Geolocators map the wintering grounds of threatened Lesser Kestrels in Africa

Aim  To identify the wintering grounds of the threatened western European Lesser Kestrels to focus conservation efforts in those areas.
Location  Huelva Province, southern Spain, as breeding range, and western Africa (Senegal and Mauritania), as wintering range.
Methods  We used archival light level geolocators (1.5 g) to map the wintering areas and determine some characteristics of the migratory journeys of 20 adult Lesser Kestrels from the Iberian Peninsula tagged in 2007.
Results  Thirteen geolocators were recovered the following breeding season (2008) after attachment in 2007. Four recovered geolocators provided useful data. According to kernel density analyses, kestrels wintered near the Senegal River (border between Mauritania and Senegal). Pre-nuptial migration took longer than the post-nuptial migration, which may be the consequence of a loop migration.
Main conclusions  Geolocators have solved a crucial conservation question (i.e. the winter destination of western European Lesser kestrels), and these devices have thus proved useful to determine the location of the winter quarters of small sized migratory species. Our data indicate that European Lesser Kestrels winter in West Africa, in accordance with previous suggestions based on scattered observations during the winter months. This valuable information should serve to focus conservation efforts both in northern Senegal and southern Mauritania. Large roosts gathering thousands of lesser kestrels had been recorded in these areas over the years, but there was no previous confirmation of individuals staying all winter long. Specific and sustained protection of the roost sites, where the birds may be most vulnerable, should be sought in conjunction with local authorities.     

10. OFFICIAL ANNOUNCEMENTS

Anderson, P.C., Kok O.B. &; Erasmus, B.H. 1998. Diet, body mass and condition of Lesser Kestrels Falco naumanni in South Africa. Ostrich 70(2):112-116.

A total of 229 Lesser Kestrels Falco naumanni shot by airport personnel as part of their bird control programme, was obtained from the Bloemfontein and Kimberley airports during the 1984/85, 198986 and 1986/87 austral summers. Analysis of stomach contents of non-breeding individuals visiting South Africa's Free State and Northern Cape Provinces indicated that Arthropoda comprise 90% of the diet, with Solifugae (30%), Orthoptera (23%). Chilopoda (20%) and Isoptera (10%) being the most important food items. Vertebrates were virtually absent from the diet. No sex-related dietary differences were found. Lesser Kestrels are opportunistic invertebrate feeders which mainly utilise available and most abundant prey species. Female birds are significantly heavier than males, but the latter maintain higher body fat reserves for the larger part of their stay in South Africa.     

Individual variation in migratory movements and winter behaviour of Iberian Lesser Kestrels Falco naumanni revealed by geolocators

The population decline of the Lesser Kestrel Falco naumanni has been the subject of studies across its Western Palaearctic breeding range, but little is known about its use of pre‐migratory areas or African wintering quarters. We used geolocators to describe the temporal and spatial patterns of Portuguese Lesser Kestrel migration and wintering behaviour. Data on the complete migration were obtained from four individuals and another three provided further information. Prior to southward migration, Lesser Kestrels showed two different behaviours: northward‐orientated movements to Spain and movements in the proximity of the breeding area. Autumn migration took place mostly in late September; spring departures occurred mainly in the first half of February. Wintering grounds included Senegal, Mauritania and Mali, with individuals overlapping considerably in Senegal. Movements registered within the wintering grounds suggest itinerant behaviour in relation to local flushes of prey. During spring migration, birds crossed the Sahara Desert through Mauritania, Western Sahara and Morocco before passing over the Mediterranean to reach Portugal. Autumn migration lasted 4.8 ± 1.1 days, and spring migration lasted 4.1 ± 0.3 days. The mean daily flight range varied between approximately 300 and 850 km for an entire journey of around 2500 km. Effective protection of roosting sites in both pre‐migratory and wintering areas and maintaining grasshopper populations in Sahelian wintering quarters appear crucial in preserving this threatened migratory raptor across its African–Eurasian flyway. There was no evidence of any deleterious effects of fitting birds with loggers.     

7.—CORRESPONDENCE

Pepler, D., Martin, M., Fouche, F. &; VAN Hensbergen, B. 1994. Radionuclide analysis of Lesser Kestrels Falco naumanni and the origins of populations overwintering in southern Africa. Ostrich 65: 122–126.

