Ittuhrig, J. P. 
19 & 
19 
Most birds this AM were quietly sitting on eggs, preening, or 
sitting on eugoty nests. When incubating, the bird often sleeps with 
head held erect and eyes shut, and rarely with head over back in- 
between wings. Unemployed birds always sleep with head over back. 
Sitting birds do not rework the nest or attempt to maintain it in any 
way unless the mate brings it materials for the nest. A bird gathering 
twigs brings these to a sitting bird which then takes the twig and 
weaves it- into the nest. The arriving bird always calls, but the 
taking (sitting) bird nay not. The placement of new materials in the 
nest is always done by the sitting bird, never by the arriving bird. 
Single birds were seen to gather sticks also, but on arriving at their 
nest sight they looked about and usually lost interest in continuing 
to build. It may be that 2 things are necessary for nest building - 
a pair, and in later an egg. The truth may be that eaeh part of the 
behavior of these birds requires a releaser (C.F. Tinberger)- That is 
the presence of an egg releases incubation in one of a pair while the 
presence of that bird incubating stimulates the mate to gather more 
materials to complete the nest, these acts in turn cementing and in¬ 
suring the duration of the pair-bond when the Incubator accepts the 
preferred stick or twig. I have the impression that a bird, accepting 
a stick stimulates the offering bird greatly - A bird having an offered 
stick accepted simply "looks pleased." 
Capulatory behavior may be stimulated by the nest building activities. 
Once I watched a bird bring a stick to another sitting on the edge of 
an incomplete nest sons egg. The sitter accepted the stick and gurgled 
