If this is based on bird spotters, I'd say the national bird spotting organizations don't report or watch for the same birds.
replyThat’s the more likely hypothesis, but I also wonder if different land management practices could be influencing a map like this. Agriculture in Poland is much more fragmented than in Germany - smaller fields of different crops, often separated by meadows and forests, creating lots of niches for biodiversity. In Western Europe you’re more likely to see giant, mechanised monoculture fields as far as the eye can see, leaving less space for agrarian-landscape wildlife.
replyThe birds remained part of the schengen zone and have freedom of movement :)
replyAlways been a bit jealous of birds for their freedom. It comes at a cost of course, but so does being human.
replyFreedom and brains.
replyReminds me how "bird brain" is sometimes used as an insult, when they're some of the smartest animals with very densely connected brains. https://www.dhanishsemar.com/writing/bird-brains
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