Wind effects on the migration routes of trans-Saharan soaring raptors

Vidal-Mateo, J., Mellone, U., López-López, P., De La Puente, J., García-Ripollés, C., Bermejo, A. & Urios, V. (2016). Wind effects on the migration routes of trans-Saharan soaring raptors: geographical, seasonal, and interspecific variation. Current Zoology 62: 89–97. doi: 10.1093/cz/zow008 (Open Access)

Abstract:

Wind is among the most important environmental factors shaping birds’ migration patterns. Birds must deal with the displacement caused by crosswinds and their behavior can vary according to different factors such as flight mode, migratory season, experience, and distance to goal areas. Here we analyze the relationship between wind and migratory movements of three raptor species which migrate by soaring–gliding flight: Egyptian vulture Neophron percnopterus, booted eagle Aquila pennata, and short-toed snake eagle Circaetus gallicus. We analyzed daily migratory segments (i.e., the path joining consecutive roosting locations) using data recorded by GPS satellite telemetry. Daily movements of Egyptian vultures and booted eagles were significantly affected by tailwinds during both autumn and spring migrations. In contrast, daily movements of short-toed eagles were only significantly affected by tailwinds during autumn migration. The effect of crosswinds was significant in all cases. Interestingly, Egyptian vultures and booted eagles showed latitudinal differences in their behavior: both species compensated more frequently at the onset of autumn migration and, at the end of the season when reaching their wintering areas, the proportion of drift segments was higher. In contrast, there was a higher drift at the onset of spring migration and a higher compensation at the end. Our results highlight the effect of wind patterns on the migratory routes of soaring raptors, with different outcomes in relation to species, season, and latitude, ultimately shaping the loop migration patterns that current tracking techniques are showing to be widespread in many long distance migrants.

Response of three migratory raptors to crosswinds in spring (upper panel) and autumn (lower panel). Egyptian vulture’s routes are shown in (A) and (D); booted eagle’s routes in (B) and (E); and short-toed snake eagle’s routes in (C) and (F). Colors indicate drift (green), compensation (blue), and overcompensation (orange) in daily segments

Response of three migratory raptors to crosswinds in spring (upper panel) and autumn (lower panel). Egyptian vulture’s routes are shown in (A) and (D); booted eagle’s routes in (B) and (E); and short-toed snake eagle’s routes in (C) and (F). Colors indicate drift (green), compensation (blue), and overcompensation (orange) in daily segments

Consistency in long-distance bird migration: contrasting patterns in time and space for two raptors

Vardanis, Y., Nilsson, J.-Å., Klaassen, R. H. G., Strandberg, R. & Alerstam, T. (2016). Consistency in long-distance bird migration: contrasting patterns in time and space for two raptors. Animal Behaviour 113: 177–187. doi: 10.1016/j.anbehav.2015.12.014
PDF in ResearGate.net

Abstract :

As the evolutionary responses to environmental change depend on selection acting on individual differences, disentangling within- and between-individual variation becomes imperative. In animal migration research, multiyear tracks are thus needed to estimate the individual consistency of phenotypic traits. Avian telemetry studies have recently provided the first evidence of individuality across space and time in animal migration. Here, we compare repeatability patterns of routes and timing between two migratory birds, the marsh harrier, Circus aeruginosus, and the osprey, Pandion haliaetus, as recorded by satellite tracking. We found interspecific contrasts with low repeatability in timing and duration and a high repeatability in routes for ospreys, but the reverse pattern for marsh harriers. This was mainly caused by (1) larger between-individual variation in routes for ospreys (broad-front migration) than for marsh harriers (corridor migration) and a higher degree of repeated use of the same stopover sites among ospreys, and (2) higher within-individual consistency of timing and duration among marsh harriers, while individual ospreys were more flexible. Our findings suggest that individuality in space and time is not a shared trait complex among migrants, but may show adaptive variation depending on the species’ life history and ecology.

Voir aussi:

Trierweiler, C., Klaassen, R. H. G., Drent, R. H., Exo, K.-M., Komdeur, J., Bairlein, F., & Koks, B. J. (2014). Migratory connectivity and population-specific migration routes in a long-distance migratory bird. Proc. R. Soc. B 281: 20132897.

Maps showing the routes of eight adult ospreys (first row) and six adult marsh harriers (second row) that completed at least one round trip between the breeding grounds in Sweden and the wintering quarters in West Africa during 1996–2012

Maps showing the routes of eight adult ospreys (first row) and six adult marsh harriers (second row) that completed at least one round trip between the breeding grounds in Sweden and the wintering quarters in West Africa during 1996–2012. Each panel highlights the three individuals with most repeated journeys of each species (a: OM1; b: OM2; c: OF1, d: MHM1; e: MHF1, f: MHF2; see Table 1 for details) in blue (autumn) and red (spring), as well as the trips of all other individuals of the species in grey

Costs of migratory decisions: A comparison across eight white stork populations

Flack, A., Fiedler, W., Blas, J., Pokrovsky, I., Kaatz, M., Mitropolsky, M., Aghababyan, K., Fakriadis, I., Makrigianni, E., Jerzak, L. and Azafzaf, H., Feltrup-Azafzaf, C., Rotics, S., Mokotjomela, T. M., Nathan, R. & Wikelski, M. 2016. Costs of migratory decisions: A comparison across eight white stork populations. Science Advances 2(1): p.e1500931. doi: 10.1126/sciadv.1500931 (Open Access)

Abstract:

Annual migratory movements can range from a few tens to thousands of kilometers, creating unique energetic requirements for each specific species and journey. Even within the same species, migration costs can vary largely because of flexible, opportunistic life history strategies. We uncover the large extent of variation in the lifetime migratory decisions of young white storks originating from eight populations. Not only did juvenile storks differ in their geographically distinct wintering locations, their diverse migration patterns also affected the amount of energy individuals invested for locomotion during the first months of their life. Overwintering in areas with higher human population reduced the stork’s overall energy expenditure because of shorter daily foraging trips, closer wintering grounds, or a complete suppression of migration. Because migrants can change ecological processes in several distinct communities simultaneously, understanding their life history decisions helps not only to protect migratory species but also to conserve stable ecosystems.

