Palaearctic Migrants Research Articles

Agonistic behaviour of Palaearctic passerine migrants at a stopover site suggests interference competition

Records of interspecific agonistic behaviour of Palaearctic passerine migrants from their Afrotropical wintering grounds are rare. There are, however, no detailed observations from stopover sites where individuals might concentrate and depress resources that are critical for fat-depleted birds in times of high energy demand. We recorded intraspecific and interspecific interactions of Palaearctic migrant passerine birds at Ouadâne, Mauritania, a stopover site in the Sahara desert. In spring 2003 we made casual records of all aggressive behaviour we observed, whereas in spring 2004 we used focal sampling of foraging birds to record the frequency of aggression. We found that interspecific interactions occurred more often than intraspecific interactions but their relative frequency differed between species. There were also mass-dependent species hierarchies. A comparison with other studies showed that in Willow Warblers the frequency of interspecific aggression was significantly higher at the stopover site than in the wintering grounds farther south. We cannot assess the adaptive advantage of agonistic behaviour, as our approach does not consider the allocation of aggressive interactions in relation to other activities and its influence on the birds' energy balance. Nevertheless, our observations suggest interspecific interference competition because inferior individuals are temporarily deprived of food, which may influence the fitness of migrants.

Raptor population decline in West Africa

The roadside counts conducted in 1969–1973 through Burkina Faso, Mali, Niger and northern Cameroon (9 712km) were repeated in 2000–2004 by the same observer, using the same methods, during the same season. Overall, 28 837 Falconiforms from 51 species were recorded. The four large vultures decreased dramatically (98%) outside protected areas. The Hooded Vulture also collapsed over wide regions, but survived locally. Medium-size and large eagles, and the Secretary Bird, similarly declined >90% outside, but not inside, national parks, where woodland species also reach their highest frequency. Other African raptors were either stable or decreased significantly (e.g. Black Kite and Chanting Goshawk 35–70%). Among Palaearctic migrants, Common and Lesser Kestrels declined sharply, Short-toed Eagle, Montagu's and Pallid Harriers less significantly, and Marsh Harrier and Booted Eagle increased. Widespread habitat degradation, overgrazing, desertification, hunting pressure and heavy use of pesticides are probably involved in this massive loss of biodiversity. Protected areas, though covering <2% of the region, will be critical in the conservation of eagles and vultures. Les mêmes recensements de rapaces le long de 9 712km de routes (observateur, méthode et saison) effectués en 1969–1973 à travers le Burkina Faso, Mali, Niger et Nord Cameroun, ont été répétés en 2000–2004. Au total, 28 837 Falconiformes de 50 espèces y ont été identifiés. Les quatre grands vautours ont considérablement diminué hors des zones protégées (>98%). Le percnoptère brun ne se maintient plus que dans quelques régions. Les grands aigles et le serpentaire ont aussi diminué de >90% en dehors, mais non à l'intérieur, des parcs nationaux où tous les rapaces liés aux boisements atteignent leur abondance maximale. Les autres rapaces africains sont restés stables ou ont diminué significativement (35 à 70% pour le Milan noir et l'autour chanteur par exemple). Parmi les migrateurs paléarctiques, crécerelle et crécerellette ont fortement diminué, circaète et busards cendré et pâle ont diminué modérément, tandis que busard des roseaux et aigle botté ont augmenté. Dégradation générale des habitats, surpâturage, désertification, pression de chasse et utilisation des pesticides sont probablement impliqués dans ces diminutions qui reflètent une érosion générale de la biodiversité. Les aires protégées, bien qu'elles couvrent <2% des pays étudiés, joueront un rôle majeur dans la conservation des aigles et des vautours.

Changes in densities of Sahelian bird species in response to recent habitat degradation

