News from the pheasant-tailed jacana field project
August 2019, Guantian, Taiwan
We started the first field season on 20th June in Taiwan. The place is wonderful: we are studying a population of pheasant-tailed jacanas Hydrophasianus chirurgus resident in the Jacana Ecological and Educational Park, in south-west Taiwan near Tainan city. The Park consist of a series of small ponds managed to provide good breeding habitat for jacanas, and currently has an estimated population of around 100-120 breeding birds.
The park is separated in two parts: one part is focussing on public education. There are observatories where we can seat behind wooden panels and, without disturbing the birds, we have a good view on some nests. From 9:00 until 17:00 this area is open to public and it is very nice to see how many people are interested in the pheasant-tailed jacana.
The second area is for preservation it is an area protected where the public is not allowed, and disturbance is reduced. However, as there is no hide, I spent quite some time building one from bamboos in order to be able to observe behaviour without disturbance. It is a bit conspicuous and needed several reparations after some hard rain and wind but as the birds get used to see the hide, it does work.
The study is conducted in collaboration with the team of Prof Ya-Fu Lee (National Cheng Kung University, Taiwan) and staff of the Jacana Park lead by Ms When-Chen Lee (the Park’s director). We have got immense and invaluable help from both of our host teams to start our work in Taiwan (Nolwenn even got a scooter for the daily travels to the Park!). The jacana population and their breeding is continuously monitored by the Park (see their last report here: http://www.taipeitimes.com/News/taiwan/archives/2018/08/21/2003698916). There is a staff member whose job is to find and follow the nests which she is doing incredibly well and find most of the nest during laying. Nolwenn is also getting good at finding new nests. The nests are often quite visible, and in those nests the number of eggs can be reliably counted through telescope.
This year the breeding started in April, and the breeding season is usually long extending to September/October. By the time of our arrival the chicks from several early broods were already hatched, but due the high number of replacement clutches and start of second clutches there are also a large number of nests in different stages of incubation and new clutches still appear continuously. In the last few years typically 100-150 clutches were found in the Park during a breeding season.
However, the nest success is very low. It is difficult to know why a nest somehow disappears as, most of the time, we do not witness its fate. As far as we know a nest failure can be caused by water snake eating the eggs, hard rain flooding the eggs, big fishes bumping the nest or eating the chicks and finally there are some bird of prey and egrets which can apparently also eat some small chicks.
During the first few weeks we started to learn how to recognise the sexes (this species is sexually monomorphic, so sometimes it is not obvious whether you see a male or a female jacana) and also developed the counting method we are to use for estimating the adult sex ratio of the population.
Catching adults and chick has not been yet a good success but we are working hard to try new techniques and we are hopeful in our future success in this matter.
Since we didn’t manage yet to ring the adults, Nolwenn spent the first weeks identifying some individuals thanks to the black pattern on their head and the white pattern on their wing. Besides, we can recognize male and female thanks to a clear size dimorphism where the females are bigger than the male.
Based on the experiences during these first weeks, the project is very promising: the place and the population is excellent, the observation of adult birds and their broods is easy at least in some areas of the Park. There are several challenging problems, however, especially regarding the catching and ringing of the birds, but hopefully we can find solutions. Andras left Taiwan on 3rd July (with hoping very much to return next year for a longer period!), while Nolwenn, with help by our collaborators, is going to continue the fieldwork until mid September.
Photos are owned by Dr Nolwenn Fresneau & Dr András Liker