ABSTRACT
This chapter focuses on the hematologic profile the avian during its breeding cycle. It is accepted that breeding behavior of birds can lead to recognizable adjustments in the physiology of a given bird. During the long incubation period the male and female petrels alternate incubation and foraging, typically in shifts lasting one week or more while the partner fasts on the nest. The free-living seabird Calonectris diomedea is also an appropriate model to investigate whether it is a fixed investor or a flexible investor in regard to its selection of choices during the breeding period. The fixed investment hypothesis in regard to wild Cory’s shearwaters was tested by experimentally increasing the cost of flying and analyzing the consequences on the blood picture, body condition of the experimental birds and condition of their chicks. Blood samples were obtained at the time of egg-laying, hatching, chick-rearing and once from the chicks when they were 80-days-old.
