Environment Protection and Biodiversity Conservation (Wildlife Conservation Plan for Seabirds) Instrument 2022
30Wildlife Conservation Plan for Seabirds
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Marine debris can affect seabirds either through ingestion or entanglement. Most of the marine debris affecting seabirds is derived from consumer waste. Many species ingest considerable quantities of plastic and other marine debris, which has a wide range of lethal or sub-lethal effects. The debris can cause physical damage, or perforation, mechanical blockage or impairment of the digestive system, resulting in starvation. Chicks appear to be at greater risk than adults because of their high rates of ingestion and low frequency of regurgitated casting of indigestible material. When the plastics are regurgitated to chicks, the physical impaction and internal ulceration are likely to lower survival. In addition, the chick receives less food, lowering its nutrient intake and increasing its chances of starvation (Fry et al. 1987; Sileo et al. 1990). For example, as part of the ongoing marine debris surveys in Gulf St Vincent, South Australia, opportunistic necropsy was undertaken on 23 carcasses of Short-tailed Shearwaters that had died and washed up on Goolwa and Waitpinga beaches. These deaths were part of a large-scale mortality of hundreds of these birds across southern Australia, probably due to poor body condition after their seasonal migration from the northern hemisphere. In the study, 70 per cent of the birds had plastic fragments in their gut, which can be passed on to their young by the regurgitation of food (see Carey 2011).
Some seabirds are also killed after becoming entangled in marine debris (Nel and Nel 1999). Such entanglement can constrict growth and circulation, leading to asphyxiation. Entanglement may also increase the bird's drag coefficient through the water, causing the animal to die due to reduced ability to catch prey or avoid predators. The rate of this source of mortality remains completely unknown for Australian species.
The problems of plastic ingestion and entanglement may affect many Australian breeding petrels and has been reviewed in Baker et al. (2002) and Rodriguez et al. (2019). While it is likely that many seabirds ingest plastic debris without it being observed or documented, and birds may become entangled in marine debris from time to time, there is currently no evidence to suggest that ingestion or entanglement are posing a significant threat to any Australian seabird species at the population level.
Section 30 - Environment Protection and Biodiversity Conservation (Wildlife Conservation Plan for Seabirds) Instrument 2022 - Wildlife Conservation Plan for Seabirds | Zoe
Artificial light associated with the urbanisation of coastal areas has been linked to increased seabird mortality (Gineste et al. 2016) and today, 56 petrel species worldwide are known to be impacted by artificial lighting (Rodriguez et al. 2017a,b,c).
All species of seabird are vulnerable to impacts from lighting. Problematic sources of artificial light include coastal residential and hotel developments, street lighting, vehicle lights, sporting facility floodlights, vessel searchlights, cruise ships, fishing vessels, research vessels, gas flares, security lighting, navigation aids and lighthouses (Montevecchi 2006, Rodriguez et al. 2012, 2017a, Raine et al. 2007, Ainley et al. 2001, Troy et al. 2011, Merkel & Johannsen 2011, Black 2005, Deppe et al. 2017).
Wildlife Conservation Plan for Seabirds 31
High rates of “fallout”, or the collision of birds with structures, has been reported in seabirds nesting adjacent to urban or developed areas (Montevecchi 2006, Rodriguez et al. 2017a, Podolsky et al. 1998). Light sourced impacts have also been reported from offshore oil platforms, including gas flares (Bourne 1979, Wiese et al. 2001, Burke et al. 2005).
Adult seabirds are less impacted by artificial lighting than fledglings.
Many procellariforms species (i.e. shearwaters, storm petrels, gadfly petrels) are vulnerable to artificial lighting during nocturnal activities which make up part of the annual breeding cycle. Adult procellariforms are vulnerable when returning to and leaving the nesting colony. They may leave or enter to re-establish their pair bonds with breeding partners, repair nesting burrows, defend nesting sites or to forage. A recent study showed artificial light disrupts adult nest attendance and thus affects weight gain in chicks (Cianchetti-Benedetti et al 2018).
Fledglings are more vulnerable to artificial light than adults due to the naivety of their first flight, the immature development of ganglions in the eye at fledging and the potential connection between light and food (see Montevecchi 2006 and Mitkus et al 2018). Emergence during darkness, believed to be a predator-avoidance strategy (Watanuki 1986) may increase vulnerability to impacts from artificial lighting (Reed et al. 1985). Artificial lights are thought to override the sea-finding cues provided by the moon and star light at the horizon (Telfer et al. 1987) and fledglings can be attracted back to onshore lights after reaching the sea (Rodriguez et al 2014, Podolsky et al 1998). It is possible that fledglings that survive their offshore migration cannot imprint upon their natal colony, preventing them from returning to nest when they mature (Raine et al. 2007). The consequences of exposure to artificial light on the viability of a breeding population of seabirds is unknown (Greisheimer and Holmes 2011).
Chronic pollution
Chemical contamination has been clearly implicated in the decline of a number of seabirds. Its relevance to the conservation of albatrosses and petrels has been reviewed by Baker et al. (2002) and includes deleterious effects through diminished reproductive success caused by eggshell thinning, embryo viability and offspring deformities. Elevated levels of chemicals and heavy metals can be found in the plasma of adults, chicks and eggs of seabirds from every continent and virtually all islands across the globe. Organochlorines and heavy metals degrade very slowly in the environment, are retained by organisms and passed along the food chain, becoming increasingly concentrated. Tributyltin (TBT), whilst its use as an antifoulant has been widely reduced, can accumulate in sediments which can then be released upon disturbance. Consequently, top order predators, such as seabirds and coastal raptors, may accumulate high levels of chemicals in tissues, a problem which is exacerbated because these birds are long-lived and highly mobile species (Falkenberg et al. 1994).
Copley (1996) reported that nutrient enrichment or coastal eutrophication was the marine pollution issue with highest priority in South Australia, particularly with regards to inshore habitat loss of seagrass off the Adelaide metropolitan area and related impacts upon fish and coastal erosion. Flow-on effects of these impacts to seabird populations are not usually obvious but are nonetheless likely to occur (Copley 1996).