I could watch them all day.

Meaning: I am able to observe the chicks for a very long period of time without getting bored.

Choice of Words: I refers to the speaker. Could is a modal verb that is used to express possibility or ability. Watch means to look at something or someone for a period of time. All means the entire amount or quantity of something. Day means a period of 24 hours or from sunrise to sunset.

Alternative Expressions

I could stare at them all day.

Meaning: This means that the speaker really enjoys looking at something or someone. It's like saying, I enjoy looking at them so much that I could spend a lot of time doing it without moving my eyes.

Choice of Words: I refers to the speaker, the person who is saying the sentence. Could is a modal verb that indicates ability or possibility. Stare means to look at something for a long time without moving your eyes. Them refers to the object or people being stared at. All means the entire amount or duration. Day refers to the period of time from sunrise to sunset. When you put these words together, the sentence means that the speaker is able to look at the object or people for a long time without moving their eyes for the entire period of time from sunrise to sunset.

I could gaze at them all day.

Meaning: This means that the speaker really enjoys looking at something or someone. It's like saying, I enjoy looking at them so much that I could spend a lot of time doing it with admiration or wonder.

Choice of Words: I refers to the speaker, the person who is saying the sentence. Could is a modal verb that indicates ability or possibility. Gaze means to look at something for a long time, often with admiration or wonder. Them refers to the object or people being gazed at. All means the entire amount or duration. Day refers to the period of time from sunrise to sunset. When you put these words together, the sentence means that the speaker is able to look at the object or people for a long time, often with admiration or wonder, for the entire period of time from sunrise to sunset.

Related Expressions