Garden BirdWatch gathers information in a way that makes it possible to measure relative change in the use that birds make of gardens. This approach is similar to that used in many other long-running BTO surveys and it is particularly suited to large-scale projects covering a wider range of different species at many different recording sites.
The sheer size of Garden BirdWatch imposes constraints on the type of research questions that can be asked and the way in which the data mat be collected. Fortunately, the type of information gathered can be either readily coded on forms that can be automatically de-coded by a scanning machine or entered using interactive web applications online. Currently, the relative proportions of participants submitting returns on paper and online are similar. Both are equally acceptable, though the web system allows users to submit greater detail and also view previous observations, no matter how submitted.
How the recording works
Participants are asked to record the birds and other wildlife using their gardens, making records from the same place (their defined 'recording area') at more or less the same time or times each week. Continuity of recording effort is more important than the quantity of recording, since this is a relative measure of garden use changing from week to week. Only species actively using the garden are recorded, so birds seen from the garden in flight are not recorded.
Participants record the maximum number of individuals of each species seen together at one point in time during the recording period. Hence, if you recorded for an hour each day throughout the week and saw two Blackbirds together on the Monday, 1 each on the Tuesday and Wednesday, none on Thursday, 3 on Friday and 1 each on Saturday and Sunday, your count for the week would be the '3' from Friday.
There are two paper recording forms. The first covers the 42 most commonly recorded birds nationally, split into two groups - a top-ten on the front of the form and the rest on the back. You can enter more detail for the top-ten than you can for the other 32 species (this is purely because of the availability of space). A second form covers all other species (including other taxa) and simply allows the recording of presence/absence. The main count forms cover a 13-week period and are returned quarterly, the other form covers the whole year.
Returned forms are scanned and the data that is extracted is then run through a series of validation programs before being stored in a database. This is the same database as used by the online system, keeping all our results together and allowing instant reporting and analysis.
Online recording allows participants to record maximum counts for all species, across all taxa. This gives us more precise information on the numbers of individuals using gardens while the two datasets (paper and online) can be combined to look at patterns of garden use. The online system features interactive validation and allows users to call up their old records and carry out simple analyses of their data.