Red-necked phalarope

Phalaropus lobatus is a bird of the family Phalaropodidae, order Charadriiformes ^[1]. It breeds on freshwater tundra ponds in the Arctic and subarctic and spends the rest of the year at sea, in saline tropical waters ^[2].

North Atlantic birds followed with geolocators wintered in the northern Humboldt Current or off Central America ^[2]. In Peruvian waters it is a migrant that breeds in the northern hemisphere ^[3]. The IUCN lists it globally as Least Concern ^[4].

It breeds on freshwater tundra ponds in Arctic and subarctic regions; the 2019 study covered 9 breeding sites, from East Greenland to western Siberia ^[2].

Outside the breeding season it is pelagic and lives in saline tropical ocean waters ^[2]. The North Atlantic breeders and those of Fennoscandia and Russia use different routes: the first travel about 10000 km over the sea to the Pacific and the second about 6000 km, largely overland, to the Arabian Sea ^[2].

In the Western Hemisphere, the main wintering area of the species is the Humboldt Current off Ecuador, Peru and northern Chile ^[5]. Of the 8 birds of the western route with complete tracks, 6 wintered in the northern Humboldt Current and 2 off Central America ^[2].

It has reversed sex roles and is polyandrous: males care for the eggs and the chicks ^[2]. Females are heavier than males: mean body mass was about 38 g in 170 females and about 33 g in 468 males ^[2].

Birds of the western route left the breeding areas on average on 9 July and reached the wintering area around 10 September, after about 74 days of travel; their longest stopover, about 12 days, was near 45° N in the Bay of Fundy, Canada ^[2]. In spring they left the wintering area on 8 May, in one documented case crossed the Caribbean in about 48 hours without stopping and were back on the breeding grounds around 1 June ^[2].

In the Pacific the birds spent about 240 days in the wintering area and moved about 1549 km in total, mostly at the beginning and end of winter ^[2].

It feeds on zooplankton, which may not track the primary productivity of the sea closely ^[2].

Tracked birds were associated with waters of high primary productivity, in both the Pacific and the Arabian Sea ^[2]. The Humboldt Current has high and fairly constant primary productivity ^[2].

In 14 cruises made between 1980 and 1995 within 370 km of the coast between 3° S and 50° S, 407 Red-necked Phalaropes were counted among 93 recorded seabird species ^[3]. In the northern sector (3° S to 15° S) it ranked 14th over the continental shelf, at about 27 birds per 100 km², and 18th over the slope, at about 12.5 ^[3].

The current IUCN assessment places it globally in the Least Concern category ^[4].

At Head Harbour, in the outer Bay of Fundy (Canada), the full migratory passage of the species was estimated at 1 to 2 million birds; the flocks began to decline in the mid-1980s and by 1990 had disappeared ^[5].

Nisbet and Veit (2015) linked the decline to the 1982/83 El Niño, which damaged marine ecosystems of the eastern tropical Pacific, where the wintering area lies ^[5]. Others have proposed that the birds changed route because of a local drop in prey, but Hunnewell and colleagues question this because Arctic breeding sites also declined after that event ^[5]. In Canada, COSEWIC designated it in 2014 as a species of Special Concern ^[5]. The authors of the 2019 study note that, as a diet and habitat specialist, the species may be vulnerable to habitat change ^[2].

In Peruvian waters the records of this bird come from ship-based observations at sea: in 14 cruises from 1980 to 1995 birds were registered within 370 km of the coast, over the shelf and slope of the northern sector (3° S to 15° S) ^[3]. Outside the breeding season it is pelagic ^[2].

Birds of the western route, which winter in the Pacific, spent on average about 240 days in the wintering area ^[2].