Monday, April 03, 2017

Male/Female Comparison Tips

Incubation is well underway!  It is possible there could be an additional egg - we'll know in a day or two.  For the next 30-some days both the male and Durand will take turns keeping the eggs at a uniform temperature.  We'll write more on the technique of incubation in another post but in the meantime, here are some tips on how to tell the 2 falcons apart.

In my experience with all of the different peregrines that have nested here since 1994, these 2 individuals are the most difficult to tell apart!  Fans will really have to look closely.  I'm continuing to collect various views for comparison but for now will start with the position of the incubating adult facing out.  Some of the tips below may not be applicable depending on which way the falcon is facing but this is a good place to start.

Probably the best field mark to rely on is overall size.  Even though the male is large for a male, he is still substantially smaller than Durand.  So far what has worked for me is just noticing how much space inside the nest box the falcon takes up:  [CLICK on the photos to enlarge]
Even if the falcon is incubating in another position than pictured here, notice how much the falcon's body fills up the area of the nest box (or not, in the case of the male) to help tell which is which.
Another subtle difference I noticed is how the male holds his wings when he is on the eggs:
The male has already established a pattern of readily covering the eggs while Durand is away.  His frequency on the eggs in addition to Durand's will give fans plenty of opportunity to compare and study the differences throughout the day.