Magpies often come to our garden. Why?

  The first time I saw a magpie here was about ten years ago. I had known the name of the bird because I had found it in a poem written by an English poet. And I had actually seen the birds when I traveled in New Zealand several years before. But, according to an encyclopedia, Hokkaido is not a habitat of them, and they only live in northern Kyushu island. So, they are designated as protected species and a natural treasure by Oita prefecture. So I was so surprised to find them here in Tomakomai. Recently, we see them here and there, and yesterday, nine magpies at a time were seen on the electric wire and on the roof of the next-door house. Of course, I often see them taking a walk. Is this because of global warming?
 
  It was cloudy, and it rained a little in the afternoon. In the morning, I stood at a crossing as a school crossing guard. Then, I walked as usual as far as Kawazoe cho.