A vagrant bird or new species?

In Japan, the long-tailed tit is a kind of cute little bird, and four subspecies have been confirmed.

The subspecies a. c. japonicus that lives in Hokkaido has almost white plumage.

On the other hand, in the northwestern part of Chiba Prefecture, where I live, individuals similar to the subspecies that have inhabited Hokkaido since the Edo period have been confirmed.

Its name is called Chiba Enaga.

This is a colloquial name, not a scientific name.

I can't find an academic report about this long-tailed tit that has a white color inhabiting my residence.

Speaking of which, I wonder if there are wild bird researchers in this country, I have no idea

Remarks:

Chiba is one of the prefectures in Japan close to Tokyo, and Enaga is the Japanese name for the bird.

The Edo period (江戸時代, Edo jidai) or Tokugawa period (徳川時代, Tokugawa jidai) is the period between 1603 and 1867 in the history of Japan

This is exactly what I have believed for a long time to be the subspecies "a. c. japonicus".👇

Aegithalos caudatus trivirgatus⇩

A website of a subspecies "a. c. japonicus"　⇩

https://www.qkamura.or.jp/cms/cash/815_20221215130134.jpg