## Abstract

Estimates of wildlife population sizes are frequendy constructed by combining counts of observed animals from a stratified survey of aerial sampling units with an estimated probability of detecting animals. Unlike traditional stratified survey designs, stratum-specific estimates of population size will be correlated if a common detection model is used to adjust counts for undetected animals in all strata. We illustrate this concept in the context of aerial surveys, considering 2 cases: 1) a single-detection parameter is estimated under the assumption of constant detection probabilities, and 2) a logistic-regression model is used to estimate heterogeneous detection probabilities. Naïve estimates of variance formed by summing stratum-specific estimates of variance may result in significant bias, particularly if there are a large number of strata, if detection probabilities are small, or if estimates of detection probabilities are imprecise.

Original language | English (US) |
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Pages (from-to) | 837-844 |

Number of pages | 8 |

Journal | Journal of Wildlife Management |

Volume | 72 |

Issue number | 3 |

DOIs | |

State | Published - Apr 2008 |

## Keywords

- Detection probability
- Double sampling
- Population estimate
- Sightability adjustment
- Stratified random sampling
- Variance estimators