20 years of BTO Garden BirdWatch

The BTO (British Trust for Ornithology) Garden BirdWatch started 20 years ago.  I joined at the beginning in 1995 and I have now submitted more than 1000 weeks of data from my garden.

I am not really one for lists but looking at the BTO website I see that over the last 20 years my ten commonest birds were:

Great tit seen in 100% of weeks

Blue tit 99%

Great spotted woodpecker 99%

Blackbird 97%

Chaffinch 95%

Robin 95%

Greenfinch 93%

Magpie 92%

Wood pigeon 91%

Nuthatch 81%

Other birds more likely than not to be seen in any given week were wren (79%), goldfinch (70%), dunnock (70%), stock dove (70%), coal tit (65%), and starling (58%).  Also rook (67%) as there used to be a rookery in the wood but all the rooks left about three or four years ago and haven't been back.  The total is 59 species.  That doesn't include yellowhammer - there was one here nearly all day on 31st December 1994, the day before the survey started, but I haven't seen one here since!

Although the data collection in Garden BirdWatch is perhaps less sophisticated than in some other BTO surveys, there are more than 10,000 participants who have contributed more than 7 million weeks' data, so it is an enormously powerful data set.  It has documented the decline in some garden birds such as house sparrow:

and starling:

BTO Garden BirdWatch has documented the increase in other garden birds such as goldfinch:

and wood pigeon: 

It also shows well the weekly variation in reporting rates for different birds.  As examples, here are blackbird:

and siskin:

If you would like to join and contribute data from your garden to the BTO Garden BirdWatch go to this page.