Friday, April 22, 2005

Blakeman on Feather Care -- And a hint for concerned readers about this year's nest outcome



Lincoln Karim sent me the picture above and asked:

What do you make of his tail feathers? First thing came to my mind was that he's brushing up against the concrete wall behind the nest. This theory only holds if he turns mostly counter-clockwise.
L.

I sent the photo to John Blakeman. He responded:

Marie,
The concerns for Pale Male's tail feather tips are understandable. The fact that they are reduced in length only on one side (the right) is, indeed, curious.
But perhaps the converse question, of why so little wear on the left side, is of equal interest. Many wild adults have much more wear, with even some broken shafts from time to time. Pale Male has kept himself in fine form.
It is getting late into the feathers' year, after a winter and early spring of much hunting , and in this year, a complete rebuild of the nest. This is rather normal feather wear. I have no concern whatsoever. Only the tips are worn, and only slightly so. This is rather normal, although feather wear can vary greatly from year to year, even with the same bird.
This may relate to the iron prongs of the nest support structure. I'd expect a new layer of branches to go over this year's when annual refurbishing begins again next January or February, tending to elevate the birds above the ironwork -- if that's the cause.
Sincerely,

John A. Blakeman


Dear Readers, I've enlarged some words in the preceding exchange between Lincoln and John Blakeman about feather wear. As we are filled with anxiety about this year's outcome -- there is still no feeding at the nest -- those words should fill us with hope about the future. If no success this year, then much hope for next year when the hawks will be building on top of an existing layer of twigs.[As, for the first time, in 1995] Yours, Marie

PS Meanwhile, we haven't completely given up hope at the Hawk Bench. But after today..

Tuesday, April 19, 2005

Blakeman answers Donna's Questions

Donna,

You asked for my comments on the Trump Parc nest, after an egg was reportedly seen rolling out of the nest on two different occasions. Apparently the birds resumed incubating after the loss of the two eggs. You asked, "What's up over there?

The peculiarities of NYC red-tail hawk nesting (and other) behaviors never cease. I've just never encountered a nest where eggs did or could roll out. That simply should never happen. Eggs often cool in poorly constructed nests, which are rather frequent in young, inexperienced pairs. But to have an actually egg role out of a nest belies some severe nest construction problems. It just shouldn't happen.

I don't know what could cause this other than inadequate construction by the adults. Might there be a local shortage of nesting materials? Perhaps, but if so, the nest shouldn't have been constructed in the first place. If the nest were poorly assembled, it should have fallen apart early on, before eggs appeared. More importantly, the sitting parents should have detected the nest's fragility and inserted some restorative twigs and sticks. Why didn't they? I don't know. Once again, weird, from a wild rural red-tail's standpoint.

If red-tails could talk, could you imagine the conversations being passed among successful adults out in the country side? "Hey Wilma, did you hear the one about that kid and his mate who tried to build a nest on some building down the Hudson in that big city? The eggs rolled out of it! Can you imagine? Stay away from the city. Who knows what will happen to a hawk that tries to live down there. The eggs rolled out of the nest! It's shameful. Are they related to anybody you know? Hope not."

Apparently, an egg remains. Otherwise, the pair would no longer sit. Let's see what, if anything else, happens.

On another subject, Donna, you asked if red-tails might not "imprint" to a particular nest type or location. You noted, quite accurately that eyasses imprint, or become psychologically attached, even fixed, on their parents, or whoever else feeds them. This can be an irretrievable problem when humans try to raise eyasses, as the little hawks quickly think humans are their parents. Things get very sticky when the eyasses start to fly and grab food from any nearby "parent," any human then see. But that's another story.

So no, I can't altogether discount a nest "imprinting" factor. Perhaps the eyasses do have a tendency to put their nests up on ledges two or three years later, when they start house (or nest-) keeping. Nonetheless, I really think remoteness and solitude, the absence of human and pet clamor and possible visitation by nest predators is most likely the reason the birds are way up on the side of New York City buildings. Notice that a number of hawks have first tried tree nests in Central Park, including Pale Male. I still think red-tails are predisposed toward tree venues, which they abandon after they individually learn that trees in Central Park seldom offer the peace, quiet, and perceived safety a motherly red-tail hen wishes for herself and her eggs and offspring.

