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Tuesday, 31 March 2015

BOU2015 Avian Tracking Conference, Ibis Virtual Issue, March 2015


Cover image for Vol. 157 Issue 2

© British Ornithologists' Union

Volume 157 Issue 2
Edited By: Paul F. Donald (Editor in Chief)

BOU2015 Avian Tracking Virtual Issue
This Virtual Issue of Ibis has been compiled to showcase some of the recent contributions published in the Journal on ‘avian tracking and remote sensing’ to accompany the BOU 2015 Annual Conference on the same theme held at University of Leicester, UK in March 2015. You can find conference related items on social media using #BOU2015.

Tracking to assess migratory movements:

Malcolm Smith, Mark Bolton, David J. Okill, Ron W. Summers, Pete Ellis, Felix Liechti and Jeremy D. Wilson

The migration route of Red-necked Phalarope populations breeding on North Atlantic islands has been subject to considerable speculation. Geolocator tags were fitted to nine Red-necked Phalaropes breeding in northern Scotland to assess whether they migrated to Palaearctic or Nearctic wintering grounds. Of four birds known to return, two had retained their tags, of which one was recaptured. This male Phalarope left Shetland on 1 August 2012 and crossed the Atlantic Ocean to the Labrador Sea off eastern Canada in 6 days, then moved south to reach Florida during September, crossed the Gulf of Mexico into the Pacific Ocean and reached an area between the Galapagos Islands and the South American coast by mid-October, where it remained until the end of April, returning by a similar route until the tag battery failed as the bird was crossing the Atlantic Ocean. The total migration of 22 000 km is approximately 60% longer than the previously assumed route to the western part of the Arabian Sea, and this first evidence of migration of a European breeding bird to the Pacific Ocean also helps to indicate the possible migratory route of the large autumn movements of Red-necked Phalaropes down the east coast of North America.

Iain J. Stenhouse, Carsten Egevang and Richard A. Phillips

The migrations and winter distributions of most seabirds, particularly small pelagic species, remain poorly understood despite their potential as indicators of marine ecosystem health. Here we report the use of miniature archival light loggers (geolocators) to track the annual migration of Sabine’s Gull Larus sabini, a small (c. 200 g) Arctic-breeding larid. We describe their migratory routes and identify previously unknown staging sites in the Atlantic Ocean, as well as their main Atlantic wintering area in the southern hemisphere. Sabine’s Gulls breeding in northeast Greenland displayed an average annual migration of almost 32 000 km (n = 6), with the longest return journey spanning close to 39 000 km (not including local movements at staging sites or within the wintering area). On their southern migration, they spent an average of 45 days in the Bay of Biscay and Iberian Sea, off the coasts of France, Spain and Portugal. They all wintered in close association with the cold waters of the Benguela Upwelling, spending an average of 152 days in that area. On their return north, Sabine’s Gulls staged off the west African coast (Morocco, Mauritania, Senegal), spending on average 19 days at this site. This leg of migration was particularly rapid, birds travelling an average of 813 km/day, assisted by the prevailing winds. Sabine’s Gulls generally followed a similar path on their outbound and return migrations, and did not exhibit the broad figure-of-eight pattern (anti clockwise in the southern hemisphere and clockwise in the northern hemisphere) seen in other trans-equatorial seabirds in the Atlantic and Pacific oceans.

Ruben Liminana, Marta Romero Ugo Mellone and Vicente Urios

Recent improvements in satellite tracking, such as the miniaturization of transmitters, have enabled the study of movements of an increasing number of bird species. The Lesser Kestrel Falco naumanni has been the subject of numerous studies but detailed information on its migration routes and wintering areas is still lacking. Here, we provide a detailed description of migration routes, timing of migration and wintering areas of Lesser Kestrels. Five adults fitted with satellite transmitters in southeastern Spain were tracked during autumn and spring migration journeys and on their wintering grounds. The overall migration duration was longer in spring than in autumn, although birds also showed longer stopovers in this season and hence the number of travelling days was lower. Lesser Kestrels covered longer daily distances in spring due to a higher frequency of nocturnal migration, rather than differences in flight speed, which did not differ between seasons. Wintering areas of Lesser Kestrels from the same breeding colony were widely spaced throughout the western Sahel along the borders of Mauritania, Mali and Senegal, approximately 2800 km from their breeding sites. The autumn migration duration of Lesser Kestrels derived from recent studies using geolocators was underestimated compared with that recorded by satellite telemetry. Given the current rapid habitat loss in the Sahel, a better understanding of migratory routes and wintering areas of other populations of this species would be important to assess its influence on population trends.

