Decline of Dunnocks around Auckland

[Selman]

I used to hear the challenge song of Dunnocks all the time during spring and summer and usually a pair nested on our property. I have not heard their song around the Waitakere ranges for at least a couple of years and I wonder if anyone else has noticed this. An unassuming little warbler like this could fade away before it was noticed

[Ian McLean]

Dunnocks are certainly not common garden birds in the Auckland region, especially compared to how they are further south. As a result of their rarity, most non birding Aucklanders would not know what they are. However, they are thinly distributed (see as per the attached NZ Bird Atlas screenshot) & in some places like Whatipu & Karekare Beach on the west coast they are relatively common in certain habitats like dune systems. They are likely more widespread than is realised, but perhaps are just going unnoticed. They are certainly absent from much of suburbia & are likely becoming rarer with increased development & more high density housing. As an example in 2021, I often saw & recorded on the NZ Bird Atlas a pair of dunnock at Sunnyvale Railway in west Auckland, but they are no longer present there.

In regard to why they are generally uncommon in Auckland & Northland, there could be a few possible reasons as follows:-

(1) The climate has always naturally been too warm & humid for them up, hence they are more common further south where it is colder like in there natural range in Europe ?
(2) The large numbers of rats in our warm northern forests, shrublands & gardens may be too much for them ? This may be in the same way that bellbirds, robins & whiteheads all became extinct north of the Waikato (excepting in predator free areas) due to the high numbers of ship rats in our northern forests.
(3) Our farmland may now be too intensive, with too much dairy farming & fewer hedgerows & orchards to provide them with refuges ?

Dunnocks are certainly a bird that we need to monitor more often in the Auckland region. Putting any sightings into the NZ Bird Atlas would certainly help to keep a track of changes in their population & distribution.

Cheers
Ian McLean