Introduction
The Acadian Flycatcher is one of four Empidonax species in Virginia and is most closely associated with understories of unfragmented lowland mixed-deciduous riparian forests that often include Eastern hemlock (Tsuga canadensis) (Fauth and Cabe 2005). The species is fairly common but can be difficult to see as individuals often sit motionless amid forest foliage for long periods. To find this olive-green flycatcher with an eye-ring and wing bars, listen for an emphatic tee-chup (Allen et al. 2020).
Breeding Distribution
Acadian Flycatchers are found throughout all three regions of the state and are most likely to occur in areas where forests predominate (Figure 1). More specifically, their likelihood of occurring in a block is positively associated with forest cover and the amount of forest edge habitat. They are much less likely to occur in highly urbanized landscapes, such as those in Hampton Roads-Virginia Beach, Northern Virginia, and Richmond, or in agricultural areas, such as in the Shenandoah Valley. This species is also slightly less likely to occur on the Eastern Shore.
» View the species’ association with habitat and/or environmental variables.
From the First to the Second Atlas (Figures 1 and 2), the Acadian Flycatcher’s probability of occurrence remained mostly the same, except for several areas where it became less likely to occur, especially in the more urbanized northern Piedmont region and the Hampton Roads area (Figure 3). These decreases in likelihood of occurrence were possibly associated with forest habitat loss and fragmentation resulting from development and intensified agriculture outside urban areas.
Figure 1: Acadian Flycatcher breeding distribution based on probability of occurrence (Second Atlas, 2016–2020). This map indicates the probability that this species will occur in an Atlas block (an approximately 10 mi2 [26 km2] survey unit) based on environmental (including habitat) factors and after adjusting for the probability of detection (variation in survey effort among blocks).
Figure 2: Acadian Flycatcher breeding distribution based on probability of occurrence (First Atlas, 1985–1989). This map indicates the probability that this species will occur in an Atlas block (an approximately 10 mi2 [26 km2] survey unit) based on environmental (including habitat) factors and after adjusting for the probability of detection (variation in survey effort among blocks). Blocks in white were not surveyed during the First Atlas and were not modeled.
Figure 3: Acadian Flycatcher change in breeding distribution between Atlases (1985–1989 and 2016–2020) based on probability of occurrence. This map indicates the change in the probability that this species will occur in a block (an approximately 10 mi2 [26 km2] survey unit) between Atlas periods. Blocks with no change (tan) may have constant presence or constant absence. Blocks in white were not surveyed during the First Atlas and were not modeled.
Breeding Evidence
Acadian Flycatchers were confirmed breeders in 195 blocks and 75 counties and found to be probable breeders in an additional 33 counties (Figure 4). Breeding confirmations were recorded across the state during the First Atlas as well (Figure 5).
Nest building was the earliest observation of breeding and was recorded in mid-May. The latest recorded breeding behavior was recently fledged young on August 31. In addition to recently fledged young, breeding was primarily confirmed through occupied nests (May 25 – August 5), adults carrying food (May 15 – August 6), and adults feeding young (June 6 – August 19) (Figure 6).
For more general information on the breeding habits of this species, please refer to All About Birds.
Figure 4: Acadian Flycatcher breeding observations from the Second Atlas (2016–2020). The colored boxes illustrate Atlas blocks (approximately 10 mi2 [26 km2] survey units) where the species was detected. The colors show the highest breeding category recorded in a block. The numbers within the colors in the legend correspond to the number of blocks with that breeding evidence category.
Figure 5: Acadian Flycatcher breeding observations from the First Atlas (1985–1989). The colored boxes illustrate Atlas blocks (approximately 10 mi2 [26 km2] survey units) where the species was detected. The colors show the highest breeding category recorded in a block. The numbers within the colors in the legend correspond to the number of blocks with that breeding evidence category.
Figure 6: Acadian Flycatcher phenology: confirmed breeding codes. This graph shows a timeline of confirmed breeding behaviors. Tick marks represent individual observations of the behavior.
Population Status
Acadian Flycatcher relative abundance was estimated to be the highest in the northern and central Coastal Plain region, eastern Piedmont region, and portions of the Blue Ridge Mountains (Figure 7).
The total estimated Acadian Flycatcher population in the state is approximately 542,000 individuals (with a range between 393,000 and 751,000). The North American Breeding Bird Survey (BBS) showed its population trend had a nonsignificant decrease of 0.17% per year from 1966–2022 in Virginia (Hostetler et al. 2023). Between the First and Second Atlas, its population trend showed a nonsignificant increase of 0.33% per year from 1987–2018.
Figure 7: Acadian Flycatcher relative abundance (Second Atlas, 2016–2020). This map indicates the predicted abundance of this species at a 0.4 mi2 (1 km2) scale based on environmental (including habitat) factors. Abundance values are presented on a relative scale of low to high.
Figure 8: Acadian Flycatcher population trend for Virginia as estimated by the North American Breeding Bird Survey. The vertical axis shows species abundance; the horizontal axis shows the year. The solid line indicates the estimated population trend; there is a 97.5% probability that the true population trend falls between the dashed lines. The shaded bars indicate the First and Second Atlas periods.
Conservation
Acadian Flycatcher populations appear to have been relatively stable in Virginia over the past several decades. However, they are often a high priority for monitoring and management, as they are excellent biological indicators of forest health (Allen et al. 2020). In Virginia, the best conservation strategy for the Acadian Flycatcher is to prevent the loss and fragmentation of mature forests, especially in areas such as the Blue Ridge Mountains, which are considered a high-quality nesting area for the species and others (Fauth and Cabe 2005).
Interactive Map
The interactive map contains up to six Atlas layers (probability of occurrence for the First and Second Atlases, change in probability of occurrence between Atlases, breeding evidence for the First and Second Atlases, and abundance for the Second Atlas) that can be viewed one at a time. To view an Atlas map layer, mouse over the layer box in the upper left. County lines and physiographic regional boundaries (Mountains and Valleys, Piedmont, and Coastal Plain) can be turned on and off by checking or unchecking the box below the layer box. Within the map window, users can hover on a block to see its value for each layer and pan and zoom to see roads, towns, and other features of interest that are visible beneath a selected layer.
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References
Allen, M. C., M. M. Napoli, J. Sheehan, T. L. Master, P. Pyle, D. R. Whitehead, and T. Taylor (2020). Acadian Flycatcher (Empidonax virescens), version 1.0. In Birds of the World. Cornell Lab of Ornithology, Ithaca, NY, USA.
Fauth, P.T., and P. R. Cabe (2005) Reproductive success of Acadian Flycatchers in the Blue Ridge Mountains of Virginia. Journal of Field Ornithology 76:150-157.
Sauer, J. R., W. L., and J. E. Hines (2022). The North American breeding bird survey, analysis results 1966–2021: U.S. Geological Survey Data Release. U.S. Geological Survey, Laurel, MD, USA. https://doi.org/10.5066/P9SC7T11.
