Research

Brown Teal research is a bit like unpicking an old jersey. We pull a thread and follow it for as long as possible, though not always sure where it will take us.

Some ideas prove fruitful, others prove to be a dead-end. But even confirming that an idea is not useful is still progress – of a sort.

Some of the research completed projects in recent years include:

	Cockle-opening by a Dabbling Duck, the Brown TealAbstract.- Many birds feed on bivalves, but only oystercatchers (Haematopus spp.) are known to prise open the shells. Brown Teal (Anas chlorotis), a dabbling duck endemic to New Zealand, were observed opening Common Cockles (Austrovenus stutchburyi) on Great Barrier Island. The teal jackhammered into the open shells of feeding cockles and quickly scooped out the flesh. Despite having the bill morphology of a typical dabbling duck, they were adept at this feeding method.
	The use of wing remains to determine condition before death in brown teal ( Anas chlorotis)Abstract – Little is known of the causes of mortality in captive-bred brown teal (Anas chlorotis) released to the wild. To test whether feeding difficulties have contributed to the poor survival of released birds, we developed a method to detect starvation using the wing fat content of brown teal. We extracted the lipids from 4 outer wing components of 17 intact brown teal carcasses. The lipid content of each component reflected the birds’ nutritional condition (based on body mass and size, and visible fat). Lipids were also extracted from the outer wing components of 7 partial brown teal carcasses, 6 of which were from captive-bred released birds whose cause of death could not be determined. All of the released teal were found to have been in very poor nutritional condition immediately before death, implicating starvation as a factor in their deaths. Improving the feeding regime of captive-bred brown teal (pre- and post-release) is likely to increase their survival.
	The fossil distribution of Brown Teal (Anas chlorotis) in NZAbstract – The distribution and relative frequency among anatids of Brown Teal (Anas chlorotis) in Holocene fossil deposits on the North, South, and Stewart Islands of New Zealand are reviewed. Brown teal remains representing 641 birds are reported from 73 widely distributed sites throughout New Zealand. The fossil sites indicate the prehistoric use of a large range of palaeohabitats including coastal sites, lakes, swamps, and forests as diverse as wet podocarp and beech forests up to 700 m altitude. There is often no direct association of these forest sites with aquatic habitats such as rivers or ponds indicating that Brown Teal were foraging often at considerable distances from such features while in forests.  In the seasonally drier eastern regions Brown Teal were confined more to aquatic habitats, though this may have been the result of competitive exclusion with Finschs duck which dominated terrestrial habitats, rather than habitat incompatibility.
	Hybridisation in Fiordland Brown Teal (Anas chlorotis)Abstract – The brown teal is an endangered duck species native to New Zealand. Once widespread, it is now restricted to Northland, Great Barrier Island and a remnant population in Fiordland. Molecular genetic studies have shown that Fiordland brown teal mitochondrial DNA sequences are more similar to those of mallards and grey ducks than to those of brown teal from the North Island. This suggests that hybridisation has taken place between the brown teal and either mallards, grey ducks or mallard-grey duck hybrids. However, allozyme and morphological studies have not provided evidence for hybridisation, and the DNA sequences obtained by the initial molecular genetic study could not be confirmed as the target sequence. This study uses the mitochondrial control region to determine the extent of hybridisation in Fiordland brown teal. All Fiordland brown teal sequences examined were found to be more similar to mallards and grey duck sequences than to sequences of brown teal from Great Barrier Island. This confirmed that hybridisation between brown teal and mallards, grey ducks or mallard-grey duck hybrids was present and extensive in the Fiordland brown teal population. The sequence data provided insufficient information to differentiate the grey duck sequences from the single mallard sequence. Accordingly it was not possible to determine whether the Fiordland brown teal were hybrids of mallards or grey ducks. Consequently it is not yet possible to determine whether hybridisation in Fiordland brown teal is a natural long-term process or an anthropogenic, short term process induced by habitat destruction and rarity. This influences conservation management decisions that will determine the future of the Fiordland brown teal. Future research will use sequences from museum specimens to examine the origin and history of hybridisation in Fiordland brown teal.
	PHYLOGENY, BIOGEOGRAPHY, AND TAXONOMY OF AUSTRALASIAN TEALAbstract – The taxonomy of the Australasain teals has been particularly unstable. Australasian Grey Teal (Anas gracilis) and Chestnut Teal (A. castanea) are widely viewed as specifically distinct, but the taxonomy of the New Zealand teals remains unsettled. Because conservation status is affected by taxonomic rank, it is important to resolve the status of the rare subantarctic teals. To estimate phylogenetic relationships of teals, we sequenced three mitochondrial DNA genes (12S, and ATPase 6 and 8 ). The resultant phylogeny unequivocally groups the Chestnut Teal with the Grey Teal, rather than with the New Zealand teals as has traditionally been held (Feming 1953). A greater level of sequence divergence occurred within the New Zealand teals than between the Grey and Chestnut teals. This diversity, together with morphological and behavioral differences, implies that the New Zealand teals should be accorded specific status as A. aucklandica, A. nesiotis, and A. chlorotis. Although it is most likely that the teal that colonized the Auckland Island and Campbell Islands originated in New Zealand, our data do not allow us to determine whether the ancestors of the Campbell Island Teal came from mainland New Zealand or the Auckland Islands. This uncertainty arises because, as our data show, the colonization events were separated by a short period of time.