As you have done your surveillance work of burrowing see birds at south pacific Island from incubation to near fledged. But I also want to add some idea and also my interpretation you can use if it is useful. I have also experience to observe see bird breeding colony both western Gull, Brand's Cormorant, palegic Cormorant and causin's Auklet at Farallone Island in Pacific Ocean during 1997. I have studied continuously three months at Farallone Islands and studied several marine birds, most of them were Burrowing nesters (Like Rhinoceros Auklet, Pacific Puffin, Pigeon Gulimet, Ashy Storm Petrels, Causin's Auklets etc. at farallone Islnd of pacific Ocean) , (Burrowing nests):During my observation I have seen that causin's Auklets came to the nest at around 19: 30-20:00 hours from the Ocean and feed their chick and returned back and this activity continue till the chick to their fledglings stage(they never came to the burrowing nests during day time for fed their chick) after that both chick and adults become disappear. I suggested that the newly fledged young birds also fly along with their parents to the ocean water  for their first visit to the habitat for own feeding at ocean water. Because, in Island habitat very rarely seen the predator during night time except birds of prey(Owl species, which is also very rare). Waterbird generally never wait for full grown fledgling stage to left their nest like tree nesting birds. For example tree hole nesting water birds like Cotton teal (Nettapus coromendelianus) leave the nest hole before fledgling and went to their parent's feeding habitat like wetlands. In this case parent help them to drop down from the nest hole by pushing them into the ground.

It might be the case that, near fledged chicks were also went to the ocean water along with their parent before full grown fledgling stage. In this case parent also help them to accompany with the chicks and travel to the bank of water by walking along with the chicks and pushed them to the water.

Prasanta kumar saikia.  Gauhati University Assam, India.

Thanks for your response Prasanta Kumar Saikia,

Your observations are interesting as we do not have burrowing seabird species where the adults assist the young, post fledging.  It appears to be a common pattern in non-procellarid northern hemisphere species. If you have any further observations on cross-fostering, I would be interested to communicate further.

thanks

We have seen this on Marion Island (Prince Edward Islands), where chicks (Pterodroma species) were attended by two other burrowing petrel species. However, the birds only attended the chicks for several hours up to several days and not up to fledging.