Least Tern

The Least Tern is the smallest tern species in Virginia, known for its squeaky, agitated calls often heard on beaches as they alert their colonies to intruders. Historically, Least Tern colonies were documented throughout coastal Virginia, including along major tributaries of the Chesapeake Bay. In the late 1800s, the species was nearly extirpated due to massive hunting pressure for the millinery industry (Howell 1911). Although their populations have since rebounded, the Least Tern remains a species of concern. Today, they nest on beaches as well as rooftops in urban areas.

Breeding Distribution

The Least Tern was well-covered during the Second Atlas by the 2018 Virginia Colonial Waterbird Survey, a coastal census conducted by the Center for Conservation Biology in collaboration with the Virginia Department of Wildlife Resources (VDWR) and The Nature Conservancy. The survey identifies nesting locations of this and other species that breed in colonies. Because the Least Tern only breeds within the survey area, there was no need to model its distribution. For information on where the species occurs in Virginia’s Coastal Plain, please see the Breeding Evidence section.

Breeding Evidence

Given the breeding biology of the species, the Least Tern is unlikely to have nested in blocks without confirmed breeding evidence (see Interpreting Species Accounts). Confirmation of breeding was based on records generated by the Virginia Colonial Waterbird Survey in 2018. Additional breeding confirmations were reported by Atlas volunteers in other years of the Second Atlas period.

Least Terns were confirmed breeders in 31 blocks (Figure 1). Most confirmations were along the Atlantic Coast of the Eastern Shore, particularly on barrier islands in Accomack and Northampton Counties. Inland breeding records were documented on tidal beaches, the constructed non-tidal Craney Island Disposal Area in Portsmouth, and on rooftops in Newport News, Norfolk, Virginia Beach, and Langley Air Force Base in Hampton. Confirmations were generally in the same areas as those recorded during the First Atlas (Figure 2).

Breeding activity commenced as early as May 3, with the chicks observed on June 6 (Figure 3). Some nests still had eggs as late as August 9. For more general information on the breeding habits of the Least Tern, please refer to All About Birds.

Figure 1: Least Tern 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. Nesting is unlikely outside of confirmed blocks.

Figure 2: Least Tern 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 3: Least Tern phenology: confirmed breeding codes (Second Atlas). This graph shows a timeline of confirmed breeding behaviors. Tick marks represent individual observations of the behavior.

Population Status

The Least Tern had too few detections during the Atlas point count surveys to develop an abundance model. However, the distribution and size of Least Tern colonies derived from the 2018 Virginia Colonial Waterbird Survey are displayed on the CCB Mapping Portal.

The Virginia Colonial Waterbird Surveys recorded a decline in the number of breeding pairs from 1,171 in 1993 to 991 in 2018 and 945 in 2023, representing a 19% decrease (Watts et al. 2019, 2024; Figure 4).

Figure 4: Least Tern population trend for Virginia’s Coastal Plain. This chart illustrates the number of breeding pairs as estimated by the Virginia Colonial Waterbird Survey (Watts et al. 2024). A data point is not included for 1998, as the Survey covered a smaller geographic area in that year. The vertical light blue bars represent the periods corresponding to the First Atlas (1985–1989) and Second Atlas (2016–2020).

Conservation

The Least Tern is classified as a Species of Greatest Conservation Need Tier III (High Conservation Need) in Virginia’s 2025 Wildlife Action Plan (VDWR 2025). While some of their nesting sites on barrier islands are protected, many others are in areas subject to significant disturbance, such as Craney Island and Grandview Nature Preserve, or on rooftops in urban settings. The species is vulnerable to extreme weather and sea-level rise, with nest sites exposed to wind, rain, and tides. Flooding from storm events and inundation can drastically reduce nesting success or even render a site unusable for that season (Beck et al. 1990). Predation also is a major threat to this and other ground-nesting species (Hunt et al. 2019).

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.

View Interactive Map in Full Screen

References