This is a list of the species I've seen by the Grand Union canal/River Colne on the Grove Estate north of Grove Mill, Watford, Hertfordshire, England, and nearby.
- Little Grebe (Tachybaptus ruficollis) - a single lonely resident when I started watching the area; joined by a second bird on 15 March 2003, and 2 pairs present in early April - nest building; extremely secretive during summer months but 3 adults, with 2 juvs, all squabbling, on 25 August 2003 confirmed breeding success! Subsequently 6 birds remained during the autumn with all still present on the last day of the year; 4 birds still present end of March 2004
- Great Crested Grebe (Podiceps cristatus) - a single on pond N of road to Grove Mansion on 25 April 2004 was the first record, subsequently moving to the main pool
- Cormorant (Phalacrocorax carbo) - often seen overhead, perched high in tall canal-side trees or fishing in canal or on large pool at dawn - up to 15
- Grey Heron (Ardea cinerea) - resident in small numbers; fishes from canal bank and on large pool
- Mute Swan (Cygnus olor)- resident; numbers high in spring 2002 with gathering of non-breeders (c.20); pair which successfully reared two young in 2002 are colour-ringed (male: "Albert" VSS-white - ringer from Oxford; female: "Victoria" 7GA-blue - ringer from Hemel) but I've not obtained any information about their origin; nesting again north of road bridge 2003 - female still incubating 6 eggs 23 April; on 5 May young had hatched but only one surviving; observed remarkable behaviour with pair driven from the fen area by a new (unringed) pair, the male of which vigorously attacked the cynet and original female, driving the latter under the water; by 6 June, only female still present - mate was never seen again - and intruding pair still defending territory, driving her off! Female not seen subsequently until 9 April 2004, when nest-building with a new mate, and on eggs by 25 April, but nest later abandoned, presumed predated
- Canada Goose (Branta canadensis) - several birds normally present, breeds; post-breeding gathering reached over 80 birds early October 2003 with a single hybrid individual of some sort
- Mallard (Anas platyrhynchos) - common resident, with c. 50 birds in late summer, including juveniles; breeds
- Mandarin (Aix galericulata) - single male low over fields (probably from large pool) mid-March 2003
- Teal (Anas crecca) - uncommon visitor
- Shoveler (Anas clypeata) - uncommon visitor, max 4 males, 2 females early spring 2003
- Gadwall (Anas strepera) - uncommon visitor, with a pair resident early spring 2004
- Tufted Duck (Aythya fuligula)- uncommon visitor; pair still present April-June 2003 may have attempted to breed but absent by August; 7 birds (4 drakes) present 25 April 2004 possibly breeding again
- Red Kite (Milvus milvus) - single over Leavesden airfield August 2003 would have been visible from the site
- Common Buzzard (Buteo buteo)- single hunting low over fields to W of the fen at dawn on 13 June 2004; also seen on a number of occasions over adjacent Leavesden airfield
- Sparrowhawk (Accipiter nisus) - occasional
- Kestrel (Falco tinnunculus) - a pair often seen hunting over fields and up to 4 birds seen together over wood
- Hobby (Falco subbuteo) - a single in June 2002 nearly collided with me pursuing Goldfinches before moving off following Swifts
- Pheasant (Phasianus colchicus) - a single female by canal on 31 January 2004; can be heard calling in adjacent woodland
- Moorhen (Gallinula chloropus) - resident, up to 20 individuals; breeds
- Coot (Fulica atra) - common resident, up to 20 individuals; breeds
- Ringed Plover (Charadrius hiaticula) - single in spring 2002
- Lapwing (Vanellus vanellus) - occasional singles/pairs and 25 over on 16 October 2003 which did not settle
- Curlew (Numenius arquata) - a single over adjacent Leavesden airfield on 25 October 2003
- Common Sandpiper (Actitis hypoleucos) - single in autumn 2002 and single adult on 31 August 2003
- Green Sandpiper (Tringa ochropus) - single on 4 October 2002; at least two birds in 2003 with a single juv on 25 August, another individual on 31 August and a single still there on 13 September
- Common Snipe (Gallinago gallinago) - occasionally seen on large pool in winter
- Common Tern (Sterna hirundo) - occasional singles or pairs along canal
- Black-headed Gull (Larus ridibundus) - up to 200 regular on the large pool
- Common Gull (Larus canus) - up to 30 regular with Black-headed Gulls on the large pool
- Lesser Blackback (Larus fuscus) - occasionally overhead
- Herring Gull (Larus argentatus) - occasionally overhead
- Wood Pigeon (Columba palumbus) - small flocks commonly observed over nearby woods
- Stock Dove (Columba oenas) - small flocks commonly observed over nearby woods
- Tawny Owl (Strix aluco) - heard calling in the neighbourhood at dawn and dusk; breeds nearby - single juv present June 2003