The Lesser Kestrel Falco naumanni has recently shown major population declines throughout its breeding range in the Palearctic Region. In order to propose integrated conservation measures, it is important to establish the origins of the population overwintering in Africa. Nineteen Lesser Kestrels collected from released over Europe after the explosion at Chernobyl in 1986. Results of the radio-activity analysis show that these birds contain levels of ¹³⁴CS and ¹³⁷Cs that is below the detection threshold of the instrumentation. The measured activity of ¹³⁷Cs is a factor 57 lower than the “expected” level of 0,460 Bq/g ash. It is suggested that these birds originate from uncontaminated regions.     

Winter diet and lead poisoning risk of Greater Spotted Eagles Clanga clanga in southeast Spain

ABSTRACT

Capsule: Diet analysis revealed high lead exposure for Greater Spotted Eagles Clanga clanga wintering in southeast Spain.

Aims: To describe the diet composition of the endangered Greater Spotted Eagle in a wintering area located in southeast Spain, and determine lead ammunition exposure through analysis of regurgitated pellets and prey remains.

Methods: Between 2008 and 2018, a total of 26 pellets, 29 prey remains and 10 direct predation observations were collected in El Hondo Natural Park, Spain. All the pellets and 10 prey remains were analysed with X-ray in order to detect metal from ammunition.

Results: Greater Spotted Eagles fed mainly on birds, with 18 different species accounting for 73.1% of prey items and 66.1% of biomass consumed. The most frequent species identified were Common Moorhen Gallinula chloropus (23.1%), rats Rattus spp. (15.4%) and Common Teal Anas crecca (8.9%). Ammunition was detected in 42.3% of regurgitated pellets and in 40.0% of prey remains analysed. Of those containing ammunition, lead shot was found in 63.9% of pellets and 25.0% of prey remains.

Conclusion: High lead shot presence in pellets and prey remains of wintering Greater Spotted Eagles in southeast Spain warns of a high risk of lead poisoning. Factors such as feeding behaviour, the large space–time overlap between the raptor presence and the waterbird hunting season and non-compliance with the ban on the use of lead ammunition are likely contributing to high lead exposure.     

Postfledging dispersal in the endangered Lesser Kestrel Falco naumanni

Much is known about the breeding period of the threatened Lesser Kestrel, but little of the postfledging period. Here, I examine the postfledging dispersal of juvenile Lesser Kestrels, based on all ringing recoveries of Lesser Kestrels ringed as nestlings in Spain and recovered before September (migration) of the same year. Of 28 juveniles recovered, 19 (67.9%) dispersed and their median recovery distance was 210 km (range 41–578 km), with significantly northern directions. No difference was found in the dispersal distance between individuals ringed as nestlings in mid-north and mid-south Spain, nor was any correlation found between the recovery distance and ringing latitude. These findings for postfledging dispersal in juvenile Lesser Kestrels seem in accordance with predictions of a mental map hypothesis for homing, but they do not exclude food as a potential factor influencing such movements. However, these postfledging movements cannot be explained by the hypothesis of gathering information for identifying a future breeding site.     

Increased hunting effort buffers against vole scarcity in an urban Kestrel Falco tinnunculus population

Capsule In years with low vole abundance birds visited hunting grounds more frequently and for longer.

Aims To describe diet composition, hunting behaviour, habitat choice and reproductive success of urban Kestrels during changing vole abundance.

Methods For five years, we studied the hunting effort of Kestrels in a medium-sized city during the breeding season. Pitfall traps were used for determining vole abundance. Kestrel diet composition was determined from pellet analyses. The number of eggs and offspring was recorded during at least two consecutive visits for each nest and each breeding stage.

Results In contrast to larger European cities, the Common Vole Microtus arvalis was a key part of the Kestrels' diet and did not fluctuate significantly according to vole availability. Reproductive success was quite high and stable throughout years with different vole abundance. In years of low vole abundance, the arrival frequency at hunting grounds and time spent there increased. During years with a low vole population, Kestrels had less hunting success and the rate of successful visits decreased. Therefore, Kestrels probably had to change hunting grounds more frequently. During low vole years Kestrels used less demanding techniques, e.g. perching, despite the lower success of these hunting techniques, to avoid extremely high energetic costs.

Conclusions An increase in hunting helps to maintain a proper diet and consequently reproductive success. Vole abundance did not change dramatically during the study period, as reported by studies from western and northern Europe. The proportion of ruderal habitats on the city periphery is higher than in more monotonous farmland habitats. Ruderal habitats can be important when Kestrels look for mammals other than voles, especially during vole scarcity.     

