Sótano de las Golondrinas was named after the numerous birds living in holes of the cavern wall. Golondrinas is the Méxican name for swallows. However, the birds of the cave are swifts (Apus apus), locally called vencejos and parrots (Aratinga holochlora), locally called Perico Quila or Cotorra de Cueva.
The cave is - amongst cavers - one of the most famous caves of the world. It is the second deepest entrance drop of the world, 376m deep, and a challenge for any caver. Going down the pit means a 20 mins. abseil to the bottom. A lot of energy transformed into heat, a problem for rope and abseil equipment.
But the way back is the real challenge! The caver has to climb up a single rope, using rope clamps, which is very exhausting. It is at least 40 mins of enormous exertion, even for extremely fit cavers a hard fight. For normal, physically fit people it more or less two hours of ascend.
And then there is psychology: the height of the cave is not the only problem, the width makes it look much easier and smaller than it really is. Our brain is not used to estimate this dimensions realistic, so the climber gets the impression to work really hard without any progression. The walls are too far away to show his movement.
The floor of the pit is covered with meters of dung from the millions of birds. This dung, the rainwater, and debris from the surface are the food base to numerous animals on the cave floor. There are millipedes and insects, snakes, and scorpions. The air is filled with smells, fungi and bacteria. It is possible to visit the floor without respiration mask, but cavers who want to explore the corners of the cave should bring such equipment. There is always the danger of Histoplasmosis and other diseases.
In the last years the cave became a sort of Mecca for base jumpers, parachutists and team building companies. This is rather positive for the locals, who had no other income until now, than their farming. They do not even have a regular road to the village, just a single lane track only suitable to 4WDs. But the increasing number of visitors also makes problems. Especially pollution is a serious problem.
To protect nature, the cavern and its unique ecosystem, the cavers agreed to use only one point at the rim for their descends. This place is equipped with bolts for the rope. Another point is the time of day, as the birds fly in and out of the cave at morning and evening. Typically they leave the cave at dawn and return at dusk. Cavers, and especially base jumpers, should avoid this time of day. (text from: ShowCaves)