Burrowing parakeet  (Cyanoliseus patagonus)

A highly gregarious species, the burrowing parakeet forms large, conspicuous colonies, which are easily located by the cacophony of noisy shrieks that they produce (2) (4). The birds form strictly monogamous, lifelong breeding pairs, which excavate nesting burrows in cliff faces, peppering them with holes (4). The largest colony, found at El Condor, Argentina, extends over nine kilometres of ocean-facing, sandstone cliff and features 35,000 active nest burrows (2) (4). A migratory species, the burrowing parakeet arrives at the breeding grounds between November and April in the northern part of its range, and in October to February further south (2). The colonies are occupied by the breeding adults for around one to two months before egg-laying commences. Established pairs generally re-use the same burrow each year, but continually enlarge it, whereas newly formed pairs must excavate an entirely new burrow. The burrow comprises a tunnel of between 80 and 250 cm long, which often runs in a zigzag, interconnecting with the tunnels of neighbouring pairs, before opening into a nest chamber in which the chicks are raised (4). A clutch of two to five eggs is laid directly onto the sandy floor of the nest chamber, where they are incubated by the female for around 24 days while the male provides food (2) (4). Fledging takes place after around 60 days, after which time the young can leave the nest, but are believed to be fed by the parent birds for a further four months (2).

Outside the breeding season, the burrowing parakeet forms large flocks of over 1,000 birds, which roost communally in trees, wires and the nesting burrows used during the breeding season (2). These flocks can travel large distances, sometimes hundreds of kilometres away from the breeding grounds (4). The diet of this species is mainly seeds and fruit, but may also include grain crops (2).