Threats to seabirds of Northern Aotearoa New Zealand

Edin Whitehead, Nigel Adams, Karen Baird, Biz Bell, Stephanie Borrelle, Brendon Dunphy, Chris Gaskin, Todd J Landers, Matt Rayner, James Russell, Northern New Zealand Seabird Charitable Trust
Northern New Zealand Seabird Charitable Trust, Auckland
Publication date:

Seabirds are the most threatened group of birds globally (Rodríguez et al, 2019, Croxall et al., 2012). Aotearoa New Zealand has both the greatest number of resident seabird species in the world (88 of a global total of ~370), and the greatest number of endemic seabird species (37) of any country (Forest & Bird, 2014). In addition, a third of all seabird species are regularly found within our Exclusive Economic Zone (EEZ) during their non-breeding periods. Despite this abundance, and the number of native seabird species surpassing the number of all native land, shore and freshwater birds combined (73), seabirds as a group remain on the fringes of public consciousness in Aotearoa New Zealand.

Here, we define seabirds as those species that spend some part of their lifecycle at sea, feeding in inshore or offshore waters. This group includes petrels, albatrosses, shearwaters, penguins, gannets, boobies, tropicbirds, frigatebirds, shags (or cormorants), skuas, gulls, terns and noddies. Many of these species are truly pelagic, returning to land only to breed, spending the rest of their lives in the marine environment. Their transboundary lifestyles in both marine and terrestrial environments means that, as a group, seabirds are subject to a large array of threats (Gaskin & Rayner, 2013; Provencher et al., 2019). Differences in their ecology and behaviour means that some may be more vulnerble to fishing practices such as long-lining (Anderson et al., 2011) or set-netting (Žydelis, Small, & French, 2013), while others may suffer more from disturbance at colony sites (Pulham & Wilson, 2015), plastic ingestion while foraging (Hutton, Carlile, & Priddel, 2008; Roman et al., 2019) or disorientation by artificial light at night (Montevecchi, 2013).

Top predatory seabirds are often used as indicators, or barometers, for the condition of the marine environment (Cairns, 1987). However, knowing the cause of changes in the productivity of seabird colonies is vital for this strategy to be used effectively, and there are many factors which can influence seabird productivity (Parsons et al., 2008). Understanding the factors that influence a population, including potential threats to specific species and how these may fluctuate over time is important in securing their long-term stability, particularly for at-risk species. Adult survival of long-lived species is crucial to population stability, and threats to this life stage of many seabirds are of particular concern (Croxall et al., 1990). As many seabirds are slow to mature and breed, the long-term population impacts of successive poor breeding seasons can only emerge years after the event (Jenouvrier et al., 2018).

Long-term monitoring studies are important in untangling the relationships between seabirds and their ecosystems, and the influence of environmental and human factors upon them.

Historically, seabirds have played a critical role as ecosystem engineers by providing marinederived nutrients to terrestrial ecosystems and physically altering the habitats they breed in by nest burrowing (Smith, Mulder, & Ellis, 2011). The loss of these species, such as from the introduction of predatory mammals, has resulted in depauperate ecosystems lacking in associated invertebrate fauna and plant species (Bellingham et al., 2010; Croll, et al., 2005; Maron et al., 2006). By eradicating mammalian predators from islands, the benefits of seabird recolonization have been well demonstrated (Jones et al., 2010, Jones et al., 2016), both in the terrestrial and surrounding nearshore marine systems (Bellingham et al., 2010; Roberts et al., 2007; Brooke et al., 2017). Nearshore reef and seaweed ecosystems benefit from nutrient runoff, while on land the plants, invertebrate, reptile and terrestrial bird faunas benefit from marinederived nutrients (Rankin & Jones, 2017).

Seabirds are thus important both for their own sake, and also the crucial role they play in the foundation of their ecosystems. We require a greater understanding of their lives and the threats that they face to make decisions regarding their conservation, as while there is ample global literature on these topics, there is very little at the local scale for the Northern New Zealand region.


This report aims to assess current and emerging threats to seabirds in Northern New Zealand, particularly the wider Hauraki Gulf region, and to identify knowledge gaps. In doing so, both research and conservation action can be prioritized to best mitigate threats to seabirds in the region. Consequently, the report aims to answer three basic questions:

1. What are current threats to seabirds in Northern New Zealand?

2. What are the knowledge gaps regarding seabird species in Northern New Zealand?

3. What are the knowledge gaps regarding threats to seabirds in Northern New Zealand?

Last updated: 2019-06-25