1953 Baltimore, Maryland) is a retired American diplomat and amateur ornithologist who most recently served as the chief of the Consular Section at the U.S. Consulate General in Frankfurt, Germany.
As Minister Counselor, he oversaw consular operations in New Delhi and the U.S. Consulates Generals in Mumbai (Bombay), Chennai (Madras), Hyderabad, and Kolkata (Calcutta).
After spending two years in the Peace Corps in Zaire, Kaestner entered the Foreign Service in 1980, and has been assigned in the past to India, Egypt, Brazil, Guatemala, New Guinea, the Solomon Islands, Colombia, Malaysia, and Namibia.
In 1989, while on a birding expedition near Bogota, Colombia, where he was a U.S. consular officer, he discovered a species new to science, the Cundinamarca Antpitta (Grallaria kaestneri), which was subsequently named after him.
In February 2024, with his sighting of an Orange-tufted Spiderhunter on the island of Mindanao in the Philippines, Kaestner became the first person to see 10,000 bird species anywhere in the world.