Extreme seasonal incidence of the silvereye (Zosterops lateralis chloronotus) in autumn of 2024 in the Perth metropolitan area, Western Australia, in response to heat and drought

@hillsflora @george_seagull @lifeisamazing @jeremygilmore

The silvereye (Zosterops lateralis, https://www.youtube.com/watch?v=HHta3iKOiR0 and https://www.inaturalist.org/taxa/202505-Zosterops-lateralis) is widespread in the southwestern part of Western Australia.

The subspecies Zosterops lateralis chloronotus (https://en.wikipedia.org/wiki/Western_silvereye) occurs in the Perth metropolitan area (https://www.inaturalist.org/observations?place_id=19379&subview=map&taxon_id=202505), where I have lived for many years.

My consistent experience in my leafy inner-city suburb, from year to year, has been - based mainly on auditory clues - that the silvereye is only noticeable over a brief period, within the autumn.

A particular pattern has been clear to me for decades, and up to the present:
Over a month or two in autumn, I notice the sibilant contact-call of the silvereye in my garden and hereabouts. By contrast, at other times of the year I neither see nor hear the species.

This has seemed to confirm a seasonal movement, in which the population moves through the suburbs - presumably northwards - about the time of the autumn equinox.

In and around my suburb, I have seen the silvereye as the most seasonal of the passerines in the avifauna.

I cannot rule out the possibility that the population is unobtrusively resident, but simply becomes audible and particularly gregarious in autumn.

However, I doubt this, because

My observations over the years have, thus, been in line with a known pattern.

However, in autumn of 2024, there has been a clear difference: the seasonal presence of the silvereye has been both accentuated and prolonged.

In 2024, the silvereye first became audible in the first half of March. I then heard and saw it in my neighbourhood on nearly a daily basis for more than two months. This indicated a temporary residency, as opposed to merely a transitional presence.

As I update this Post, it is 21 May 2024, and the silvereye

  • remains audible as I write, and
  • is still, temporarily, by far the most abundant passerine hereabouts.

What has been unusual in this context is that

For the first time in my experience, there has been noticeable mortality of Viburnum tinus (https://www.inaturalist.org/taxa/82666-Viburnum-tinus). This is a common - and usually horticulturally undemanding - hedge-plant in the Perth metropolitan area. The apparent cause is exceptional heat and drought.

A little rain fell on 30 April 2024. However, this was - remarkably - followed by several weeks of dry, warm weather. As at 21 May 2024, the silvereye remains as noticeable as it was in March of this year.

The abundance of the silvereye in Perth this autumn, and the duration of its presence, has been remarkable. This has been in apparent correlation with the exceptionally warm and dry weather throughout southwestern Western Australia.

Julkaistu maaliskuu 18, 2024 05:04 AP. käyttäjältä milewski milewski

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