Description
Census should be conducted during the spring (in temperate regions), in the early hours of the day (07.00 to 11.00), corresponding to the period of greatest activity of birds in the defence of their territory as well as in building nests and foraging (Efe 1999). To carry out the census, the listening point method (Bibby et al. 2000) should be applied, which consists of the registration of all bird species and individuals observed and heard during a period of 5 continuous minutes, in an area with a radius of 25 meters around a previously selected point (where fixed observer), and in registering the birds sampled in addition to these 25 meters, within a range of no more than 100 meters. At least 5 replicates should be made at each point count. Each replicate should be made with at least two weeks interval.
For each observation the following information should be recorded: start time, end time, number of individuals per species and estimated distance of bird to the observer.

• Calculation of the density of each species.

In order to evaluate the density of bird species per hectare and for each point count the following calculation should be made (based on Greenwood & Robinson, 2006):
D= {(n1+n2)/(πr2m)} loge{(n1+n2)/n2}
D= Density; n1= number of detected individuals in an area with a radius of <25 meters; n2= number of detected individuals in an area with a radius ≥25 meters and <100 m; r= radius of 25 meters; m= number of replicates.

Materials: Binoculars, field guide, but usually it is also needed to learn the calls (there are
typically cds or other libraries of calls available for many avifaunas); Tape measure for
initial estimation of 25 m distance.

References
Efe MA (1999) Guia prático do Observador de Aves. Associação Brasileira para
Conservação das Aves. Proaves, Rede Plaza de Hotéis.
Bibby CJ, Burgess ND, Hill DA, Mustoe, SH (2000) Bird Census Techniques. 2nd. Ed.
Academic Press, London.
Greenwood, JJD, Robinson, RA (2006) General census methods. In: Sutherland WJ (ed).
Ecological Census Techniques. 2nd Edition, Cambridge University Press, Cambridge, pp.
87-183.