The species of birds seen in the BOS includes residents, summer visitors, winter visitors, passage migrants and vagrants. This page shows the species seen regularly in the BOS, that is those that have been seen almost every year from 2000-2019. There are currently 130 such species. For each species the following information is provided:

• The number of years seen from 2000 to 2019
• The number of months each year the species is seen. This helps to distinguish visitors from residents.
• % Of Months - the percentage of the 240 months under review that the species has been recorded as being present. This provides an additional measure of occurence, though it is less accurate for species that we do not fully record. This figure is not provided for species we do not regularly record, i.e. very common species.
• Records - the number of records we hold for this species since 1982
• Max Flock - the maximum number of birds seen in a 1 km square per day
• 1km squares - the number of 1km squares the species has been recorded in. This gives a measure of the distribution. There are 1200km squares in the BOS area.
• Rank - this is a number to sort the birds into Taxonomic order, as defined by the IOC

 Note that you can sort the list by any of the column values, such as by species name.