Hydrology‐driven responses of herbivorous geese in relation to changes in food quantity and quality

East Dongting Lake is a Ramsar site and a particularly important wintering ground for herbivorous geese along the East Asian‐Australasian Flyway. The operation of the Three Gorges Dam has changed the water regime and has a significant impact on wetland ecosystems downstream. We studied the responses of two sympatric herbivorous goose species, the Lesser white‐fronted goose Anser erythropus and Bean goose Anser fabalis, to habitat change by investigating their food conditions, habitat selection, and diet composition in the wintering periods of 2016/2017 and 2017/2018, which had early and late water recession, respectively. It was expected that the contrasting water regimes would result in different food conditions and geese responses. The results showed that the food quality and quantity differed significantly between winters. As responses to the high‐quantity/low‐quality food during 2016/2017, more geese switched to feeding on mudflat and exploited plants such as dicotyledons and moss. The tall swards of Carex spp. (dominant plants in the meadow) that developed during the first growing season decreased the food accessibility during the second growing season and hindered the exploitation of newly generated shoots by the geese, which was further confirmed by our clipping control experiment. Nearly all the geese chose to feed on meadow, and Carex spp. made up the majority of their diet in 2017/2018 when there was more low‐quantity/high‐quality food. Compared with the globally vulnerable Lesser white‐fronted geese, the larger‐sized Bean geese seemed to be less susceptible to winter food shortages and exhibited more stable responses. We concluded that the food quality–quantity condition was the external factor influencing the geese responses, while morphological and physiological traits could be the internal factors causing different responses between the two species. This study enhanced the understanding of the influence that habitat change exerts on herbivorous geese in their wintering site in the context of the Three Gorges Dam operation. We suggested that regulating hydrological regime was important in terms of wetland management and species conservation.     

Causes of population declines of the Lesser Kestrel Falco naumanni in Israel

We studied the ecology of the Lesser Kestrel Falco naumanni , a globally threatened species, to identify the factors causing its gradual decline in Israel, in order to stabilize and possibly restore its numbers. Lesser Kestrels in Israel breed in colonies, both adjacent to human settlements (rural and urban) and in the countryside, where they are found especially on cliffs. In this study, observations of Lesser Kestrels were carried out in three different breeding areas: (1) an urban colony in Jerusalem, (2) a rural colony in the Alona district and (3) a cliff in the Judean desert (open landscape colony) about 10 km east of Jerusalem. The number of fledglings per nest in Jerusalem (1.91) was lower than in Alona (2.44) and the cliff (3.16). As this lower productivity was associated neither with the clutch size, with hatching success, which were similar in all three regions (about four eggs per clutch, and 80% hatched, respectively), nor with egg fertility, it probably reflects factors operating during the nestling phase. We suggest that the two main factors limiting food availability and causing nestling deaths in Jerusalem are the relatively long flight distances between the breeding and hunting sites, and the use of pesticides in the city parks and lawns. Stochastic events superimposed on such factors, such as the drought of 1999, which markedly reduced productivity, may cause pronounced fluctuations eventually affecting long-term population persistence.     

The diet of urban Magpies Pica Pica

This paper describes the diet of Magpies in the Manchester urban environment, based on analysis of stomach contents, pellets and faecal material. The diet comprised a selection of typical grassland fauna, the majority of which were surface-dwelling invertebrates. Weevils, click beetles, ground beetles, flies, caterpillars and spiders were common. However, soil-dwelling animals such as leatherjackets and worms were estimated to form a significant proportion of the weight of food. Vertebrate remains, such as those of the field vole Microtus agrestis and the House Sparrow Passer domesticus, were present at a low frequency. The most common constituents of the nestling diet were invertebrate groups that attained their peak seasonal abundance during the nestling period, which suggests that food resources may be utilized in proportion to their availability. During the winter when invertebrate material is scarce, the diet is largely composed of plant material; Magpies may experience a food shortage at this time of year. The summer diet of the adult is similar to that of nestling Magpies; neither include many eggs or nestlings.     

Feeding ecology of the Common Tern Sterna hirundo in a wintering area in southern Brazil

