Bluetit Diary    Apr 2013 (5)

Here are a few pictures of Sally and Sam so that you can follow what happens later.

This is a typical swap over where the male goes into the nest box first and the female follows.  Directly the female enters, the male leaves.

Here Sally, who has just come into the box, is at the top of the picture.  Sam at the bottom of the picture is about to leave.

Notice that both Sam and Sally have smooth uniformly coloured head feathers and without taking their behaviour into account, it would be very difficult to tell them apart.

This and the picture below show another swap over sequence.

In this picture Sam is at the bottom and Sally is coming into the box.

Directly Sally has arrived, Sam departs.  They are in the box together for less than a second.

Sam's head feathers are perhaps a little darker than Sally's, but they are both very uniform in colour over the whole of the top of their heads.