Five birds are singled out in this report on trends in breeding populations of black-fronted terns.
Tern numbers appeared to be highest on rivers with larger average flows.
Flow is also correlated with amount of food-producing habitat.
If flows were reduced significantly on higher-flow rivers, rates of population decline would accelerate.
Reduction in flows is thought to
(a) reduce foraging habitat availability - reducing productivity;
(b) increase accessibility of breeding colonies to predators - reducing survival;
(c) facilitate increased weed invasion of nesting habitats making these habitats unavailable.
A report published 2014 looks at the impacts of introduced mammalian predators on indigenous birds of freshwater wetlands in New Zealand.
The list of predators includes: mustelids (stoat, weasel, feral ferret), feral cat, rat species, house mouse, European hedgehog, brushtail possum, feral pig and domestic dog.
A report describing a trapping programme conducted during 1998-2000 in the Upper Waitaki Basin analyses trap-site data.
This report adds Harrier hawks to the list of predators given above. During the study, predators caught were: 130 cats, 158 ferrets, 631 hedgehogs, 26 stoats, 839 harriers, 55 Norway rats and 95 possums. Traps used were 3 main types of soft-catch leg-hold Victor traps with Fenn Mk6 kill traps used at a ratio of 1 for every 10 Victors.
This report (published in 2010) examines GPS tracking of feral cats which are described as a threat to native species such as the endangered black stilt.
Studied in Tasman valley, this report offers pictures and diagrams including tracking maps for 5 cats with GPS collars.
In this report the impact of predators on native birds of freshwater wetlands is reviewed. 11 of 14 extinct birds inhabited wetlands. 30 species (especially ground nesting species) are still under threat (Nov 2014). Six birds are listed as facing high risk of predation: Australasian bittern, banded rail, brown teal, fernbird, marsh crake, and spotless crake.