Monitoring the Eastern Ground Parrot with Bioacoustic methods

Kieran Aland, Ecologist at WildWise Environmental Services

Assessing the occurrence and abundance of shy, cryptic, ground-dwelling parrots in dense heath is a time-consuming and imprecise activity.

Before passive acoustic monitoring (PAM), this species was detected by trained field staff, listening for calling activity, or strategic flushing of the parrots. These methods caused considerable disturbance to the birds and their habitat. Weather conditions, human error and the physical difficulties associated with fieldwork in dense heath resulted in expensive data sets with wide margins for error and very poor repeatability.

In comparison, data collected with bioacoustic recorders provides information with high levels of repeatability over long periods of time and across large areas. The data can easily be shared and cross-examined and is generated at low cost and low-impact to the study area - and the birds!

Kieran has been monitoring the Eastern Ground Parrot for over eight years and is happy to help others develop a bioacoustic practice for monitoring these birds. Kieran has shared the following tips for capturing great acoustic data to monitor these birds in their dense heath habitat.

Eastern Ground Parrot (Image: Matt Wright)

Method

1. Species and Habitat Knowledge

Although Eastern Ground Parrots will call at any time, they engage in clearly defined periods of chorus calling, twice each day. The chorus periods occur just before dawn and just after sunset. If the birds are present, you will know. No calls, no birds.

The preferred habitat (heath communities) is shared with other species that can present a challenge to acoustic data collection and analysis. Frogs (several species) and other birds (e.g. White-cheeked Honeyeaters) potentially occur at high abundance and, when calling, can make visual analysis of spectrograms difficult.

Many of the study areas are open expanses of heath in coastal situations. Wind can become a significant factor in recorder deployments in these locations.

2. Recording Schedule Settings

Subsampling in the field can significantly reduce the volume of acoustic data required to monitor Eastern Ground Parrots. Recorders that are scheduled to collect recordings for an hour and a half, ending at dawn, and an hour and a half, commencing at dusk yield enough acoustic data to answer several questions about the birds.

Deployment periods of 14 days generally provide sufficient dawn and/or dusk chorus periods to determine presence or absence, an indication of minimum number of birds (by temporal overlap of calls) and recruitment (chick calls are distinctive). If the weather is inclement during a deployment period (e.g. extended windy periods) the recovery of the recording devices can be delayed. The advantage offered by BAR and BAR-LT recorders is the capacity for long-duration deployment, eliminating the need for equipment servicing (e.g. battery replacement).

BAT-LT set up on a Sunshine Coast field site with added sun protection to prevent overheating of the memory cards. (Image: Kieran Aland)

3. Device Set Up and Deployment Decisions

To minimise wind noise, recorders should be positioned as close as possible to the height of the dominant plants in the tallest vegetation layer. Although a sampling rate of 50dB will usually provide fit-for-purpose data, slightly lower microphone gain settings may be better during periods when frog calling, or honeyeater territorial calling, is strongest. If reliable repetition is critical to a project, it may be better to standardise microphone gain across all study sites at 47dB. For presence/absence studies, a patch of heath can be sampled with a single BAR-LT.

A sampling rate of 44.1kHz will allow distinctions to be made between the begging calls of courting adults and the begging calls of recently fledged chicks. Lower sampling rates are sufficient for presence/absence studies.

Recording of an eastern ground parrot (with surf sounds in background) recorded using the BAR-LT.

4. Summary

Because the chorus calling periods of Eastern Ground Parrots is predictable and of fairly short duration, visual screening of spectrograms can be a time and cost-effective way to analyse data. Automated signal recognition is not necessary for most projects.

The deployment of a recorder at a site of known occurrence can increase the analysis confidence at sites where occupancy is unknown.

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