Tracking to study breeding ecology, habitat use and diet:

Giuseppe De Marchi, Giorgio Chiozzi, Giacomo Dell'Omo and Mauro Fasola

We used GPS data-loggers, video-recordings and dummy eggs to assess whether foraging needs may force the low incubation attentiveness (< 55%) of the Crab Plover Dromas ardeola, a crab-eating wader of the Indian Ocean that nests colonially in burrows. The tidal cycle was the major determinant of the time budget and some foraging trips were more distant from the colony than previously known (up to 26 km away and lasting up to 45 h). The longest trips were mostly made by off-duty parents, but on-duty parents also frequently left the nest unattended while foraging for 1–7 h. However, the time spent at the colony area (47%) and the time spent roosting on the foraging grounds (16%) would have allowed almost continuous incubation, as in other species with shared incubation. Therefore, the low incubation attentiveness is not explained by the need for long foraging trips but is largely dependent on a high intermittent rhythm of incubation with many short recesses (5.8 ± 2.6 recesses/h) that were not spent foraging but just outside the burrow or thermoregulating at the seashore. As a result, the eggs were warmed on average only 1.7 °C above burrow temperature, slightly more during high tide periods and when burrow temperature was lower between 20:00 and 10:00 h, only partly counteracting the temperature fluctuations of the incubation chamber. These results suggest that low incubation attentiveness is due to the favourable thermal conditions provided by safe nesting burrows and by the hot tropical breeding season, a combination that allows simultaneous foraging by parents and the exploitation of distant foraging grounds. Why Crab Plovers engage in many short recesses from incubation still remains to be clarified but the need to thermoregulate at the seashore and to watch for predators may play a role.

Sarah E. Gutowsky, Yann Tremblay, Michelle A. Kappes, Elizabeth N. Flint, John Klavitter, Leona Laniawe, Dan P. Costa, Maura B. Naughton, Marc D. Romano and Scott A. Shaffer

Past tracking studies of marine animals have primarily targeted adults, biasing our understanding of at-sea habitat use toward older life stages. Anthropogenic threats persist throughout the at-sea ranges of all life stages and it is therefore of interest to population ecologists and managers alike to understand spatiotemporal distributions and possible niche differentiation between age-classes. In albatrosses, particularly little is known about the juvenile life stage when fledglings depart the colonies and venture to sea with no prior experience or parental guidance. We compared the dispersal of 22 fledgling Black-footed Albatross Phoebastria nigripes between 2006 and 2008 using satellite telemetry and 16 adults between 2008 and 2009 using geolocaters from Midway Atoll National Wildlife Refuge, Northwest Hawaiian Islands. Following tag deployment, all fledglings spent several days within the calm atoll waters, then travelled northward until reaching 750–900 km from the colony. At this point, fledgling distributions approached the productive North Pacific Transition Zone (NPTZ). Rather than reaching the high chlorophyll a densities on the leading edge of this zone, however, fledglings remained in areas of low productivity in the subtropical gyre. In contrast, adult albatrosses from the same breeding colony did not utilize the NPTZ at this time of year but rather ranged throughout the highly productive northern periphery of the Pacific Ocean Basin among the shelf regions off Japan and the Aleutian Islands. The dichotomy in habitat use between fledglings and adults from Midway Atoll results in complete spatial segregation between age-classes and suggests ontogenetic niche separation in this species. This research fills a large knowledge gap in at-sea habitat use during a little known yet critical life stage of albatrosses, and contributes to a more comprehensive understanding of differential mortality pressure between age-classes and overall conservation status for the vulnerable Black-footed Albatross.

