Blakeman on robins as redtail prey

Photo courtesy of http://www.palemale.com
3/8/07 [click on photo to enlarge]

Marie,

I was interested in today's photo on PaleMale.com of one of the hawks carrying a partially-consumed adult robin. Red-tails don't capture adult robins---or at least that's the conventional wisdom. This is further evidence that the Central Park red-tails have perfected some new and effective capture techniques.

I'm certain that a big red-tail can't capture a fully healthy, on-the-wing robin. When pursued in the air, the little songbird just wheels around in a tighter flight circle and hawk slides past in its weight-induced larger flight radius. As with the numerous pigeons, I think the only way the big hawks could capture a robin would be to stealthily ambush the little bird at speed while it is hopping across a lawn. Upon dropping from a high perch the hawk can reach 50 to 70 mph or more, scooting just above the ground. The robin in question was inattentive and thereby donated its accumulated proteins and lipids to an organism higher in the food web.

For those of us who know how these hawks hunt and take prey in rural areas, the robin capture, as with all of the previous pigeon ones, is just remarkable.

There can be no wonder why this species inhabits habitats from northern Mexican deserts on up to sub-alpine and northern taiga forests, and everywhere else, in ice-free North America. The bird adapts, as it has so well in recent years in New York City (and now in other urban habitats).

Personally, I can't understand why the species isn't circumboreal, living, as does the kindred rough-legged hawk, across all of northern Europe and Asia. The species must surely have recently evolved here, right after the Ice Age. Why it hasn't yet jumped across the narrow Bering Straights and taken over Eurasia is a mystery to me. If the bird can survive so splendidly in Central Park, the rest of the temperate world should be its oyster (well, vole or gerbil), so to speak.

--John Blakeman

Please note

Dear Readers,

I'll be posting here a bit less frequently until March 23 [a somewhat postponed but pretty final deadline]. Also I'll be including fewer photos -- that's the part that takes time. Be back with regular reports after that.

PS No matter what I'll report that first Phoebe as soon as it arrives.

PPS Saw the red-headed Woodpecker at 8 this morning. It's looking like the postage stamp.

Starr Saphir's Central Park walks

I posted the schedule for Jack Meyer's birdwalks on March 2. Here's the schedule for the legendary Starrwalks: [Note the two walks do not conflict. You can go on ALL of them. Spring 2007 Central Park Birdwalks Monday, April 2 through Saturday, June 2 Mondays and Wednesdays: 7:30am sharp to approx. 11am. Leave 81st Street and Central Park West, SE corner. Tuesdays: 9am sharp to approx. 1pm. Leave 103rd St. & Central Park West, parkside. Saturdays: 7:30am sharp to approx. 11am. Leave 103rd St. & Central Park West, parkside. Guide: Starr Saphir No registration necessary! All walks are non-smoking. For further information, please call Starr: 917-306-3808 (note: this is a new number). $6 ($3 for full-time students)

Mai & Blakeman discuss bark in nest

Pale Male inserting strip of bark into nest--March 2, 2007
photo courtesy of http://www.palemale.com



Below, an exchange of letters between regular correspondent Mai Stewart and John Blakeman, our Ohio hawk expert.

Hi John,

As always, I've been extremely interested to read your recent comments on Marie's website, and also was pleased to see the pix of you -- so nice to put a face to a familiar name -- and to see Savannah, as well!

My question/comment today concerns all the RTs' bark activity -- the first thought that crossed my mind is that this is wonderful, because hopefully it means that they're filling all those cracks + crannies in the nest through which wind + cold air can penetrate, as there seems to be some agreement, or at least serious thought, that that has been the reason for the failure of the eggs past two years. Bark, being dense, would be perfect (I'd think) for filling those holes + giving a more solid construction + barrier against the cold.

What do you think? Is this a possiblity? I've been so encouraged to see this nest-refinement activity going on, that I've begun to have more hope for the eggs this year. What are your thoughts? As always, so many thanks for sharing your knowledge + ideas w/ us!

Best, Mai

Blakeman replies:

Mai,

I, too, am encouraged with the placement of the new lining material in the 927 nest. The nest looks a bit taller, also. The insertion of bark indicates, I believe, that the pair feels a need to stop air flow through the bottom of the nest. The bark itself won't actually do that very well, as air easily moves between the bark fragments. Bark doesn't make much of a hermetic seal.

But it provides a strong, dense base upon which the finer lining materials such as grass and leaves can added. They really stop the air flow and hold in the heat from the mother's naked brood patch. It's like the insulation of a good winter down coat. If the loose (lining) insulation sinks down into the sticks below, it doesn't serve its purpose well. The bark provides a solid base upon which the sitting hawk can tuck the loose lining around the eggs before she settles down into the nest.

So far, very encouraging.