Faster migration in autumn than in spring: seasonal migration patterns and non‐breeding distribution of Icelandic whimbrels Numenius phaeopus islandicus

Icelandic Whimbrel migration routes as tracked by geolocators, between 2012 and 2016, in autumn (A–B) and spring (C–D), displayed separately for each sex (male: A and C; females: B and D). Polygons represent kernel densities of 95, 75 and 50%, from pale to dark, respectively, for winter (orange) and stopover areas (blue). The yellow circle represents breeding site.

Authors: Carneiro, Camilo ; Gunnarsson, Tomas G.; Alves, Jose A.

Year: 2019

Publication: Journal of Avian Biology

Publication Link:

Access: Open

Affiliations: C. Carneiro, T. G. Gunnarsson and J. A. Alves , South Iceland Research Centre, Univ. of Iceland, Laugarvatn, Iceland. CC and JAA also at: Dept of Biology and CESAM, Univ. of Aveiro, Campus de Santiago, Aveiro, Portugal.

Corresponding Author: C. Carneiro,

Funding: This work was funded by RANNIS (grants: 130412052 and 152470-052), the Univ. of Iceland Research Fund, FCT (grants: PD/BD/113534/2015 and SFRH/BPD/91527/2012), the Portuguese Polar Program and CESAM (UID/AMB/50017 -POCI-01-0145-FEDER-007638), FCT/MCTES through national funds (PIDDAC), with co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020.

Keywords: geolocator, migration duration, migration speed

Abstract: Migration is fundamental in the life of many birds and entails significant energetic and time investments. Given the importance of arrival time in the breeding area and the relatively short period available to reproduce (particularly at high latitudes), it is expected that birds reduce spring migration duration to a greater extent than autumn migration, assuming that pressure to arrive into the wintering area might be relaxed. This has previously been shown for several avian groups, but recent evidence from four tracked Icelandic whimbrels Numenius phaeopus islandicus, a long distance migratory wader, suggests that this subspecies tends to migrate faster in autumn than in spring. Here, we 1) investigate differences in seasonal migration duration, migration speed and ground speed of whimbrels using 56 migrations from 19 individuals tracked with geolocators and 2) map the migration routes, wintering and stopover areas for this population. Tracking methods only provide temporal information on the migration period between departure and arrival. However, migration starts with the fuelling that takes place ahead of departure. Here we estimate the period of first fuelling using published fuel deposition rates and thus explore migration speed using tracking data. We found that migration duration was shorter in autumn than in spring. Migration speed was higher in autumn, with all individuals undertaking a direct flight to the wintering areas, while in spring most made a stopover. Wind patterns could drive whimbrels to stop in spring, but be more favourable during autumn migration and allow a direct flight. Additionally, the stopover might allow the appraisal of weather conditions closer to the breeding areas and/or improve body condition in order to arrive at the breeding sites with reserves.

Supplementary Materials:

Intrusive Methodologies: 40 Icelandic Whimbrels were caught on the nest using a net trap. They were fitted with color tags and a geolocator was attached to a flag on the tibia. Birds were recaptured one or more years later using the same technique.

Citizen Science: None

Conservation: Not discussed

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