2010 Special Report

By Anouk Hoedeman

This was an unusual year for the Ottawa Peregrine Falcon Watch. Our resident breeding pair, Diana and Connor, didn’t manage to hatch any eggs. But they did confound the experts, and may have broken the record for the longest known brooding by Peregrine Falcons.

Peregrine Falcon with three eggs, Ottawa, 2 June 2010. Photo by Anouk Hoedeman

The first sighting of Ottawa’s Peregrine Falcons for the 2010 season was on March 17, when Scott Holliday observed a male at the southeast corner of the Crowne Plaza Hotel at Albert and Lyon Sts. On March 18, he reported seeing three different falcons at same time: a male flying overhead, a female flying from the southeast corner of the Crowne Plaza to the southwest corner of Place de Ville Tower A, and a third falcon of unknown sex on the same ledge of the Crowne Plaza at same time.

Nesting began with a false start, with a female seen brooding near the northwest corner of the Crowne Plaza during the week of April 18. On April 26, Chris Traynor (Falcon Watch veteran and chair of the OFNC Birds Committee) reported that he could find no sign of either falcons or eggs.

Bernie Ladouceur observed two falcons at the Crowne Plaza on April 29. By May 4, they had established a second nest on the southeast side, in the same spot as the 2009 nest. They were presumed to be Diana, who has been breeding here since 2006, and Connor, the resident male since 1998.

On May 14, Chris confirmed that they were sitting on three eggs, although the precise date that full-time incubation began is unknown. He continued to monitor the nest periodically until the end of May. During this time, he noted a difference in the eggs’ colouring: one was significantly paler than the other two.

In June, I began alternating daily monitoring duties with Chris. This consisted of one of us visually observing the nest, usually around 5 p.m., from a vantage point on the roof of 360 Albert (Constitution Square Tower I), located across the street from the Crowne Plaza. The standard procedure was to watch through a spotting scope until the adult got up to turn around, to turn the eggs or to switch places with its mate. We left once we had confirmed the number of eggs and checked for signs of imminent hatching.

Chris went on vacation on Friday, June 18. A full 35 days had elapsed since he confirmed the presence of three eggs, so we suspected that they would not hatch. I agreed to continue checking every day for another week in case full incubation had started later than we thought.

Eve Ticknor contacted the Ministry of Natural Resources to ask if they would like to collect the eggs for examination. On Sunday, June 20, I saw that the falcons were still incubating the eggs as usual, with no change in behaviour, so we asked that the eggs not be collected until the nest was abandoned.

On Tuesday, June 22, I found Diana on the nest, and a pale egg with a small hole in the shell lying about 15 to 30 cm outside the nest. It appeared that the hole was made from the outside. I could not see the egg moving, and Diana did not appear to be paying any attention to it, so I concluded that she had discarded the egg, and assumed she would soon abandon the nest.

I waited to see the status of the other two eggs. When Diana stood up, I saw three eggs in the nest: one pale and two darker. She had laid another egg!

Peregrine Falcon with four eggs, Ottawa, 22 June 2010. Photo by Anouk Hoedeman

My experience with and knowledge of bird breeding and nesting behaviour had until this year been limited mostly to domestic fowl, i.e. raising chickens, ducks and geese while growing up on a hobby farm. Still, this seemed highly unusual: a bird laying a new egg while continuing to incubate an earlier clutch in the same nest. I had never heard of such a thing.

Nor, it turned out, had anyone else. I contacted a number of experts and organizations, among them my fellow OFNC Birds Committee members, the Canadian Peregrine Falcon Foundation, and the Cornell Lab of Ornithology. They in turn consulted other experts. But no one could recall a similar occurrence among any bird species, much less explain our local raptors’ nesting behaviour.

Neither could anyone tell me if the new egg might be fertilized. So I continued to monitor the nest every day to see if Diana would lay any additional eggs. On Wednesday, June 23, the egg that had been outside the nest was gone, and I presumed it had been eaten by one of the adults. After a week with no new developments, I began checking every second day, then every third. I saw no new eggs, but realized there was no way of verifying that the two dark eggs now in the nest were from the original clutch, i.e. one or both could have been discarded and replaced in the same way as the pale egg. In fact, I could not even tell for certain that the pale egg now in the nest was the one laid on June 21 or 22, i.e. it could have been the one from the original clutch, and the new one could have been discarded.

The adults continued to tend to the nest as usual through July. Any new egg, if fertilized, would be due to hatch near the end of the month, so, I checked daily from July 21 to 26. Chris conducted the last few nest checks while I went on vacation. He reported that the Peregrines were still brooding on Aug. 6, but had abandoned the nest by Aug. 24. We don’t know exactly what day they left, but since the three eggs were still perfectly intact on Aug. 24, they probably continued sitting well beyond Aug. 6.

Based on Chris’ reports, we can be certain that Diana and Connor spent at least 94 consecutive days brooding, which to our knowledge is unprecedented. (Chris did hear from a Finnish raptor expert who once had a Tengmalm’s Owl still sitting after 92 days.)

We look forward to Diana and Connor trying again next year. Let’s hope they have better luck — and a much shorter brooding period — in 2011.

Additional observations:

  • The falcons appeared to be accustomed to my presence on the roof of Tower I, and never showed any aggressive behaviour towards me. The adult on the nest often fell asleep or preened as I watched, and the other adult, if present, usually perched on a radio tower two blocks south, at 440 Laurier St. W., or occasionally on Tower II or on the east ledge of the Crowne Plaza.
  • It was difficult to conclusively tell the male and female apart by their appearance unless they were near each other. Variations in the bird’s placement on the nest, the quality of light and the viewing angle made it difficult to differentiate them by size alone. However, it was often possible to tell which one was on the nest by the way it moved and behaved, although this may have been related less to actual differences in their overall behaviour and more to the amount of time the bird had spent on the nest when observed.
  • The male, Connor, usually appeared more alert and active. He kept a more upright posture, moving his wings and tail and cocking his head more frequently and more emphatically. He seemed more curious, and reacted more obviously to passing birds and insects, and to sounds such as sirens.
  • The female, Diana, usually appeared calmer and stiller, and kept a lower profile, posture-wise. However, she often appeared noticeably restless during the period from approximately June 14 to 20, sometimes picking at stones and debris around the nest, briefly lifting objects with her beak and then dropping them.
  • Since 2006, Diana has incubated a total of 14 eggs, of which six have hatched (four male, two female). Horizon, the resident female from 1997 to 2005, incubated a total of 25 eggs, of which 13 hatched (six male, seven female).
  • The Ottawa Peregrine Falcon Watch has recorded one other instance of total nest failure: In 1999, Horizon incubated four eggs unsuccessfully.
  • Because they are not banded, the exact ages of Ottawa’s resident falcons are unknown. Diana joined Connor late in 2005, after Horizon’s death, so she is believed to be at least six years old. Connor arrived as an adult in 1998, so is at least 13 years old.

Contacts:

Eve Ticknor
Peregrine Falcon Watch Coordinator
Ottawa Field Naturalists Club

Chris Traynor
Chair, Birds Committee
Ottawa Field Naturalists Club
ctraynor59@yahoo.ca

Anouk Hoedeman
Peregrine Falcon Watch volunteer

 

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