Post-release effects on reintroduced populations of hihi
Panfylova, Julia ; Bemelmans, Ellis ; Devine, Chris ; Frost, Peter ; Armstrong, Doug - \ 2016
Journal of Wildlife Management 80 (2016)6. - ISSN 0022-541X - p. 970 - 977.
capture-mark-recapture - hihi - MARK - New Zealand - Notiomystis cincta - post-release effects - reintroduction - survival
Modeling survival of reintroduced populations is critical for understanding population dynamics and therefore making appropriate management decisions. We analyzed survival data collected over the first 2 years after a reintroduction of hihi (Notiomystis cincta), an endangered New Zealand forest bird, to Bushy Park, a conservation reserve in New Zealand enclosed by a predator-exclusion fence. We constructed a set of candidate models representing different hypotheses about the effects of age, sex, and post-release acclimation on survival, and used model averaging to obtain parameter estimates reflecting the relative support for the models. In combination with fecundity data, we constructed a stochastic population model incorporating uncertainty in parameter estimation, and used this to project population dynamics over the next 10 years. The survival analysis indicated that female survival was unusually low over a 6-month acclimation period; hence, this initial low survival was not reflected in the estimates of long-term survival obtained through model averaging. The resulting projections showed that although population growth was highly uncertain, there was a negligible probability of extinction over the next 10 years, therefore indicating that the existing management regime (i.e., supplementary feeding and nest box maintenance) should be continued. In contrast, if post-release effects had not been accounted for, the projections would have shown a high probability of decline under this management regime.
Verification of Egg Farming Systems from the Netherlands and New Zealand Using Stable Isotopes
Rogers, Karyne M. ; Ruth, Saskia Van; Alewijn, Martin ; Philips, Andy ; Rogers, Pam - \ 2015
Journal of Agricultural and Food Chemistry 63 (2015)38. - ISSN 0021-8561 - p. 8372 - 8380.
authenticity - barn - carbon - diet - egg albumen - free range - isotope - Netherlands - New Zealand - nitrogen - organic - supermarket
Stable isotopes were used to develop authentication criteria of eggs laid under cage, barn, free range, and organic farming regimens from The Netherlands and New Zealand. A training set of commercial poultry feeds and egg albumen from 49 poultry farms across The Netherlands was used to determine the isotopic variability of organic and conventional feeds and to assess trophic effects of these corresponding feeds and barn, free range, and organic farming regimens on corresponding egg albumen. A further 52 brands of New Zealand eggs were sampled from supermarket shelves in 2008 (18), 2010 (30), and 2014 (4) to characterize and monitor changes in caged, barn, free range, and organic egg farming regimens. Stable carbon (δ13C) and nitrogen (δ15N) isotopes of 49 commercial poultry feeds and their corresponding egg albumens reveals that Dutch poultry are fed exclusively on a plant-based feed and that it is possible to discriminate between conventional and organic egg farming regimens in The Netherlands. Similarly, it is possible to discriminate between New Zealand organic and conventional egg farming regimens, although in the initial screening in 2008, results showed that some organic eggs had isotope values similar to those of conventional eggs, suggesting hens were not exclusively receiving an organic diet. Dutch and New Zealand egg regimens were shown to have a low isotopic correlation between both countries, because of different poultry feed compositions. In New Zealand, both conventional and organic egg whites have higher δ15N values than corresponding Dutch egg whites, due to the use of fishmeal or meat and bone meal (MBM), which is banned in European countries. This study suggests that stable isotopes (specifically nitrogen) show particular promise as a screening and authentication tool for organically farmed eggs. Criteria to assess truthfulness in labeling of organic eggs were developed, and we propose that Dutch organic egg whites should have a minimum δ15N value of 4.8‰ to account for an organic plant derived diet. Monitoring of New Zealand egg isotopes over the past 7 years suggests that organic eggs should have a minimum δ15N value of 6.0‰, and eggs falling below this value should be investigated further by certification authorities.