Sincerely,

John A. Blakeman

Monday, April 18, 2005

Blakeman answers some previous questions

4/17/05

Marie,
Got some time this afternoon. I was to do a nice 50-acre prairie burn, but rain doused that idea, quite literally.
Mai Steward submitted some good questions. Here are my thoughts.
1. I've been wondering about all the digging / footwork that goes on in the nest, as noted by Donna Brown -- are the hawks just making the nest more comfortable for themselves (esp. Lola, since she spends so much time just sitting there), or is there another reason for this foot activity, perhaps connected with the incubation of the eggs?
Mai, Donna and some others have noted this. I don't know what it is. I don't recall my captive breeders doing any over-the-eggs-dance, and I don't recall seeing this in wild nests. But the birds do a lot of wiggling, rocking, and maneuvering when settling down. Perhaps this appears to be digging, from distant, lateral viewpoints. But it may also be a real digging motion. Perhaps this relates to the pigeon spikes below the nest. Perhaps the birds are repositioning lining materials as they feel the ends of the spikes below the nest. Nesting red-tails often reposition lining and even some feathers around the eggs in the nest. But I'll have to plead ignorance on this.
2. I've noticed how protective PM is of the nest site, it's really cute and touching -- probably this is deeply ingrained instinct -- and also how Lola seems to know, many minutes in advance, of PM's arrival, even when he's out of sight -- as reported by Donna Browne, Lola's head is up, she's alert, looking intently in the very direction from which PM soon swoops in .
Remember, red-tailed hawks are animals of vision, not smells, or even much of sounds. What they see is essential to their lives. And they have remarkable eyesight, as everyone knows. So yes, they are in constant visual contact, or at least they have a good perception of where the other mate is when out of site. Lola, when sitting on the nest, has a very good idea of what Pale Male is up to when he comes into sight. If he’s got a food morsel, she can see it from across the Park or way down the street. If PM comes back with nothing, she understands that he’s gliding in to give her a breather, a chance to stand up, defecate (“slice”), and even take off on wing for a time. (We human dads aren't nearly so instinctively understanding and accommodative of the similar needs of our wives have while tending to our children. We have some lessons to learn here.)

