The month of May is the best time to hear (and perhaps see) a Cuckoo. They can be heard almost anywhere in the area, including Mercer Wood.
The last Cuckoo I actually saw was on the riverside at Morton on May 25th 2017.
A cuckoo was virtually the first bird heard calling on our recent dawn chorus walk in Mercer Wood on May 6th 2018, and there was a cuckoo calling in Castle Hill Wood on May 12th 2018.
Cuckoo (picture from Wikipedia)