwest and East always swallow hard when reading this datum. None of us has ever seen more than three eggs or eyasses in the wild nests we study, and we understand exactly why.
Egg production, along with successful eyass fledging, depends critically upon ample food - abundant prey animals to kill and eat. The records of four and five eggs and eyasses are primarily from the West, where the prey situation is very different from the East, South, and Midwest. In the Rockies and more western areas of the continent, there are a number of ground squirrel species that are extremely abundant in the first half of the year. These are easily captured by red-tails, allowing for maximum egg and eyass production.
Here, in the East and Midwest, the red-tails have no ground squirrels to sustain high reproductive rates. Our rural hawks mostly depend on the gerbil-sized meadow vole, Microtus pennsylvanicus. There are ample, but not abundant numbers of these. Consequently, our wild red-tails most commonly produce just one or two eyasses; occasionally three, in prime meadow habitat areas in years when the vole populations are at a cyclical high (about every 4 to 7 years).
But an Eastern nest with four eyasses? Not possible when parents depend upon voles as the prime prey species.
But in New York and Philadelphia, the red-tails that have learned to nest in cities that no longer depend upon voles. Manhattan simply doesn't have any, and only a very few  (if any) are available to the Franklin Institute hawks in the more open, grassy meadow areas within a mile of that nest.
Instead, these urban red-tails have learned to exploit new prey species, primarily the urban rat and pigeon. Yes, a moderate number of tree squirrels are taken, but the prime prey species are rats and pigeons, with rats predominating.
And that's what happened at Fordham last spring. The haggards simply loaded up on abundant rats in the area and the formel was able to produce a whopping four eggs. Subsequently, and equally remarkable, the parents were able to find and kill enough rats to keep all four eyasses in good growing health, allowing them to fledge - a remarkable achievement, afforded only because of the abundance of rats in the area.
So, yes, four eggs and eyasses are possible, but only under the most ideal conditions. First, the parents must be accomplished, experienced hawks. They can't be making any hunting mistakes while learning to provide the requisite resources for four eggs or eyasses. Secondly, the required resources - the rats in this case - simply must be open, visible, and captured. Clearly, all of this aligned at Fordham last year. But all and all, that was an anomaly. I wouldn't expect it to recur.
And I would hope that it wouldn't. Although four eyasses fledged at Fordham and could be seen parked around the area in early summer, their fates, although successfully fledged, were diminished by competition for food, especially in the last half of the summer. Lots of eyasses are not always best. All four may have starved in late summer.
Such is the fate of Western red-tails, where abundant ground squirrels produce giant broods. All is well for them until mid summer, when the vegetation in those arid regions goes dry and dormant. The ground squirrels then go into estivation  or summer hibernation. They crawl into burrows, curl up, go to sleep, and wait for cooler, moister conditions in autumn.
But this leaves large populations of young red-tails without ample prey to capture. The vast majority of the young hawks simply starve to death in the last half of summer. A few learn to hunt and kill voles (as in the East), and eke out a meager existence. After a year of this, those become accomplished hunters who can survive the seasonal loss of easy prey. But the vast majority of young red-tails simply starve. Life is tough for them, once off the nest.
So let's not wish for four eggs or eyasses at the Franklin Institute or at New York University. Two or three will be fine.
It's a spectacle in any regard, and we are so blessed to observe the hawks at both of these fine institutions.
And now that we know a bit more about their biology, their stories are even more intriguing.
--John Blakeman

Tuesday, March 20, 2012

Egg #3 is here!

Right on schedule at about 11:30 AM today (Tuesday)

More to follow later!

Waiting for Egg #3

Following the excitement of the second egg's arrival on Saturday, the formel appeared more tired and lethargic than on Wednesday with the first egg, when she more or less bounced in, laid the egg, and headed out.

She spent most of this weekend sitting on her eggs,

... occasionally getting up to turn them,

... and settling back down again.

I checked in with John Blakeman about the difference in her behavior and he commented:

"Her lethargy with the second egg is to be expected. Producing the first egg wasn't overly stressful, as she had full, yet-untapped resources to accomplish this, but the second egg came from reduced protein, calcium, and fat reserves.  She loses a lot of serum-mobilized fats, proteins, and some carbohydrates, along with an egg-full of plain water in the production of each of those first two eggs. Producing a third egg will be even more stressful, both physiologically and psychologically. The restraining results of this last "eggnancy" should be apparent. 

But she will be well. She's done this all before, so successfully. She's being well provided for by the tiercel. She will recover in a week's feeding and rest in the first full week of real incubation. Right now, she's not sitting tightly. She hasn't begun full, coordinated, irrevocable incubation. That will commence with the third egg."
--John Blakeman

But the formel does get up to stretch and spend some time away from the nest.  Sometimes, the eggs are left on their own for several minutes, which is not a problem as they can be left uncovered for up to 20 minutes or more.

The tiercel also loves to take his turn on the eggs.

It can be quite difficult to tell the difference between mom and dad when they are on the nest. Here are pictures of each bird sitting in an almost identical spot on the nest



At night, however, it is the formel who settles onto the nest and stays till dawn.

