Migration

When the migration of a species is consistent and predictable this is referred to as obligatory migration[2]. This includes seasonal mass, long distance movement between feeding and breeding grounds undertaken by birds and whales. Most of these species return to the same areas year after year.

Facultative migration is the irregular movement of biota, often in response to conditions or resources[2]. For example, some individuals of a species may not migrate one year because there are adequate resources for breeding, but the next year they may migrate to another area. Facultative migration is not as predictable and may not involve all individuals, with some individuals not moving and those that do move starting at variable times.

Wetland dependant animals that migrate include those that travel over large transcontinental distances like migratory waterbirds, whales and turtles, or those moving smaller distances in and out with the tide, or up and down through the water column in diurnal migration (plankton)[1]. Many of the larger wetland species that migrate across several countries are recognised under international agreements and conventions that are incorporated into Australia’s federal and state legislation protection measures.

Many shorebirds in Australia migrate every year to breed in Arctic, sub-Arctic and other far northern wetlands of Asia and Alaska where food resources are abundant and nest sites plentiful during the northern summers[4].Other waterbirds undertake more irregular movements within Australia to suitable wetland habitat, when conditions are favourable, such as large migration of Pelicans to Currawinya Lakes to breed during major flooding events in the Paroo catchment.

Biota living in the water column (pelagic), or close to the sea floor (demersal) can often have migratory life phases including migrations between freshwater and saltwater[6]. Migration is part of the lifecycle of many fish species so they can access spawning grounds or follow rich feeding habitats (see Aquatic Fauna Passage).

Adult freshwater eels (Anguilla sp.) migrate thousands of kilometres from upstream freshwater wetlands to tropical marine waters to spawn[5]. Once spawning has occurred the adult eels die, and eel larvae (a leptocephalus) start travelling back towards the coast. During their travel in marine areas larvae transform into glass eels (eel form but translucent) and then again into brown elvers when they move into freshwaters and travel upstream to start their adult life[5].

Migration triggers for estuarine and marine species include daylength (light), tides, currents, freshwater inputs and water temperature. Changes in ocean temperatures and current circulation patterns due to climate change, including the warming and speeding up of the East Australian Current, are redistributing estuarine and marine species that live in the water column or have pelagic lifecycle phases[3].

Links and References

• Shorebird migration - WetlandInfo
• Turtles and migration – tracking
• Legislation for migratory animals
• Migratory species in Australian government policy and legislation
• East Asian Australasian Flyway for migratory birds - WetlandInfo
• Australian Migratory Shorebird Habitat Directory
• National Directory of Important Migratory Shorebird Habitat

References

1. ^ Begon, M & Townsend, CR (2020), Ecology: from individuals to ecosystems, p. 1, Wiley, Hoboken, NJ.
2. ^ a b c d Dingle, H & Drake, VA (1 February 2007), 'What Is Migration?', BioScience. [online], vol. 57, no. 2, pp. 113-121. Available at: https://doi.org/10.1641/B570206 [Accessed 3 September 2023].
3. ^ García Molinos, J, Hunt, HL, Green, ME, Champion, C, Hartog, JR & Pecl, GT (3 December 2022), 'Climate, currents and species traits contribute to early stages of marine species redistribution', Communications Biology. [online], vol. 5, no. 1, p. 1329. Available at: https://www.nature.com/articles/s42003-022-04273-0 [Accessed 12 October 2023].
4. ^ Geering, ADW, Agnew, L & Harding, S (2007), Shorebirds of Australia. [online], CSIRO Pub., Victoria, Australia. Available at: https://www.publish.csiro.au/book/5345/ [Accessed 13 November 2020].
5. ^ a b Pusey, B, Kennard, M & Arthington, AH (2004), Freshwater fishes of north-eastern Australia, CSIRO.
6. ^ Rubenstein, DI & Hack, MA (2013), 'Migration', in Encyclopedia of Biodiversity. [online], Elsevier, pp. 309-320. Available at: https://linkinghub.elsevier.com/retrieve/pii/B9780123847195000952 [Accessed 12 October 2023].
7. ^ Science, Q, sector=government & corporateName=Department of Environment and (15 June 2021), 'Give whales a wide berth during migration season', Department of Environment and Science, Queensland. [online] Available at: https://www.des.qld.gov.au/our-department/news-media/mediareleases/2021/give-whales-a-wide-berth-during-migration-season [Accessed 27 October 2023].

Last updated: 23 October 2023