Estimation of parrot and hornbill densities using a point count distance sampling method. Marsden, S. J. Ibis, 141(3):377–390, Behav. and Environ. Biology Group, Department of Biological Sciences, Manchester Metropolitan University, Chester Street, Manchester M1 5GD, United Kingdom, 1999.
abstract   bibtex   
The suitability of point count distance methods for estimating densities of tropical parrots and hornbills was assessed during surveys in Indonesia. The methods will perform well, so long as the following are considered. (1) Enough bird records must be accumulated to model species' detection curves precisely. For some species, around 2000 point counts may be needed and, in very rare species, the method may not be appropriate. Pooling data across habitats, species or years may increase precision in cases of small sample size. (2) Point counts are likely to be less biased than line transects because bird detection rates close to the recorder may be higher and there may be less chance of double-counting birds. Distances greater than 400 m between census points are unnecessary. (3) Count periods lasting ten minutes may be needed to ensure that most birds close to the recorder are detected. Controlled flushing of concealed birds after the main count period may also be appropriate. (4) The best time of day for census is the period when bird detectability is high but bird mobility low. For many large avian frugivores, this corresponds to the period between one hour after dawn and 10.30 h. (5) Records of flying birds must be excluded from density calculations. In the species studied, between 2% and 20% should be added to density estimates to compensate for the exclusion of flying birds.
@ARTICLE{Marsden1999,
  author = {Marsden, S. J.},
  title = {Estimation of parrot and hornbill densities using a point count distance
	sampling method},
  journal = {Ibis},
  year = {1999},
  volume = {141},
  pages = {377--390},
  number = {3},
  abstract = {The suitability of point count distance methods for estimating densities
	of tropical parrots and hornbills was assessed during surveys in
	Indonesia. The methods will perform well, so long as the following
	are considered. (1) Enough bird records must be accumulated to model
	species' detection curves precisely. For some species, around 2000
	point counts may be needed and, in very rare species, the method
	may not be appropriate. Pooling data across habitats, species or
	years may increase precision in cases of small sample size. (2) Point
	counts are likely to be less biased than line transects because bird
	detection rates close to the recorder may be higher and there may
	be less chance of double-counting birds. Distances greater than 400
	m between census points are unnecessary. (3) Count periods lasting
	ten minutes may be needed to ensure that most birds close to the
	recorder are detected. Controlled flushing of concealed birds after
	the main count period may also be appropriate. (4) The best time
	of day for census is the period when bird detectability is high but
	bird mobility low. For many large avian frugivores, this corresponds
	to the period between one hour after dawn and 10.30 h. (5) Records
	of flying birds must be excluded from density calculations. In the
	species studied, between 2% and 20% should be added to density estimates
	to compensate for the exclusion of flying birds.},
  address = {Behav. and Environ. Biology Group, Department of Biological Sciences,
	Manchester Metropolitan University, Chester Street, Manchester M1
	5GD, United Kingdom},
  file = {:Marsden1999.pdf:PDF},
  owner = {eric},
  subdatabase = {distance},
  timestamp = {2006.11.05}
}

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