Spatial and temporal patterns in population change for Barn Swallow, from the North American Breeding Bird Survey #NABBS.
Increasing across most of its range until the early 1980s. Since then decreasing and most strongly in the north.
This change-point in the 1980s is common for most species of swallows, swifts, and nightjars in North America.

Northern Cardinals decreased until 1979, then increased until 2005 and have been stable since the (blue on map = increase, red = decrease). The increases have been at the northern and western edges of their range, and since 2005, they've been decreasing in the south.
#NABBS #BiologicalMonitoring #Birds #PopulationTrends #NorthernCardinal #NOCA

Pine Warblers increased across their range from 1966 - 2000 (blue regions on maps). Since then they've been fluctuating but overall relatively stable. That survey-wide stability is a composite of decreases in the south (red coloured regions in south) and ongoing increases in the north (blue coloured regions).
#NABBS #BiologicalMonitoring #Birds #PopulationTrends #PineWarbler

Here's another species that provides an interesting contrast:
American Kestrel, apparently cyclical pattern in time that is largely consistent across the species' range.
#AmericanKestrel
#NABBS
#CitizenScience
#BiologicalMonitoring #mcmcStan #birds