3. Regarding the ledge-nesting of not just PM, but also the younger pair on CPS, I thought this was the result (esp. in PM's case) of harassment by crows and blue jays -- that PM + mate had attempted several times to create nests in trees, but they were forced to give up because these birds made it impossible for them -- or am I mistaken? In fact, all the birds in CP live quite close together, compared to out in the wild -- Was this a factor in PM's retreat to 927?
This is an interesting, even plausible reason for the abandonment of initial tree nests inside the Park per se. But, I don't think so. Doubtless, red-tails can be harassed unmercifully by crows and jays, and they often just retreat to some distant perch when so pestered in non-breeding areas. But don't forget that should a red-tail elect to do so, it can grab a mobbing jay or crow right out of the sky.
We know from one or two very well done studies that most birds are able to detect the aggressive intentions of red-tailed hawks, especially as they relate to the hawk’s hunger. I've personally seen this with perched captive red-tails in my backyard, and occasionally with wild eyasses out on their first personal hunts in July. If a red-tail is hungry and on the hunt, many species of smaller birds can detect this from the hawk’s body stance. The hawk leans over and has an “I'm hunting” look. Humans can discern this after a bit of time. (This is a wonderful experience for me. As I travel down country roads and see red-tails perched, I can almost always read the bird’s mind set, as expressed by it’s posture. I can tell when it’s hunting, loafing, or watching nearby threats. It’s all body posture. Birds have learned this instinctively.) If the hawk is hungry, songbirds will mob the hawk, trying to drive it off. If it’s not hunting, the other birds pay no attention to it. as it presents no threat.
But here’s a remarkable story, one that my compatriot doing the two-year study of Ohio red-tails observed. It was noted that almost all red-tail nests in flat, Lake Plain northern and northwest Ohio had the remains of male red-winged blackbirds. Red-wings commonly nest in harems in hayfields and along ditches. A proud, testosterone-warped male (with the bright red epaulet wing feathers) stands guard over his several wives raising young in nests within the male’s territory. Now a red-tail can't possibly capture a free-flying, diligently observant red-winged blackbird. When being chased by a hawk, they fly too adroitly to be captured. We wondered for some time where and how so many red-tails were capturing so many red-wings, and why they were always just males, never a female.
The answer may relate to jay and crow harassment in Central Park tree nests. (Or, maybe it doesn't – but it’s good story, anyway.)
Here is what was observed. Red-tails are famous for “doing the rounds,” for punctually moving from one hunting perch to another while circulating around a hunting territory. At 10:30 AM a resident male could be seen sitting in a particular tree, peering out over the landscape for prey. Every day at about 10:40, the bird would then take off and fly a half mile to another, well-used hunting perch. After a time there, the bird would move on again. In watching this every day, we were able to put dots on maps signifying perches, along with arrival and departure times. The hawks are noted to be very methodical and punctual in covering the entire hunting territory, often several square miles. None of this was random wandering.
It was noted, however, that when moving from hunting perch to hunting perch, the hawks often passed over hay fields or stretches of roadside ditches with resident red-winged blackbird populations. And as mentioned above, the patriarch red-wing males could see that the hawk passing above was on the hunt. The red-wing flew up to the passing hawk on the first day, mobbing as it flew over. It was trying to protect its females and young in the nests below. Just as soon as the hawk passed out of the red-wing’s territory, the blackbird dropped back down to attend to its females.
But because the hawk flew over the red-wing area each day on its hunting rounds, the red-wing male (males being males), became ever more perturbed with the passing hawk. Each day, the mobbing red-wing would fly every closer to the passing red-tail. At first, the blackbird stayed 4 or 5 feet away in its pesterings. The next day, it got closer. Finally, on a final day, after being impossibly emboldened, the red-wing actually dropped down onto the red-tail’s back – a fatal mistake. At this point the hawk turned over and snatched the red-wing out of the air with instant ease.
This was seen several times, and we are absolutely certain that by flying repeatedly over the red-wing areas day after day, the red-tails were setting up the red-wings for an easy, effortless kill. They deliberately suckered the red-wing males in by slightly slowing their flight and dropping down to just 20 or 30 feet above the nests of the blackbird nests below each day. The red-wing males perceived, quite erroneously, that they were successfully driving off the marauding red-tail each time. But in fact, the red-tails were setting things up for an easy meal for their eyasses back at the nest. The hawks had to fly over the red-wing territories each day anyway while making their hunting circuits. It was an easy and smart thing to lure in the hapless, testosterone-polluted blackbird males. Smart hunters, our red-tails.
What might that have to do with blue jay and crow harassment around a tree nest in Central Park? I have no doubt that should a red-tail wish, it could easily reach up and grab a mobbing jay or crow, after luring it in. Red-tails can maneuver their legs and feet as quick as cat, and they have a very long reach. If a Central Park red-tail wanted to put an end to smaller-bird harassment, I think it could very quickly.
Well why, then, didn't that happen? Not sure. But jays and crows, as we know, are very intelligent. If one is lost to a scheming hawk, the others will have the good sense to retreat and stay way. Obviously, the Central Park red-tails didn't grab many crows (or any at all). As I asked before, were the hawks overly occupied and concerned with the large numbers of ubiquitous Central Park animals that seemed to pose a continuing threat to nests and eggs? Those, of course, may have been both humans and dogs, species the hawk knows that it can't fend off by a quick punch of an extended leg.
Your observation that bird populations in Central Park are compressed and compacted is astute. That may be the real answer. Collectively, there may be too many birds, mammals, and other environmental disruptions too close to the nest to allow calm and peaceful nest building and incubation. The confluence of other species of birds, wild mammals, multitudes of people, dogs, bicycles, and whatever else frequents Central Park, is too great to allow normal red-tail nesting in trees just above this persistent clamor. I continue to marvel at the disruptions that Central Park red-tails abide; ones that my wild rural hawks wouldn't at all.
My wild, rural red-tails might ask a Central Park hawk, “Are you nuts? How can any self-respecting red-tail live here with all of this?”
4. If the younger hawks in CP are PM offspring, are their mates, as well? (Which would probably not be good for their reproduction, as JB has mentioned) Or is it possible that other female hawks were somehow attracted to these males, the way PM's mates have just shown up?
Mai, you got this question quite right. If all or the majority of CP red-tails are Pale Male progeny, we are watching a chapter near the end of the book, which will be a tragedy, expressed in the final chapters with accounts of failed nests, genetically deficient eyasses, and the eventual loss of the formerly productive, aged-out parents. The genetic difficulties of inbreeding are surely a problem for red-tails as much as any other species. If all the red-tails are related, even with different mothers, the inbreeding loads on the population will eventually overwhelm it. Unless some unrelated outsiders elect to come in to broaden the genetic base (or have in the past), we would be watching only a curious, even aberrant natural history diversion, not a continuing red-tail occupation of Central Park.
Therefore, I'd like to think that at least the mates of the 927 progeny are unrelated. Once again, everyone can see the unparalleled value of banding data. As before, we are guessing. Until we can get some reliable ID info, we'll just have to hope and guess.
There may be so many prey species in Central Park, so many easily captured pigeons, squirrels, and rats, that parents are neither motivated (by hunger or shortage of food specimens) to drive out the new eyasses each summer, nor to drive out nearby new nesting residents. There may be too much food around, allowing offspring to hang around home and never go off to college or work (to a new, distant territory). If all the hawks are related, this is going to genetically complicate matters rather lethally in a generation or two.
Lots more to ponder. Super observations and questions. As always, wish I had more definitive answers. But those of us who initially study wild species in wild habitats (even in Central Park) are always frustrated by the inherent murkiness of our understandings. None of this is physics, where hard numbers quantify the truth. It’s all a bit “soft,” but wondrously so. Everyone, keep watching and thinking,.
Sincerely,

