Reference for Zevachim 128:11

במתניתא תנא ציפרא מלבר אוחז גפיו בשתי אצבעות ושני רגלים בשתי אצבעות ומותח צוארו על רוחב שתי אצבעותיו ומולק וזו עבודה קשה שבמקדש

In a Baraitha it was taught: The bird is without:<span class="x" onmousemove="('comment',' It is grasped face-downward to the palm of the hand, so that its nape is uppermost.');">¹⁷</span> he holds its wings in two fingers and its two legs with two fingers, stretches its neck over the width of two fingers, and pinches it off; and this was a difficult rite the Temple. This and no other?

Jastrow