Saturday, March 17, 2007

Will the cold be bad for the eggs? John Blakeman says no

From Donna Browne's blog:

While Donna's in Wisconsin, Katherine Herzog has been monitoring the Fifth Ave. nest. She had the question, below, for John Blakeman, which Donna forwarded to Ohio:

Today [3/15] the temperature is supposed to plummet and they're predicting rain and snow (up to half a foot) for the next couple of days. I thought PM and L had escaped that wrath of winter weather but at least the clutch is complete and the eggs are not as vulnerable as when they had just been laid?? That's the question I have for John Blakeman: Are the eggs more vulnerable (softer?) when they first come out; and are therefore more susceptible to damage when the weather is severe...cold, wind and snow. Or are they impervious to radical temperature/weather changes?

And John Blakeman's answer-


As bad as the weather might be for humans and other un-feathered creatures who have to purchase and don weather-fighting appurtenances, the hawks are well-provisioned for whatever weather might happen. How many times since the Pleistocene (the Ice Age) has there been cold, thick snows in March?

No problem. The feathers of the hawks easily accommodate the weather, and the eggs are tucked in those feathers and touch the warm naked brood patch on the female's belly. As bad as the weather might be for us, for the eggs it will be nicely warm and cozy up in the nest.

And because they are new eggs, the cold weather---should it cool the eggs for a period----will have no effect. First, the eggs are the strongest right now, with a full thickness of shell. As the eyass grows in the egg it produces carbon dioxide, as do we. This soaks into the watery fluids of the egg and forms a dilute carbonic acid, which in the next four weeks will slowly react and consume much of the egg shell. This weakens it, allowing the baby hawk to poke through the egg at the proper time, a process called pipping.

We are a long from that. Now, the egg is strong and firm, allowing the mother (and sometimes the father) to carefully roll the eggs every hour or so. This keeps all of the internal membranes properly suspended. Unrolled eggs don't grow properly and die (a concern with the pigeon prongs, which might keep the eggs from rolling naturally within the nest bowl).

Actually, raptor breeders know that freshly laid eggs can be stored for a few days, even a week or so, at 40 degrees F without harm. The female does this in the nest by sitting higher on her first eggs, keeping them somewhat cool and retarding embryonic development. When the last egg is laid (the second or third where the parents have sufficient food -- just one often in my rural Ohio areas where corn and soybeans predominate and retard mouse and vole populations), the female hunkers down for the beginning of full incubation with the warm brood patch in contact with the eggs.

This process of starting true incubation at the same time for all of the eggs helps assure all of the eyasses will be the same size during growth, allowing a somewhat equitable distribution (or grabbing) of food. This doesn't often happen in golden eagles, where one eaglet almost always grows earlier and faster than its sibling. The larger eaglet always then just kills and consumes the lessor bird. Golden eagles only fledge one eaglet because of this Cain and Able conflict, regardless of the amount of food the parents bring to the nest. Fortunately, it's not so with our less greedy red-tails.

It doesn't matter what the outside temperature or snow mass might be. Against the female's brood patch, all is well.

But nest watchers are likely to note disconcerting periods of apparent inattention as the adults are away from the nest for up to a half hour. We are not sure on this, but it appears the periodic 15- or 20-minute periods of egg cooling are beneficial. As the egg cools down to, say 70 degrees from the 100-degree+ incubation temp, oxygen can diffuse into the egg at the reduced temperatures. Periodic cooling is probably very important.

So don't be alarmed when the nest is left unattended for short periods in the coming weeks.

Somehow, it all works.

--John Blakeman

Thursday, March 15, 2007

Jack's spring birdsong report

Wrong season, right bird - Black-capped Chickadee
Photo by Lloyd Spitalnik

Jack Meyer writes

New singers on Wednesday were Song Sparrow, several Dark-eyed Juncos, and Black-capped Chickadee (fee-bee song).


Reminder from Marie --- Jack's Spring Birdwalks begin on March 29th. Here's the info again:

Walks will be Thursday through Sunday, from March 29 to May 27

Walks leave at 7:30 AM from 72 Street & Central Park West. (NE corner.)

The cost is $6. No reservations are needed.

If there are any questions, you can reach him at:
212-563-0038 (Not after 8 PM please)

Wednesday, March 14, 2007

Incubation questions

Mom and chicks -- 2003

Last Saturday was the first day Lola spent the night on the nest. People have been looking at photos on and wondering if it's possible to tell if incubation has actually begun. Here's Blakeman's response:

Right now, there's no way of knowing for sure if there's an egg. The birds aren't fully hunkered down in brood-patch-on-eggs incubation yet. There may be an egg, but one or two others may be descending the fallopian tube, so real incubation hasn't really started.
I start counting incubation days when full, intense incubation starts, when the female sits very low in the nest.
An egg can be laid and left un-incubated at refrigerator temperatures without harm. Incubation doesn't really start until the brood patch is physically in touch with the eggs and that won't happen until the last egg is laid.
So, we must just wait patiently.

Tuesday, March 13, 2007

Youngest phoebe-spotter

Liliana Speiser - February 2007

On March 11, one day after the first phoebe was seen by Ben Cacace at the north side of the Reservoir, David Speiser, one of Central Park's hot-shot birders, posted the following item on e-birds:

Observers: David & Liliana Speiser
An Eastern Phoebe was present in the Conservatory Gardens in Central Park at around 3:30- 4:00 PM today. It was directly East of the bathrooms along the path.

That makes Liliana the youngest phoebe-spotter of the season. She'll celebrate her first birthday next week.

Her father informs me that she has also seen an Ivory Gull. But can she pick it out of a flock of a hundred more common gulls? I forgot to ask David that question.

Monday, March 12, 2007

We'll settle for two

Lola -- her first year --and two chicks on April 1, 2002

Looks like incubation has begun at the Fifth Ave nest as of Saturday or Sunday. Keep your fingers crossed...

Sunday, March 11, 2007

Quick updates

Photos below from Bruce Yolton's site Http:// where you'll find many more great photos and more info on eclipse, woodpecker, and also hawks and monk parakeets. This is just an update on stories I posted recently

two views of the total moon eclipse of March 3, 2007
taken on west side of the Reservoir

Red-headed Woodpecker on 92 and Riverside Dr.
on 3/3/07

Ben sees first Phoebe

Ben Cacace []
sent this e-mail yesterday, March 10. The Spring Migration has now officially begun. Guess I'd better head for the park!

I'm at the Apple store on 5th Ave. Just wanted to let you know I saw an Eastern Phoebe at the south end of the reservoir [emphasis mine] and soon after Tom Fiore got on the bird. This was around 7:15a this morning.

All the best.

Ben added a few details on e-birds:
The Phoebe was seen flying into a leafless bush on the south edge of the reservoir well west of the South Gate House. Tom Fiore was also there to see the bird. A couple stopped by the feeders later on letting us know they spotted a Phoebe at Sheep Meadow today.