It perhaps seems unusual that the tiercel is so involved in sitting on the eggs in these early days while we await the arrival of the third egg.  Last year, John Blakeman shared some fascinating insight into the psychology of the hawks at this crucial time of egg laying:

"The tiercel's lengthy sitting upon the eggs (but it's not incubating yet at this early stage with another egg yet to come) is of no concern. Neither bird is yet in full incubation mode, especially the female. She almost surely has a third egg growing and descending her fallopian tube. Producing a third egg is particularly demanding, both physiologically and psychologically. 
Frankly, she's just in no mood to be sitting around on the nest on eggs. It may be far more comfortable to be standing, to allow gravity to assist in the flow of the new, last egg down the fallopian tube. She's eager to get that last egg formed and laid. When that happens, when she's relieved of the stress of egg formation, everything will change. Incubation will begin in earnest, with a profound compulsion by the formel to sit tightly and convey lots of body heat to the eggs across her naked brood patch under the feathers of her belly.
The tiercel, like fathers everywhere, just scratches his head trying to figure out the anomalous behaviors of his "eggnant" mate. Dutifully, he sits over the eggs and protects them. He'll be relieved when he can head off each morning to hunt for both his mate and himself. He really wants to be out there hunting and killing things for his mate. And his mate will have a tremendous compulsion to stay on the nest and begin another year incubating eggs and raising eyasses."
--John Blakeman

But for today, as we wait hopefully for a third egg, both hawks took their turn on the nest.  Here's dad...

... and here's mom.  Her wings often hang a little lower along her body, revealing that distinctive white line down the middle of her tail, more noticeable than dad's.

 Here is a sequence from today of her standing up to stretch a little...

... then preen her feathers.

Suddenly, there was a headless hawk as she reached way underneath herself to start rolling the eggs.

 As she rotated the eggs, she moved around them...

... until she had them where she wanted them,

... and then settled back down,

 ... looking out on the blazing March sun we enjoyed today in Philadelphia.

If all goes to the schedule - as it has for the past three years - the third egg should arrive on Tuesday, sometime in the middle of the day.

Saturday, March 17, 2012

Egg #2 is here! UPDATED

On a gorgeous sunny Saturday morning, egg #2 arrived at about 10:00 AM.  We have still not seen more than a glimpse, but Joe Debold managed to get this quick screen capture.

Stay tuned for more news and pictures!


At 11:20 AM the formel finally stood up and left the nest and we finally had a good view of both eggs.

Friday, March 16, 2012

More about Egg #1

Two days ago on Tuesday, it seemed that this beautifully constructed nest would never house eggs because the tiercel insisted on bringing an endless supply of paper, plastic and unidentifiable trash to line the nest bowl.  No matter how many times the formel cleaned house...

... back he would come with yet another load, poking and fussing it into place.

Then he would step to the front of the nest and look out as if to locate his mate in a nearby tree and say, "Well, how about THAT piece I just brought in!"

On the rare occasions that she flew in, the formel spent hardly more than 30 seconds on the nest.  Even when dad left her a tasty mouse morsel, she would grab it and go find a nice smooth, neat monument on which to eat her snack instead of that trash strewn nest.  Hawk watchers started to wonder how and when the eggs would ever get laid.

And on Wednesday, the tide of trash rose higher.....

... and higher in the nest.

Yesterday (Wednesday) was windy, and some of it blew away. By mid-morning, the formel was on the nest...

...and finally seemed more interested in staying there for a while.

Then she settled deep into the nest bowl.

We don't know for sure when she laid the egg, but when she stood up and left the nest around 1:00 PM, there it was, nestled on the remaining piece of plastic she deemed worthy enough for her egg!

When she returned a few minutes later, the plastic had shifted slightly over the egg...

... and when dad showed up, he immediately moved into action, twitching the plastic fully over the egg,

... and then settled himself into the nest bowl.

When the formel returned, it took a couple of minutes of her pointedly staring at him...

... before he got the hint...

... to let her move back to her egg.

He left to rustle up a tasty rodent, and she decided it was time to start shifting that pesky plastic.

She moved it away from the egg and out of the nest bowl.

It stayed on the edge of the nest for a while

... but within the hour it was gone, leaving the nest finally looking a more normal environment for eggs, though there was still quite a bit of paper lining the nest bowl.

This morning (Thursday) dad was crouched over the egg along with a piece of newspaper...

... while his mate was out hunting - successfully, as it turned out.  This is a family that definitely shares the household responsibilities!

When she moved down into the nest bowl, he adroitely shuffled the paper away from the egg as he shifted out of her way.

However, this piece of paper caught her eye (how could she miss it?)

... and she clearly wanted it back in the nest bowl.

Over the next few minutes, she tugged and tore at it, getting it just where she wanted it around the egg.

She shredded off some strips and tucked them down.

And then pushed away the larger pieces.

She kept starting to sit back down on the egg...

... then standing up.

More paper pushing...

And then after all that - poof - she was gone.

But within literally 10 seconds dad zoomed in to take his turn on the egg. He LOVES everything about this nest and taking care of the egg.

It is likely that egg #2 will show up sometime on Friday.  Eggciting times to be sure!