Sex determination of Red-tailed Hawks

Kara C. Donohue and Alfred M. Dufty, Jr. wrote an excellent paper about using size measurements and weight to determine sex in Red-tailed Hawks, Sex determination of Red-tailed Hawks (Buteo jamaicensis calurus) using DNA analysis and morphometrics, J Field Ornithology, Vol 77, Issue 1, pp. 74-79.

This paper shows how hard it is to tell a Red-tail’s sex.  I would caution anyone who thinks they can quickly tell a Red-tails sex by simple observation to think twice before declaring the sexes of our two Cathedral fledglings.

Update: This note sparked a discussion between Donna Browne and John Blakeman about this year’s fledglings sexes on Donna’s blog, palemaleirregulars.  My comments above were to start a discussion about the sex variations beyond just height.  I think Donna and John are exploring this very well on her blog.

Rainy Sunday

I went up to the Cathedral early Sunday afternoon during the break in the rain.  I was able to find one hawk before a downpour occurred.  The fledgling was on a chimney on the Cathedral School.  After the rain started, the fledgling flew into the scaffolding on the southern section of the Cathedral School. I bet it was looking for a dry spot.

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Lazy Summer Afternoon

Summer Friday’s allowed me to get out of work early and go up to the Cathedral around 2 p.m.  I was the only one hawk watching when I arrived, and looked high and low for the hawks.  I searched the Cathedral exterior from Morningside Drive and 113th Street, the St. Luke’s building, the Cathedral grounds, and Morningside Park but came up empty.

I parked myself on a bench overlooking Morningside Park, hoping to at least see the parents fly over the park.  I started drinking some iced tea, relaxing on a hot, humid summer day, and then looked up.  I was pleasantly surprised to see both fledglings within 10 feet of each other. Finally, I could hawk watch from a bench!

The fledglings, who have become difficult to tell apart, stayed in the tree until the early evening when their father brought them a rodent for dinner.

When dinner arrived one of the fledglings, who I assume was the precocious first fledgling, went directly to the Cathedral to be fed.  The other fledgling, who I assume is the second to fledge, still seems to be having troubles gaining altitude and took a sensible route.  It went downhill (south) to cross the street and then worked its way up north.

As I was leaving, Fledgling I was eating the rodent, which looked to be a rat. It was then joined by its sibling, Fledgling II, who looked to have gotten a bite or two before Fledgling I mantled over the prey.   Robert Schmunk reports that Fledgling II got second pickings later in the evening.

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The white area seen on the back of a Red-tailed Hawks had has a great name, the Cryptic Occipital Spot.  There is an excellent paper written about the spot, The Cryptic Occipital Spot in Accipitridae (Falconiformes), published in 1977 by John C. Hafner and Mark S. Hafner.
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The adult female on a building on 108th or 109th, which I think is a Verizon switching office.  The standard 301 W. 110th perch had a construction crew working on the roof all afternoon.
The adult male on the St. Savior cross delivering dinner.
Fledgling II in a tree.  The fledgling less than a week off the nest still isn’t well practiced when it comes to flying.
Fledgling I, two weeks off the nest, is now an accomplished flier and gets to dinner first.

A Fledgling Goes To School

Up at the Cathedral this evening, we got to see both of the parents and at least one of the fledglings.

The adult female on a cross on the edge of the St. Savior chapel.
The adult female from another angle.
A fledgling on the roof of the St. Martin chapel.
The adult male arrives and stays briefly on the Archangel Gabriel.  He heads off towards Central Park after about fifteen minutes.
The fledgling preens for awhile…
…before moving back and forth from one corner to another…
…and after a few minutes flies to the Cathedral School building.  When it moves to the Cathedral building it appears to land perfectly.  Another hawk follows, and it misses the roof and glides down a step slate roof to a gutter and stays out of sight.  We think we’ve seen two fledglings but can’t be sure.  The mother had left the cross on the St. Savior chapel and one of the hawks could have been her.
We walk around the Cathedral, and find the adult female on a water tank on South 110th.
We walk around to Amsterdam and into the Cathedral grounds.  Walking behind the school building we find a fledgling on the gutter it slid into earlier.
As we leave the Cathedral grounds, the adult female has returned to the Archangel Gabriel.

Relaxing On A Hot Day

The two fledglings relaxed on a hot, 90 degree day.  I was at the Cathedral in the early afternoon on Sunday.  Fledgling I was sitting on a fifth floor windowsill of a St. Luke’s building half way between 113th and 114th Street on Morningside Drive.

Fledgling II was heard begging periodically, but took over an hour to find.  It was in a tree on the south side of 113th about 20 feet in from Morningside Drive.

Both hawks looked to be doing nothing more than just trying to stay cool.

Fledgling I trying to stay cool.
The adult female landing on 301 West 110th Street.
Fledgling 1
The adult female circled the area of the tree which had Fledgling II, landing on St. Luke’s, in the tree and on the Cathedral.
It looked as though she was trying to coax the fledgling  to come out to an easier place to feed.
All attemps to get the fledgling to move failed.
Fledgling 2
She kept trying to coax the fledgling to move.
But Fledgling 2 stayed put.

I hope you have enjoyed this series of posts about the St. John the Divine nest.  It has been fun bringing a near daily report of the activities in Morningside Heights.  Work commitments and vacations in June and July will prevent me from keeping up this daily pace.  Expect to see posts only around the weekends for the next two months.

More from Saturday

After taking a break in the early afternoon, and a detour to Riverside Church, I returned to the Cathedral.

The hawk watchers up at the Cathedral compared their estimates for fledge dates today.  The question of the day was, Did we have a precocious fledgling followed by a normal fledgling?, Or a regular fledgling followed by a reluctant one?  The general consensus was that we had a precocious, first fledgling.

A photograph I forgot to post from earlier in the day of the adult female being bothered by a Mockingbird.
Three Peregrines come to attack the adult female.  They were so fast, I couldn’t get a picture of all of them.
The Peregrines leave.
A fledgling on the scaffolding.  At this point, I can’t tell them apart for sure.
The fledgling disappears, and after awhile one appears on St. Luke’s.  This looks to be the new playground for the young hawks.
Still preening.
The young hawk experiments with the strong breeze.
The adult female.
Who soon leaves…
…picks up some left over prey from earlier in the day…
…and heads off to St. Luke’s
The young hawk continues to play in the wind.
It soon moves about 15 feet on St. Luke’s after having some troubles finding solid footing.
The mother returns to the Cathedral, near St. Matthew.