noun
colony site; breeding grounds; rookery
Refers to a location where animals, especially birds or marine mammals, gather in large numbers to breed or nest. Often used in ecological or wildlife contexts.
この島はアザラシの群生地として知られている。
This island is known as a breeding ground for seals.
海岸の崖にはウミネコの群生地がある。
There is a black-tailed gull colony on the coastal cliffs.
繁殖地 is a more general term for 'breeding ground' or 'breeding area', while 群生地 emphasizes the gathering of a large group (colony).
Compound of 群生 (ぐんせい, 'growing in clusters' or 'living in colonies') + 地 (ち, 'land' or 'place'). The alternative form 群棲地 uses 棲 (dwelling) to emphasize habitation.