Habitat loss in the Sahel region of West Africa has been pronounced, due to anthropogenic effects and (potentially) climate change. Although strong links have been found between conditions in the Sahel and subsequent breeding populations of certain Palaearctic migrants, the effects of these fluctuations upon Afrotropical species are unknown. We repeated bird censuses (Dec 1993 to Jan 1994, Dec 2001 and Dec 2002) at Watucal Forest Reserve, northern Nigeria, an area of rapidly degrading Sahelian woodland. We predicted declines in the abundance of woodland bird species with deforestation. For the purpose of setting up an experimental control, we also repeated bird censuses in adjacent farmland habitats that had already been deforested by the first census period: we predicted no change in abundance of farmland bird species. Tree density at Watucal decreased significantly by 82% over the eight-year period. The number of birds counted per point, the total number of species recorded per point, and the Shannon diversity index, all declined significantly in Watucal, but there was no significant change in adjacent farmland. Of those species that were reasonably abundant in either census period, 22% (n = 41) at Watucal showed a significant change in abundance between periods: all of these species showed a decline. In contrast, only 4% (n = 23) showed a significant change in abundance (a decline) on farmland. Of the seven species that disappeared from Watucal between periods, 100% were classified as broadly woodland species and, of the eight species that were only recorded in 2001/02 at Watucal, 63% were classified as scrub or open species. Given that Watucal is a protected area, the degree of deforestation and concomitant changes in bird abundance suggest that the Sahel is likely to be undergoing major changes in bird diversity.

Moult of three Palaearctic migrants in their West African winter quarters

Some theories about moult strategies of Palaearctic passerine migrants assume that birds adapt timing of moult to environmental conditions such as rainfall on their African wintering grounds. Species wintering in the northern tropics should limit moult to the period shortly after their arrival at the end of the rainy season. Passerine migrants wintering in West Africa should also moult more rapidly compared to related species or conspecific populations that moult elsewhere. We investigated the moult of melodious warblers Hippolais polyglotta, willow warblers Phylloscopus trochilus and pied flycatchers Ficedula hypoleuca wintering in Comoe National Park, Ivory Coast, between October 1994 and April 1998. In contrast to previous studies we did not restrict our analyses to moult of flight feathers but also included moult of body feathers. The results differed partially from the general assumptions of previous authors. Melodious warblers moulted twice: a complete moult shortly after their arrival, and a moult of body feathers and in some cases some tertials and secondaries in spring. Willow warblers moulting flight feathers were found between December and March with the majority moulting in January and February. Primary moult was not faster compared to populations moulting in central Africa and South Africa. Body feather moult varied strongly among individuals with birds in heavy moult between December and April. Pied flycatchers moulted body feathers and tertials between January and April. Birds with growing feathers were found throughout the whole period including the entire dry season. Moult strategies are thus not readily related to a few environmental factors in general and our results show that factors other than mere resource availability during certain times on the wintering grounds are likely to govern the timing of moult.

Population densities and community structure of birds in riverine forest in the lowveld of Swaziland

Population density and community structure of birds were studied at three sites in riverine forest in the lowveld of Swaziland. Birds were surveyed monthly using a standard point count technique. A total of 101 species of birds was recorded. Species richness at the three sites ranged between 70-76 species. Population density was similar at the three sites and ranged between 24.0-31.2 birds ha-1. Biomass of birds was also similar at the three sites. Resident birds accounted for 74% of all species, but made up 97% of the individuals and biomass. There was a relatively large number of vagrant species, but they only accounted for <1% of the individuals and biomass. Species richness of intra-African and Palaearctic migrants was low, and they contributed little to total bird density or biomass. In terms of diet, the majority of birds were insectivorous, followed by the mixed diet category. Frugivores, though few in number, contributed significantly to biomass. Granivorous species and raptors contributed insignificantly. The avifauna of riverine forest in Swaziland is compared with similar habitats in southern Africa and with that of Acacia savanna and broadleaved woodland in Swaziland.

A preliminary assessment of the habitat selection of two Palaearctic migrant passerine species in West Africa

We investigated the habitat selected by two Palaearctic migrants (Pied Flycatcher, Ficedula hypoleuca, Willow Warbler, Phylloscopus trochilus) in a patchy landscape in Ivory Coast and compared it with the habitat selection of Afrotropical species in the same foraging guilds. Transect counts were used to test the hypothesis that migrants use more open and more seasonal habitats and have a broader use of habitats compared with resident species. Habitats compared were, in order of decreasing tree density, gallery forest, an isolated forest and bush/tree savanna. The isolated forest had the most pronounced seasonal changes (deciduous trees) and was the one with the most diverse vegetation structure. The habitat where both migrants were most frequent was the isolated forest, and thus occurred in the habitat with the most pronounced seasonal change. Diversity of habitats selected was highest in migrants but in the Pied Flycatcher this was possibly an artefact due to subdominant individuals being excluded from the preferred habitat by territorial birds. Potential competition for habitat with Afrotropical species was found to be low.