Kurt K. Burnham and Ian Newton

Little information exists on the movements of Gyrfalcons Falco rusticolus outside the breeding season, particularly amongst High Arctic populations, with almost all current knowledge based on Low Arctic populations. This study is the first to provide data on summer and winter ranges and migration distances. We highlight a behaviour previously unknown in Gyrfalcons, in which birds winter on sea ice far from land. During 2000–2004, data were collected from 48 Gyrfalcons tagged with satellite transmitters in three parts of Greenland: Thule (northwest), Kangerlussuaq (central-west) and Scoresbysund (central-east). Breeding home-range size for seven adult females varied from 140 to 1197 km2 and was 489 and 503 km2 for two adult males. Complete outward migrations from breeding to wintering areas were recorded for three individuals: an adult male which travelled 3137 km over a 38-day period (83 km/day) from northern Ellesmere Island to southern Greenland, an adult female which travelled 4234 km from Thule to southern Greenland (via eastern Canada) over an 83-day period (51 km/day), and an adult female which travelled 391 km from Kangerlussuaq to southern Greenland over a 13-day period (30 km/day). Significant differences were found in winter home-range size between Falcons tagged on the west coast (383–6657 km2) and east coast (26 810–63 647 km2). Several Falcons had no obvious winter home-ranges and travelled continually during the non-breeding period, at times spending up to 40 consecutive days at sea, presumably resting on icebergs and feeding on seabirds. During the winter, one juvenile female travelled over 4548 km over an approximately 200-day period, spending over half that time over the ocean between Greenland and Iceland. These are some of the largest winter home-ranges ever documented in raptors and provide the first documentation of the long-term use of pelagic habitats by any falcon. In general, return migrations were faster than outward ones. This study highlights the importance of sea ice and fjord regions in southwest Greenland as winter habitat for Gyrfalcons, and provides the first detailed insights into the complex and highly variable movement patterns of the species.

Tracking for conservation:

Carlos Palacín, Juan C. Alonso, Carlos A. Martín and Javier A. Alonso

A detailed knowledge of the habitat requirements of steppe birds living in farmland habitats is necessary to identify agricultural practices compatible with their conservation. The globally threatened Great Bustard Otis tarda is a partial migrant in central Iberia, but factors affecting its winter habitat use have not been identified. We assessed habitat differences between breeding and wintering areas and winter habitat selection of radiotagged migrant female Great Bustards in central Spain. Of 68 tagged females, 35% moved to wintering areas located 64.3 ± 24.0 km south of their breeding areas, and 80% wintered in a single area of c. 236 km2. A census of the population in this area identified it as one of the most important wintering areas of this species in the world, holding c. 1500 individuals. There were significant differences between breeding and wintering habitats of individually marked migrant females. Compared with breeding areas, wintering areas of migrant females were located further from roads and urban nuclei, had lower human population densities and area of urban developments, and a higher diversity of land-use types, with less cover of cereals and more vineyards and olive groves. Within this area, radiotracked migrant females preferred sites with more vineyards and a lower land-use diversity. Our results highlight the importance of traditional Mediterranean dry farmland mosaics, and suggest that different conservation strategies are needed for migrant and resident populations in winter to secure the conservation of suitable wintering habitat for Great Bustards in the Iberian Peninsula.

Andrea C. Bowling, Julien Martin and Wiley M. Kitchens

The degradation of habitats due to human activities is a major topic of interest for the conservation and management of wild populations. There is growing evidence that the Florida Everglades ecosystem continues to suffer from habitat degradation. After a period of recovery in the 1990s, the Snail Kite Rostrhamus sociabilis population suffered a substantial decline in 2001 and has not recovered since. Habitat degradation has been suggested as one of the primary reasons for this lack of recovery. As a consequence of the continued degradation of the Everglades, we hypothesized that this would have led to increased movement of juvenile Kites over time, as a consequence of the need to find more favourable habitat. We used multistate mark-recapture models to compare between-site movement probabilities of juvenile Snail Kites in the 1990s (1992–95; which corresponds to the period before the decline) and 2000s (2003–06; after the decline). Our analyses were based on an extensive radiotelemetry study (266 birds tracked monthly over the entire state of Florida for a total period of 6 years) and considered factors such as sex and age of marked individuals. There was evidence of increased movement of juvenile Snail Kites during the post-decline period from most of the wetland regions used historically by Kites. Higher movement rates may contribute to an increase in the probability of mortality of young individuals and could contribute to the observed declines.

Alexandre Villers, Alexandre Millon, Frederic Jiguet, Jean-Michel Lett, Carole Attie, Manuel B. Morales and Vincent Bretagnolle

Populations of the Little Bustard Tetrax tetrax in the farmlands of Europe have declined greatly over the last century. In Western Europe, France now holds the only remaining migratory population, which currently numbers fewer than 300 displaying males. However, the movements of these birds are virtually unknown, in spite of the important implications of this information for the conservation of this species. We identified migratory movements and overwintering areas of French migratory populations, using wild individuals fitted with satellite or radio-transmitters. Little Bustards completed their migration journey over a relatively short time period (2–5 days), with nocturnal migration flights of 400–600 km per night. All birds overwintered in Iberia. In addition, we tested the consequences of captive rearing on migratory movements. French wild adults and French captive-bred juveniles behaved similarly with regard to migration, suggesting that hand-raising does not alter migratory movements. However, birds originating from eggs collected in Spain and reared in western France did not migrate, suggesting a genetic component to migratory behaviour. These results therefore suggest that a conservation strategy involving the release in France of birds hatched from eggs collected in Spain may imperil the expression of migratory movements of the French population. More generally, to maintain the integrity of native populations, the introduced individuals should mimic their migratory movements and behaviour.

