Bob:
Catgirl, thanks for that interesting report. That would certainly be consistent with my hypothesis, and it might not be just pigeons that are in short supply. For what it's worth, John Blakeman says pigeons make up a substantial part of an urban hawk's diet because there are so many of them that there are bound to be plenty in the city that are less adept at escaping the hawks. Rock doves (actually pigeons in a rural setting) are apparently much harder to capture because they've learned about predation by hawks, whereas their city kin, who have only encountered hawks relatively recently, are naive or unskilled at dodging raptors.
Sallyis:
8:11 a.m. Jay still on eggs. Good morning folks! I turned on to see eggs alone in the nest, then Jay came in so I relaxed and caught up! Observer, Weeyin, I see you are the early ones again today! Bob, thanks for the commentary and excellent videos, as usual! Your hypothesis seems plausible to me, although they could also be being distracted by intruders which would disrupt their routine and perhaps tire Jay out from chasing them off. I think the prey he brought was perhaps a starling, it seemed to be blackish with those iridescent feathers and no tail. I saw birdy legs when Jay first landed on the bar with with it. Poor Jay did what he always does when Kay returned--he left, not know she would leave with the prey I guess, and obviously she didn't know the prey was there at first! I just hope the same incident doesn't occur today with falling temperatures.
As a point of reference, at the rehab where I volunteer we feed our rehabbing red tails about 100-150 grams per day, depending on the bird's size and needs, and our resident education RT's maintain weight on about 100 grams per day. 125 grams is about 1/2 of a medium-sized rat that you might see at a pet store minus the entrails, 1/2 - 1 quail depending on size (the quail we use are about the size of a pigeon or slightly smaller, I think), or 3-4 mice, and the mice we use are about the same size as the wild mice I have caught in my garage! I have no idea what the food requirements are of a wild red tail, but they are certainly higher than that of a captive bird which does not have to expend energy to survive and hunt.Also, when Jay rolled the eggs a little while ago around 8:00 I think, I got to get a good look at that process. He rolled the first one into the second one so they both turned nearly all the way over (I watched the spots on the first egg move) and though they appeared to roll right back where they came from, when the first egg stopped it was definitely in a much different position than it had been before, according to the position of its spots.8:17 Jays rolls eggs and resettles facing 12:30. 8:32 Jay still on the eggs. Hope Kay comes back having eaten well!EDIT: For those of you who are totally freaked out about the food, we have freezers full of frozen rats, mice and quail that we defrost and cut into portions-I don't kill live animals to chop up for them! AHH!!!
Catgirl:
Taking a quick look at posts and looking at time - was just by the nesting area. At 11:49 I could see a hawk circling off to the south of the nest. I relocated to that area but could not find any sign of any hawk. I guess Kay is enjoying her day out - cold front just came through, not sure if there
will be any rain but temp is dropping, some good gusty winds. Did not see a single pigeon in the immediate area today. Edit addition: but I always see squirrels and the smaller birds at the neighborhood smorgasbord. Just fewer and fewer pigeons over the last few days. I hope to have a chance to go look again later today.
To be continued...
Bob
=
And from John Blakeman--
Bob,
I couldn't find anything here I would disagree with. All pretty astute observations and comments.
The pigeon factor may be big. No pigeon should ever be caught by a red-tail. The hawks are too slow, and the pigeons too fast. Now New York pigeons are a thing apart, as it New York City itself (and wonderfully, of course). There, the pigeons are often on the ground eating tossed grain, where they can be plucked off by a strafing red-tail zipping unseen around a building or bush.
I'm betting that was happening also in Tulsa last season. But all of the dumb, unobservant (read that as usually young, inexperienced) pigeons got taken. The older, observant adults decided to vacate the area this season, accounting for the reduced numbers of seen pigeons in the area.
And red-tails like squirrel flesh, but in rural and wild areas these tree rodents are very, very hard to capture. The wild squirrels have been selected for avoidance of hawk predation. Dumb city squirrels haven't been, and they can be easily taken, especially when the squirrels are on the ground and can't zip around behind a branch when a hawk approaches at speed.
But they, too, will learn the ways of predating hawks and will become much harder for them to capture. That's exactly why the preferred prey of red-tails across the continent is are voles or other small, mouse-like rodents who have no way of escaping capture. Those may be harder to find at the Tulsa nest site.
In summary, the prey animals at the Tulsa site are surely a lot more wary and discerning. The dumb pigeons and squirrels have all been reduced to hawk flesh. The survivors have their honed wits about them, making life a bit more difficult for the resident hawks. Life is not so easy anymore, it seems. The easy pickings are gone. Next year, there may be only one or two eggs in the nest, a common response to the reduced availability to prey.
--John Blakeman
From me--D.B.
The Cornell Lab of Ornithology not only has many experts on native birds, they also have an expert on pigeons. The Lab also runs Pigeon Watch, a program in which urbanites, often young people, take field notes on their local pigeon flocks. When I was running the Hell's Kitchen Bird Park, we too participated in the program, and we found in New York City, and I understand in other urban areas as well, pigeon flocks are rather firmly ensconced in an about two block area.
If there are areas to nest, the most important factor in keeping a stable flock size, and a steady food supply, even when there are resident hawks
the pigeons will stay within the boundaries of their "home" area.
I have seen numerous examples in which nearly every single day, when the pigeons flock together waiting for someone who feeds them, or for a carriage horse to spill his oats, or the pigeons have found some sort of windfall, that the resident hawk glides in and grabs one of the their number. Day, after day, after day.
Yes, the more experienced pigeons are looking out for the hawks, but the hawks are also expanding their bag of hunting techniques. The hawks get better at hunting the pigeons, and the pigeons get better at watching out for the hawks.
