Tuesday, February 26, 2008

Cathedral Hawk Update and John Blakeman Answers my Questions about Lost Mates--Just in Case.

Isolde atop Gabriel's wing on the roof of St. John's, last season.

In regard to the possibly missing Tristan, the male of the Cathedral Nest pair--

I'd emailed Hawk Watcher Stella Hamiliton about the fact that there had been an injured hawk sighted in Morningside Park last week and we hadn't had a confirmed sighting of Tristan in some days. Stella works in the area of the Cathedral Nest, if at a bit of a distance, and she is very sharped eyed when it comes to Red-tails. She's the one who discovered that Pale Male and Lola spend time over at the Beresford.

Stella called me this afternoon. Her vantage point, is a window in the hospital where she works. She spent her lunch hour watching the Cathedral and any other spare moment she could find which were few. Her only sighting was of a single hawk perched on the stature of Gabriel on the roof of the cathedral. She surmised it was Isolde but it wasn't a 100% confirmation.

She'll keep looking, as will Rob Schmunk, and we hope to have it all sorted out soon.

As I said before, keep your fingers crossed.

Next a response from expert John Blakeman,

I asked John Blakeman’s opinion on a few questions pertaining to Red-tail behavior.

The first, whether Red-tails would predate Peregrine eyasses on the nest if they could get away with it?

And second, if a Red-tail should loose his or her mate—

a. Would the bird realize the mate was dead if he or she saw the mate’s body?
b. How long would it take the remaining Red-tail to take a new mate?

Here's what John had to say---


Would a Red-tail kill an eyass Peregrine? Sure would. A Red-tail sees no difference between a pigeon squab on a ledge and a helpless little peregrine eyass. Of course, the stooping peregrine parents will make a difference. A hungry Red-tail will not miss seeing a stooping falcon overhead. It's not a matter of whether Red-tails will prey upon Peregrine eyasses. It's a matter of whether the Peregrine parents will stoop at the intruding big, lumbering Red-tail. In virtually every case, they will.

A more crucial factor in wild Peregrine nests, in those in the range of Great-horned Owls, is nest predation by these night-flying monsters. Peregrine restoration efforts have always aimed at restoring wild, rural, cliff-nesting Peregrines. Initially, as so well known in greater New York, the falcons took up nesting residencies on buildings and bridges. The original wild Peregrine aeries along the Hudson, at the Palisades and other cliff sites, remained un-occupied for many years. The same thing occurred at traditional Peregrine nest sites along the Mississippi and at other Midwestern cliffs.

Then, a few years ago, a few of the old traditional wild peregrine nests became occupied. Offspring from the many urban Peregrine nests finally began to be attracted to the original wild nest sites. Falcon restorationists were legitimately gratified.

Unfortunately, Great-horned Owls cleaned out virtually every Peregrine aerie. For a time, it appeared the Peregrines might not be able reoccupy traditional wild nest sites because of the big owl.

But in recent years eyasses have been fledged from wild cliff aeries. It appears that the first colonizing falcon parents, having "grown up" in urban areas, were rather unaware of the lethal intents of local owls. The parents were too inattentive regarding these silent but lethal giants. Now, however, they have learned and keep a keen eye out for Great-horned Owls. They harass or kill these birds when spotted. The owls have recognized the danger and now avoid Peregrine nest areas. Finally, Peregrines have learned how to successfully fledge eyasses from wild cliff nests. It's a great conservation success.

It's also interesting to note what may be an undescribed physiological factor. Peregrines have inordinately large eyes. And more significantly, in ways that aren't yet clear, they are able to capture small birds flying in the dead of night. Here at an Ohio Peregrine nest at Toledo, researchers were amazed on a number of occasions to record at sundown every food remnant at the aerie. Then, the next morning, they checked to see if anything changed over night.

Inexplicably, sunrise food surveys at the nest frequently showed new dead birds and feathers which had been captured in the dead of night. Consequently, the adults were radio-tagged, so they could be followed. Stunningly, they would fly NE out over Maumee Bay and out over night-black Lake Erie, where they apparently were plucking night-flying migrant birds.

We know that European Kestrels, and almost surely, American ones, too, can see up into the ultra-violet spectrum. It may be that Peregrines can also see down into the infra-red spectrum, which would allow them to see heat-glowing little dickey-birds flying across Lake Erie to Ontario in the dead of night.

If that's so, they could also see a lumbering, infra-red glowing Great-horned Owl flying silently through the night sky -- whereupon it could get its vertebrae crushed in a 100-mph night-time stoop.

For whatever reason, Great-horned Owls are now only very infrequent killers of nest-bound Peregrine eyasses.

About new mates in Red-tail pairs where a bird dies or flies off. No, I don't think the remaining mate cognitively "knows" that its mate has died, even if it sees the dead carcass. Instead, it's the absence of the mate's pair-bonding behaviors that control things. Without the mate flying around at close quarters, sitting on nearby perches, and working at the nest, the remnant bird then begins to begin to behaviorally "connect" with new "floaters" that so quickly drift into the territory.

"Floaters" are full adults, but unmated. Reproductive hormones affect them exactly as with mated birds. And it seems that there is a somewhat hidden or phantom population of floaters circulating perhaps widely between mated-pair territories in winter. For Red-tails and a number of other diurnal raptors, it is well known that upon the death of a pair member, a new mate can come into the territory and begin mating, nesting, and copulating duties within just a few days.

I noted yesterday that it appears that Tristan, one of "The Divines" at the cathedral north of Central Park is missing, presumed dead. If so, most unfortunate. But I wouldn't be surprised if a new Tristan II makes an appearance this week or so. (Perhaps the name should remain "Tristan," but with the program indicating that this year, the role will be played by a new understudy.)

[Rob Schmunk may have seen Tristan with Isolde since that report. D.B.]

The death of adult hawk pair members is a part of hawk life. The birds are able to quickly adapt. Things will work out, just as they did so often when Pale Male lost a mate.

--John Blakeman

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