The usefulnes of Biometrics for the study of avian connectivity within Europe. A case study with blackcaps Sylvia atricapilla in Spain
Published: Volume 59(1), June 2012. Pages 75-91.
Original Title: La utilidad de la Biometría en el estudio de la conectividad migratoria en Europa. Un caso de estudio con currucas capirotadas Sylvia atricapilla en España
The use of biometrics in studies of migratory connectivity is still relatively infrequent in Europe. This is partly due to the fact that biometrics is a less accurate tool when compared to ringing recovery data, or such techniques as stable isotope analyses, use of geolocators or satellite telemetry. Combination with one of these (recovery data) allows us to test the usefulness of biometrics in connectivity analyses, as well as to evaluate/quantify the influence of migratory behaviour on phenotypic traits such as flight morphology. We used historical recovery data, together with flight morphology data obtained from a consistent collection protocol during a three-year ringing programme carried out at seven sites in Spain (within the eastern half of Iberia), to test the usefulness of flight morphology for analysing spatio-temporal distribution patterns of migrants at a population scale. Blackcaps Sylvia atricapilla were used as our avian model. Two hypotheses were tested: (1) whether migrant blackcaps use the shortest flyways between their breeding and non-breeding areas, so that blackcaps entering Iberia through more eastern flyways come from breeding regions further east, and (2) whether the species is a leap-frogging migrant, in which populations from more northerly regions overwinter further south than those of more southerly origin. Blackcaps entering Spain through the western Pyrenean flyway (WF) had more westerly origins than those entering through the eastern Pyrenean flyway (EF). Blackcaps captured in the WF had more rounded and shorter wings as well as relatively longer tails than those from the EF, indicating a more marked long-distance migration morphology in the EF. However, blackcaps from the EF did not come from more distant regions, so flight morphology was not linked to distance travelled from the region of origin. The fact that both recovery data and biometrics differed between flyways suggests that here flight morphology is an adequate tool with which to study population-associated connectivity patterns. No evidence of leap-frog migration was detected in the study area where
biometric data were obtained.