Many of you have asked us about the status of the peregrines on the Washington Mutual Tower this year. Thank you for your patience. Here is a brief summary of the events so far this year.
A new pair of falcons established occupancy at WAMU last year (2006) after both Stewart and Bell passed on. This pair produced one male eyass and one female eyass, which we banded on 6 June.
This year (2007), Ruth Taylor checked the box early in the season (March 16) and was surprised to find 4 eggs already in the nest scrape. This was several weeks earlier than we would have expected, since this pair began laying eggs the first week in April last year. She was also puzzled because they were not being incubated at that time. This is really unusual. We discussed the matter and thought that perhaps they failed early on, possibly because they laid so early in the cold spring season.
A short time later, when Ruth re-checked the eggs, she found a female incubating. Again, we were surprised but delighted to see a bird in the nest box. We thought that everything might be back on track.
However, when Ruth visited the site last Wednesday (April 18), she got the biggest surprise thus far. There are now eight eggs in the scrape! This is very unusual for peregrines. The normal clutch size is four. The largest number of eggs reported in the literature that I am aware of is seven. And all those were thought to be from a single female.
We have never seen this happen before in Washington. After considerable discussion, the most plausible scenario is that there were two different adult females involved. The first falcon laid the initial clutch but probably died. A second adult female was recruited (indicating a large floating population) and laid the subsequent clutch. It is very unlikely that the current WAMU female just set a world record for peregrine eggs but stranger things have happened. We'll see what happens with her next year.
Dr. Steve Herman suggests that if they were laid by two different females then the eggs should have detectable color variations. We'll try to have a look at that next week.
Unfortunately, the presence of eight eggs in the scrape creates a major problem. Peregrines are "designed" to incubate four eggs. They will have a difficult time covering more eggs, particularly the smaller adult male. So it is likely that some or all of the eggs have suffered from incomplete incubation. It is possible that one or more could survive and hatch. Again, time will tell.
In the meantime, Mark Prostor is planning to set up the video camera on the site as soon as the necessary connections become available. Stay tuned, and thank you all for your patience.