Population densities and community structure of birds in broadleaved woodland in the lowveld of Swaziland

Population density and community structure of birds was studied at three sites in broadleaved (combretaceous) woodland in the lowveld of Swaziland. Birds were surveyed monthly using a standard point count technique. A total of 94 species of birds was recorded. Species richness at the three sites ranged between 57 and 73 species. Population density was similar at the three sites and ranged from 11.8 to 13.9 birds/ha. Biomass of birds was also similar at the three sites. Resident birds only accounted for 49% of all species, but made up 85% of the individuals and 82% of the biomass. There was a relatively large number of vagrant species, but they only accounted for 10% of the individuals and 14% of the biomass. Species richness of intra-African and Palaearctic migrants was low, and they contributed little to the bird density or biomass. In terms of diet, most birds were insectivorous, with mixed diet and granivorous species contributing approximately equally to biomass. Frugivorous species and raptors contributed little. The avifauna of broadleaved woodland in Swaziland is compared with that of other broadleaved woodlands in southern Africa and with that of Acacia savanna in Swaziland. Broadleaved woodland in Swaziland appears to support an avifauna which is depauperate compared to that of Acacia savanna, but not distinct from it.

Long-term trends, seasonal abundance and energy consumption of waterbirds at Rietvlei, Western Cape, South Africa, 1950–1997

Waterbird counts at Rietvlei, a freshwater wetland in the Western Cape, were analysed for four periods: 1950–56, 1961–67, 1980–85 and 1992–97. Ninety-eight species of waterbirds were recorded during these counts. Palaearctic migrants predominated during summer, with Curlew Sandpipers, Calidris ferruginea, being the mast abundant species in all years, except in the 1960s and 1950s when Red-knobbed Coots, Fulica cristata, and Ruffs, Philomachus pugnax, outnumbered them respectively. Red-knobbed Coots and Yellow-billed Ducks, Anas undulata, were the most numerous species during winter in all years. The numbers of waterbirds at Rietvlei have shown a progressive increase since the 1950s, reaching over 8300 birds in the mid-summer of 1997. The increase in abundance of several species is attributed to changes in the water regime and habitat availability at the wetland. In terms of waterbird abundance, Rietvlei is the most important temporary vlei in the Western Cape and it ranks 16th in terms of waterbird abundance compared with all South African coastal and inland wetlands for which counts are available. In the light of Rietvlei being proclaimed a nature reserve, a conservation management plan for the area is discussed.

Training Kenyan bird ringers

Jackson, J. 2000. Training Kenyan bird ringers. Ostrich 71 (1 & 2): 342. Capturing and ringing birds is a fundamental ornithological field technique, and one that underlies much bird conservation research. In several countries, particularly in Britain and parts of western Europe, ringing is largely an amateur activity. Enthusiasts ring birds in their free time and take part in national surveys, enabling the effective monitoring of bird populations and movements. Until recently ringing in Kenya has been undertaken almost entirely by a handful of expatriate researchers and enthusiasts. Over the last 1CL15 years, it has also been largely confined to one site: Ngulia in Tsavo West National Park. Ringing effort has targeted Palaearctic migrants, mainly ignoring Afrotropical birds. The number of amateur and professional Kenyan ornithologists is fast increasing, but only a handful have any ringing experience. The remainder lack the resources to obtain the necessary equipment or the opportunity to undergo the long training required to become a qualified ringer. In June 1994, the, Nairobi Ringing Group was formed, based at the Department of Ornithology, National Museums of Kenya, Nairobi. The Group provides an opportunity for interested Kenyans to train as amateur ringers to a high standard, using departmental equipment and expertise. Ringing takes place twice weekly at the Nairobi Museum grounds and monthly at a constant effort site in a forest near Nairobi. Excursions have been made to other sites including Lake Magadi, for training in ringing waders, and Ngulia. The Group has a core of seven to ten members and a further 30 have taken part to varying degrees. Over 2 500 birds have been ringed so far and much learned about the identification, ageing and moult of the commoner species.

Habitat selection and coexistence of migrants and Afrotropical residents

In this paper I discuss factors that influence the habitat choice of small migrant birds on their Afrotropical wintering grounds and the ecological isolation of migrants and residents. The main characteristic of migrants is the use of resources which are sporadic in space and time. The majority of migrants occur in seasonal savannas and open woodland, mostly using temporarily and locally abundant food sources generally unused by residents. Migrants are more eurytopic and exploit more open parts of the habitats than ecologically similar tropical species. In some guilds, the foraging speed and rate of migrants is higher and they use their wings more often in comparison to residents. There is weak evidence that niche shifts of residents are induced by the arrival of migrants. Overt interspecific interactions seem to be infrequent, except in a guild of ground‐feeding birds which rely on a rather predictable but poor food supply. In this guild, residents, but not intra‐African migrants, dominated Palaearctic migrants in aggressive encounters irrespective of body‐size. In contrast to this, dominance was size‐dependent among wintering Palaearctic migrants.

