Trophic ecology of Calidris canutus rufa over-summering at Faro Querandí, Buenos Aires, Argentina

FERNANDEZ J; LOREDO MA; CHIARADIA N.; ISACCH JP; GONZÁLEZ P; MARTÍNEZ CURCI N.

Congreso; 9na reunión del grupo de aves playeras del hemisferio occidental; 2022

The coasts of the Pampas biome (Southern Brazil, Uruguay and Buenos Aires province in Argentina) represent the main congregation area of over-summering (i.e. birds that do not migrate to the breeding grounds for one or more years) Calidris canutus rufa from the Tierra del Fuego population. About 5% of this population was recorded at Faro Querandí, in Buenos Aires province, Argentina during the austral winter of 2021. The importance of the site for C. c. rufa was previously unknown and there is no information about trophic requirements of the species there. We assessed food availability by benthic sampling conducted in July 2021 and characterized the diet and the intake rate by analyzing faecal samples and video-sequences of focal individuals between May and August 2021. Donax hanleyanus and Amarillodesma mactroides were the most abundant macroinvertebrates found in the benthos, which in turn were found in all analyzed feacal samples (D. hanleyanus Fo = 1 and A. mactroides Fo = 0.93) and were consumed at a rate of 2.41± 1.41 individuals/min. Available sizes ranged from 6.63 to 19.58 mm., while the sizes consumed ranged from 7.76 mm to the maximum available size. It is important to highlight the marked use of A. mactroides by C. c. rufa since this bivalve suffered a drastic population decline. Today its populations are recovering suggesting the importance of continuing to monitor the interaction between a threatened shorebird and a trophic resource of conservation concern.