The Red-throated Loon is the most widespread member of the loon family, with a circumpolar distribution. Red-throated Loons were a focus of this study in the mid-Atlantic because European studies have indicated that they experience long-term, localized disturbance and displacement from wind energy facilities, as well as related activities such as vessel traffic.
Download Mid-Atlantic Wildlife Studies: Distribution and Abundance of Wildlife along the Eastern Seaboard 2012-2014. This 32-page summary publication explores aspects of the mid-Atlantic ecosystem; describes our survey and analytical approaches; and presents a range of results, featuring several case studies on specific species or phenomena.
The Executive Summary for the technical report is also available here.
Red-throated Loons are long-lived and experience high adult survival. In North America, they breed primarily on freshwater or brackish ponds and small lakes on the Arctic tundra. They likely form monogamous pairs and often return to the same nest site over multiple years.
Red-throated Loons spend winter in temperate coastal ocean waters, migrating singly or in small groups within a few miles of the coast. They primarily eat fish on the breeding grounds, in addition to aquatic invertebrates and an occasional frog. Red-throated Loons are the only loon species to forage in marine habitats year-round.
The Red-throated Loon has a Conservation Status of Least Concern from the International Union for the Conservation of Nature, due to its broad range and large population size, despite a population trend indicating a decline. Fisheries are a major source of adult mortality, via bycatch of birds in nets.
Red-throated Loons were most consistently observed within within approximately 20 km of shore. This differed from Common Loons, which were more widely distributed across the study area. Telemetry data indicated that Red-throated Loons preferentially used shallow nearshore waters over flat sandy substrates while wintering in the mid-Atlantic, particularly around the mouth of Chesapeake Bay and south along the Virginia and North Carolina coasts. Modeled boat survey data indicated that proximity to shore was the strongest predictor of Red-throated Loon abundance, followed by relatively cold sea surface temperature, and primary productivity (low in spring, high in winter).
Satellite tagged individuals left the study area between late March and early May, largely following the coast north to breeding grounds. Greatest offshore movements occurred during this departure from the study area. During fall migration, loons arrived in the study area between mid-November and late December. Most individuals stopped over in Hudson Bay and moved either to the Gulf of St. Lawrence or the Great Lakes before flying to Delaware Bay and following the coastline south.
Red-throated Loons were most commonly observed on the boat-based and digital aerial surveys between November and May. No individuals were observed in July-August from either survey method.
Satellite tracked Red-throated Loons arrived in the study area between mid-November and late December, and departed beginning in late March, with all birds gone by May. A time variant kernel density model of satellite telemetry data was developed to improve our understanding of the species’ use of the landscape through time. The movement video generated from this model is shown here.
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