Habitat use by Palaearctic migrant passerine birds in West Africa

Data on passerine migrants in West Africa published since the works of Moreau j 1972) and Curry‐Lindhal (1981) are reviewed and new information on wintering ranges are summarized. An important feature of West Africa as a wintering zone is the presence of the two great river basins of the Senegal and the Niger, which are responsible for the Sahel being far richer than would be expected at this latitude. This ‘paradoxical’ or ‘green’ Sahel is under the threat of agricultural developments and of increasing desertification. Conversely, Palaearctic migrants can take advantage of the new‐savanna/forest mosaics and agricultural developments which have replaced the rain forest.

Recent prospects on trans‐Saharan migration of songbirds

Many palaearctic migrants in tropical Africa have to cross the inhospitable land of the Sahara desert. Moreau (1961, 1972) hypothesized that these migrants crossed the Sahara in a single non‐stop flight. Recent field data, however, revealed that some migrants stop‐over in suitable desert habitats. The majority of grounded migrants showed a high body‐mass and fat‐loading, indicating sufficient reserves for onward flights. Further evidence on resting periods, retrapping rates and experiments with caged migrants supports the hypothesis of an intermittent migratory strategy, with regular stopovers during the day and flight at night, for some desert‐crossing passerines.

Perspectives on Palaearctic and Nearctic bird migration; comparisons and overview of life‐history and ecology of migrant passerines

In this paper we compare ecological attributes of tropical migrant passerines from the Nearctic and western Palaearctic, focusing particularly on habitat association patterns during both breeding and wintering seasons. Three regions were compared: Europe, western and eastern North America. Breeding bird census data from 32 studies (each including at least four stages of forest succession) were used to assess the association patterns of breeding habitats among tropical migrants. For each species we calculated an index of habitat diversity and habitat preference.Tropical migrants preferred earlier successional stages than other birds in Europe. The opposite was true in eastern North America. In eastern North America, tropical migrants tended to be associated with a smaller range of serai stages than other passerine species. In their winter quarters, Palaearctic migrants live primarily in open habitats, such as savannas, whereas eastern Nearctic migrants make more frequent use of evergreen forests. Migrants from western North America show the greatest match between breeding and wintering habitats.We relate the results to the taxonomy and probable history of contemporary avifaunas and vegetation formations of the Old and New World. Taxonomically, tropical migrants from different parts of the Holarctic are less closely related to each other than residents and short‐distance migrants. Tropical and temperate avifaunas are more closely related to each other in the New World than in the Old World. Conservation implications of the between‐continent differences are briefly discussed.

Seasonal patterns of occurrence of Palaearctic migrants in southern Africa using atlas data

A statistical method, using presence/absence data from monthly fieldcards, to describe the phenology of migration is developed. The method uses the generalized linear model to fit a Fourier series to binomial‐type data giving the proportion of fieldcards reporting a species. A method for estimating mid‐arrival and mid‐departure dates, and residency period is also developed. The methodology is applied to data collected during the ‘Southern African Bird Atlas Project’ for the following species: Willow Warbler Phulloscopus trochilus, Red‐backed Shrike Lanius collurio, European Swallow Hirundo rustica, White Stork Ciconia ciconia, Steppe Buzzard Buteo buteo and European Bee‐eater Merops apiaster.

Fidelity to non-breeding site in some species of birds in Senegal

The authors report the results of observations and experiments on the site fidelity, home range and homing success in some species of birds captured and banded at the ORSTOM Ornithological Station of Mbour (Senegal) during the non-breeding season (November-December 1988 and 1989). While some bird species range over a wide area or are found in our study area only during migratory movements, most of the species investigated, which include both local birds and palaearctic migrants, display a tendency to spend the winter in a home plot of very limited size. In addition, homing experiments were carried out by displacing and releasing the birds at sites 5 km from the capture station. Globally, our results are in agreement with the reports on similar investigations in the Mediterranean area: among the species investigated, strong site fidelity, as revealed by high recapture percentages in non-displaced birds, does not necessarily lead to good homing performances after passive displacement. On the whole, the commonest species of small birds which spend the winter in our study plot show different kinds of relationship between individual birds and their habitat with respect to home range, site attachment and homing success.

