Hematology of the long-distance migrant red knot (Calidris canutus rufa) in three sites of the northward migration

D'AMICO, V.; BERTELLOTTI, M.; BAKER, A.

Barcelona, España

Congreso; 31st Annual Meeting of the Waterbird Society; 2007

Hematological and plasmatical parameters were measured in long-distance migrant red knot, Calidris canutus rufa in the southernmost wintering area Rio Grande, Argentina (November 2005) and two stopover sites during the same season of the north migration toward the Canadian Arctic breeding grounds, the first one in San Antonio Oeste, Argentina (March 2006) and the last one in Delaware Bay, USA (May 2006). We obtained blood samples from birds captured with cannon net and analyzed red blood cells, hematocrit, and plasma parameters (total proteins, albumins, globulins, cholesterol, triglycerides and glucose). Hematocrit in migrating birds tends to be high as it is the case of red knot. Even hematocrit was not significant different among sites, it showed the highest value in the wintering site, which could be related to the physiological adjustments to the north migration. The wider range of hematocrit found for rufa red knot out of the rest five subspecies, can be related to the need of oxigen store due to rufa, has the longest flights between breeding, stopover and wintering sites. Although, red blood cells were not significant different among sites they were higher in the stopover sites which may alliviate the increased aerobic requirements during the long flight. Immature erytrocytes were also higher in stopover sites reflecting a the production of erytrocytes during the migration. The values of plasmatical parameters depend on the species and are affected by food quality, environment factors,  and diseases. We found elevated levels of total proteins and triglycerides in the stopover sites which can be associated with an increase of dietary protein intake and an increase of the mass gained in these sites. Triglycerides were even higher in Delaware Bay, which could be related to the requirement of nutritional and physical condition to reach the breeding grounds. The values of cholesterol were higher in the stopover sites where birds must ingest high quality food to continue the last leg of the migration. Glucose in birds is consumed very fast, almost all is used to energetic storage for the migratory flight, which can explain the different concentration in the sites. We found lower values when birds are in migration than when they are in the wintering areas. Summarizing, the differences detected in the parameters were related to the activities of birds in each particular site. The most of biochemical values were higher in the stopover sites where birds feed and accumulate reserves for onward migration. The results were similar to those reported for other sandpipers. These results can serve as a benchmark to evaluate nutritional and health condition of birds in future.