|Birds||< Waterbirds >||Reptiles|
Seabirds depend on marine ecosystems at least during a major part of their life cycle. Figure 4.8 shows the high number of migrants within seabird families, which has been name-giving for entire genera such as Oceanodroma or species such as the white-faced storm-petrel (Pelagodroma marina).38 A considerable number of species among the petrels, storm-petrels and albatrosses is pelagic, undertaking wide foraging trips of up to several 1000 km, but returning to their colonies, which are often confined to tiny islands (Figures A2.54-A2.57). This site fidelity exposes them to similar threats as other island species, which are particularly vulnerable to introduced species such as rats, cats or cattle, or become easy prey for hunters. Other species such as gulls and terns have large breeding ranges, sometimes extending far inland to freshwater habitats, river margins or lakes (Figures A2.60-A2.61). The arctic tern (Sterna paradisaea) holds the record among all migratory animals, migrating 20,000 km two times a year from pole to pole. Consequently, most seabirds are characterised by migration between areas outside national jurisdiction and those under the jurisdiction of one or more states.
With 66 red-listed species, seabirds hold a sad record among migratory birds (Figure 4.5, see p. 71). A frightening number of 32 species was upgraded to one of the "threatened" categories (CR, EN, VU: see Figure 4.2), 18 of which have not been listed at all within the Red List 1996. Though part of these changes are a consequence of taxonomic splitting within the albatrosses (Nunn 1996) and the petrels39, they clearly reflect the consequences of direct and indirect threats from fisheries.
The conservation status of albatrosses (Diomedeidae) is particularly bad. Of the 20 species contained within the IUCN Red List 2000, 16 (80%) have a threatened status (CR, EN or VU). As already noted by Croxall & Gales (1997), this is the highest proportion of threatened species in any bird family having more than a single species. The CMS lists 2 albatrosses on Appendix I (Figures A2.54, A2.55), and 12 further species on its Appendix II. Note that albatross taxonomy is undergoing changes, and that CMS and the GROMS database40 still uses the conservative nomenclature with a total of 16 species, but 23 subspecies (all covered by CMS). The most serious threat is longline fishing, but Croxall (1997) mentions additional threats listed in Table 4.7.
Fig. 4.8: Number of migrants within seabird families.
Total bar: species numbers within the family, according to del Hoyo et al. (1992, p. 69ff).
Black: number of migrants. An asteriks and numbers in brackets indicate major deviations in species numbers, according to new taxonomic data.
Abb. 4.8: Anzahl der wandernden Arten innerhalb der Seevögel.
Balken (gesamt): Artenzahlen innerhalb einer Familie nach del Hoyo et al. (1992, S. 69ff).
Schwarz: Anzahl wandernder Arten. Sternchen und Zahlen in Klammern weisen auf wesentliche Veränderungen der Artenzahlen aufgrund neuer taxonomischer Erkenntnisse hin.
|Tab. 4.7: Threats identified for albatrosses (according to Croxall 1997)||Tab. 4.7: Gefährdungen für Albatrosse (nach Croxall 1997)|
|Longline fishing||[...] the latest – though potentially most serious threats [...] an actual or potential problem for nearly all species of albatross|
|Introduced predators||Rats, cats, mustelids, pigs and cattle [...] there is a need for persistent vigilance to prevent inadvertent release of predators to any island where albatrosses breed|
|Habitat degradation (on land)||[...] restriction of breeding area by humans; some evidence of climatically-induced changes|
|Habitat degradation (at sea)||The progressive degradation of habitat at sea [...] is proceeding, but at largely unknown rates and with uncertain consequences [...] may have more serious long-term effects.|
|Pollutants (Plastic)||Probably all species ingest plastics nowadays [...] dead chicks had more plastic and lighter body mass|
|Pollutants (Organochlorides)||It is likely that all albatrosses [...] have detectable concentrations of DDT and PCBs, but few studies are available|
Several seabird species have already become extinct. The enigmatic "Riesenalk" – the arctic "penguin" – was extirpated by hunting as early as early as 1844, but we will never know exactly if it was a migratory species. Though listed as "Critically Endangered" by Hilton-Taylor (2000), the Guadeloupe Storm Petrel (Oceanodroma macrodactyla) is generally considered extinct and has not been observed at Guadeloupe Island, Mexico, since 1912. The remaining five species of critically endangered seabirds have extremely low population numbers, the rarest being the Amsterdam albatross, with a breeding population of only 20 pairs (Figure A2.55). The Townsend shearwater (Puffinus auricularis) and the Chinese crested tern (Sterna bernsteini) are critically endangered, but not listed by the CMS, and consequently suggested for future incorporation into its appendices, as they both do cross international boundaries during their migrations (see Table 4.8). Sterna bernsteini seems to migrate from China to the Tropics, but is virtually unknown, and possibly even extinct (del Hoyo et al. 1996).
Ten species of petrels (Procellariidae) are already listed by CMS, taking into account their bad conservation status. Pterodroma cahow, P. phaeophygia and P. sandwichensis are listed on Appendix I (see Figures A2.56, A2.57). Another Appendix I species, the Japanese murrelet (Alcidae: Synthiloramphus wumizume) is facing similar threats, but restricted to a small breeding area in Japan (Figure A2.59). Three additional murrelets and seabirds from various families such as skimmers, penguins and gannets are threatened, and therefore suggested here for listing by CMS (Table 4.8). In addition, the International Red List 2000 diagnoses knowledge gaps ("Data Deficient") for three species of storm petrels (Oceanodroma markhami, O. hornbyi and O. matsudairae), and probably suffer from similar threats as their congeners.
An analysis of the main threat category according to the IUCN Red List 2000 (Hilton-Taylor 2000) reveals that 32 seabird species are threatened by "accidental mortality", probably mainly due to fishery. A closer look into case studies reveals that entanglement and bycatch from fishery is the major problem affecting seabirds. For the Japanese murrelet (Synthliboramphus wumizume), incidental by-catch by high-seas drift nets accounts for 10% annual mortality (Figure A2.59, and references therein).
Indirect negative effects of fisheries are entanglement by lost fishing gear ("ghost fishing") and depletion of food resources by human over-exploitation. A detailed analysis of distinct fisheries, in particular long-line, on albatrosses was performed as part of the Australian Threat Abatement Plan, which led to a detailed action plan with implementation scheme, and a preliminary MoU (Norman 2000). Further aspects of the detrimental effects of fisheries are discussed within the sections on marine mammals, turtles and fishes.
|38||Greek: Okeanos = ocean, dromas = walking.|
|39||The spectacled petrel (Procellaria conspicillata) is listed as a separate species by the IUCN Red List 2000 (Hilton-Taylor 2000), but is considered as a subspecies of the white-chinned petrel, Procellaria aequinoctalis, on CMS Appendix II.|
|40||The "new taxonomy" is listed as "important synonym" within the species or population table.|
|Birds||< Waterbirds >||Reptiles|
This document should be quoted as part of the publication "Riede, K. (2001): The Global Register of Migratory Species Database, GIS Maps and Threat Analysis. Münster (Landwirtschaftsverlag), 400 pp." + CD
by Klaus Riede