Nutritional management of Great grey shrikes
In the spring of 2003 twelve eggs of the Great grey shrike, were taken from the wild to develop working protocols such as the chick hand-rearing feeding protocol. Six growing diets were formulated using a variety of ingredients and proportions that changed according to the age and requirements established for the chicks. The amount of food was offered as a percentage of body weight, starting at 25% and increased progressively until 50%. From day 30 of age onwards, a meat-ball diet was formulated and offered alternatively with life insects during the week. During the first month chicks were weighed daily and the diet consumed by each chick was registered. Eighty three percent of the chicks hand-reared from day 1 reached adulthood without any clinically apparent health problem. The survival rate and average daily weight gain of the chicks were very similar to those observed by the San Diego team working with L. ludovicianus mearnsi.
In spring of 2004, 13 chicks of the same species between 5-8 days old were taken from three wild nests. The aim was to test the 2003 protocols and adapt them to the new situation. It has been documented that hand-rearing one-week old chicks is much more successful and less demanding than rearing chick from day 0. Chicks caught from the wild, weighed two times more than the same age chicks hand-reared from day 0. The same diet protocol as in 2003 was used, but a few adaptations were made. Chicks from both experiences reached adult weight (57 g average) in the same number of days (27). In this second experience, all the chicks reached adulthood without any apparent health problem.
At the beginning of March of 2004, the 2003 hand-reared chicks were paired, and two of the pairs bred (one of them twice). The complete development of the parent reared chicks was recorded with a camera allocated on top of the nest. Although chicks were not weighed to avoid interfering too aggressively with the animals, some chick rearing behaviors could be registered, like number of times the chicks were fed by adults and several observations of the type of ingredients the adults provided to the chicks were also recorded. These results could be compared with the results obtained by recorded images taken from wild nests of both L. excubitor and L. minor.
The feeding protocol used to hand-rear L. excubitor may be applicable to hand-rear L. minor since both species are biologically very similar.