Hoare J.M.,Science and Technical Unit |
Monks A.,Landcare Research |
O'Donnell C.F.J.,Science and Technical Unit
Wildlife Research | Year: 2012
Context Many conservation decisions rely on the assumption that multiple populations will respond similarly to management. However, few attempts have been made to evaluate correlated population responses to management or to identify traits that could be used to predict correlations. These assumptions are central to the use of the 'population indicator-species concept' (the idea that population trends of one species can be used as an index of trends in other species) for measuring the effects of key ecological drivers. Aims We investigated correlations among bird population trends in a mixed podocarphardwood forest in New Zealand in which introduced mammalian pests are controlled. We analysed trends in the abundance of 18 bird species (primarily passerines) over a 10-year period, using data from 5-min bird counts. Methods We used a Bayesian modelling approach to identify short-term correlations in population trends among species and to investigate whether ecological traits can be used to predict these correlated trends. Key results Population increases were detected in 9 of the 18 bird species over the 10-year period of the study. Population trends were correlated for 10% of species pairs (of which 81% were positive correlations). Correlations among seven of the nine species that increased in abundance were always positive; these species form a potential indicator pool. However, traits were not useful for predicting correlated population trends. Conclusions Bird species affected by a shared ecological driver (predation) can exhibit correlated population trends when introduced predators are controlled, but correlations cannot be predicted by similarity in ecological traits. Implications We advocate for testing consistency of correlations at multiple sites so as to validate the evidence-based use of the population indicator-species concept as a cost-effective alternative to monitoring whole communities. © 2012 CSIRO.
Hoare J.M.,Science and Technical Unit |
Melgren P.,Inland Revenue |
Chavel E.E.,Science and Technical Unit
New Zealand Journal of Zoology | Year: 2013
Basic biological information is critical to evaluating conservation requirements for native taxa, but is lacking for many cryptic New Zealand lizard species. Southern forest geckos (Mokopirirakau Southern Forest) are known only from anecdotes, museum specimens and discoveries of an individual at each of three sites during recent surveys in the Catlins. We used systematic searching, photo identification and radio telemetry at one of these sites (Tahakopa Valley) to investigate habitat use of southern forest geckos. Forty-five hours of searching in 2010-2011 yielded 28 sightings of 17 individuals including four juveniles (indicating that a breeding population exists). Most geckos were found by searching a boulder used as a diurnal retreat site or in mānuka (Leptospermum scoparium). Two geckos were radio-tracked; both remained within 5 m of capture and exhibited primarily nocturnal behaviour. We recommend further survey work to identify populations and monitoring to evaluate the need for conservation intervention. © 2013 The Royal Society of New Zealand.
Greene T.C.,Science and Technical Unit |
Dilks P.J.,Science and Technical Unit |
Westbrooke I.M.,Science and Technical Unit |
Pryde M.A.,Science and Technical Unit
New Zealand Journal of Ecology | Year: 2013
Robust and reliable information is required to measure impacts of aerial 1080 operations on non-target bird species. We examined the impact on seven forest bird species of an aerial pest control operation using 1080 cereal baits to poison possums (Trichosurus vulpecula) within Waitutu Forest, Fiordland National Park. The survival of South Island kaka (Nestor m. meridionalis) and ruru (Ninox novaeseelandiae) was monitored using radio telemetry, and replicated bird counts within and external to the operational area were used to monitor changes in numbers of grey warblers (Gerygone igata), kaka, kereru (Hemiphaga novaeseelandiae), riflemen (Acanthisitta chloris), robins (Petroica australis) and tomtits (P. macrocephala). All radio-tagged kaka known to be present within the operational area prior to the application of toxic baits (n = 15) were alive 6 months later. None of the 11 radio-tagged ruru present during the operation died from 1080 poisoning. One ruru found dead (cached in a hole) following the application of toxic baits was tested for the presence of 1080, and none was found. It is likely that this bird was killed or scavenged by a predator. Transect counts of tomtits and grey warblers provided the largest sample sizes and most interpretable results. There was no evidence of any negative impact of 1080 for these species. Similarly, independent measures from point counts conducted annually since 2006 at two locations within the operational area also failed to highlight any declines in distribution or relative abundance attributable to the application of 1080 baits for six of the bird species monitored. We recommend (1) further pest control operations within the Waitutu area to prevent further deterioration in diversity and size of bird populations and (2) the continuation of monitoring programmes capable of assessing direction and rates of change in key demographic parameters for the bird populations living there. © New Zealand Ecological Society.