De Balispreeuw : "Its decline to virtual extinction in the wild is primarily attributable to
unsustainable, illegal trapping in response to worldwide demand for the cage-bird trade. This threat continues despite the fact that the whole population is now confined within a national park and has been the subject of a specific conservation programme."
Wildvangst vanwege de wereldwijde vraag naar kooivogels is dus de belangrijkste reden van de slechte status van Balispreeuw
De Hawaiigans: "The development of agricultural systems by the Polynesians, and later by European settlers, resulted in the extensive loss and alteration of habitat (Olson and James 1991). A lack of suitable habitat, especially for rearing young, is the most important limiting factor,
combined with predation by the introduced small Indian mongoose Herpestes auropunctatus (except on Kaua'i), dogs, cats, pigs and rats (Black
et al. 1994, Black 1995, H. C. Baker and P. E. Baker
in litt. 1999, T. C. Telfer
in litt. 1999, A. Marshall, D. Hu and K. Misajon
in litt. 2007).
"The species benefits from a suit of protected areas, including Hawai'i Volcanoes and Haleakallâ (Maui) national parks, Kîlauea Point (Kaua'i) and Hakalau Forest (Big Island) national wildlife refuges, and several state sanctuaries (Banko
et al. 1997, C. Terry
in litt. 1999). Extensive research has been conducted on factors limiting population growth (e.g. Bailey and Black 1995, Rave 1995, Rojek and Conant 1996). Predators are controlled, and supplementary food and water are sometimes provided at particular sites (C. Terry
in litt. 1999, A. Marshall, D. Hu and K. Misajon
in litt. 2007). Despite the low average fledging success rate recorded in the Hawai'i Volcanoes National Park from 1989-1999, this was more than double the rate in the previous 15 years, owing to predator control and supplementary feeding during breeding seasons (Rave
et al. 2005). Other efforts have involved habitat restoration and reducing human disturbance, especially to breeding birds (Rave
et al. 2005, A. Marshall, D. Hu and K. Misajon
in litt. 2007). Releases of captive birds continued until the late 2000s (A. Marshall, D. Hu and K. Misajon
in litt. 2007), but have now ceased. Translocation of birds from Kaua'i to other islands is on-going, as there is a large population at Kaua'i Lagoons, near the airport (A. Marshall
in litt. 2012). "
Hawaiiganzen hebben dus erg veel last gehad van geïntroduceerde huisdieren, terwijl de toename van deze soort de afgelopen jaren met name tot stand komt door locaties te beschermen en door predatoren onder de duim te houden. Het uitzetten van de vogels wordt blijkbaar niet meer gedaan.
Laysaneend: "Historic declines on Laysan leading to the near-extinction of the species are attributed to
introduced rabbits and more recently the parasitic nematode
Echinuria uncinata, coupled with drought (Work
et al. 2004). Since the severe range contraction of the species from the main Hawaiian Islands
after the introduction of rats, stochastic events that have already occurred include: the accidental introduction of noxious competitors, extreme weather, and disease epizootics. "
en voorgestelde beschermmaatregelen:
"Continue to monitor the population size and health on both Midway Atoll and Laysan Island. Continue to enhance nesting habitat on Midway by planting native bunch grasses. Enhance brood-rearing habitat on Midway Atoll with small fish-free freshwater wetlands with abundant cover. Use translocation and ecosystem restoration to re-establish four additional populations of Laysan Ducks. On Laysan, continue to stabilise dunes by planting native vegetation (Moulton and Marshall 1996). Restore freshwater wetlands on Lisianski and Kure Islands prior to potential re-introduction. Ensure strict procedures to prevent the accidental introduction of exotic plants, invertebrates and animals (Moulton and Marshall 1996). Control exotic plants likely to negatively impact the species. Conduct further alien predator eradications to create potential for reintroduction to other larger higher elevation islands.
After restored predator-free habitat is available, create a new genetically managed captive population within Hawaii to provide birds for reintroductions to other Hawaiian islands (Reynolds
et al. 2006). Investigate the feasibility of vaccinating at least some birds in the Midway Atoll population against avian botulism (Work
et al. 2010)."
Dus ook de Laysaneend heeft last gehad van geïntroduceerde soorten, terwijl IUCN adviseert om op Hawaï zelf te kweken voor uitzet van Laysaneenden, overigens pas nadat alle andere problemen zijn verholpen.
Al met al haal ik hier nou niet bepaald het succesverhaal van gehouden dieren uit, eerder het tegenovergestelde. Peter, kan je misschien kijken of je het succes van het Trinidad verhaal hier kan plaatsen, ik begrijp dat jij daar wel toegang toe hebt en het zou je verhaal wat beter ondersteunen.