Ground predator alarm

Ground dwelling birds will most reliably give off ground alarm (more often mobbing alarm than flee alarm) during their nesting season when they have the most to lose, and hence the most to defend. Some super-uptight species however seem to always feel riled up by intruders into their territories, regardless of the season. Around here the White-browed Scrubwren and Yellow-throated Scrubwren are perfect examples of this type of vigilant undergrowth character profile, which makes them ideal teachers for field naturalists tracking ground predators.

Listen to this Yellow-throated Scrubwren having a massive tantrum over me disturbing it at the bird bath. Pay particular attention to the start of the alarm call where the scrubwren lets me know I’m cramping its personal bathing space through emitting a series of sharp, short clicks. I have been around these bossy little forest birds long enough to understand that such clicking sounds mean “hey buster, stop right there, you’re making me feel nervous”.

But on this occasion, I wanted to capture the whole alarm sequence, so I deliberately kept moving forward into its personal space, riling the poor fellow up and provoking an escalation in response. Sorry about the background ruckus caused by a party of indiscreet Sulphur-crested Cockatoo.

Here’s the same scrubwren alarming at me again a few days later but this time we encountered each other in the forest.

Now have a listen to these next two ground alarm recordings of a Yellow-throated Scrubwren giving its mobbing alarm at a basking python (first recording) and then a Lewin’s Honeyeater gets involved, alarming at the same python a little while later (second recording).

It’s not always apparent to me whether these predator-specific vocalisations should be regarded as mobbing calls or proper flee alarm but, given that neither the scrubwren or honeyeater are facing an immediate existential threat to their person (by me or the python, who is clearly hunting pademelons), I’m thinking we should regard their calls as a type of mobbing alarm vocalisation.

The next recording is a collective mobbing alarm effort led by Lewin’s Honeyeaters (loud rasping calls) but also including additional audio muscle from a Yellow-throated Scrubwren (that’s the cranky-sounding Geiger-counter call), White-browed Scrubwren (high pitched scolding throughout) and finally an Eastern Yellow Robin (piping call half way along) and even a normally rather demure Red-browed Firetail gets roped in near the end (very high-pitched whistling sounds). The python completely ignored them.

Lastly, let’s hear from a less commonly encountered bird of the rainforest, one of my absolute faves actually, the Pale-yellow Robin. These sweet-natured little darlings are basically the introverted siblings of the more self-confident and larger Eastern Yellow Robin. In this recording I came across a Pale-yellow Robin issuing a series of soft, rasping alarm calls at some unseen ground predator that for the life of me I couldn’t locate. I suspected it must have been a Green Tree Snake (a notorious nest raider for small songbirds nesting near the ground).

Ground Alarm Similarities

Ok, so you’re out in the forest, maybe at your sit spot (see my writing on sit spots), and you start hearing something that could be ground alarm (mobbing or flee alarm)…but how do you discern between ground alarm and just birds going about their normal business? Maybe it’s just a squabble over nectar? Or, even if you do decide it’s definitely alarm, how do you work out whether it’s a ground predator or aerial?

That last bit is going to be super important to you in the field because it will determine whether you look up (fast) or keep watching the ground for the approaching predator.

Here’s some common attributes of ground alarm to listen for:

1. Most ground alarm has a harsh, scolding, squelchy or hissing quality to it.
2. Ground mobbing alarm is persistent and often repetitive without much variation, other than going up and down in pitch or rapidity in response to the predators’ movements, while flee alarm is more explosive and short-lived
3. The sound will be localised to a discreet spatial zone and won’t move quickly (unless the predator is a mammal on the move).
4. If you can see the actual birds making mobbing alarm look carefully at where their body postures seem to be directing attention – they will often form an ‘cone of alarm’, with the point of the cone marking the location of the predator.
5. Most ground alarm you’ll encounter in Australia will be mobbing alarm calls whose purpose is to draw attention of the predator’s presence. It is a signal to recruit the help of additional birds (including other species) in persuading the predator to leave the area.
6. The greater the diversity and volume of alarm calls, the more threatening the predator is perceived to be by the birds involved (say if the python starts ascending a tree rather than just basking).

Now let’s focus on aerial predator alarm calls.