BTO Codes explained

Before I start, I should mention that some of these codes below relate to information that can only be gained from examining the bird in the hand. We are licensed to catch, handle and ring wild birds and are intensively trained to do so safely. Should you wish to learn more or become involved you will find information on the sidebar.

This post is for those of you who sit there scratching your head trying to work out what codes ringers use! I'll start with a simple one as I may be using it myslef later: IRG = Ivel Ringing Group.

Species codes you may come across for most of the common species you will see on this blog:

Listed in alphabetical order starting with 5 letter code (used by ringers) then some shorter codes (that some people still use) and then species names.

BARGO = BY = Barnacle Goose
BLABI = B = Blackbird
BLACA = BC = Blackcap
BLUTI = BT = Blue Tit
BULLF = BF = Bullfinch
CHAFF = CF = Chaffinch
CHIFF = CC = Chiffchaff
COMTE = CN = Common Tern
DUNNO = D = Dunnock
GARWA = GW = Garden Warbler
GOLDF = GO = Goldfinch
GRSWO = GS = Great Spotted Woodpecker
GRETI = GT = Great Tit
GREFI = GR = Greenfinch
GREWO = G =Green Woodpecker
LESWH = LW = Lesser Whitethroat
LOTTI = LT = Long Tailed Tit
MEAPI = MP =Meadow Pipit
REDWI = RE = Redwing
REEBU = RB = Reed Bunting
REEWA = RW = Reed Warbler
SEDWA = SW = Sedge Warbler
SONTH = ST = Song Thrush
WILWA = WW = Willow Warbler

Species codes for ringers came about (as far as I can tell) for 2 main reasons - to save ringers from writing (or now typing) out the full species name for each bird they catch. Secondly, if we didn't have standardised codes, a lot of people would make up their own and then those lovely people who collate all the records (and those who study the data) would be confused thus invalidating the data and we couldn't have that!

You may have noticed that the 5 letter codes are normally made up of the first 3 letters of the first word and the first two of the second. For example (as above) Blue Tit would become BLUTI. Common exceptions are where birds have 3 words in their name such as Great Spotted Woodpecker that becomes GRSWO or ones such as Wren, Robin and Jay as they stay as they are!

Age codes:

J = Juvenile
Odd numbers = bird hatched in a known year
Even numbers = known to be at least of certain age but exact year of hatching unknown

1 = Pullus (i.e. a chick in the nest)
1J = Fledged, but flying so weakly it is obvious it hasn't gone far from the nest.
2 = Fully grown bird but we don't know what year it hatched (including this one)
3 = Definitely hatched this year
3J = Definitely hatched this year and still in juvenile plumage
4 = Hatched last year or before
5 = Definitely hatched last year (also 2CY = 2nd calendar year)
6 = Hatched 2 years ago or before
7 = Definitely hatched two years ago
8 = Hatched 3 years ago or before
9 = Definitely hatched 3 years ago

And so on ...

M = Male, F = Female: These codes are usually used in conjunction with an age code (e.g. 5M = a male definitely hatched last year). However, in some species we are not able to sex the bird except during the breeding season.

BP = Brood Patch

BP explained: This is for females only whilst incubating eggs/young in the nest (we have to be careful though as in some species males have false brood patches - i.e. they do some/all of the incubating themselves).

The following codes are related to the brood patch (where 0 = not breeding and 5 = finished breeding - n.b. this does not mean they sucessfully reared young)

BP0 = Absent
BP1 = Has started to loose feathers on its breast
BP2 = Significant number of feathers lost on its breast but skin still well defined
BP3 = Skin thickened and engorged, veined and red with broad wrinkles
BP4 = Skin has thin wrinkles, engorgement has gone but skin still stretched
BP5 = Feathering over

CP = Cloacal protuberance (the male appendage).

F = Fat score

F Explained: This is how much fat a bird is carrying and ranges from 0 (none) to 7 (a hell of a lot!). Birds carry fat for 2 reasons a)to survive long and cold nights and b) as a source of energy (usually for use whilst migrating).

CES = Constant Effort Scheme.

CES explained: This is where ringers make 12 visits to the same place and put the same nets up at the same time of day during spring and summer. Each visit must take place in one of 12 periods (10 or 11 days per period) between the end April and the end of August. For example, visit 1 this year is between 29th April and 8th May, visit two is between 9th May and 19th May and so on. This is standardised across the country so that it can stand up to scientific scrutiny.

Site Codes

Please note that not all these sites are publicly accessible and we may be deliberately vague (or omit codes/sites altogether) to protect privacy and/or to protect vulnerable species from disturbance.

PCP = Priory Country Park, Bedford
SAS = Sandy Smith Nature Reserve, Clophill
CHA = Chalton
BLU = Blunham
BRM = Bromham Lake Local Nature Reserve (LNR - another code!)
CAR = Carlton
GAE = Gamlingay
HCP = Harrold & Odell Country Park
ROX = Roxton
THO = The Thorns, Everton
STO = Stockgrove Country Park
WGP = Willington Gravel Pits
NOR = Elms Farm area, Bedford

If you come across anything on this blog that you do not understand, please leave a comment and we will respond as soon as we can.

Here endeth the explanation ... for now!