TERCEL:

Male Peregrine Falco peregrinus, Faucon pèlerin.

2 occurrences (tassel-gentle, tercel)

No wonder this bird ranks among the top in falconry as it is the fastest flying bird in the world, swooping down on its prey at around 200 mph!

Its vernacular name arises from the fact that the male is a third smaller than the female, hence also its French name of tiercelet.

This is the "gentle" bird:

Hist! Romeo, hist! O for a falconer's voice

To lure this tassel-gentle back again.

(ROM 2 2 158-9)

To "lure" the bird meant to call it back using both a special call, something like "Hillo, ho, ho, boy, come, bird, come" (HAM 1 5 118) by which Hamlet answers in a familiar and friendly fashion Marcellus's greeting, and a lure. This last is a device made of a piece of cloth or fake bird, attached to a cord that would attract the falcon back.

Flying at the river or at the brook was, with the fly at the heron (see HANDSAW), the most popular form of hawking. In this case the "quarries" were water-fowl, and the followers could be for the most part on foot instead of mounted as was necessary for the "flight at the heron".

the falcon as the tercel, for all the ducks i'th'river

(TRO 3 2 52 p, emphasis added)

The whole idea of this sport is admirably rendered in the passage which opens the second act of 2 HENRY VI:

QUEEN MARGARET

Believe me, lords, for flying at the brook,

I saw not better sport these seven years' day:

Yet, by your leave, the wind was very high,

And, ten to one, old Joan had not gone out.

KING HENRY (to Gloucester)

But what a point, my lord, your falcon made,

And what a pitch she flew above the rest!

To see how God in all his creatures works!

Yea, man and birds are fain of climbing high.

SUFFOLK

No marvel, and it like your Majesty,

My Lord Protector's hawks do tower so well;

They know their master loves to be aloft,

And bears his thoughts above his falcon's pitch.

GLOUCESTER

My lord, 'tis but a base ignoble mind

That mounts no higher than a bird can soar.

CARDINAL BEAUFORT

I thought as much; he would be above the clouds.

[...]

Believe me, cousin Gloucester,

Had not your man put up the fowl so suddenly,

We had had more sport. (aside to Gloucester)

(2 1 1-15 [...] 47-9, emphasis added)

With the two lines: "To see how God in all his creatures works! / Yea, man and birds are fain of climbing high." (2 1 7-8) the parallel with political affairs starts, and the tone of this description of a fine day spent at hawking is then strangely altered for the strongest dramatic effect.