Benefits of Modelling Abundance for Rare Species Conservation: A Case Study With Multiple Birds Across One Million Hectares

Abstract

Aim

Many management programs that are based on the needs of rare or threatened species are ineffective because they fail to collect enough data to reliably estimate abundance and map distributions for their target species. Information that does exist for rare species is often based on presence-only data, because it is difficult to collect sufficient data on abundance for such species. We targeted 10 rare bird species that were excluded from a recent study due to insufficient data. For these species, we aimed to (a) collect sufficient abundance data, (b) identify important locations and (c) estimate population sizes.

Location

A large reserve system (~1 M-ha) in south-eastern Australia.

Methods

We undertook intensive field surveys, using repeat area searches of 660 independent 25-ha sites, totalling 2640 hours of surveys (2-h surveys; two surveys per site). We used N-mixture models to estimate abundance whilst accounting for imperfect detection.

Results

This survey effort returned enough high-quality data on nine rare bird species to identify important locations and estimate their population sizes. To illustrate potential applications of mapped important locations, we used our results to assess the likely impact of a planned burn program in part of the study region. We identified planned burns that are likely to have a significant impact on important locations for rare species that may not have otherwise been identified. Populations were generally larger than previously estimated using expert opinion. For example, our population estimate for the threatened Red-lored Whistler (Pachycephala rufogularis) was ~16 times larger than the previous estimate.

Main Conclusions

Our results show (a) the benefits of using abundance to identify important locations for rare species, (b) the value of developing bespoke survey methods for estimating abundance of rare species with low detectability and (c) a pathway for the application of mapped important locations in conservation land management.