Northern House Wren

The Northern House Wren is a small, inconspicuous bird with a loud and ever-present song. In fact, they sing so frequently that it is easy to tune them out, like a fan running in the background. However, the Northern House Wren is not to be dismissed. These birds are prodigious nest-builders, constructing multiple “dummy” nests and filling available cavities with sticks. In Virginia, Northern House Wrens often outcompete other cavity nesters, such as Eastern Bluebirds (Sialia sialis) and Tree Swallows (Tachycineta bicolor), for nesting sites. They can be aggressive, even removing eggs and young of other species from their nests (Johnson 2020).

In 2024, the wide-ranging House Wren species was split. Birds in North America became Northern House Wren, and their relatives in Central and South America became Southern House Wren.

Breeding Distribution

Northern House Wrens are found throughout Virginia, but they are most likely to occur in developed areas, such as Fairfax, Norfolk, and Roanoke, and in rural farming areas, such as the Shenandoah Valley (Figure 1). Accordingly, the likelihood of Northern House Wrens occurring in a block increases as the amount of agricultural and developed areas and forest edge habitat increases, while it decreases as the number of different habitat types and amount of forest, shrubland, and grassland habitat increase. In addition, its likelihood of occurring is consistently higher in the Mountains and Valleys region than in the Piedmont and Coastal Plain regions.

Between the First and Second Atlases (Figures 2 and 3), the likelihood of Northern House Wren occurrence decreased across a broad area of the central and southern Piedmont region, while remaining mostly constant across the Mountains and Valleys region (Figure 3). While probable occurrence remained constant in the Coastal Plain region as well, there were some small potential areas of increase along the coastline. The decreases in the Piedmont region are consistent with the population declines experienced by this species during the same period (see Population Status).

Figure 1: Northern House Wren 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: Northern House Wren 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: Northern House Wren 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

Northern House Wrens were confirmed breeders in 350 blocks and 88 counties and found to be probable breeders in an additional 12 counties (Figure 4). However, while breeding occurred in all regions, breeding confirmations were most densely recorded in the Mountains and Valleys region and clustered near urban areas in the Piedmont and Coastal Plain regions. During the First Atlas, fewer breeding observations were recorded than during the Second Atlas, but it is important to note that survey effort was considerably less and may account for this difference (Figure 5).

The earliest confirmed breeding behavior was recorded on April 24, when occupied nests were documented. Other frequently recorded breeding behaviors were nests with eggs (April 28 – August 4), recently fledged young (May 19 – September 13), and nests with young (May 21 – August 12) (Figure 6).

For more general information on the breeding habits of this species, please refer to All About Birds.

Figure 4: Northern House Wren 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: Northern House Wren 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: Northern House Wren phenology: confirmed breeding codes. This graph shows a timeline of confirmed breeding behaviors. Tick marks represent individual observations of the behavior.

Population Status

Northern House Wrens are closely connected to human development and agricultural areas. Their relative abundance was estimated to be highest in the Mountains and Valley region with pockets of high abundance near developed areas in the Piedmont and Coastal Plain regions (Figure 7).

The total estimated House Wren population in the state is approximately 316,000 individuals (with a range between 237,000 and 423,000). Based on the North American Breeding Bird Survey (BBS), the House Wren population declined by a significant 1.39% annually from 1966–2022 in Virginia, and between Atlas periods, House Wrens decreased by a significant 1.84% per year (Hostetler et al. 2023; Figure 7).

Figure 7: Northern House Wren 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: Northern House Wren 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

Although they have experienced a decline in Virginia, Northern House Wrens are common and widespread throughout their range and are not considered to be a species of conservation concern. In Virginia, there are no dedicated conservation projects underway for the species. Homeowners managing Eastern Bluebird or other types of nest boxes should be aware of Northern House Wren competition, but like all songbirds, they are still protected under the Migratory Bird Treaty Act, and their nests and eggs should never be destroyed.

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