The long term consistent data built year-by-year makes the data set interesting for studying trends. Are species increasing or decreasing, or are they stable over time? Which one(s), and (further down the line) - why?
The number of birds caught and as well as the species mix varies between the years. Random factors as wind and general weather determines both how many birds pass Falsterbo and our chances catching them. Rain and strong wind ruin the mist netting for instance.
Over long time with data from earlier years, the differences between the years become less striking and it is possible to sense trends. These suspicions can be tested statistically. To be possible the species in question must be ringed in decent numbers every year. Some species not caught at all (or only rarely) earlier, but now appearing regularly, can also be included in these studies.
The bird observatory build four time series. Three of those are based on ringing and give comparable data over the years. These series are:
Here we showcase our data concerning trends based on our ringing data.