Tuesday, June 03, 2008

John Blakeman on Pale Male and Lola's Eggs, The Three Fordham Eyasses, and Bullying for Better Male Behavior as a Factor for Bigger Females

Photographs of the Fordham nest by Christopher Lyons
Hopping and flapping is becoming the favorite behavior except of course for eating.

Look closely to the right, yes there's the third eyass popping her head up above the twigs.

The most mature eyass stalks and eyes the photographer.

One looks and one preens and then...

...something catches their interest acutely. Perhaps a parent and they hope there's food on the way?

With the announcement that NYC Audubon has arranged for egg retrieval at Pale Male and Lola's nest, and with high hope that a diploid test will be run, and that samples of DNA procured, a few words from John Blakeman on the matter--


It will be so helpful -- and now, so timely -- to retrieve the unhatched eggs at the 927 nest, those of Pale Male and Lola. With warm weather, it's getting late, and the eggs may begin to chemically degrade or even rot (bacterial degradation).

It would be so helpful to know if the eggs were fertile, if they had been the result of normal copulation. This would affirm Pale Male's fertility, and discount the explanation that he's now reproductively over the hill, unable to sire offspring.

Yes, Pale Male is getting up in years. He's older than most wild Red-tails. But none of his observed behaviors have diminished in any measure. He hunts with full alacrity, perches and flies with full speed, power, and duration, helps with nest refurbishment in a normal manner, and continues to copulate with Lola numerous times each day before eggs are laid. Behaviorally, he's still quite The Man.

But is he "shooting blanks," as it were? Only a proper analysis of Lola's eggs can now answer that ever more important question.

Eggs have been retrieved in the past. Unfortunately, as I understand it, they were analyzed only for certain pesticides, on the presumption that recent reproductive failures at 927 Fifth Ave had been chemically induced. No pesticides were discovered (not to be confused with the modern coagulant rodenticide poisonings that recently zapped the three Riverside eyasses).

If possible, two things need to be done with retrieved 927 eggs. They should be carefully dissected by someone familiar with egg development and embryonic or chick tissues and organs. Can any primordial or developed tissues be discovered in Lola's eggs? Let's hope so. (Well, let's really FIND OUT. We've been hoping now for a long time.)

Secondly, DNA samples from each egg should be retrieved and archived. DNA samples, from known, molted feathers from adults, and DNA from retrieved, unhatched eggs (or in the case of the Riverside eyasses, from the dead carcasses) should be gathered and genomically characterized. From a library of DNA samples from as many NYC-area Red-tails as possible over the next several years, the "relatededness" of all of these birds could be discerned.

Is there any significance to this, beyond the typical, warm attributions of "family" among the NYC hawks? Decidedly. Are the Red-tails now breeding in greater New York City all closely related, descended from Pale Male or a few other patriarchs (or matriarchs)? Or, have these birds drifted in from all over the East Coast, being essentially unrelated?

If they are closely related, there is the prospect of inbreeding-caused genetic and behavioral problems. The aberrant reproductive behaviors of the former Trump Parc pair, which has nested further into the urban hardscape canyons of typical Manhattan (apparently unsuccessfully this year), may be a result of this genetic relatedness. Personally, I'm not at all excited by the possibility that a good number of NYC or Manhattan Red-tails might be direct, recent descendants of Pale Male. For human monarchies, that sort of thing makes good stories and legends (if not good biology). For wildlife, genetic isolation is a long-term prescription for disaster.

So, the collection of DNA samples from NYC Red-tails would be an important scientific effort, providing some of the biggest and most complex parts of the urban Red-tail puzzle. Right now, we've got this jigsaw puzzle nicely laid out on the table. About three-quarters of the picture are pretty much filled in. We now know what the urban Red-tails hunt, what they feed to their eyasses, how many eggs they are able to produce, where the nests are, how they are built, and when most of these activities occur.

But we don't know if the birds are all related. That could tell us if the population is genetically isolated and open to inbreeding difficulties in coming generations.

There are a host of other unknowns that could be investigated, but they are too lengthy and detailed to be related here. Checking the cells of the 927 eggs, to see if chromosomally they are diploid, meaning that they were fertilized, would be a good start. Getting some DNA from the eggs would be a further step, allowing the first pieces of the genetic map of NYC Red-tails to be constructed.

--John Blakeman
(I'm hoping against hope that both a diploid test and samples for DNA testing will be possible this season. D. B.)

Pam Greenwood of GMU, in a former post weighed in with a theory for reverse sexual dimorphism which she derived from observations of Bald Eagles and now she's sent an example of the behavior in Eagles--

Hi Donna

Here are some observations from the Blackwater weblog bearing on the "female as bully" idea. The eagle father on that nest this year was a very poor provider and there was quite a bit of discussion about it. This was the source of my claim that female eagles have been seen to bully the male if he doesn't do his job.

Pam Greenwood


"Well, as many of our cam watchers know, we had previously been worried about the small amount of food that the father eagle had been bringing to the nest while the parents were incubating the eggs. Today the father eagle did not bring a meal to the nest, despite the fact that the mother and new chick were counting on him to do so. The mother eagle appeared to do most of the incubating — although it’s possible the father did perform that duty some of the time, because he has shown that he will sit on the nest with the eggs. But beyond that, he was not at the nest much.

The mother eagle fed our new chick some pieces from the leftover item in the nest (what we think was possibly a small mammal), but clearly the mother needs the father eagle to be the provider right now, and it’s still a mystery why the father is not hunting more. We could guess that the father is not healthy or has some kind of physical problem, but we did see him bring a fish to the nest not that long ago, and he’s obviously feeding himself, so we gather he is capable of hunting.

The main problem now is that the mother cannot do both the nest-sitting and the hunting, mainly because eaglets cannot control their own body temperatures for the first few weeks of life. So while the mother is capable of hunting, she would need the father to sit on the chick and egg while she is gone.

So the mother has a few options: 1) She can wait and hope the father starts hunting; 2) She can try to get the father to sit on the nest, and then go hunting herself; 3) She can try to use her bigger size and bully the father into doing more of his job. We do know from a story our ranger told me that during incubation a few weeks ago, he saw the mother eagle leave the Eagle Cam nest and go harass the father, who was perched at the Osprey Cam nest. The result was he returned to the Eagle Cam nest and began incubating.

Mother eagles harassing males into performing their nest duties is not uncommon. Canadian biologists saw a female eagle calling and calling to a male who would not return to the nest. Eventually she flew at him, and using her bigger size, almost knocked him off his perch. He then went back to the nest and took over incubation."

I have to admit, I like it as a possible contributing factor to large female raptors. Certain behaviors in raptors don't seem to be as chemically imprinted as one might suspect they would be after observing their smaller songbird counterparts who seem to be often more hard wired when it comes to nest behavior.
Donegal Browne

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