The wintering diet of Common Terns Sterna hirundo was studied by using 714 pellets collected on roosting sites at the mouth of the Lagoa dos Patos and on adjacent coastal beaches, in Rio Grande do Sul, southern Brazil, from March 1999 to February 2000. A total of 12 340 individual prey items of 35 different food types was found. Fish was the most important food type in the diet, constituting 32% by number and 93% by mass. Insects contributed 67% by number but only 3% by mass. The main food types were sciaenid fishes Paralonchurus brasiliensis, Micropogonias furnieri, Cynoscion guatucupa and Macrodon ancylodon. Several of these are important commercial species; fisheries potentially impact food availability to the terns, and terns may contribute significantly to the natural mortality of these fishes. Clupeiform fishes, the urophycid fish Urophycis brasiliensis and flying ants (Camponotus sp.) were also important. Species composition of the diet (food types), both by number and by mass, differed significantly between months. Prey sizes ranged in length from 12.7 mm to 217.4 mm. The average estimated total length of fish taken was 77.7 mm, but the mean differed significantly among prey species. The importance of demersal sciaenids to the diet of the Common Tern, a surface predator, may be explained by their association with aquatic predators, especially adult Bluefish Pomatomus saltatrix and Striped Weakfish Cynoscion guatucupa, and the Franciscana Dolphin Pontoporia blainvillei, which drive these fish to the surface. The occurrence of flying ants in the diet was related to offshore winds, which carried these insects out to sea. The occasional high availability of insects possibly changed the cost/benefit relationship of several food types, causing diet changes. The high number of prey species, the temporal variations in the composition of the diet and the wide range of prey sizes are evidence of the high dietary plasticity of the Common Tern, at wintering areas in southern Brazil.     

Population fragmentation leads to isolation by distance but not genetic impoverishment in the philopatric Lesser Kestrel: a comparison with the widespread and sympatric Eurasian Kestrel

Population fragmentation is a widespread phenomenon usually associated with human activity. As a result of habitat transformation, the philopatric and steppe-specialist Lesser Kestrel Falco naumanni underwent a severe population decline during the last century that increased population fragmentation throughout its breeding range. In contrast, the ubiquitous Eurasian Kestrel Falco tinnunculus did not suffer such adverse effects, its breeding range still remaining rather continuous. Using microsatellites, we tested the effects of population fragmentation on large-scale spatial patterns of genetic differentiation and diversity by comparing these two sympatric and phylogenetically related species. Our results suggest that habitat fragmentation has increased genetic differentiation between Lesser Kestrel populations, following an isolation-by-distance pattern, while the population of Eurasian Kestrels is panmictic. Contrary to expectations, we did not detect significant evidence of reduced genetic variation or increased inbreeding in Lesser Kestrels. Although this study reports genetic differentiation in a species that has potential for long-distance dispersal but philopatry-limited gene flow, large enough effective population sizes and migration may have been sufficient to mitigate genetic depauperation. A serious reduction of genetic diversity in Lesser Kestrels would, therefore, only be expected after severe population bottlenecks following extreme geographic isolation.     

Mechanisms of colony selection by first‐year Lesser Kestrels Falco naumanni

In colonial species, first‐time breeders may use the number of settled conspecifics in colony selection, but such a relationship is confused by the correlation between colony size and nest‐site availability. To distinguish conspecific attraction from neutral colony selection, we experimentally increased nest availability for first‐year Lesser Kestrels Falco naumanni, allowing us to dissociate the number of vacant nest‐sites from colony size at the arrival time of first‐year birds. Under natural conditions, the number of first‐year birds settling was positively correlated with both the number of philopatric and the total number of breeding pairs (colony size) already settled. However, the probability of occupation of experimentally manipulated nests by first‐year birds was independent of colony size. In experimental colonies, the number of first‐year birds settling was positively correlated with the number of manipulated nest‐sites but not with the number of conspecifics. Overall, these results support a neutral colony selection by first‐year Lesser Kestrels based on nest‐site availability.     

The influence of sample size on the determination of population trends in the vulnerable Lesser Kestrel Falco naumanni overwintering in South Africa

Reliable measures of population sizes of endangered and vulnerable species are difficult to achieve because of high variability in population sizes and logistic constraints on sample sizes, yet such measures are crucial for the determination of the success of conservation and management strategies aimed at curbing declines in population size. In this study, we use bootstrap confidence intervals to assess the effects of sample size on the reliable determination of roost size in the vulnerable Lesser Kestrel Falco naumanni overwintering at a large communal roost in South Africa. Using results from a unique five-season daily survey, we show that the currently recommended number of replicate sample counts (international action plan for the Lesser Kestrel) of three censuses per season is too low to reliably assess roost size. Bootstrap confidence intervals asymptote at 40–60 censuses per season, with 50 being the modal value. We recommend 50 censuses per season as the optimal sample size. We were also able to show that the population size of Lesser Kestrels at this roost significantly increased over each of the first four seasons of the study period and decreased slightly in the final season.     

Diet of the black-headed heron Ardea melanocephala during the breeding season in South African grasslands

The diet of the black-headed heron was studied using analysis of pellets and prey remnants (225 prey items identified) collected from four sites in South African Highveld Grassland, transformed into cultivated fields. Small vertebrates comprised the staple food of chicks. Rodents were the most important vertebrate prey. Otomys irroratus comprised ca. 50% of the total biomass of vertebrate prey consumed. The diet was supplemented by small lizards, snakes, frogs and fishes. Grasshoppers, beetles, crabs and other arthropods were occasionally preyed upon.     

