Hi Derek,
Spend a day sampling the delights of the Oakwoods around Loch Lomond.
-Assuming you have a car or pushbike head up the east side of Loch Lomond through Balmaha towards Rowardennan -this is a single track road with passing places. Drive for about 5 (?7) miles passing through two hamlets (Buchanan Smithy & Milton of Buchanan) & look for a cottage on the right side of the road called Anchorage cottage (the loch is on the left side) -just past this the road bends & climbs -> a forestry comission road/track is then apparent on the right (with a closed gate visible further up the track) -park here (but don't blockthe track) > walk into the oakwoods on the opposite side of the road & follow the track 150-200m to where it joins the West Highland Way(WHW).
Turn right on the WHW & walk for about 750m along the track which climbs steeply -at the top of this wooded hill there is a sign for a B & B on the WHW track -the area around here is excellent for Wood Warbler -usually with eye level views. The slope to the south adjacent to the WHW path holds a Redstart territory with others on either side (this area is also good for Tree Pipit & Blackcap).
Return to the car & drive on for about 1-1.5km to reach a forestry Comission car park at Sallochy. There are tracks/signed walks leading up the hill opposite the car park > these pass through woodland & up onto open ground which can hold chats, wheatear, Meadow Pipits, & Cuckoo (Golden Eagle is a possibility if you're really lucky!). Back at the car park -if you walk down to the loch you can join the WHW as it heads north along the shoreline to a small picturesque bay (Grey Wagtail, Common Sandpiper). Beyond this the WHW approaches & skirts some buildings (Glasgow University Ecology Dept) before drifting west along a track. The WHW then turns sharply right off this track up through the woods > ignore this & keep on the track which rises somewhat with some oak woodland & the loch to your left. This area has lots of concrete bird boxes (Pine Martin-proof) for an ongoing Blue Tit survey but there are also good numbers of Pied Flycatcher in this area as well as more Redstart, Wood Warbler, etc.
Another trip worth considering is a boat trip to Inchcailloch island from Balmaha -mainly woodland birds though I think it's been a few years since Capercaillie were last seen on the island.
The Endrick Mouth is not far from Drymen & seems to get more than its fair share of good birds.
A climb up Ben Lomond could yield Ptarmigan though being at the southern end of the bird's breeding range it's not numerous here.
A boat trip to Ailsa Craig is something else worth considering but the drive from Drymen to Girvan could take almost 2 hours (see:
http://www.ailsacraig.org.uk/ ). It takes about 2 hours to drive to Anstruther on the Fife coast where there is a daily sailing to the Isle of May ( see:
http://www.isleofmayferry.com/may.asp ). If you fancy either of these you would need to book in advance.
Hopefully others can also offer a few suggestions.
Have a good time!