So to answer this question lets first look at what the Quran says

 

2:187

....And eat and drink until becomes distinct to you the thread [the] white from the thread [the] black of [the] dawn ......

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The root letters for "thread" is also used in 7:40 

It says 

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7:40 ..until the camel passes through the eye of a needle.....

So it isn't a thick thread but a bit thicker than a hair.

 

Bayanna meaning "distinct" or clear.

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So when you can clearly, distinctly make out a white hair in the blackness of dawn.

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Now to Birds

For every reference of birds please click on the below link

Every reference of Bird in the Quran

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Quran gives many examples of where not only do we learn from observing birds,

but also from the examples they set.

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Here are 3 quick examples

 

Knowledge from observation:

16:79 Have they not looked at the birds held in the atmosphere of the sky? No one holds them up except God. In that are signs for a people who believe.

 

Praise Allah:

21:79 So We gave Solomon the correct understanding, and both of them We have given wisdom and knowledge. And We commissioned the mountains with David to praise, and the birds. This is what We did.

 

Teaching mankind procedures:

 5:31 So God sent forth a raven to scratch the land and show him how to deal with the body of his brother. He said: "Woe to me! Am I not even able to be like this raven and deal with the body of my brother?" So he became of those who regretted. 

 

Birds also give us another important lesson in life:

SALAH

24:41 Do you not see that everything in the heavens and the earth glorifies God? Even the birds in formation, each knows its contact prayer and its glorification. And God is fully aware of everything they do.

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kullun qad AAalima salatahu watasbeehahu 

each knows its contact prayer and its glorification

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Birds are nature's alarm clocks and according to the above ayat,

they know when Salah should be. 

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It's not hard to imagine ancient civilizations using birds singing as an alarm clock. We still use it today, prime example, roosters are still used at numerous farms.

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To further strengthen this theory.

27:24-26 And I found her and her people prostrating to the sun instead of Allah, and has made fair-seeming to them the Shaitaan their deeds, and averted them from the Way, so they (are) not guided, That not they prostrate to Allah, the One Who brings forth the hidden in the heavens and the earth and knows what you conceal and what you declare,

Allah (there is) no god but He, (the) Lord (of) the Throne the Great."

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These ayats are the only time we hear the speech of a bird and it's chosen word is that of a believer (as good as any counterpart human Muslim could have worded it)

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In his explanation to Sulamain, he mentions their prostration to the sun instead of Allah is averted from the way.

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This speech means birds are not interested in the sunrise but more concerned in waking up and glorifying Allah with contact prayer.