==Ecology==
According to Perfect Memento, fairies do not require food to stay alive, and there's only been cases of fairies eating food because they seemed delicious. However, they do have taste, and they like food that human children like. Luna Child is an exception for liking coffee. Coffee was too bitter for Cirno to drink. Also, they drink alcohol and do get drunk.

Perfect Memento commented that fairy maids receive no wage, but are instead given food, tea, and freedom. There are many depictions of fairy maids drinking tea.

So fairies can eat, but do not need it.

Fairies have never been seen to go to the bathroom or take a shower. There was a scene in Touhou Sangetsusei where a fairy changed clothing, and in all scenes so far, they change into clothes of the same design as before. There was also a scene where the Three Fairies of Light stole some maid clothing from the Scarlet Devil Mansion.

Since fairies participate in spell card battles which are are the activities of women and children, this means that fairies are women and children, and all fairies to appear so far have been female.

==Activities==
Many fairies see playing mischief on humans as their purpose in life. In Touhou Sangetsusei, they often steal and pick up ingredients and tools, like coffee. The Kourindou has also been a victim to this before. They appear to be disliked by humans.

Cirno is well-known for freezing frogs. Also, there was a scene where she played hide-and-seek with Daiyousei. They also go went on a "trial of guts" at the Hakurei Shrine where the three fairies of light and youkai participated. Fairies often play with each other and other species.

According to Sakuya Izayoi, fairy maids are rarely of any use in the Scarlet Devil Mansion, and are unsuited towards performing complex tasks, relating to how fairies are not very smart.

Since fairies maids do at least exist, it means they are at least able to do some tasks a maid can. They have been confirmed to wash clothes, cook, and play musical instruments. Thus, despite not being smart, they can still perform a variety of tasks.

==Turning into youkai==
Several statements have implied that fairies can turn into youkai. Luna Child was told by Yukari, "You are the closest to a youkai" in Touhou Sangetsusei. In Phantasmagoria of Flower View, Eiki Shiki told Cirno, "Although you are a fairy, you possess great power... At this rate, you will not be able to return to your original power of nature and you may receive damage... In other words, that means death. If you die, then we will most definitely judge you."

Thus, Eiki says that a fairy with such great power like Cirno has may not be able to rely on the powers of nature that created them, and thus stop being a fairy. By ceasing to be a fairy, they lose the immortality that fairies possess, and will therefore be able to die.

There has not been a case of a fairy turning into a youkai yet, however.

==Strength and Danger==
Fairies are weak. They often appear as generic weakling enemies alongside spirits, and often appear in game just for the sake of being defeated. Unlike spirits, though, most fairies can speak, according to one of ZUN's emails. Daiyousei is an exception for having a greater amount of power among the fairies.

When the three fairies of light, who are considered stronger among the fairies, together fought Yukari Yakumo, they were unable to inflict any damage and were called "very weak." In Perfect Memento, the fairies Cirno and Sunny Milk were evaluated with danger level "low." Akyuu wrote that it is safe to even go take revenge for their mischief by capturing them. However, Cirno and Lily White are comparatively strong, so they can be dangerous to the ordinary human.

Sometimes they play "pranks that go too far" like making humans fall from cliffs, and that would be a dangerous aspect of them. Thus, Akyuu recommended to take caution in places where a fairy might be there.

Sunny milk once said that Lily White was dangerous and one must not get close to her. According to Akyuu, Cirno is one of the stronger of the fairies, and since she is used to battle, Cirno has the upper hand even if she goes against all Three Fairies of Light at the same time. Among the fairies, she also has a greater tendency to fight, which makes her more dangeorus than normal fairies.

According to Eiki Shiki's words, Cirno's power may eventually surpass that of a fairy's.

In Touhou Sangetsusei, the Three Fairies of Light have had their power levels remain constant throughout.

Daiyousei was remarked to be "one with power among the fiaries." Thus, to normal fairies, she has more power than the average one but not enough to match Cirno's level.

The fairies appear very powerful in Fairy Wars, but it was in Cirno's perspective.

==Intelligence==
Fairies are dumb. For example, in the manual for Fairy Wars, it was remarked, "when the war ends, they will completely forget everything they said." They are about on the level of an elementary schooler, but there is also variation. Here are examples of things that they can do:

:'''Talk'''
::Lily White has been depicted to speak more than "spring is here." In fact, all fairies are able to speak, according to one of ZUN's emails.
::It has been remarked that they would not understand more difficult talk. Perfect Memento mentioned that when one encounters a relatively more dangerous fairy like Cirno, one could get away by confusing them with a riddle.
:'''Write'''
::Sunny Milk writes kanji in Touhou Sangetsusei. Cirno writes everything in Hiragana. She sometimes makes mistakes.
:'''Read'''
::This follows from how they can write. Also, according to Bohemian Archive in Japanese Red, Cirno reads the Bunbunmaru Newspaper, meaning she is able to at least understand the kinds of opinion pieces written in them. Also, in Hisoutensoku, she begs for Aya Shameimaru to write more about her, indicating that she takes at least somewhat of an interest in it.
::Luna Child likes to read the Bunbunmaru Newspaper. When there's something she doesn't know, namely about family altars, she goes to do research by reading about it in books, and it appears that she understands it at least somewhat.
:'''Cook'''
::Star Sapphire cooks. The things she cooked appear to require the usage of fire, pans, and knives.
::Sunny Milk and Luna Child ran a successful food stall, meaning they are also capable of a good level of cooking.
::Fairy maids have also cooked.
:'''Remember winter events during spring'''
::In the spring, Cirno remembered the three fairies declaring war back in winter. However, she forgot about it until spring arrived.
::Luna said that the event where they destroyed Cirno's house was "something that happened way back," which could indicate bad memory or mean that they have a greater sense of time passing than that of a humans.
:'''Run a stall'''
::In Sangetsusei, the Three Fairies of Light were seen running a stall at the Hakurei Shrine. Sunny Milk was selling Oden, Luna Child was selling alcohol, fuuki miso, yakitori, and pig legs, and Star Sapphire was selling yoyotsuri, and they looked like they were a success, but nobody bought the out-of-season shaved ice (mizuaji) from from Cirno. Cirno also didn't know why nobody bought it.
::Thus, fairies are at least able to understand how running a business works, and able to perform the tasks that are require to prepare and run it.

==Economic impact==
Since they don't require food, and live within nature, they generally have no need for money. However, the Three Fairies of Light get coffee to prepare it, and therefore need to obtain the ingredients needed for it.

Fairies steal things as a prank, but they've said that they never steal money. The three fairies have visited the Myouren Temple without needing to disguise the fact that they're fairies, indicating that despite their mischief, there is no overt hatred against them.

Since three Fairies of Light were able to be successful in running a food stall, some fairies are able to earn money depending on their will.