Desperate times call for desperate measures: non-food ingestion by starving seabirds

Abstract

Food deprivation may decrease selectivity in food; however, (1) whether animals can cross a selectivity threshold whereby they ingest non-nutritive items ('non-food') in lieu of food (engaging in pica/lithophagia), (2) their behaviour, or (3) the implications of these behaviours are not documented. By examining carcasses of seabirds that ingested pumice of known provenance prior to death, we provide insights into whether wild animals starve because they have eaten non-food, or whether they eat non-food because they are starving. We investigated ingestion of pumice and plastic in carcasses of short-tailed shearwaters Ardenna tenuirostris following a significant starvation mortality event (also known as seabird wreck), during which millions of shearwaters died along the eastern Australian coastline in 2013. We found that the stomachs of 96.5% of 172 seabirds sampled contained pumice or plastic at the time of death. We used global location sensors to track the 2013 shearwater migration and overlaid these tracks with the dispersing pumice raft from the 2012 Havre underwater volcanic eruption, Kermadec Islands, New Zealand. We determined that shearwaters in a starved state had ingested pumice 12-41 h before death, indicating that starving or food-stressed seabirds exhibit reduced prey discrimination. The provenance of the ingested plastic was not known. Ingestion of non-nutritive items has serious implications for wildlife, particularly long-lived or migrating species. Additional risk to already nutritionally compromised animals includes dietary dilution, gastric foreign body obstruction and toxicity. With a projected changing climate and increased marine pollution and over-exploitation of resources, this study has implications for the interaction of stressors, mass mortalities and exacerbation of existing threats to marine species.

Coastal ecological impacts from pumice rafts

“…The same feeding behaviour is also seen in the fin whale ( Balaenoptera physalus ) and basking shark ( Cetorhinus maximus ), two marine species studied with regard to environmental pollution by microplastic debris 43 . When marine wildlife such as turtles, seabirds, and whales mistake floating plastic waste for prey, most die of starvation, as their stomachs become filled with plastic debris 44 , 45 . We are concerned that a similar situation may occur with filter-feeding fishes mistakenly consuming pumice stones.…”

“…On the island of Okinawa, pumice covered a wide area of the coast, which may alter the behavior patterns of various organisms associated with the area. Although the Okinawa rail is not a seabird a recent study reported that migratory birds ingest pumice stones when they were starving 45 . Changes in the behaviors of migratory birds in areas where pumice rafts occupy fishing areas or have been washed ashore may require more attention.…”

Plastic additives and legacy persistent organic pollutants in the preen gland oil of seabirds sampled across the globe

“…As migration southbound is swift and direct (Carey et al, 2014), ingested plastic/associated contaminants likely reflect exposure in the North Pacific. Most (88%) short-tailed shearwaters retain ingested plastic in their gut when traveling south (Roman et al, 2021b). Therefore, the significant detection of multiple additives in the preen gland samples from this species is not unexpected.…”

A City-Wide Emissions Inventory of Plastic Pollution

“…Over the past several decades, there has been growing awareness of the ubiquity of plastic pollution in the natural environment − and the multitude of impacts it has on living organisms and ecosystems. − Plastic pollution is a chemical stressor: it leaches toxic substances over time, − which may induce hepatic stress, affect reproductive success, and lead to increased rates of mortality in living organisms. , Plastic can also cause physical damage through entanglement − or through a false sense of satiation , when it is ingested. Plastic can alter the cycling of carbon and nitrogen as it breaks down. − The multidimensional nature of plastic pollution makes it a wicked problem that transcends geographic boundaries, warranting global cooperation.…”

“…5−8 Plastic pollution is a chemical stressor: it leaches toxic substances over time, 9−11 which may induce hepatic stress, 12 affect reproductive success, 13 and lead to increased rates of mortality in living organisms. 13,14 Plastic can also cause physical damage through entanglement 15−17 or through a false sense of satiation 18,19 when it is ingested. Plastic can alter the cycling of carbon and nitrogen as it breaks down.…”