Audiomoth Recording

Recently I acquired a couple of Audiomoth, a low-cost, full-spectrum acoustic logger, and decided to try and make some recordings to try and ‘evaluate’ them as an alternative to other more expensive recorders.

I placed one above a swamp in a council-park near my residence, and configured it to make half-hour recordings. After downloading the data I was reasonably satisfied with the output but was grateful that wind and artificial noise was fairly minimal.

I’ve posted a short .mp3 audio-clip converted from the original .wav file to demonstrate the effectiveness of the recorder. Have a listen and see how many frog and bird-species that you can find present.

 

Short 1.5 minute clip

 

Unfortunately it isn’t feasible to display an image for the full 30 minute clip

 

I am hoping to use Audiomoth for scientific data-gathering and possibly ‘Sound-scapes’ so would welcome any comments or constructive-criticism.

 

The Mt Glorious ‘Thrush’ debate

 

Recently an interesting debate has arisen amongst local birders in South-east Queensland. Along the Great Dividing Range of Australia from Far-north Queensland to South-west Victoria two species of ‘Zoothera’ thrush can be found, the Russet-tailed (Zoothera heinei) and Bassian (Zoothera lunulata). Both seem to be present in dense forest but often at different altitudes.

As you can see they can look very similar in plumage, however to the ‘trained ear’ their songs are easy to separate.

Russet-tailed Thrush Zoothera heinei (© Greg McLachlan XC351196)
Bassian Thrush Zoothera lunulata (© Marc Anderson XC233919)

 

If this wasn’t hard enough a new problem has arisen recently, the ‘introduced’ Eurasian Blackbird (Turdus merula) has begun to ‘colonize’ SE Queensland, and has been seen and heard ‘vocalizing’ around Mt Glorious over the past 5 years. They are very easy to identify by sight, however they share a very similar song to the Bassian Thrush.

Eurasian Blackbird (Turdus merula) (© Yong Ding Li XC152407)

In the past most experienced birders agreed that the Zoothera thrushes identified on Mt Glorious were almost always Russet-tailed, however recently some local birders are adamant that they are seeing and hearing Bassian Thrushes (possibly migrating) through the area, usually around March. Given that research has suggested that Bassian (which can usually be found at higher-elevations at Lamington NP, Qld and Border Ranges NP, NSW) is a sedentary species these sightings have been questioned, and it appears that these records unfortunately are not accompanied by images or video. One resident and very-competent birder has recorded a ‘song’ but admits that she didn’t get ‘confirmation’ visuals and it has been suggested that the recording is actually the song of a Eurasian Blackbird (See below)

Original recording_unedited
Spectrogram of original recording_unedited
An edited version of original filtered and spaces between song decreased.
Spectrogram of edited version

The first (original) audio (and Spectrogram) is difficult to interpret so using Audacity software I’ve ‘filtered’, added gain to it and removed space between vocalizations, to highlight the patterns in the sound. Please compare this with the audio and images of other Bassian Thrush and Eurasian Blackbirds, to my ear the original looks (..and sounds!) very similar to the other Bassian and quite different from the Eurasian Blackbird, however I have only chosen the calls of recorded birds from Australia amongst the 2982 on the Xeno-Canto site. (Note: There are only 9 Bassian Thrush uploads on this site!)

Bassian Thrush (Bunyip, Victoria)
Bassian Thrush song from Royal NP, NSW ©Marc Anderson
Spectrogram of Bassian Thrush song from Royal NP, NSW ©Marc Anderson
Bassian Thrush song from St Helens, Tasmania © John Holley

 

Eurasian Blackbird from Dartmoor UK
Blackbird recorded in Strahan Tasmania © Patrik Åberg
Spectrogram of Blackbird recorded in Strahan Tasmania © Patrik Åberg
Blackbird recorded in Coburg, Victoria ©Nick Talbot
Spectrogram of Blackbird recorded in Coburg, Victoria ©Nick Talbot

Personally, after going through all these calls and others online I think the two species sound quite individual and the spectrograms only enhance this, to me, the Bassian seems more repetitive and ‘structured’ where the Blackbird tends to sound slightly more random.Please analyse the spectograms and let me know which species you think is singing on the ‘original’ recording, It is probably worth analyzing other recordings online on various sites:

Initially I tried to create a ‘poll’ to record viewer-choice but it was a rather to difficult to administer, if you would like to express an opinion please just leave a comment.

Links to other online audio sites

Xeno-Canto: Zoothera_lunulata : Turdus merula

Macauley Library: Zoothera lunulata : Turdus merula

HBW: Zoothera lunulata : Turdus merula