The seasonal separation of primary and secondary moult in Palaearctic passerine migrants on the Sudan coast

In six Palaearctic passerine species caught in autumn on the Sudan Red Sea coast, adults with fully moulted primaries still retained most or all of their old secondaries. This seasonal split of the moult of the two flight feather tracts is discussed, and the strategy is compared with more typical moult suspension.

Rapid moult among palaearctic passerines in West Africa‐ an adaptation to the oncoming dry season?

Moult of some palaearctic migrant passerines was studied at a wintering site in northern Ghana, West Africa. We present data on moult pattern and estimated moult duration for a sample of species. Savi's Warbler Locustella luscinioides, Woodchat Shrike Lanius senator and probably Grasshopper Warbler Locustella naevia deviated from the ordinary descendent moult sequence. Different measures of moult speed (moult speed of retrapped individuals, growth of individual feathers, wing raggedness and first date of completion of moult) showed unexpectedly rapid moult among individuals of several species, notably the Great Reed Warbler Acrocephalus arundinaceus and the Sedge Warbler A. schoenobaenus. The rapid moult might be an adaptation to a limited period of abundant food which comes to an end at the beginning of the dry season.

Spring weights and fat deposition of palaearctic passerine migrants in Senegal

This paper compares the patterns of weight and fat‐class of Palaearctic passerine migrants trapped at two sites in Senegal in spring 1986. Despite considerable variations in some species (Reed Warbler Acrocephalus scirpaceus and Subalpine Warbler Sylvia cantillans) the great majority of the birds trapped had weights well above the breeding and wintering levels and showed clear evidence of premigratory fattening. In the Yellow Wagtail Motacilla flava and Chiffchaff Phylloscopus collybita some individuals weighed more than twice as much as others. Mean values of fat‐classes of first captures and retraps differed significantly. Species could be divided into two different groups: (a) those (Sand Martin Riparia riparia. Yellow Wagtail and Pied Wagtail M. alba) with small variation in fat classes (12%‐23%), and (b) those (Chiffchaff, Subalpine Warbler, Reed Warbler and Redstart Phoenicurus phoenicurus) showing a high variation in fat‐class (39%‐55%). Birds of the first group had a significantly higher mean fat‐...

MOULT, WEIGHT AND BIOMETRICAL DATA FOR SOME PALAEARCTIC PASSERINE MIGRANTS IN ZAMBIA

Summary Loske, K.-H. & Lederer, W. 1988. Moult, weight and biometrical data for some Palaearctic passerine migrants in Zambia. Ostrich 59:1-7. Twelve Palaearctic passerine species were observed and trapped in February/March in Central Zambia. For Sand Martin, European Swallow, European Sedge Warbler, Great Reed Warbler, Willow Warbler and Tree Pipit weights, measurements and moult stages are given. In Sand Martin and European Swallow no correlation between weight and moult was found. Primary and secondary moult was in progress in both species. Tail moult was more advanced in European Swallows. European Sedge Warbler moult showed little synchronization between individuals, and irregular moult was often recorded. Willow Warblers showed unusually high weights and little synchronization within secondary moult. The majority of the birds investigated showed moult of the body plumage. The results are discussed in comparison with data from other parts of Africa.

WADERS (CHARADRII) AND OTHER WATERBIRDS AT LANGEBAAN LAGOON, SOUTH AFRICA, 1975–1986

Summary Underhill, L. G. 1987. Waders (Charadrii) and other waterbirds at Langebaan Lagoon, South Africa, 1975–1986. Osrrich 58: 145–155. Langebaan Lagoon was surveyed for waterbirds at midsummer and midwinter between 1975 and 1986. The median number of birds counted in summer was 37 500, of which 34 500 were waders (93% of the waders being Palaearctic migrants). Curlew Sandpiper (59,2%), Grey Plover (10,5%), Sanderling (8,3%), Knot (8,1%) and Turnstone (5,7%) were the major components of the summer wader population. The median number of birds in winter was 10 500, of which 4500 were flamingos and 4000 waders. For Palaearctic waders, the median winter population was 11,5% of the median summer population, but varied between 2,5% and 30,1%. For species of wader which breed in the Taimyr Peninsula, Siberia, a three-year cycle in the numbers of birds overwintering was detected, with large numbers in 1977, 1980, 1983 and 1986. Birds feeding on invertebrates consumed 126,9 kJ m−2 yr−1, or 24% of the total produ...