- Kingfisher (Alcedo atthis)- may have bred in area 2003 - 3 birds present at large pool in summer; regularly seen fishing at the large pool; pair seen on road embankment near bee hives in spring 2004
- Common Swift (Apus apus) - common summer visitor
- Green Woodpecker (Picus viridis) - occasionally heard calling in nearby woodland; sometimes feeding on canal path
- Great Spotted Woodpecker (Dendrocopos major) - regularly heard calling and drumming in nearby woodland
- Lesser Spotted Woodpecker (Dendrocopos minor) - a calling male in the large lime N ponds to N of road to Grove Estate house, flying off W to woods N of house, 27 March 2004; the same morning but 1.5hrs earlier another calling male in top of a lime in the avenue leading S from Grove Mill, about 800m SSW of the first location and probably a different bird
- Swallow (Hirundo rustica) - common summer visitor and passage migrant
- House Martin (Delichon urbica)- common summer visitor and passage migrant; breeds in housing estate to east; at least 40 birds present post-breeding summer 2003
- Sand Martin (Riparia riparia) - uncommon passage migrant
- Skylark (Alauda arvensis) - scarce resident, breeding on estate land to SW and on airfield to NE
- Meadow Pipit (Anthus pratensis) - scarce resident and passage migrant; max 14 birds feeding in long grass, January 2004
- Pied Wagtail (Motacilla alba) - uncommon resident
- Grey Wagtail (Motacilla cinerea) - common resident, at least two pairs bred 2002; feeds on canal bank and around large pool; bred successfully again in 2004
- Wren (Troglodytes troglodytes) - common resident, breeds
- Hedge Sparrow (Prunella modularis) - resident in small numbers
- Robin (Erithacus rubecula) - common resident, breeds
- Blackbird (Turdus merula) - common resident, breeds
- Fieldfare (Turdus pilaris) - occasional winter visitor
- Song Thrush (Turdus philomelos) - common resident, breeds
- Redwing (Turdus iliacus) - regular autumn and winter visitor
- Mistle Thrush (Turdus viscivorus) - resident in small numbers
- Sedge Warbler (Acrocephalus schoenobaenus)- held territory on canal bank at tiny fen just north of A41-M25 link road bridge 2002; back there on 5 May 2003 but subsequently moved to large pool; two territorial birds at large pool in June 2004
- Blackcap (Sylvia atricapilla) - summer visitor, several pairs breed
- Common Whitethroat (Sylvia communis) - summer visitor, 2+ territorial pairs in 2002 but breeding area scrub now eliminated by estate; singing male still present at Grove Estate bridge with at least three birds on the A41-M25 link road embankment in May-June 2004
- Lesser Whitethroat (Sylvia curruca) - single in spring in the hawthorn hedge
- Chiffchaff (Phylloscopus collybita) - uncommon summer visitor, from mid-March; numbers boosted by migrants latter in summer, reaching well into double figures
- Willow Warbler (Phylloscopus trochilus) - uncommon passage migrant; 2 singing birds on 25 April 2004, one in willows on island and other N of A41-M25 link road bridge opposite fen
- Spotted Flycatcher (Muscicapa striata)- uncommon visitor, seen in tall trees at The Wharfs and by the Grove Mill itself, but seems not to be a regular resident breeder
- Long-tailed Tit (Aegithalos caudatus) - regular visitor/resident
- Coal Tit (Parus ater) - occasional in winter with other tits
- Blue Tit (Parus caeruleus) - resident
- Great Tit (Parus major) - resident, breeds, e.g. in drainhole under road bridge
- Nuthatch (Sitta europaea) - uncommon visitor; single with tit flock at "The Wharfs", late August 2003
- Jay (Garrulus glandarius) - occasional visitor; 2 pairs in territorial dispute at Grove Mill itself 5 May 2003
- Magpie (Pica pica) - common resident
- Jackdaw (Corvus monedula) - commonly observed overhead throughout the year
- Rook (Corvus frugilegus) - commonly observed overhead throughout the year
- Carrion Crow (Corvus corone) - resident in small numbers; regular individuals present daily throughout the year
- Starling (Sturnus vulgaris) - fairly scarce resident, but at least one pair nests in a tree hole on the estate and small groups often roam the area; occasionally roosts in hedge by large pool
- Chaffinch (Fringilla coelebs) - common resident, breeds
- Greenfinch (Carduelis chloris) - resident, breeds
- Goldfinch (Carduelis carduelis) - resident, often seen around the large pool, breeds; peak number 25 with Siskins 17 October 2003
- Siskin (Carduelis spinus) - common winter visitor, frequenting riverbank alders; absent in summer
- Lesser Redpoll (Carduelis flammea) - uncommon visitor
- Bullfinch (Pyrrhula pyrrhula) - scarce resident, one pair often seen in canal-side hawthorn hedge
- Linnet (Carduelis cannabina) - regular visitor in small numbers, most frequently on the embankment N of large pool
- Reed Bunting (Emberiza schoeniclus) - occasional visitor in small numbers; territorial pair at large pool 2003 with 2+ juvs seen in August; still in regular song from island in 2004
