Sacrifices brought from fowl are not formally zevahim, which are limited to animals that are slaughtered in an ordinary fashion. These sacrifices are prepared for sacrifice by means of melikah, where the kohen will pierce the neck of the bird with his fingernail (see Vayikra 1:14-17 and 5:8-10). The Mishnah on today’s daf describes this preparatory service, and the Gemara quotes a baraita that describes it as the most difficult service that was performed in the Temple.
What was involved in the service of melikah?
Rav Zutra bar Tuviah quotes Rav as teaching that the kohen would hold the wings with two fingers and the legs with two fingers stretching out the bird’s neck, and the bird would be killed by means of the kohen‘s thumbnail. According to thebaraita, the bird’s body was held in such a way that it was outside the hand of the kohen, and – while holding the wings with two fingers and the legs with two fingers – the kohen would kill the bird with his thumbnail.
According to Rav Ovadiah mi-Bartenura, as well as the Rambam, the kohen would hold the bird in his left hand according to one of the two opinions, and would perform melikah with the thumb of his right hand. This parallels cases of slaughter in the Temple, where both hands are used. The Shittah Mekubetzet quotes Tosafot as suggesting that the entire melikahservice was done with the right hand (as depicted in the above illustrations). According to this approach we can easily understand why this service is considered to be the most difficult one, since the bird had to be held and killed with a single hand.