wcaptain

They move to another island in Tolo Harbour to breed.

Agree with John that nesting egrets and herons have a poor yr. I expect there will be around 700 nests this yr which is just about 2/3 of previous yrs.

We have a hot winter and drier April and May.  Weather is easy to be blamed but a study of local egrets and herons suggests weather is insignificant in determining the abundance of nests. So, it may relate to more parameters ... abundance of fish? air pollution? sea temperature? sea current?

Captain

wcaptain

Hi Alan and Mike,

As egrets still breed in Tolo Harbour, so I doubt whether marine pollution is the explanation of the change of breeding pattern of terns and egrets.

In fact, the water quality of Tolo Harbour is improving (because they pump the semi-treated sewage to Victoria Harbour). You could see the 1986-2005 report at

http://www.epd.gov.hk/epd/misc/marine_quality/1986-2005/index.html

I guess it may relate to weather, human disturbance and fish availability. As terns are migratory, so some disasters happened along the migratory route may affect the breeding of terns in HK.

Captain