Notes on the diet of urban Kestrels

This paper seeks to quantify the diet of urban Kestrels in Manchester through pellet analysis. Birds comprised 76% of prey taken (passerines predominating) and rodents 22%, while invertebrates accounted for only 2%. Passerine remains are difficult to identify in raptor pellets, but the indication is that the House Sparrow is much the most significant prey.     

Benefit of migration in a female sika deer population in eastern Hokkaido,Japan

The major factors affecting migration in large herbivores have been shown to be access to food resources and the risk of predation. Three migratory types of deer (resident, north migrant and east migrant) occur within a wintering female sika deer (Cervus nippon) population in eastern Hokkaido, Japan. We tested the hypothesis that north and east migrants feed on a higher quality diet than residents during summer, based on analyses of fecal nitrogen content. Fresh fecal pellets were collected in 18 summer ranges in the wintering area, northern area and eastern area between 1–5 August 2000. Fecal nitrogen content for all sampling sites was positively correlated with elevation, but was not correlated with distance from the wintering area. North migrants that inhabited higher (above 300m elevation) summer ranges fed on a higher quality diet than residents. In contrast, the dietary quality of east migrants that migrated over a long distance and inhabited lower (below 300m elevation) summer ranges was similar to that of residents. We conclude that east migrants may have gained significant benefit from the use of agricultural pastures with low population density conditions and without hunting; however, the recent population control program has reduced this benefit by avoiding the use of pasturelands.     

Investigating the influence of local weather conditions and alternative prey composition on the breeding performance of urban Eurasian Kestrels Falco tinnunculus

Capsule: Local weather conditions, but not a city-associated diet composition, influence the breeding performance of urban Eurasian Kestrels Falco tinnunculus.

Aims: We aim to explore the impact of diet composition, specifically a high proportion of avian prey, on the breeding performance of urban Eurasian Kestrels under different weather conditions.

Methods: The Eurasian Kestrel is known to exploit cities and occurs in the study area of Vienna, Austria (415?km²) at high breeding densities of 89–122 pairs/100?km². Unlike their rural conspecifics which specialize in voles, urban Kestrels are generalists, preying on passerines and mammals, but also reptiles and insects. We explore this alternative diet through pellet analyses along an urbanization gradient over a 5-year period and link diet to reproductive performance, taking local weather conditions into account.

Results: Our results showed that weather had a greater influence on breeding performance than did diet. Warm and dry weather during the arrival and courtship period was correlated with earlier egg-laying, higher nestling survival and an overall higher breeding success. Dry winters increased the proportion of mammalian prey, whereas low temperatures and high rainfall during the nestling phase increased the proportion of avian prey. Overall, a more diverse diet was also associated with higher rainfall, but only during the arrival and courtship period.

Conclusion: Our research shows a stronger connection between breeding performance and weather conditions than between breeding performance and diet composition, although there may be indirect effects of weather on prey availability which augment the impact of diet on reproductive output in the Eurasian Kestrel.     

Diet of sympatrically breeding Southern Carmine Bee-eater Merops nubicoides and White-fronted Bee-eater Merops bullockoides

The Southern Carmine Bee-eater Merops nubicoides and White-fronted Bee-eater Merops bullockoides are insectivore, cavity-nesting bird species, both of which occur in the Zambezi Region, north-eastern Namibia. I examined there the diet composition of these species by an analysis of prey remnants. The Southern Carmine Bee-eater chick's diet consisted of exclusively insects, represented by seven orders. The most numerous were orthopterans and beetles (40.9% and 26.1%, respectively; n = 582 prey items). Hymenopterans (18.7%) and bugs (12.9%) supplemented the diet, whereas dragonflies (Odonata) and moths (Lepidoptera) were preyed only occasionally. In the diet of the White-fronted Bee-eater, nesting at the same site, beetles were the most important prey (81.2% of all 101 prey items identified), with scarabaeids comprising more than half of the beetle diet. In comparison with the White-fronted Bee-eater, a lower proportion of beetles, but much larger proportion of orthopterans were recorded in the diet of the Southern Carmine Bee-eater. In both bee-eater species, hymenopterans appear to be less important than was expected. The essential difference in the proportion of main prey groups recorded in Southern Carmine and White-fronted Bee-eaters breeding at the same site may represent a shift in food niche due to both temporal segregation in breeding, and differences in food preferences (feeding sites).