Pectoral sandpiper

Calidris melanotos is a shorebird of the family Scolopacidae described by Vieillot in 1819; it is listed in Spanish as «correlimos pectoral» and in English as «pectoral sandpiper» ^[1]. It breeds on the Arctic tundra of Siberia and North America and spends the rest of the year mainly in southern South America, Peru included ^[2]. During the Arctic summer males compete for females so intensely that they almost stop sleeping ^[3]. Its global category on the IUCN Red List is Least Concern ^[4].

It is a medium-sized sandpiper with a fairly long neck, a short, dark, barely curved bill and yellowish or greenish legs; its most useful feature is the brown, finely streaked breast that ends in a clean edge against the white belly ^[2]. In flight it shows a faint pale bar on the wing and a wide black patch on the rump and upper tail coverts ^[2].

Males and females differ greatly in size ^[5]. In Saudi Arabia, 2 birds that resembled Calidris pugnax and Calidris minutilla were identified as this species after comparing their diagnostic features, among them the contrast of the breast ^[2].

It breeds from the Yamal Peninsula to the Chukotka Peninsula, in Russia, and from western Alaska to eastern Canada; its northernmost breeding sites are on Devon Island and the Taimyr Peninsula ^[5]. The North American population winters in southern South America, from southern Bolivia to the far south of Argentina; birds breeding in Siberia apparently fly east first to join that same route, while a few take another through East Asia to south-eastern Australia and New Zealand ^[5].

One banding record shows the scale of these journeys: a bird banded on 20 September 1961 near Saskatoon, Canada, was shot on 28 May 1963 by the Yana River, in Yakutia, north of the Arctic Circle ^[6]. It also turns up as a vagrant far from its route; in Saudi Arabia 2 adults were seen on 2 May 2025, the third record for the country ^[2].

In Peru it is described as common throughout the country, on muddy shores, beaches, lake margins and marshes ^[7]. In the breeding season it uses the flat, wet tundra of coastal plains, and the female places the nest on slightly drier spots, such as hummocks, within the marshy tundra ^[5].

It is polygynous: males reach the breeding grounds from late May and defend display territories, females arrive a few days later and incubate and raise the chicks on their own ^[3]. With light around the clock, males perform aerial displays and fight other males while hardly sleeping, and when females are scarce they fly thousands of kilometres to try other breeding sites ^[3].

That effort shows in the blood: in 1040 samples taken over 9 seasons near Utqiagvik, Alaska, mean haematocrit was 58.9 in males and 49.8 in females, a gap of 9.1 points that is more than twice the one described for any other bird ^[3]. Between its winter quarters and the tundra it travels between 7000 and 14000 km ^[3].

At Churchill, Manitoba, a nest with 4 eggs was found in 1983 in open, wet subarctic tundra: a shallow scrape lined with leaves and other plant debris, hidden on one side by a clump of dry grass ^[8]. There, males were seen courting, with a low, fluttering flight while giving booming sounds ^[8].

Incubation lasts 22 days on average ^[5]. In north-east Greenland, outside its known breeding range, 3 females have laid clutches of 4 eggs since 2016, but none hatched; in the 2 nests whose eggs could be opened there were no embryos, and no male was seen near the nests, so these females had probably not mated ^[5].

Females choose breeding sites rather opportunistically and seldom return to the same place from one year to the next, which forces males to move about like nomads in search of a mate ^[5].

On the Peruvian coast it mostly uses shores and shallow areas. At the Ventanilla Wetlands, in Callao, one group rested on the shore of a lagoon and another fed in a seasonally flooded area ^[7]. At the Caucato wetland, in Pisco, every individual counted was on the lagoon shore, and because of its low relative abundance it was one of the scarcest species in the study ^[9]. On the sea shore of San Andrés, also in Pisco, it is listed as a Nearctic migrant of the sandy beaches and of the stony and rocky beaches ^[10].

Its global category on the IUCN Red List is Least Concern ^[4].

Its breeding range seems to be shifting: in eastern Canada it has spread eastward, and the nests found in north-east Greenland could herald an expansion linked to warming, which may at the same time be worsening conditions at the southern edge of its North American breeding range ^[5].

In Peru, the authors who recorded it for the first time in the Ventanilla Wetlands, a regional conservation area in Callao, stress that wetland as a resting site for migratory birds from the north ^[7]. At Caucato, a small and relatively disturbed wetland, the authors propose using their counts for management and conservation plans ^[9].

In the Ventanilla Wetlands, a regional conservation area in Callao, about 27 individuals were counted on 4 May 2022, 1 on 6 December 2022, 2 on 9 February 2023 and 1 on 13 May 2023; it is also a new record for the nearby Laguna El Mirador ^[7]. That lagoon already had 2 records on the eBird platform, from 16 February 2020 and 31 March 2022 ^[7].

On the sea shore of San Andrés, in Pisco, the censuses counted 32 individuals in January 2023 and 14 in December 2024 ^[10]. At the Caucato wetland, also in Pisco, 14 individuals were recorded, all in the counts from September to December ^[9].