Elements of biology entail a certain ‘eww’ factor – and studying the diet of seabirds certainly fits that description. In research into the foraging habits of Buller’s albatross, a threatened endemic species from southern New Zealand, published in the journal Plos one in 2017, scientist Dr Susan Waugh and colleagues discovered more than they bargained for, when examining the regurgitates of young albatrosses at the nest.
The Te Papa team discovered that the Buller’s albatross were being unusually resourceful in their selection of foods to feed young chicks – they found the heads, feathers, and feet of chicks of sooty shearwaters (tītī) at several nests, including observing an adult bird attempting to feed a large bolus of these items to its chick. The chick was a little too small to ingest this gruesome offering, and let it drop to the ground.
This bird was later GPS-tracked, and made several visits to active muttonbirding sites, where traditional harvest involves the collection and processing of sooty shearwater chicks, preserved in fat over months for later consumption.
Albatrosses raise their fluffy chicks over several months, and can feed hundreds of kilometres from the nest to nourish their hungry brood of one. The GPS-tracked birds in the study frequented the rich southern waters of New Zealand, but mainly used the Foveaux Strait area, and within 100 km of their nest sites during the 2016 Te Papa study.
This region also contains the main New Zealand nesting grounds of the sooty shearwater, which nest in their millions on many offshore islands around New Zealand. The nesting sites near Stewart Island are traditional harvest grounds for Ngāi Tahu iwi, and the tītī (juvenile sooty shearwaters) harvested at these sites have sustained the traditional owners over the course of centuries.
It seems that this ‘recycling’ practice by the albatrosses may have been going on for some time, as participants in the tītī harvest noted that they often saw Buller’s albatross attending the areas where the viscera, heads, and discards from the tītī harvest are disposed of along coastal cliffs and bays.
In dietary and tracking studies of these birds in the 1990s, researchers found that they concentrated their efforts around the Foveaux Strait area in the period when the tītī harvest was getting underway, and had noted that there were clumps of feathers in the diet samples taken from young albatross chicks in the harvest period (April and May).
Curiously, the average hatching date for Buller’s albatross chicks coincides with the start of the tītī harvest (the first week of April). It would take a sustained and detailed study to determine whether there was a dependence of the albatrosses, or causality in the timing of their breeding cycle, that could be attributed to the tītī harvest. But it would be intriguing to learn more about how traditional environmental practices influence the ecosystem – could it be that the ‘left-overs’ from the harvest of tītī are helping to sustain populations of endangered albatrosses?
- Waugh SM, Poupart TA, Miskelly CM, Stahl J-C, Arnould JPY (2017) Human exploitation assisting a threatened species? The case of muttonbirders and Buller’s albatross. PLoS ONE 12(4): e0175458. https://doi.org/10.1371/journal.pone.0175458