Noisy data can mask a signal
When determining whether an observed increase is real, we must separate the signal from the noise.
Unfortunately bird count data is noisy: fluctuations in counts from year to year are expected due to reasons not related to bird abundance (e.g. poor weather making birds less or more active, observer effects, etc), as well as factors that cause shorter term changes in abundance (food availability and predation pressure).
Distinguishing the long-term population signal from the sampling noise can be difficult (see Figure below). Fortunately there are methods that can make it possible.
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