First, you should start with an introduction that explains what you will be discussing in the letter. In this case, you would introduce the topic of building eagle nests or monitoring eagle nests.
Next, you should make your argumentative claim. This is the main point of the letter, and it should be clear and concise. You could argue that building eagle nests is the best option, or you could argue that monitoring eagle nests is the best option.
After making your claim, you should provide reasons and details to support it. These reasons and details should be specific and relevant to the topic at hand. For example, if you are arguing that building eagle nests is the best option, you could provide reasons such as the fact that it provides a safe and secure environment for the eagles to live in, or that it encourages the eagles to stay in the area.
Finally, you should conclude your letter by summarizing your argumentative claim and restating your reasons and details. You could also include a call to action, encouraging the principal to take action based on your argument.
Remember to proofread your letter carefully before submitting it to your principal. Good luck!