The first documentation of the Nearctic–Paleotropical migratory route of the Arctic Warbler

Abstract

The Arctic Warbler (Phylloscopus borealis) is a cryptically plumed songbird with an uncommon Nearctic–Paleotropical migratory strategy. Using light‐level geolocators, we provide the first documentation of the migratory routes and wintering locations of two territorial adult male Arctic Warblers from Denali National Park and Preserve, Alaska. After accounting for position estimation uncertainties and biases, we found that both individuals departed their breeding grounds in early September, stopped over in southeastern Russia and China during autumn migration, then wintered in the Philippines and the island of Palau. Our documentation of Arctic Warbler wintering on Palau suggests that additional study is needed to document their wintering range. Our study provides hitherto unknown information on stopover and wintering locations for Arctic Warblers and indicates that this species may migrate further overwater than previously thought.

Autumn migration tracks of Helopsaltes grasshopper‐warblers from Northeast Asia support recent taxonomic assignments

“…This differs from Arctic Warblers tagged in Alaska, which performed a long westward detour through Chukotka and Yakutia before turning south and flying over mainland East Asia toward their wintering grounds (Adams et al, 2022).…”

“…The Pallas's Grasshopper‐warbler from the Kolyma River valley most likely made its first stopover on the Schantar islands in the Sea of Okhotsk (Figure 1 ), suggesting that grasshopper‐warblers breeding north of that sea might cross it instead of detouring around it. This differs from Arctic Warblers tagged in Alaska, which performed a long westward detour through Chukotka and Yakutia before turning south and flying over mainland East Asia toward their wintering grounds (Adams et al, 2022 ).…”

“…A few species deviate from these general patterns. For example, a Blue‐and‐white Flycatcher Cyanoptila cyanomelana was tracked from its breeding grounds in mainland Russian Far East to a wintering site on the islands of the Philippines (Heim et al, 2022 ), and Arctic Warblers Phylloscopus borealis breeding in Alaska and wintering in Philippines and Palau might follow a loop migration pattern, taking a mainland route during autumn migration, but the island route during their spring migration (Adams et al, 2022 ).…”

From Siberia to Indonesia: tracking the migration of the Arctic Warbler Phylloscopus borealis

“…We limited the grid for the possible route to latitudes between − 10 and 65 and longitudes of 85 to 150. We de ned that birds can migrate through areas up to 700 km away from the shore and can stay in areas up to 100 km away from land since long over-water ights with possible stays on very small islands seem possible in this species based on a previous study (Adams et al 2022).…”

“…in Thailand (Round et al 2015(Round et al , 2016. To understand the spatiotemporal distribution of the three species, it is therefore necessary to 1) catch birds during the non-breeding season to take measurements and assess plumage details necessary for identi cation (Round et al 2015), or 2) to analyse genetic samples (Round et al 2016), or 3) to track birds from the breeding grounds with geolocators (Adams et al 2022).…”