Learn Farsi: بعضی از پرنده‌شناسان عقاب را یک پرنده‌ی تیزبین و شکاری می‌دانند. - Some ornithologists consider the eagle a sharp-sighted and predatory bird.

This is because the two adjectives are linked by و (and). In Farsi, when you list parallel adjectives for a single noun, you only use the Ezafe to connect the head noun (پرنده) to the first adjective. The conjunction و takes over after that, so تیزبین doesn't take an Ezafe.

The verb می‌دانند normally means 'they know'. How does it mean 'consider' in this sentence?

This is a common phrasing. The structure [object] + را + [characteristic] + دانستن translates to 'considering [object] to be [characteristic]'. So literally it means they 'know the eagle as a sharp-sighted bird', which we naturally translate as 'consider'.

What are the building blocks of the word پرنده‌شناسان?

It breaks down into three parts: پرنده (bird), شناس (the present root of شناختن, meaning to know or recognize), and the plural suffix ان which is used for people. The شناس root is commonly used to create words for experts or scientists, similar to '-ologist' in English.

Why does عقاب have the direct object marker را if it represents eagles in general?

In Farsi, when referring to an entire class or species as a whole concept, it is treated as a definite noun. Since the eagle is the specific concept being acted upon (considered) by the ornithologists, it takes .