John A. Blakeman

Blakeman on the Kestrel's Demise

I sent Steve Watson's letter about the demise of his nesting male kestrel Dash to John Blakeman, just as Steve had suggested I do. Below is his realistic, not unexpected response. Then after that I am including Steve's letter I received last night. He had read Blakeman's response. He too, as you will see, is realistic. But Hope is the thing with feathers.



Marie,
The loss of the Pasadena kestrel tiercel is unfortunate, albeit by a natural element, another avian predator, a hawk even.. The death of the little falcon is gruesome enough, but things are not likely to go well for the surviving mate and the developing eggs the pair was incubating. It is highly unlikely that the female will be able both hunt to feed herself and also remain on the eggs to keep them warm enough to stay alive. The only hope is that a large, easily accessible prey population (such as numerous grasshoppers or mice) is right outside the nestbox. Given that this is on institutional grounds, I doubt that the female will be able poke her head out of the nestbox, find a food animal to capture, quickly drop down on it, consume the prey, and then promptly resume her requisite incubation duties. The poor female has too many required tasks to accomplish. Without the supporting male, things don't augur well for the kestrel family.
And even if the eggs were to hatch right away, the single falcon would be hard-pressed to find sufficient food to raise the eyasses.
Almost surely the incubating female will be driven by hunger to leave incubation and head out for food. Her chances of consistently finding, capturing, and consuming it in 10- to 20 minutes, time after time, probably three or four times a day until the eggs hatch, and additionally until the eyasses are 6 to 10 days old, when they can stay warm by themselves, are very bad.
All of us need to confront the cold, natural reality that what happens to the prey of our beloved red-tails and kestrels also happens, from time to time, with our hawks as well. Unlike the plot of a novel or movie, we don't get to presume that nature's story will always turn out as we prefer. Accept the fact that nature is it not always as we wish it. Nature (to personify it -- an error) has no concerns about individuals, only populations. The kestrel population of Southern California is probably fine. Our observed family is now in disarray, with the eggs soon to die, leaving the mother a widow and alone. Cruel and disheartening, but coldly authentic.
If the mother kestrel escapes any future attacks of the sharp-shinned hawk and survives (very likely), she will retreat to a normal day to day life of personal hunting, to eat and survive. It's almost surely too late for her to find another male who could copulate and sire young this late in the season. A reproductive year has been lost. Things will have to resume next year, with a new male.
This isn't the first time this has happened. Things will work out, but again, only from the perspective of an entire kestrel population. This pair is no more. The remaining female could be killed, or she could survive, mate with an new male next year, copulate, and bring off a new brood of four kestrel eyasses. But that's next year's story. For now, we can only contemplate.
I recommend that the nest box not be cleaned out. Remove only the dead eggs. Leave the lining material in there Kestrels prefer older, settled lining material. Next November, you might want to take a peek inside and see that enough wood chips, excelsior, or other material remains. Merely add enough to make up the difference of what was compressed or lost. Don't take it all out. Do that in the second or third year after young have grown up in there, cleaning out the mutes and old food debris. Sadly, there won't be any of that this year.
Does everyone understand that life in nature is cold, cruel, harsh, even unforgiving for all? This episode authenticates it. Be careful about inappropriate, even romantic explanations for what has occurred. It's real nature, not always as we'd like.
I thank Steve for arranging for the camera. Do it again next year, when we might be able to see a kestrel family being raised.
Sincerely,

John A. Blakeman