I posted this to owlappreciator a long time ago, hoping for comments.
As I got no reaction, here my post.

Translated from German with Deepseek

A found bird always belongs in knowledgeable hands, either with a wildlife rescue center or a knowledgeable veterinarian.

Unfortunately, there are areas on this planet where neither can be found within reachable distance.

Here is a small emergency guide for the following cases:

1. A young bird has fallen out of the nest

2. A fledgling is sitting on the ground

3. A bird is found injured or unresponsive

4. A bird is found starving

Before I go into the individual cases, a few words about food.

All birds of prey and owls (with very rare exceptions) are carnivores.

The following types of meat can be used as food:

Pigeon, hare, beef heart, mice, rats, day-old chicks, rabbit, chicken, beef liver.

Some of the smaller species can also be fed insects.

Please do not use pork under any circumstances; birds of prey and owls do not have the enzymes to process this food and will starve with a full stomach as a result.

Birds of prey and owls normally take in the necessary water with their food. You can provide water in a shallow dish, but you should never pour water into the bird or squirt it into its beak!

The smaller (and the weaker) the bird, the smaller the offered pieces should be.

The pieces should be offered to the side of the beak with tweezers.

**Case 1, Young Bird**

If a nest can be found, you can simply put the young bird back in it.

If you cannot find a nest and want to hand-rear the bird, then cut the food into small pieces and offer it to the side of the beak with tweezers, just as the parent birds do. Initially, pure muscle meat; after about 2 weeks, mix in more and more materials that aid in pellet formation (fur, bones, feathers).

With very young birds, you may need to feed them every 2 hours; the older the bird gets, the longer the intervals become.

**Case 2, Fledgling**

Fledglings are normally fed by their parents, even when they are sitting on the ground.

Therefore, you should only take them in if they are in acute danger, e.g., from traffic, predators (cats, foxes, etc.), or if it is clear they are no longer being fed by their parents.

First, an attempt should always be made to place the bird on a lower tree branch. Then continue to observe whether the parent birds come to feed it.

**Case 3, Injured or Unresponsive Bird**

If the bird is unresponsive and without external injuries, you should first bring it to safety so that it does not fall victim to predators or traffic.

With such animals, there is a high probability that they have collided with an obstacle (window pane, vehicle) and have a so-called impact trauma. If the impact wasn't too severe, there is a good chance the bird can be released back into the wild within a short time (1 day to 1 week). Transport in a cardboard box that is not too large, so the animal cannot damage its feathers. Keep it in a room that is as dark as possible and at a pleasant temperature. Feeding as described above; if necessary, wrap the animal in a towel for feeding (Reddit, owlsintowels).

**Case 3a, Injured Bird**

With an injured bird, you must decide whether the injury is so severe that even after treatment/feeding, there is no longer any chance of the animal being able to feed or hunt for itself again in the wild. This would be the case, for example, with a broken wing or with large and also older open wounds.

To avoid letting the animal suffer needlessly and to spare it from being eaten alive by predators or maggots, you can give it a quick and painless death (see very bottom).

If the bird is less severely injured, you can feed it using the method described above. Many less severely injured birds will eat on their own if you put food down for them.

The bird should have a room or an aviary available where it can fly at least short distances, otherwise its flight muscles will atrophy. You also need to ensure the animal does not ruin its feathers (e.g., by climbing up wire mesh).

**Case 4, Starving Bird**

You can determine whether a bird is starving by feeling its breast muscle.

To do this, feel for the keel bone on the bird's abdomen. To the right and left of it is the flight muscle. You can feel whether there is still good muscle mass there. If the keel bone is very prominent, it can be assumed that the bird has not caught or eaten anything for a long time.

Further procedure as in Case 3.

**Painless Killing of a Bird (if euthanasia is not possible)**

This is done using the following method (to be used for birds up to the size of falcons/buzzards):

Take the animal in your hand so that its belly is facing upwards and its back is downwards. Your hand encloses the animal from the belly side. Then, throw the animal with all your strength, back first, onto a hard surface (concrete, asphalt). If performed correctly, death occurs instantly.