Within a monitoring context, abundance data have been used to quantify the status of bird populations and to measure changes in population status over time (Lambert et al. 2009). Avian abundance has also been used as a response variable in evaluating the effects on bird populations of natural or anthropogenic environmental changes, and of management and conservation decisions (Lambert et al. 2009). Abundance data can be collected at a variety of scales (Lambert et al. 2009), ranging from the local to state, regional, national and international scales. Avian abundance data may be collected through a census that aims at a complete count of all birds within a survey boundary, or through a sampling approach that focuses on a representative subset of locations within that boundary (Gregory et al. 2004). Species that are spatially highly-clumped, conspicuous, or rare and occurring within a restricted range or at a limited number of sites are more amenable to censuses (Gregory et al. 2004). Census-based protocols and programs are not dealt with in this Guide (except see Arctic PRISM / double sampling).
In this section we present information on a number of sampling-based protocols designed to collect abundance (and other) data for different functional or habitat-based avian groupings, including land birds, marsh birds, shorebirds and waterbirds. While the majority of these protocols are designed as breeding season surveys, programs that include protocols for surveys of wintering landbirds (Christmas Bird Count) and migrating shorebirds (PRISM) are also included.
Gregory, R.D., D.W. Gibbons and P.F. Donald. 2004. Bird census and survey techniques. Pages 17-56 in W.J. Sutherland, I. Newton and R.E. Green, editors. Bird Ecology and Conservation; a Handbook of Techniques. Oxford University Press, Oxford.
Lambert, J. D., T. P. Hodgman, E. J. Laurent, G. L. Brewer, M. J. Iliff, and R. Dettmers. 2009. The Northeast Bird Monitoring Handbook. American Bird Conservancy. The Plains, Virginia. 32 pp.