Wednesday, March 09, 2005

JOHN BLAKEMAN ON THE PIGEON vs. RAT DEBATE

Marie,

Donna Browne sent me another wonderfully provocative email, pondering if pigeons might not be such a prominent part of the CP red-tails’ diets. She carefully noted that Pale Male seems to be bringing large numbers of rats to Lola. Rats are appearing as nuptial food offerings more frequently than expected. This prompted my response below.

Donna,

In my red-tail heart of hearts, I think CP red-tails really prefer rats over any other food item. They will take any vertebrate that is easy to catch, but I don't think we should so quickly write off the Norway rat, as perhaps we are presently doing with the preponderance of recent pigeon capturing data
I'd be really careful in presuming that what we see the birds capturing is actually representative of what they take altogether. Yes, a bunch of pigeon captures were surely witnessed. But has anyone seen how, where, and how frequently rats are taken? Rat captures are likely to be much more discrete, even almost secretive. Red-tails can capture rats with great success, if the rodents pop out during the daytime. I had a falconry red-tail that reveled in early-evening rat captures, so I've seen this close at hand. The details are too lengthy to describe here, but the red-tailed hawk's cunning and prowess at taking these large rodents is superb.

I've watched with awe as my falconry red-tail captured Norway rats in a rural ditch. Their ability to see where the rats are running, and their ability to calculate and be at a perfect interception point for capture is remarkable. Pale Male and Lola, while sitting around Central Park, certainly have noted both rat holes and the behaviors of emerging rats. Like my falconry bird, they have learned to wait any length of time until the rat is sufficiently away from cover before attempting a pursuit. In their hunt, they will almost always dive toward the rat hole or cover, not directly at the rat. They have learned that when alarmed the rat shoots right back into the cover, using a known rat walkway. The hawks have seen these and use the rats' innate escape behaviors to their hunting advantage. It's not a wild goose chase. It's a well-calculated lethal game the hawks play with the rodents -- and more often than not, our birds win.

Continue to track pigeon captures. By any measure, pigeons are a major food source. But let's try to get a better handle on the rat factor. It’s likely to be larger than we currently think. The best way to do this will be to record as many food sightings at the nest as possible. Let's see what the ratio of pigeons to rats to squirrels to others is at the nest. I think this will be more representative of normal day-to-day hunting patterns (at least during the breeding season).

Where are these rats being hunted? When are they being captured? Are they full-sized adults, or half-sized new pups?

We continue to elucidate the remarkable ecology and behavior of the Central Park red-tails. Keep me posted.

Sincerely,

John A. Blakeman