2 April 2008
On February 17th I was startled by a photo from the University of Pittsburgh falconcam. In it the leg bands on the male peregrine were not the same color as those on Erie, the resident male since 2002. If this was indeed true it meant that Erie was gone, replaced by another male peregrine.
I should have been clued in to the difference in behavior that began in November 2007, but I was too new to peregrines and the birds were both banded so I started there. (Click here to jump to the behavioral clues.)
Rather than jump to a conclusion without more evidence I decided to investigate, comparing new webcam photos to prior years and searching for evidence of band colors. Band numbers are impossible to read on the webcam because over-the-web images are such low resolution.
Over a period of 6 weeks I examined more than 4,500 photos. Eventually I couldn’t ignore what I was seeing. This is indeed a new male. Since we don’t know his name yet, my friend Karen and I have nicknamed him Erie2 or “E2” for short.
Here’s how I decided this bird isn’t Erie.
Way back in 2002 we identified Erie by a digital photo which clearly showed his band numbers. Shown at left are Erie’s leg bands: his right leg pink, his left leg black/red T*/W.
At right for comparison is the February 17th photo of E2’s bands: his right leg is silver, his left leg black/green.
Could these be Dorothy’s bands? No, her right leg is pink – not silver – though her left leg is black/green. Besides, the original photo had both birds in it and after looking at thousands of photos I can tell who is who. And further, neither bird ever shows black/red bands so neither of them is Erie.
I also compared their physical appearance. Erie always had a marked color contrast between his back and tail.
Here are two courtship photos with the males in similar poses. On the left Erie (pale back with dark wing tips and tail) is leaving the nest last year after bowing to Dorothy. This was 6 days after he won the territory battle. On the right E2 is leaving the nest this spring. E2 is uniformly gray with much less contrast.
The difference in appearance is also noticeable when the males incubate the eggs.
Again, Erie is on the left in a 2005 photo showing a strong color contrast between back and tail. E2 on the right has much less contrast.
When did E2 arrive? Was there a fight?
Karen and I and Dr. Tony Bledsoe have compared our observations. As far as we can tell there was no fight because Erie disappeared before E2 arrived. We think Erie disappeared in October. There was a long period when we saw only Dorothy at Pitt. Then in mid-to-late November we saw several things that we now realize meant a new peregrine was taking over:
- Dorothy and E2 did lots of courtship flying in late November and early December, something that never happened at that time of year between Dorothy and Erie. January was Erie’s normal time for courtship.
- In November, December and January, E2 repeatedly attacked the red-tailed hawks at Central Catholic. Erie never cared about those red-tails unless they came to campus.
- E2 doesn’t perch in Erie’s favorite places on the 32nd and 28th floors. This is a minor point but it adds up.
Though my friend Karen and I grieved a bit for Erie, life goes on.
Dorothy is happy with E2. They have 4 eggs to incubate and he’s helping with incubation more than Erie did in recent years. So who are we to complain?
Now if we could just read his bands!
To read my latest blogs about peregrines, click here.
Watch the Pitt peregrines live at their nest on the National Aviary’s falconcam.