The effects of fitting tracking devices on birds:

Fabián Casas, Ana Benítez-López, Jesús T. García, Carlos A. Martín, Javier Viñuela and Francois Mougeot

Capturing and marking free-living birds permits the study of important aspects of their biology but may have undesirable effects. Bird welfare should be a primary concern, so it is necessary to evaluate and minimize any adverse effects of procedures used. We assess short-term effects associated with the capture, handling and tagging with backpack-mounted transmitters of Pin-tailed Pterocles alchata and Black-bellied Pterocles orientalis Sandgrouse, steppe birds of conservation concern. There was a significantly higher mortality (15%) during the first week after capture than during the following weeks (< 2.5%) in Pin-tailed Sandgrouse, but no significant temporal mortality pattern in Black-bellied Sandgrouse. In Pin-tailed Sandgrouse, mortality rate during the first week increased with increasing relative transmitter and harness weight regardless of season, and with increasing handling time during the breeding season. There were no significant differences in mortality rate between study areas, type of tag, sex or age or an effect of restraint time. These results suggest the use of lighter transmitters (< 3% of the bird's weight) and a reduction of handling time (< 20 min), particularly during the breeding season, as essential improvements in procedure to reduce the mortality risk associated with the capture, handling and tagging of these vulnerable species.

Peter Dann, Leesa A. Sidhu, Roz Jessop, Leanne Renwick, Margaret Healy, Belinda Dettmann, Barry Baker and Edward A. Catchpole

Tagging is essential for many types of ecological and behavioural studies, and it is generally assumed that it does not affect the fitness of the individuals being examined. However, the tagging of birds has been shown to have negative effects on some aspects of their lives. Here we investigate the influence of tagging on apparent survival. We examined the effects of flipper bands and injected transponders on the apparent survival of adult Little Penguins by comparing the survival probabilities of 2483 Little Penguins marked at Phillip Island, Australia, between 1995 and 2001 in one of three ways: with bands, with transponders or with both. The design of the study and our method of analysis allowed us to estimate tag loss and ensured that tag loss did not bias the survival estimates. Birds marked with flipper bands had lower survival probabilities than those marked with transponders (with apparent survival probabilities in the first year after tagging of 75% for banded birds and 80% for birds fitted with transponders, and in subsequent years of 87% for banded birds and 91% for birds fitted with transponders). We estimated both band and transponder loss probabilities for the first time, and found that transponder loss probabilities were substantially higher than band loss probabilities, particularly in the first year after marking when the tag loss probability was 5% for transponders and 0.7% for bands. Survival probabilities were lower in the first year after marking than in subsequent years for all birds. Studies of penguins that have used flipper bands to identify individuals may have underestimated annual adult survival probabilities, as banded penguins were likely to have lower than average survival probabilities than those of unbanded birds. The higher annual survival probabilities of individuals marked with transponders indicate that this should be the preferred marking technique for Little Penguins. However, future studies will, like ours, need to consider the higher rates of transponder loss when estimating survival, possibly by double-tagging some birds.

Ainhoa Mateo-Moriones, Rafael Villafuerte and Pablo Ferreras

A better knowledge of chick survival rates is required to enable understanding of the population dynamics of gamebirds and to develop management measures to conserve their populations. The Red-legged Partridge Alectoris rufa is a highly valued game species in Spain but its populations have declined in recent decades. A lack of appropriate monitoring methods has been a limitation in gaining information on the mortality of Red-legged Partridge chicks. We developed methods for the effective radiotagging of chicks in captivity and applied these methods in the field in northern Spain to estimate survival during the first 5 months of life. The most effective method for radiotagging captive chicks between 3 and 8 days old involved gluing small tags directly to the skin in the interscapular space using cyanoacrylate adhesive. Backpack harness tags attached with elastic bands were the most effective method of radiotagging 4-week-old chicks. Predation was the main cause of chick mortality identified during the field experiments. Survival between hatching and 5 months of age was estimated to be 16–21%. The lowest survival rates occurred during the first 7 days of life (62–70% cumulative survival) and this period seems to be a major determinant in the life history of the species.

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