Pigeons also breed year round though more slowly in cold weather. In New York City the slow months are November, December, January, and February in the less desirable nest sites. I have seen successful nests in all those months in better more protected sites on buildings. Particularly when there is a regular food source.
There is usually a new crop of young pigeons by mid to late March. I would have expected nearly the same schedule in Tulsa. Has something disrupted the usual pigeon breeding schedule?
According to an earlier report from Catgirl, the bird feeders in the area are still going strong so that isn't the problem in the sudden dearth of pigeons.
What about nesting areas?
Has there been any major demolition of older decorative buildings, buildings with terraces, or a building netted over, in the area? In other words, was a major nesting area destroyed?
Has there been an influx of Starlings? They steal pigeon nesting areas and are far harder for hawks to catch. Beyond being lower calorie and audibly crunchier if they are caught.
By the way, there has been some major bad weather lately. Actually bad weather can sometimes be a windfall for hawks. Many fledgling pigeons can be blown into buildings or otherwise injured making them extremely easy to pick off. They are the proverbial "sitting ducks" for hawks.
Also hawks are not above eating recently dead prey which they did not make "recently dead". Some Red-tails will raid pigeon nests of chicks.
But we haven't seen any pigeons being brought to the nest. Jay couldn't find or catch pigeons, which he was perfectly capable of doing last season, yet this season he was reduced to bringing nesting materials to a ravenous and extremely unhappy Kay.
Now to Kay, and her 45 minute to 4 hour breaks and soccer ball crop. That crop was not filled with rodents. That crop was likely full of pigeon.
I asked the Tulsa Hawkwatchers about whether Jay was bringing food? And if he was, what it was? They kindly filled me in, and there was a startling lack of observations of his bringing food at all regularly and when it did come it seemed minuscule. And she was crying all the time with a mostly flat crop.
Kay started taking somewhat longer breaks, and would come back with a slightly rounded crop and still cry. I know this is anthropomorphic but Kay was "beside herself" about something. And she was hungry a lot of the time. I could tell from watching Bob McCargar's videos.
Was her woe, the lack of prey in the immediate area? Did she know what that might eventually mean? Was she trying to tell Jay, that he would have to give up guarding the territory so closely and go farther afield for food? At times she actually looked like she was attempting to chase him away, ie. go further, find prey.
Finally ravenous, being bigger, just having laid eggs, and needing calories to keep herself warm in inclement weather, (She sat in an open platform, in high wind, being covered with snow, while sitting the eggs. It appears that she had to go far afield herself to find enough food to keep from starving. Hence the longer breaks to possibly find pigeons , and returning with a gorged crop.
That is my hypothesis anyway at the moment. Subject to change when new information arrives.
And a last note, as there has been what seems to be a sudden severe drop in the pigeon population according to the watchers, and if there have been no big disruptions in the pigeon food supply or nesting areas, might I suggest the two biggest reasons for sudden drops in pigeon populations in NYC as a possibility?
The two causes of sudden catastrophic pigeon population collapse in NYC are from poison and from netting/trapping. It might behoove those on the ground in Tulsa to try and find out if either of those two things have been going on in the neighborhood.
Usually though, with poisoning, there will be pigeons lying around dead which can and likely would poison a very hungy hawk who couldn't afford to be choosy as she had eggs to sit and couldn't be gone from the nest long.
Is it possible that someone is netting or trapping pigeons in that area?With netting and trapping, large numbers of birds just flat disappear in the blink of an eye.
How is netting done? Someone arrives with a panel truck or pick up with a cap, they lay a large net on the sidewalk or in an open area at a time not many people might be around and then dump rice or bird seed on the net area. The pigeons arrive to feed, more pigeons arrive, and then the net is pulled. The net and the pigeons are bundled up into the truck. The pigeons are then sold to restaurants for squab on the menu or to hunting clubs where the pigeons are released from a cage and shot for "pigeon shoots".
A doorman in NYC on the street the Bird Park was on, had been feeding a small flock of a few dozen pigeons, for years. He arrived for work one day and they had disappeared. His friend from the garage across the street rushed over and told him the flock had been netted off the sidewalk at six that morning. The doorman was heart broken. It is one thing for a hawk to do what hawks do, but quite another for humans to take the entire flock and destroy the "ecosystem". Doormen, parking lot attendents, any one who does some of their work on the street, are very good sources of information about what happens in a neighborhood.
It looks like without the pigeons, the hawks can't make a go of the TV tower nest. Whatever is causing the population drop might be something that needs investigating, just in case it is manmade.
If Kay and Jay are to return for further nesting under the eye of the KJRH Hawk Cam, they need something to eat besides the few small rodents that are out in the daylight.
Oh yes, an addendum about trapping--it sometimes takes place on the roofs of buildings making the traps somewhat hard to find in most areas. But the Tulsa watchers are lucky, as the TV tower is taller than the surrounding buildings, I's think that an inspection could be made of the rooftops to check for box traps, sticky tape, and all the other gross things people do to decimate pigeons, right from the nest area, particularly with the added plus of a TV camera.
Sometimes trapping is done for no other reason than someone just doesn't like pigeons.
And of course there might be some other cause all together for the shortage of prey that hasn't been thought of yet. The reason for the scientific method, indeed! A hypothesis is put together, a kind of best guess, it is then tested to see if it is the causative factor. No? New hypothesis, and test that one.
I heard a scientist on the radio say something I liked very much the other day, FUNDAMENTAL SCIENCE IS DRIVEN BY CURIOUSITY.
And just think, that really is why all of us are here, isn't it. Burning curiosity, the need to watch what happens, the need to figure out why what happened just did happen....and on and on. The world is never boring for the curious, there is always more...
Donegal Browne