Migratory behavior of juveniles from eight different White Stork populations

Fig. 1. Migratory behavior of juveniles from eight different White Stork populations (Flack et al. 2016)

 

Irreplaceable area extends marine conservation hotspot off Tunisia: insights from GPS-tracking Scopoli’s shearwaters from the largest seabird colony in the Mediterranean

aGrémillet, D., Péron, C., Pons, J.-B., Ouni, R., Authier, M., Thévenet, M. & Fort, J. 2014. Irreplaceable area extends marine conservation hotspot off Tunisia: insights from GPS-tracking Scopoli’s shearwaters from the largest seabird colony in the Mediterranean. Marine Biology 161: 2669-2680.  doi:10.1007/s00227-014-2538-z

Abstract:

Recent meta-analyses identified conservation hotpots at the scale of the Mediterranean, yet those may be crude by lack of detailed information about the spatial ecology of the species involved. Here, we identify an irreplaceable marine area for >95 % of the world population of the Scopoli’s shearwater (Calonectris diomedea), which is endemic to the Mediterranean and breeds on the island of Zembra off Tunis. To this end, we studied the three-dimensional at-sea movements of 50 breeding adults (over a total of 94 foraging trips) in 2012 and 2013, using GPS and temperature–depth recorders. Feathers were also collected on all birds to investigate their trophic status. Despite Zembra being the largest seabird colony in the Mediterranean (141,000 pairs), the per capita home-range of Scopoli’s shearwaters foraging from this colony was not larger than that of birds from much smaller colonies, indicating highly beneficial feeding grounds in the Gulf of Tunis and off Cap Bon. Considering depleted Mediterranean small pelagic fish stocks, supposed to be Scopoli’s shearwater prey base, we therefore speculate that birds may now also largely feed on zooplankton, something which is supported by our stable isotopic analyses. Crucially, shearwater at-sea feeding and resting areas showed very little overlap with a conservation hotspot recently defined on the western side of the Gulf of Tunis using meta-analyses of species distributions relative to anthropogenic threats. We therefore propose a major extension to this conservation hotspot. Our study stresses the importance of detailed biotelemetry studies of marine megafauna movement ecology for refining large-scale conservation schemes such as marine protected area networks.

Ringing and tagging with a GPS mounted on TDR of Scopoli’s Shearwater (Calonectris diomedea), Zembra Archipelago, Tunisia

Ringing and tagging with a GPS mounted on TDR (temperature–depth recorders) of Scopoli’s Shearwater (Calonectris diomedea), Zembra Archipelago, Tunisia (photo: Initiative PIM).

The importance of northwest African stopover sites for Dutch, German and Danish Montagu’s Harriers

From 2005 to 2011, 34 adult Montagu’s Harriers (Circus pygargus) were fitted with satellite transmitters in three different subpopulations in northern Europe by the Dutch Montagu’s Harrier Foundation.

This is the first study to describe in great details the migration system of a Palaearctic-African long-distance migrant. The results of this unique long-term and large scale satellite tracking project were recently published in the Proceedings of the Royal Society B:

Trierweiler, C., Klaassen, R. H. G., Drent, R. H., Exo, K.-M., Komdeur, J., Bairlein, F., & Koks, B. J. (2014). Migratory connectivity and population-specific migration routes in a long-distance migratory bird. Proc. R. Soc. B 281: 20132897. doi: 10.1098/rspb.2013.2897 (free access)
PDF also available from the University of Groningen

The study discovered a previously unknown major stopover area in northwest Africa (northeastern Morocco and northern Algeria, figure 3). This area is used extensively both in autumn and spring, predominantly by birds travelling via the western route (i.e. birds from The Netherlands, western Germany and Denmark). In autumn, Montagu’s Harriers made a large number of lengthy stopovers in these northwest African sites. In autumn, 25% of all stopovers were located in northern Africa, whereas in spring 45% of all stopovers were located in this region. Furthermore, in autumn 46% of all individuals made a stopover, whereas in spring 88% of the birds stopped in this region.

This study shows once more that for effective conservation of migratory animals, key stopover sites (where these animals spent a good amount of time both in spring and autumn) need the same attention as the final destinations of the journey (breeding and wintering areas).

A male Montagu’s Harrier (Circus pygargus) is being fitted with a satellite transmitter. Sødernes (DK), July 2011. Picture by Henning Heldbjerg

A male Montagu’s Harrier (Circus pygargus) is being fitted with a satellite transmitter. Sødernes (DK), July 2011. Picture by Henning Heldbjerg

Main stopover sites for Montagu’s Harrier (Circus pygargus), for (a) autumn and (b) spring migration.

Main stopover sites for Montagu’s Harriers (Circus pygargus), for (a) autumn and (b) spring migration.
http://dx.doi.org/10.1098/rspb.2013.2897