Zhang Er, 35, spent his childhood in the centre of Beijing hunting frogs, catching dragonflies and fishing in the moat that runs next to the demolished city walls.
When he grew up, his passion for nature and wildlife led him to become a vet at Beijing Zoo and later a documentary maker filming wild birds around the capital.
He has spent 10 years visiting all the wetland parks in the suburbs to document wild bird species. He feels many people living in the city have lost interest in the wildlife around them and hopes his films can bring people back to nature.
How did you first get involved in observing and documenting wild birds?
It was in my second year at university, when I first went with a bird-watching group on a trip to the mountains. The trip was organised by the Friends of Nature, which is one of the largest NGOs in Beijing specialising in environmental protection. This interest in wild birds has never left me.
Tell us about your work at Beijing Zoo and what made you leave after five years?
I studied veterinary medicine at Beijing University of Agriculture. So after graduation, I became a vet at Beijing Zoo. As a young vet with little experience, I was assigned to take care of the pheasant department because the birds were smaller and easier to look after than big animals such as elephants or tigers. We had several hundred pheasants in our department. The main part of my job was to give them injections to prevent diseases. It wasn't easy at all. Unlike pet animals, these wild birds are hard to get close to and can easily get scared. But what depressed me most was that by the time they showed signs of illness it was already quite serious and no matter how hard I tried, I could not save the lives of these beautiful birds. So I left after five years and went back to bird watching. Soon afterwards I began making television documentaries on wild birds.
What was your first project about?
It was commissioned by the Wild Duck Lake National Wetland Park in the Yanqing district of Beijing. I was given three years to record on film the activities of all the wild bird species in the 6,800-hectare reserve. It is the largest wetland reserve in Beijing with about 280 wild bird species. I recorded nearly 1,000 hours of footage and made two short documentaries. They won prizes at the Walker Film Festival in Beijing in 2011 and 2012. The festival is an annual event to promote outdoor exploration and environmental protection.
Have you ever received any professional training in making television documentaries?
No, I have never attended a television or film school. After I left Beijing Zoo, I worked for one year as a cameraman for a television channel where I learned on the job about filming and editing. Since I was little, I have always been fascinated by films about animals and the relationship between man and animals. After I grew up, I enjoyed watching animal programmes from the BBC and the Discovery Channel. So it's natural that once I grasped all the necessary skills in filming, wildlife became my subject.
What is your secret in filming wild birds?
Filming wild birds is a challenge both physically and mentally. You need to have knowledge of their behaviour and find their gathering places. During filming, you need patience to slowly approach the birds. Sometimes you also need to camouflage yourself or leave your mini-camera beside the birds while you control it from a distance. It is both challenging and fun.
Can you tell us some of the best moments you captured of wild birds that made you really proud?
It was one early summer in a wetland park in the Huairou district where I filmed newly hatched mandarin ducks that climbed to the top of a deep tree hole and bravely jumped to the ground. Because they are so tiny and light in weight, they bounced back from where they landed. They are so adorable.
What about the wild bird population in central Beijing? How are birds faring?
Because we have a lot of hard surfaces in the city, the only suitable places left for birds are parks. But more birds in parks doesn't mean their population is growing. I feel the wild bird population is decreasing both in the city and in the suburbs. The loss of breeding grounds and the ongoing drought in Beijing in recent years may be part of the reason. But wild birds are great at adapting to the changes of habitat. Although many old buildings in the city centre have installed nets under eaves to stop birds from nesting, you do see them find homes in other places which are busy and noisy.
What are you doing to bring your message of raising awareness of wild birds to the public?
Me and my friends have set up a page called Film Nature at v.qq.com  where people can find out about our wild bird programmes. I feel that few people in cities pay attention to the wild birds around them. Maybe they think birds have nothing to do with their jobs and their daily lives. Children also spend a lot of time inside on their computers and playing games. But we and the birds all live in the same environment. Air pollution can harm our health, and I'm sure it also does no good to the lungs of these lovely little birds. I hope my films can help people, especially children, regain their interest in observing and appreciating the beauties of wildlife in nature.