Which of the parent birds shown below (a or b) appears to have greater fitness explain?

Based on the information provided, it is not possible to accurately determine which parent bird has greater fitness. Fitness is a measure of an organism's ability to survive and reproduce in its environment. To assess fitness, one would need to consider multiple factors such as lifespan, the number of offspring produced, and the offspring's survival and reproductive success across multiple generations. Without detailed data on these factors, it would be inappropriate to make a judgment about which parent has higher fitness.