Use an itchthyornis to gather fish for it. The buff increases efficiency.

Tame to this kill fish and drag there body to it and once tamed if you feed them more dead fish corpses it will build up and lay a golden egg which is used as a buff to certain dinos or oil or a player buff

Feeding them sabertooth salmon seems to work the best.

Put it in a taming box these birds are an easy kill for predators

Taming an ichthyornis will allow you to gather the corpse by setting it on hunt and retrieve, after the fish is killed it will deliver the corpse right to you and you can tame the Hesperornis

Use a horse to lasso it, then you can move it around to new fish spawns when the area gets cleared. The horse can also step on the duck to pin it down, or simply use the lasso to keep it close while tribemates gather fish.

Can't be picked up by anything while they are wild. They do aggro on you, and can walk through door frames, so you can kite them to a taming pen then use an itchy to bring those succulent salmon to you. Tamed a 140 last night in about 20 minutes.

One of the worst things you need to tame for kibble, but this is how to do it:
1. Craft a wooden cage
2. Aggro it onto land
3. Place cage on top of it
4. Spend an hour killing fish and dragging them to it, feeding it through the bars carefully or you’ll open the cage and let it out.
5. You let it out, didn’t you? Pick the cage up and trap it again.
6. Watch out for that ichth- It stoke your fish... and half the stuff in your inventory. Kill it.
7. Cuss in frustration at every piranha on the Ark trying to eat you, then feed them to it too.
8. Finally finish taming the dumb bird - now just remember to keep feeding it fish forever.

Oh and watch out for Argentavis in the area, they like corpses and they don’t like you even if you’re carrying the corpse. They’ll steal your fish and then try to kill you.

I picked it up with a grappling hook, then jumped on my wyvern & flew it to a safer place to tame with lots of salmon. I also threw a tent over it to stop it from wandering off. Best way to tame. So much easier.

Terribly long to tame it ...terribly long

Build a pen to lock them in and then bring fish to it to tame and earn yourself a golden egg to make kibble

Lasso, drag onto a trap boat, then ride around to the fish. Bigger the fish, faster the tame.

Can’t tame in snow cave on extinction.

If you insist on taming one without an Ichthythornis, a good thing to be aware of is that the Hesperonis will sometimes be unable to eat a fish it kills, swimming back and forth to try and "find" it.
You can pick up a fish it's killed and feed it to it, and it counts for tame progress.
Also be aware that if you drop a fish you've killed, it can eat your fish off the floor and it will not give tame progress.

Feeding them sabertooth salmon seems to work the best.

Use an otter or itchyothornis to collect fish for you then go to the hesperornis and feed it the collected fish. They love sabertooth salmon so target those.

Tame a icthycornis and make it grab a fish it works way better in fact that is the correct way to do it or intended

Make one wooden floor with Four Window frame walls and ramp trap. Than lure it inside by leting it atack you when Come close. Destroy the ramp to not get wandering dilo inside. Than use your Ichthyornis to get some golden fish and bring that to feeding Window or you Can get fish by your self using spear. Wish luck

The best way to tame it is to get fishes from a Ichtyornis. Salmons are the best.

Can be knocked out and then be taken wherever needed by shooting it with a grappling hook. Take it where you want it, let it wake up, start feeding. Also can be taken into a 1x1 trap if youd like to keep it safe and in the same spot. Can fit through a door so no doors allowed.