Other Peregrine Projects > USA Peregrines
OH / Cleveland - Terminal Tower - 2009-15
carly:
Part Deux - as I exceeded the post limit :-\
Whatever the scenario, the absence of eggshell remains is curious. In 2007, the broken eggshell could be seen in the nest box for days after it broke. Peregrines will sometimes consume the eggshell remains after the chicks hatch. Possibly for the seven minutes that SW was in the head tuck posture she was consuming the shell fragments right after the egg broke. It is odd that her abdominal feathers did not appear to be soiled. In 2007 SW’s belly feathers were wet from the liquid contents of the egg. Scott Wright’s photos from Tuesday do show what appears to be albumen from the broken egg adhering to two of the surviving eggs.
Though it is a disappointment that S/W will not have another 4 chick season, this is precisely why Peregrine Falcons have clutches of 3 or 4 eggs. This annual productivity compensates for the inevitable losses that occur with eggs, chicks, fledglings and juveniles. Clutch size is a balance between how many young the adults can successfully parent given available internal and environmental resources and the need to produce adequate numbers to sustain the population.
Will there be some evidence at the nest that might indicate what really happened to the mysterious egg? By now it is doubtful. So we might never know the real story.
carly:
From the website, the official explanation of the exploding ( :P ) egg!
[b]The Case of the Missing Egg[/b]
A mystery unfolded on Monday, 5/29/2010 at the nest on the terminal tower’s 12th floor. 4 eggs in a tight clutch at 12:05 pm. One minute later SW moves over the eggs in an awkward pose as if she is turning the eggs. Ranger shows up at the right side of the nest platform but SW stays in the same pose for the next seven minutes. She finally settles down over the eggs. At the next shift change when the eggs are visible at 3:42 pm, there are only three eggs and no sign of the fourth, no eggshells, nada. What gives?
First, it is not without precedent for SW to lose an egg. It happened in 2007. She laid her first egg, then her second. A day later the second egg broke. She followed with a third and fourth egg. The first egg was covered with the egg whites and yolk from the broken second egg and she avoided incubating the egg for a time. Only the third and fourth eggs hatched that year giving us Erie and Treasure. Erie died at the Terminal later that summer. Treasure is part of a pair at Port Colbourne in Ontario.
So what might have caused the egg to break? Possibly disturbance at the nest site might have caused either S/W or Ranger to accidentally break the egg. We know Peregrines to be very careful and effective parents. However, this is Ranger’s first experience as an incubating adult and he could have been clumsy when attending the eggs. That being said, there is no evidence from the Falconcam archives at the time to suggest that anything was amiss with SW or Ranger. Quite the contrary, everything appeared normal.
Another possibility is that there was an inherent structural deformity in the egg. The formation of the egg in the oviduct of the female is an extremely complicated and resource intensive process. All of the ingredients needed to cook up one new peregrine falcon chick have to be assembled and neatly packaged in a supremely well-designed calcium carbonate container. And this packaging is accomplished in roughly 24 hours. Disturbance to the female at this time or internal challenges, such as pesticides, disease, poor quality diet, or age could compromise the process of forming the shell. The resulting egg lacks the necessary structural integrity and collapses under the weight of the female as she attempts to incubate.
Do any of these attributes apply to S/W? Disease – no, she seems to be very fit and active. Diet - no, she is dining on the finest selection of pigeons, songbirds, woodcock and other birds that a Peregrine Falcon could hope for.
Pesticides or other environmental contaminants are always a possibility with Peregrines. After all it was DDT and other organochlorine pesticides that endangered Peregrine Falcons in the first place. Though DDT was banned over 30 years ago, it is still present in the environment although not at levels that threaten Peregrines. Other toxins like PCBs are a constant threat. New threats are cropping up. For example, polybrominated diphenyl ethers (PBDE), chemicals widely used as flame retardants, have been identified in Peregrine Falcon eggs in Sweden, Greenland and elsewhere, far from the original source or use of the chemical. What effect these contaminants might have on Peregrines is not well understood.
In S/W’s case however, there is nothing in her past history to suggest any difficulty in producing healthy eggs. Quite the contrary, she has been downright prolific.
That leaves age. SW is 12 years old. Falconers that propagate Peregrines in captivity often report that productivity dramatically drops by the 14th year and they usually retire their birds from breeding at that time. The Peregrine Falcons on display at the Cleveland Museum of Natural History, Lou and Jean, were obtained from a breeder who retired them for just this reason. SW is creeping up on that age where you might expect to see some egg failure.
Or in the end, perhaps some physical disturbance, passing trauma or environmental stress occurred just before the laying of that egg that compromised the formation of its eggshell. It was simply a ‘bad egg.’ The egg would not have exploded as some have speculated. It would have simply collapsed.
The Peregrine Chick:
--- Quote from: carly on March 31, 2010, 04:52 ---One of SW's eggs may have exploded - they said it looked blue - so now she has three?! This happened to her before apparently. What causes that TPC? She's around 12 I believe, would age be a factor or does this type of thing just happen sometimes?
--- End quote ---
As amazing a peregrines are, explosive eggs are not one of their many talents. Looking at the snow in the box, it may be that there was already a flaw with the egg and the cold made it freeze and break ... she or he might have rolled it out knowing there was a problem and ... and ... and ... that's the best I can come up with. Or I guess the egg could have broken and they broke it up, might that not look like an explosion? All just wild guesses on my part Carly - I will be very interested to hear what the Cleveland folks say ...
... in case we get exploding eggs too ;)
carly:
One of SW's eggs may have exploded - they said it looked blue - so now she has three?! This happened to her before apparently. What causes that TPC? She's around 12 I believe, would age be a factor or does this type of thing just happen sometimes?
Alison:
Sw laid her fourth egg this morning. Since she and Ranger are incubating in the snow, I haven't had a chance to see the eggs.
Here is Ranger incubating; he must be a little smaller than SW, since he does not fill the circle:
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