When comparing the impact on a raptor's weight gain, which food is most effective?

Duck is considered the most effective food for promoting weight gain in raptors due to its higher fat content compared to other options like chicken neck, washed meat, or rabbit. Fats are calorie-dense and provide a significant energy source, which is crucial for a bird's weight gain. Raptors, when in a growth phase or needing to bulk up, benefit from a diet that includes foods rich in both protein and fat. Duck provides a good balance of these nutrients, making it particularly effective in helping raptors increase their weight.

In contrast, chicken neck and washed meat are generally lower in fat and calories, which may not support substantial weight gain as efficiently as duck does. Rabbit, while offering beneficial protein, tends to have a leaner composition and may not provide enough caloric intake for optimal weight gain when compared to duck. Thus, duck stands out as the most appropriate choice for encouraging weight gain in raptors.