Assessing habitat use and availability by Buff-breasted Sandpiper (Tryngites subruficollis) in South America.

LANCTOT, R.B.; BLANCO, D.E.; OESTERHELD, M.; PIÑEIRO,G.; BALBUENO, R.A.; GUERSCHMAN, J.P.

Termas de Puyehue – Chile

Congreso; VII Neotropical Ornithological Congress; 2004

Neotropical Ornithological Society

Buff-breasted Sandpiper (Tryngites subruficollis) is a species of high conservation concern within the United States, Canada, Argentina and Brazil. Once numbering in the hundreds of thousands, the population size of the species is now estimated to be as low as 15–20,000. We surveyed Buff-breasted Sandpipers at 285, 128 and 171 locations in Argentina, Uruguay and Brazil, respectively, during 1999 and 2001. Then, we associated bird distribution with both vegetation heterogeneity and unsupervised classifications of satellite imagery. Densities ranged from 0.11 individuals/ha in Argentina to 1.08 in Uruguay, and 2.18 in Brazil. Buff-breasted Sandpipers were found primarily in pasturelands that were heavily grazed by livestock. The species was positively associated with halophytic steppes in all three countries, and negatively associated with humid mesophytic meadows, mesophytic prairies, and rice fields in at least one country. Satellite image analysis indicated that 38% (Brazil), 53% (Uruguay), and 64% (Argentina) of the main wintering range was suitable for the species. These estimates surely overestimate the real area used by the species as the habitat-bird associations were weak, the heterogeneity of unsupervised image classes were either too fine or too coarse, and not all unsupervised classes were sampled relative to their availability. Future efforts to estimate habitats used by Buff-breasted Sandpipers need to more finely divide habitat types so that, for example, tall and short grass pastures can be differentiated. The large population decline during the past century also makes it likely that Buff-breasted Sandpipers do not use all the areas that are suitable. Additional study is needed to determine how the species distributes itself and moves throughout their winter range during the austral summer. Also, additional ground surveys are needed in vegetation units and unsupervised satellite imagery classes that were poorly sampled to adequately test their use by Buff-breasted Sandpipers.