I was about to start writing this when Ann-Kathryn Schlesselmann’s email popped up in my inbox, with the news that her PhD thesis is completed and now available. Ann-Kathrin has been researching the genetics of black-fronted terns/tarapirohe for the past few years. Her findings represent a significant breakthrough on several levels, and a clear signal that we must start managing South Island rivers as interlinked rather than isolated systems. Ann-Kathryn summarises as follows:
“In a nutshell, there are five key points that have come out of my research:
- Black-fronted terns have 1) high levels of genetic diversity; 2) low genetic differentiation between breeding colonies; 3) no genetic signature of isolation-by-distance; however, 4) a phenotypic signature of isolation-by-distance consisting of increasing body size with increasing latitude. Conservation management should consider the whole South Island as one conservation unit, consisting of a metapopulation of black-fronted terns. Conservation actions should be targeted on a catchment-scale throughout the South Island so that natural colonisation and abandonment of breeding sites is possible.
- Recruitment failure is of primary concern leading to a small effective number of breeders (Nb~ 700 adults) and therefore a loss of genetic diversity at an increased rate. Management actions are urgent and should seek to improve breeding success, including hatching and fledging success as well as post-fledging survival. To ensure long-term survival, I suggest a minimum target for the effective number of breeders be set to Nb ~ 1,316 adults, which equates to an effective population size of Ne~ 1,000 adults (Frankham et al. 2014) based on the conversion of Waples et al. (2014).
- Impacts on nesting success of black-fronted terns differ between areas and outcome monitoring of management interventions is necessary to establish whether goals set are achieved. Further testing of combinations of habitat creation and predator control is necessary. A detailed write-up of clearing islands as a management tool in the lower Waitaki River can be found here.
- Monitoring demographic and spatial trends is crucial to assess the status of black-fronted terns. This includes braided river bird surveys or species-specific range surveys. These surveys should be paired with regular genetic monitoring (e.g. every 5 years) to assess the effective number of breeders. Sampling chicks in consecutive seasons throughout the whole breeding range and estimating the effective number of breeders will provide the most precise estimate of extinction risk in the short- and long-term. Together, braided river bird counts, range surveys, and genetic monitoring will enable ongoing assessment of progress towards conservation goals.
- The natal site, breeding site, and wintering site fidelity (migratory connectivity) is still not fully understood and research on the demographic connectivity between breeding sites throughout the whole annual cycle is needed. This could ensure that protection of the species throughout its whole range and life cycle can be achieved.”
In addition to her primary research, Ann-Kathrin also identified native southern black-backed gulls/karoro (Larus dominicanus) as primary predators of black-fronted tern nests, and that nesting success was low, independent of island vegetation cover.
On a personal note, I would like to congratulate Ann-Kathrin on completing her PhD!
Braided Rivers Partnership Project
This newsletter also marks the end of the three-year Braided Rivers Partnership Project . The project, funded by DOC and Lotto, was successful in developing several ongoing partnerships across Canterbury and wider afield, and in raising the profile of and advocating for the protection of globally rare braided river ecosystems. Lotto has granted us a further $30,000 over 3 years to consolidate the project. ECan has also granted us $15,000, a portion of which will be used to organise another Braided Rivers Seminar, 26 June 2019 (date yet to be confirmed by Lincoln University).
River bird surveys
Courtesy of the inclement weather and subsequent high water levels, some recent bird surveys have had to be postponed and upcoming surveys may yet need to be postponed. As the decsion to do so is often made quite late (generally the night before), please check with the respective organisers before heading out. Survey dates and organiser contacts are on the calendar of events.
The results from these surveys are added to the ‘rivers‘ pages by river name, as they come in. Preliminary results for the Makarora River are now available here.
This will be our last newsletter of 2018, as I am off to Canada on Wednesday until January, so Merry Christmas everyone and I wish you a safe and happy festive season.
Noho ora mai,
- Black-backed gull control on the Hurunui River.
- The black-billed gull colony has returned to the Ashley Rakahuri River. About 2,500 birds are settling in nicely about 500m below SH1 bridge…however, just as I was about to send this newsletter, these photos of the colony just came in from Grant Davey showing the impact of what 140 cumecs (at the gorge) is doing. As my son said, ‘Like Venice, except with lupins.’
- Russell lupin: iconic to Mackenzie Country or invasive weed? It’s time for this so-called ‘icon’ to be publicly branded for what it is: a destructive out of control pest species that are destroying far rarer and more important New Zealand icons: our braided rivers.
- The rewards of trapping around the Ashley River estuary
- Banded dotterels of Kaikoura -check out the latest webcam images, including the use of ‘exclosure’ nesting cages.
- A new chemical pest lure for rats (think how much we can save on eggs!)
- Researchers study new ways to stop bait going mouldy (Predator FreeNZ)
- Building dams is not just bad news for our rivers.
- The Canterbury Water Management Strategy: outgoing chair Andy Pearce reflects on the origins of the Regional Water Management Committee and the development of a multi-stakeholder collaborative process.
- Why do birds lay different coloured eggs? They’re the only living amniotes that have replaced white with multiple colours and a dash of patterns. Turns out, it started with the dinosaurs (Nature; open access)
- World’s biggest bird may have been as blind as a bat (Science; open access)
- Global pattern of nest predation is disrupted by climate change in shorebirds (Science; open access)
- A lesson in effective science communications: ‘What I learned from pulling straws out of a turtle’s nose‘ (Nature; open access)