Integrating count effort by seasonally correcting animal population estimates (ICESCAPE): a method for estimating abundance and its uncertainty from count data using Adelie penguins as a case study

• Main Authors: McKinlay, J, Southwell, C, Trebilco, R
• Format: Article in Journal/Newspaper
• Language: English
• Published: C C A M L R Ti 2010
• Subjects: Mathematical Sciences; Statistics; Biostatistics; Nestor; Antarc*; Antarctica
• Online Access: http://www.ccamlr.org/en/system/files/science_journal_papers/12mckinlay-et-al.pdf; http://ecite.utas.edu.au/101969

This work describes a parametric bootstrap model for standardising animal count data toa common reference point of breeding chronology for species with a complex temporalfunction of sampling availability. ICESCAPE (Integrating Count Effort by SeasonallyCorrecting Animal Population Estimates) is a suite of routines that implements a generalabundance estimator accounting for availability bias, detection bias and samplingfractions less than unity. Within this resampling framework, all reported measures ofuncertainty associated with originally published counts are propagated through to thefinal adjusted estimates. Adjustment for availability bias is achieved by applying anadjustment factor based on independently measured time series of availability throughouta breeding season. Such time series are typically collected at only a limited number ofsites, so surrogate availability information for a site is used when none exists. Importantly,a common standardisation procedure allows site-specific estimates to be aggregated toachieve region-scale population estimates. By way of illustration, the method is appliedto several examples of published studies of Adlie penguin abundance at breeding sitesin Antarctica. These examples focus on adjusting counts of adults to an effective numberof breeding pairs, although the software has been developed to accommodate adjustmentand aggregation of other count objects typical for penguin species, such as occupied nestor chick counts. While tailored for Adlie penguins, the method and implementation issufficiently general to be easily adapted for other colonial land-breeding species showingseasonal variation in availability to sampling methodology.