“…This mechanism was described for the black‐tailed godwit L. limosa islandica (Alves et al ), another Icelandic breeding wader, which although migrating shorter distances, individuals wintering in Iberia move first to an area closer to Iceland (e.g. Britain or the Netherlands), likely to be able to appraise conditions in the breeding areas (Gunnarsson and Tómasson , Alves et al ).…”
Section: Discussionmentioning
confidence: 90%
“…1). A cross‐species comparison shows that species wintering closer to Iceland generally show a stronger correlation between timing of arrival and weather conditions in Iceland, than species wintering further away (Gunnarsson and Tómasson ). This suggests that whimbrels’ stopover closer to Iceland may facilitate tuning of arrival on the breeding grounds.…”
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.
“…This mechanism was described for the black‐tailed godwit L. limosa islandica (Alves et al ), another Icelandic breeding wader, which although migrating shorter distances, individuals wintering in Iberia move first to an area closer to Iceland (e.g. Britain or the Netherlands), likely to be able to appraise conditions in the breeding areas (Gunnarsson and Tómasson , Alves et al ).…”
Section: Discussionmentioning
confidence: 90%
“…1). A cross‐species comparison shows that species wintering closer to Iceland generally show a stronger correlation between timing of arrival and weather conditions in Iceland, than species wintering further away (Gunnarsson and Tómasson ). This suggests that whimbrels’ stopover closer to Iceland may facilitate tuning of arrival on the breeding grounds.…”
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.
“…)d.f. F p parameter (±s.e. )( a ) year12.690.102−0.13 (±0.08) individual535.31< 0.001 error229 temperature11.760.1860.23 (±0.17) individual536.44< 0.001 error229( b ) year14.78 0.042 −2.55 (±1.17) pair141.310.289 error18 temperature11.76 0.018 −4.04 (±1.55) pair146.440.446 error229Figure 1.The annual change in first spring arrival date of black-tailed godwits in south Iceland reported by Gunnarsson & Tómasson [6] (closed circles: y = −0.55 x + 1221, r 2 = 0.62, n = 21, p < 0.001), and the date on which the first individually marked black-tailed godwits were recorded on passage sites in Iceland (open circles: y = −0.61 x + 1332, r 2 = 0.5, n = 14, p < 0.005).Figure 2.Dates of spring arrival into Iceland of ( a ) 54 individually marked black-tailed godwits recorded on arrival in between 4 and 8 years, from 1999 to 2012 (filled circles, ordered from earliest to latest) and the rates of change (open circles, days per year) in a...…”
Recent advances in spring arrival dates have been reported in many migratory species but the mechanism driving these advances is unknown. As population declines are most widely reported in species that are not advancing migration, there is an urgent need to identify the mechanisms facilitating and constraining these advances. Individual plasticity in timing of migration in response to changing climatic conditions is commonly proposed to drive these advances but plasticity in individual migratory timings is rarely observed. For a shorebird population that has significantly advanced migration in recent decades, we show that individual arrival dates are highly consistent between years, but that the arrival dates of new recruits to the population are significantly earlier now than in previous years. Several mechanisms could drive advances in recruit arrival, none of which require individual plasticity or rapid evolution of migration timings. In particular, advances in nest-laying dates could result in advanced recruit arrival, if benefits of early hatching facilitate early subsequent spring migration. This mechanism could also explain why arrival dates of short-distance migrants, which generally return to breeding sites earlier and have greater scope for advance laying, are advancing more rapidly than long-distance migrants.
“…Iceland supports numerous Arctic Tern colonies that are widely distributed and are exposed to a broad range of local environmental conditions, including weather, access to feeding grounds and oceanic conditions. In addition, their pole-to-pole migration (Egevang et al 2010) and late arrival on the Icelandic breeding grounds (Gunnarsson & Tómasson 2011) means that individuals are on a tight schedule for breeding, which may make them particularly sensitive to environmental changes. Their body condition could reflect environmental conditions experienced during migration but this is also likely to be influenced by local conditions in Iceland, because nesting typically occurs 3-4 weeks after arrival.…”
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