I have had a few requests from people visiting Hemel for Easter who wanted to know where to go birding in the area so I have copied here my quick(ish) response with details of where to get both quantity & quality of species without travelling around too much...
If you want to go birding immediately around Hemel then the best spots at this time of year are
(1) The Water End & Great Gaddesden area - at the moment WHITE WAGTAILS, YELLOW WAGTAILS & WHEATEARS can be found in the horse paddock at times here: Grid Ref. to paste to Google maps 51.779245,-0.515996 . SWALLOWS & HOUSE MARTINS have arrived here: 51.782365,-0.501319 . There is a walk you can do & add to published on this map: http://www.chilternsaonb.org/uploads/files/Walks_and_Rides/Gade_Valley.pdf .You will also find all sorts of other birds around this area, it is good for RED KITE, BUZZARD SPARROWHAWK, KESTREL, LAPWING, REED BUNTING, YELLOWHAMMER, SKYLARKS, RED-LEGGED PARTRIDGES, GREY WAGTAIL, MEADOW PIPIT, CHIFFCHAFF, BLACKCAP, GADWALL, KINGFISHER, LITTLE EGRET & GREY HERON. WHITETHROATS will be returning now along with HOBBY if you're very lucky. A little harder to find but are are around are RAVEN & GREY PARTRIDGE. This area is also good for seeing BROWN HARES on the farm fields.
(2) Similar can be seen at Piccotts End Pools & the surrounding fields & woods here: 51.774147,-0.488058 , but you will have to park at either Piccotts End village or the Red Lion pub & walk to the footpath that runs along the back of the pools. At the moment here there is singing GARDEN WARBLER & WILLOW WARBLER too. The area is also very good for LONG-TAILED TIT, COAL TIT, GOLDCREST, TREECREEPER, NUTHATCH, GREEN & GREAT SPOTTED WOODPECKERS. You may also see the CANADA X GREYLAG GOOSE Hybrid at either of these sites. You could do a walk connecting the two sites as there is a footpath that almost links them here: 51.777944,-0.49265 .
(3) If you fancy a walk along the canal you will get all the expected birds there but I would recommend taking in the section behind KLAS Kings Langley Fishery where CETTI'S WARBLER has been sticking around recently, you have to be lucky to get a glimpse but the amazing explosive song alone is worth it. Lots of the other tree dwelling warblers here, good for KINGFISHER & you can see TUFTED DUCKS, GREAT CRESTED & LITTLE GREBES looking through the hedge across the lakes. You can check out what's about around Hemel & what I see as it's seen at http://hemelbirding.blogspot.com/ .
(4) If you fancy going slightly further afield it would be wrong not to visit at least one of either the 4 Tring Reservoirs (Wilstone, Marsworth, Startops & Tringford), Wildlife Trust's BBOWT flagship reserve - College Lake, Ivinghoe Hills (Ivinghoe Beacon, Gallows Hill, Steps Hill, Incombe Hole), or Pitstone Hill (with view over Pitstone Quarry). These are all within reach of each other & would provide a wealth of birds of all habitats including rare migrants passing through at the moment. You can see info on what's about at these places here: http://birdingtringreservoirs.blogspot.co.uk/ & here: http://www.fotr.org.uk/ .
Last but certainly not least, keep an eye on the Herts Bird Club website for sightings of birds around Hertfordshire here: http://www.hnhs.org/birds/ , & be sure to report anything good you see to share with others & add to the very valuable records of birds in Hertfordshire here: http://www.hnhs.org/birds/recordssubmission.php .
Hope that helps you decide what to do, enjoy your Easter in Hemel. Dan.