Interpreting Species Factsheets
The factsheets on the 860+ species presented here accompany the State of India’s Birds 2020 report (link below). Here is an explanation of the various elements of the factsheets. All depictions of distribution range size and abundance trend are based on checklists uploaded by birdwatchers to the eBird platform.
Distribution range map
The map represents the recorded and likely current range of a species, as assessed from eBird reports between 1 June 2014 and 31 May 2019. The cell size is 50x50km; at this resolution, only 267 of 1683 cells (ie 16%) in India lack any information, and this proportion falls to 7% if one considers only those 979 cells falling entirely within India. Species have been categorized as either resident or migratory. For resident species, all cells where the species was reported are shaded with dark colour. Light shaded cells represent neighbouring cells in which birdwatchers have uploaded <100 checklists, but have not reported the species; therefore these represent cells where the species may occur, but presence is not confirmed. Cells with 100 checklists or more, in which the species has not been recorded, are left uncoloured to indicate likely absence of the species. For migratory species, only cells where the species has been reported ‘regularly’ (during three or more years in the five-year period) are shaded in dark colour. All other records are represented by ‘X’s to indicate that the species is not regularly reported there. A cell is considered part of the summer range of a species if it has been ‘regularly’ reported from within during the period from 25 April to 5 August. Similarly, winter range is determined by the regular presence of the species between 20 November and 1 March but not during the summer. A cell is considered part of the passage range of a species if it has been regularly reported there at times outside the summer or winter.
Sample sizes (number of complete checklists) underlying the distribution maps
Abundance trend graph
The value for every year (or range of years) represents the percentage change in the abundance index (frequency of reporting) of the species in that year relative to abundance before the year 2000. However for species that do not have enough data (‘Data Deficient’) to estimate long-term trends (relative to before 2000), but for which current (past 5 years) trends can be calculated, the value for each year is the percentage change in abundance index relative to the year 2014. In the graphs, the shaded area represents the uncertainty (the 95% confidence interval — see below). See the State of India’s Birds 2020 report (linked below) for more details.
Long-term Trend: This is the change in the index of abundance (frequency of reporting) in 2014/15 relative to before 2000. A value of -15% indicates that there has been a 15% decline in frequency of reporting over that time period.
Current Annual Change: This is the average annual change in frequency of reporting from 2014/15 to 2018/19. A value of -3% indicates that there is an average annual decline of 3% in frequency of reporting over this 5yr time period.
Distribution Range Size: This is the estimated area within India that the species occupies. It is based on actual reporting locations, supplemented by an estimate of the area over which the species might occur, even though it has not yet been reported yet.
CI: This refers to the 95% Confidence Interval, which is a measure of the uncertainty in any estimate. All estimates shown here should be interpreted taking into account their uncertainty. For example, if the estimate of Distribution Range Size is 200,000 km and its CI is 5,000 km then the best guess is that true Range Size is somewhere between 195,000 km and 205,000 km. Similarly, if the estimate of the Long-term Trend is -15% and its CI is 5% then the best guess is that the actual Long-term Trend is somewhere between -20% and -10%.
An Excel file with these estimates and more information on all species assessed can be downloaded at the link below.
The categorization of Long-term Trend, Current Trend, Distribution Range Size, and overall category of conservation concern are described in the State of India’s Birds 2020 report, linked below. IUCN Global Red List categories, and Indian Wildlife Protection Act schedules are as of 2019.
Graphs, maps, and infosheets (where available) can be downloaded and used with or without modification, in accordance with the Creative Commons license assigned.