Kay. Let's go into the summoning proper. You should remember the default summoning process. You make a blood contract with the crows and then through you sacrificing your blood, you are able to summon the animal. You will be chakra, weave several handseals and press your palm against a physical surface to summon the animal.
(Kuchiyose no Jutsu) - Summoning Technique
Rank: B
Type: Defense/Attack/Suplementary
Range: N/A
Chakra Cost: 20
Damage points: N/A
Description:
To summon the creature the ninja will wipe blood on his hand, perform the Boar → Dog → Bird → Monkey → Ram handseals and then touch the ground or another object, where a sealing formula will appear. Though it appears that as long as significant pressure is placed against the blood in some form, the summon will be complete, most summoning uses use a solid surface, though in some cases it can even be done mid air. There can be variations to the summoning steps, some ninja like Temari will wipe blood on her fan, then by swinging the fan the animal is summoned. Other ninja like Orochimaru wipe the blood across a snake tattoo on their arm first, then touch the ground. Others will clap their hands directly like Nagato through the use of his Animal Path. The user must have signed the contract with the creature he wants to summon but the technique can be used to summon a generic creature of that contract (B-Rank) which will have no special traits or abilities beyond those normal to the rest of the animals in the contract. The animal is always summoned on the mark that appears upon slamming the users hand or, if not the case, always in short range of the user.
(Kuchiyose no Jutsu: Satsujin Konmei no Karasu) - Summoning Technique: Murder of Crows Confusion
Type: Supplementary
Rank: C
Range: Short-Long
Chakra: 15
Damage: N/A
Description: Summoning a massive swarm of crows, they will fly around the target, causing confusion with their dark forms and quick movement. With the target distracted by the crows, the ninja can strike more easily. Also the mass of crows can obscure any retreating ninja. When no longer needed, the murder of crows will simply puff away in smoke.
Now depending on which style you want whether the default wiping blood on palm or other custom methods, summon a massive swarm of crows to surround me.