Monday, April 07, 2008

UPDATE: Battle of Peregrine Nesting Box and Dad Peter Gets Points

Photograph of the Buffalo, NY, Peregrine Falcon nest box, Mom, and last season's eyasses, courtesy of
Here is a wonderful update on the Peregrine formel who was protecting her eggs and nest box from a female intruder, sent in by Eileen of NY.


I'm copying this to you from a Dutch woman named Nora posting on the CMNH Falcon Forum:

"Jan van Dijk searched the archived images and reported on the Dutch forum (I translated the message for you):

April 6

Till 17:20 all is well; Mariken incubates.

At 17:24 a young female appears on the ledge (she has been seen before in the last couple of weeks). She almost comes in the box, but Mariken keeps on incubating. (Mariken only puts up her feathers)

At 17:34 an unknown adult female comes straight in the box and fights with Mariken. This battle continues for about 8 minutes, and both females step out on the ledge now and again.

From 17:42 till 18:38 the intruding female (leg bands from Germany?) checks the box and shuffles the eggs.

At 18:49 Mariken returns. She rolls the eggs back into the nest cup and incubates till 19:41.

At 19:41 Peter takes over egg-duty and incubates till the next morning April 7, 10:15!!!

On April 7, at 10:15 Mariken takes over incubating and all seems quiet and well.

The question is, did Mariken (and maybe together with Peter) chase off the intruding adult female between 18:38 and 19:41?

Anyway, Mariken must have been pretty upset, not returning to the box for the night.
Peter did extraordinary well last night: it was freezing and that stunning male incubated 14 hours on end without changing position!

Let's hope all eggs are intact and that intruding female won't return."

I've been watching these nests for several years (vicariously, of course). There are other nest boxes in the region and most of the birds winter-over rather than migrate.

In other territory battles I've seen, the tiercel will often avoid "on the ground" fighting with a falcon, most likely as he'd lose being so much smaller. Tiercels seem to limit their defense to the air, often tag-teaming with the bonded falcon, both putting up a vigorous fight.




Thank you so much for sending the update. This is wonderful.

We've often discussed whether Red-tailed Hawk tiercel's ever spend the night sitting the eggs and so far we've never had a strict confirmation that they do. But here we see that Peregrine tiercels do most definitely sit overnight. Peter gets many points for brooding in below freezing temperatures while putting in a full 14 hours worth of nest time.

Does Peter feed the eyasses as well? We've found that some Red-tailed males do and others don't. It seems to depend on exactly how the domestic chores have been worked out between the individuals in the bonded pair.

Donegal Browne


Karen Anne said...

Oh, wow. So what I thought was the resident female, agitated, rolling the eggs apart, was the intruder apparently up to mischief. This fits in with that Darwinian stuff about destroying offspring not one's own, if that's what was going on.

She actually managed to drive away the resident female for awhile, yikes. I hope the intruder will please stay away.

Hurray for the Dad. This reminds me of the hero Dayton Dad who last year managed to raise his fledglings after their Mom disappeared.

Karen Anne said...

Are the young female at 17:24 and the adult female at 17:34 two different intruders? Poor Mariken...

17:42 till 18:38 seems a long time for the eggs to be uncovered...

Karen Anne said...

Is the almost hour the eggs were unincubated likely to be fatal...

Karen Anne said...

Froona reports two of the three eggs hatched this afternoon.

Karen Anne said...

The third egg has hatched. (The fourth egg was broken some time ago.)

Kind of amazing to me that three eggs survived, considering they were apparently left uncovered for about an hour and also disturbed by the intruder female.