The State of Yellow-bellied Flycatchers
Regionally: Slightly declining 
The mean (thick, dark brown line) annual estimate of Yellow-bellied Flycatcher abundance—calculated as the annual sum of estimated Yellow-bellied Flycatcher within the local area (a 4-hectare circle) surrounding all 791 Mountain Birdwatch sampling stations. The lighter vertical bars represent the 95% Bayesian credible interval (a measure of the uncertainty around the abundance estimates).
Yellow-bellied Flycatcher was not one of the original Mountain Birdwatch species monitored between 2000 and 2010, but so little is known about this species that we felt compelled to contribute to the scientific knowledge of the Moss Tyrant. Yellow-bellied Flycatcher populations in our region appear to have declined in recent years across the Mountain Birdwatch region (mean annual regional trend = -1.28%, 95% Bayesian credible interval = -2.56% to 0.05%). Declines are greatest in the Catskills of New York (mean annual regional trend = -6.27%, 95% Bayesian credible interval = -10.26% to -1.11%) where this species has gone from uncommon (46 individuals detected in 2011) to almost absent (6 individual birds detected in 2022). The North American Breeding Bird survey reports an annual decline of approximately -2.5% and -4.2% for Yellow-bellied Flycatchers in Vermont and New Hampshire respectively, and overall declining trends (-0.2% per year) for the Atlantic Northern Forest (the northeastern U.S. plus Southeast Canada).
Mean annual population trends and population change (with 95% Bayesian credible intervals [CRI]) for Yellow-bellied Flycatcher from 2010 through 2022. A red dot
indicates strong evidence for a negative trend. An orange dot 
indicates weak evidence for a negative trend. A blue dot 
indicates weak evidence for a positive trend. Strong evidence is suggested for a trend when the probability of population increase or decrease (from 2010 to 2022) equals or exceeds 95%; conversely, weak evidence is suggested for trends where the probability of change is <95%.
| Region | Mean annual trend (%) | Trend 95% CRI | Probability of decrease | Probability of increase | Population change (%) 2010-2021 | Population change (95% CRI) |
|---|---|---|---|---|---|---|
| All regions | -1.28 | (-2.56, 0.05) | 0.97 | 0.03 | -14.28 | (-26.73, 0.56) |
| New York (state) | -2.18 | (-4.19, 0.00) | 0.97 | 0.03 | -23.24 | (-40.15, 0.00) |
| New York (Catskills) | -6.27 | (-10.26, -1.11) | 0.98 | 0.02 | --54.00 | (-72.74, -12.5) |
| New York (Adirondacks) |  -1.66 | (-3.79, 0.59) | 0.93 | 0.07 | -18.20 | (-37.10, 7.26) |
| Vermont | -2.32 | (-4.33, -0.26) | 0.98 | 0.02 | -24.54 | (-41.18, -3.03) |
| New Hampshire | -0.82 | (-2.42, 0.82) | 0.84 | 0.17 | -9.41 | (-25.47, 10.32) |
| Maine |  0.12 | (-2.07, 2.46) | 0.45 | 0.55 | 1.47 | (-22.22, 33.90) |
Globally: Increasing
The vast majority (>95%) of Yellow-bellied Flycatchers breed in Canada where this species is increasing in numbers, particularly in the northern part of their range. The discovery of new breeding populations recently in eastern Alaska also suggests a global population growing northward. Data collected by the USGS Breeding Bird Survey indicate that populations in the Northeast U.S. and adjacent Canada have been declining at an average rate of ~-0.2% per year. Recent climate modeling predicts that Yellow-bellied Flycatchers will be absent from the lower 48 U.S. states by ~2080, and that 73% of its current breeding range will become unoccupied as this species moves northward.
