Demographic analysis
Using 1,766 BBS routes from 1968-2021, we estimated the range-wide trend
in population size to be -0.29% per year (95% CI: -0.57, -0.02).
Trends among the breeding populations were variable (Table 2). The
Northern Temperate breeding population was estimated to be increasing by
0.67% per year (95% CI: 0.33, 1.01). The Southern Temperate breeding
population was estimated to be declining by 0.34% per year (95% CI:
-0.75, 0.06), but the credible intervals were overlapping 0, thus
indicating potential stability in that population. The remaining three
populations (Basin Rockies, Maritime Provinces, and Western Boreal) were
all estimated to be declining and had negative values for the upper
bounds of the 95% credible intervals. The Northern Temperate population
had the highest relative abundance of 3.70 (95% CI: 3.09, 4.52),
followed by Maritime Provinces (1.96; 95% CI: 1.57, 2.49), Western
Boreal (0.66; 95% CI: 0.52, 0.84), Southern Temperate (0.15; 95% CI:
0.13, 0.17), and Basin Rockies (0.01; 95% CI: 0.01, 0.02). The density
of the number of birds per BBS route was highest in the Maritime
Provinces (30.56; 95% CI: 24.33, 38.60), followed by Northern Temperate
(15.16; 95% CI: 12.68, 18.54), Western Boreal (1.66; 95% CI: 1.31,
2.10), Southern Temperate (0.67; 95% CI: 0.58, 0.78), and Basin Rockies
(0.16; 95% CI: 0.10, 0.25).