Recovery of the endangered Chatham petrel (Pterodroma axillaris): A review of conservation management techniques from 1990 to 2010

Abstract

a b s t r a c tConservation of gadfly petrels, some of the most threatened seabirds, is frequently dependent on long-term research and management. We review 20 years of a program preventing the extinction of the Chatham petrel (Pterodroma axillaris), a New Zealand endemic once declining due to intense burrow competition from another native seabird. Breeding success in the early 1990s was unsustainably low (10-30%). Recovery measures started in 1992 when Chatham petrel burrows were converted and artificial entrances blockaded to exclude broad-billed prions (Pachyptila vittata). Pair and burrow fidelity were enhanced, though prions still posed a threat during Chatham petrel chick-rearing. Breeding success improved when prions were culled, however a less intensive and contentious solution was to introduce burrow flaps in 2001 which reduced interference from prospecting prions. Subsequently, breeding success increased to a mean 80% per annum. Finding burrows, primarily using radio-telemetry, increased those under management from eight in 1990 to 217 in 2010 when spotlight surveys indicated 72% of juvenile birds had fledged from managed burrows. Chick translocations to two other islands and increasing population size (from 200-400 birds in 1990 to an estimated 1400 birds by 2010) has improved the species IUCN status from Critically Endangered in 1990 to Endangered in 2013.

Are artificial burrows efficient conservation tools for seabirds? A case study of two sympatric shearwaters on neighbouring islands and guidelines for improvement

“…Wooller et al, 1990;Mougin et al, 2002;Sanz-Aguilar et al, 2008. Thus, shearwaters breeding in natural cavities were presumably older and more experienced, and poor reproductive performances in the initial years of artificial burrow occupation are to be expected unless artificial burrows substantially improve breeding success by reducing egg damage, habitat deterioration, intraand inter-specific competitions or predation (Priddel and Carlile, 1995;De León and Mínguez, 2003;Bolton et al, 2004;Libois et al, 2012;Gummer et al, 2015). Yelkouan and Scopoli's shearwater reproductive success tended to decrease over the few years that a pair started breeding in artificial burrows.…”

“…They can be used to supplement available suitable breeding habitat (Priddel and Carlile, 1995;Lalas et al, 1999;De León and Mínguez, 2003;Bried et al, 2009;Madeiros et al, 2012;Sherley et al, 2012), increase breeding success and adult survival (Byrd et al, 1983;Priddel and Carlile, 1995;De León and Mínguez, 2003;Bolton et al, 2004;Libois et al, 2012;Sherley et al, 2012), decrease inter-specific competition for nesting habitat (Wingate, 1977;Ramos et al, 1997;Sullivan and Wilson, 2001;Bolton et al, 2004;Gummer et al, 2015), establish new breeding sites when coupled with chick translocation and/or vocal attraction (Podolsky and Kress, 1989;Bell et al, 2005;Miskelly and Taylor, 2004;Priddel et al, 2006;Miskelly et al, 2009;Carlile et al, 2012;Gummer et al, 2015), and make the study of breeding biology and habits easier and less disturbing (Wilson, 1986(Wilson, , 1993Bolton, 1995;Gaston, 1996;Gummer et al, 2015). Occupancy rates of artificial burrows generally increase over time and high rates (N20%) have been reported for many seabird species either from the first breeding season after artificial burrow installation (Wilson, 1986(Wilson, , 1993Bolton, 1995;Ramos et al, 1997;Lalas et al, 1999;Sullivan et al, 2000;Bried et al, 2009), or from 2 to 4 breeding seasons after installation, as occupancy rates can take years to build up …”

“…However, artificial burrow occupancy rates have remained low (b6%) in some petrel species, even after 3 or more years of artificial burrow provision (Podolsky and Kress, 1989;Cruz and Cruz, 1996;Miskelly and Taylor, 2004). Productivity of seabirds using artificial burrows has been shown to be as high as or higher than that of those breeding in natural burrows from the first year of breeding, mainly due to protection from predators and adverse weather conditions, stabilisation of fragile sites, reduction in egg damage and in inter-or intra-specific interferences (Byrd et al, 1983;Wilson, 1986;Bolton, 1995;Priddel and Carlile, 1995;De León and Mínguez, 2003;Bolton et al, 2004;Bried et al, 2009;Libois et al, 2012;Gummer et al, 2015). However, the productivity has been lower in some petrels using artificial burrows because of predator control failure or unidentified causes (Podolsky and Kress, 1989;Cruz and Cruz, 1996).…”

Effects of threat management interactions on conservation priorities

“…Managing locations in close proximity can result in both cost savings and increased management effectiveness. For example, clustering artificial tunnels for threatened burrow-nesting birds facilitates nest maintenance and results in better nesting success (Gummer et al 2015). Another example is invasive species control that is more successful when neighboring land owners cooperate as a group in preventing weed spread or invasive predator dispersal into adjacent properties, resulting in more effective management across a landscape (Epanchin-Niell et al 2009;McLeod et al 2010).…”

Using miniaturized radiotelemetry to discover the breeding grounds of the endangered New Zealand Storm Petrel Fregetta maoriana

“…,b, Gummer et al . ). The potential of telemetry to discover hitherto unknown breeding sites has received little attention, with primary examples coming from research of Northern Hemisphere alcids (Bradley et al .…”