BREEDING DENSITY AND NEST SITE CHARACTERISTICS OF THE PEREGRINE FALCON FALCO PEREGRINUS MINOR IN THE SOUTHWESTERN CAPE,SOUTH AFRICA

Pepler, D., Van Hensbergen, H.J. & Martin, R. 1991. Breeding density and nest site characteristics of the Peregrine Falcon Falco peregrinus minor in the southwestern Cape, South Africa. Ostrich: 62: 23–28.

A survey of nest sites and nest site characteristics is used to obtain an estimate of the breeding density of the Peregrine Falcon Falco peregrinus minor in the southwestern Cape, South Africa. The breeding density from a small intensively studied area around the town of Stellenbosch is extrapolated to the region. This extrapolation is justified since nest site characteristics suggest that suitable sites are widespread in the region. Lower and upper estimates of 48 and 95 pairs respectively were obtained for the area above 300 m. This gives densities of one pair per 199 km² for the lower estimate and one pair per 100 km² for the upper estimate. For the entire study area the densities are one pair per 806 km² and 407 km² respectively.     

Migration of a Peregrine Falcon Falco peregrinus calidus from Saudi Arabia to Cape Town as revealed by satellite telemetry

In boreal autumn 1995, we tracked a migrating adult Peregrine Falcon Falco peregrinus calidus from the border of Saudi Arabia and Yemen to near Cape Town, South Africa, a distance of 6 346?km. While on migration it covered 288?km d?1, on average. During its migration in Africa it migrated faster than any other Peregrine tracked so far using satellite telemetry. Falco p. calidus is an uncommon, but regular, migrant to southern Africa, where it overlaps with the resident F. p. minor, but no other bird has been tracked so far south.     

Characteristics of Peregrine and Lanner Falcon nesting habitats in South Africa

Jenkins, A.R. 2000. Choracteristics of Peregrine and Lanner Falcon nesting habitots in South Africa. Ostrich 71 (3&4): 416-424. Peregrine Falcon, Falco peregrinus, and Lanner Falcon, F. biarmicus, nesting habitats in South Africa are described in terms of nest ledge, nest cliff and scree slope parameters, ond the environmental context of each site. Data were collected in a tropical study area where Peregrines and Lannen occurred in sympatry, from an allopatric south temperate Peregrine population, and opportunistically for bath species from other sites throughout the country. Elevation, ledge size, cliff size ond vegetation structure accounted for about 80%of the variation in falcon nesting habitots between species and between populations within species. Peregrines used larger nest ledges on higher, more elevated cliffs than Lanners, overlooking mare open, structurally complex Vegetation. Temperate Peregrines used smaller ledges on lower cliffs, overlooking vegetation that provided less refuge for overflying prey than subtropical pairs. Temperote Peregrines selected nest sites to minimize the negative effects of spring roinfall. Tropical Peregrines may have selected sites to maximize hunting and provisioning efficiency.     

Organochlorines and mercury in the eggs of British Peregrines Falco peregrinus

The levels of various contaminants were measured in 550 addled and deserted Peregrine Falco peregrinus eggs obtained in Britain during 1963-86. In this period the population was recovering from a low level imposed by organochlorine pesticides. Over the whole period, HEOD levels declined in eggs from both inland and coastal regions, while DDE levels declined in eggs from inland regions. At the same time, shell-indices improved. PCB levels increased in eggs from inland regions. At any one time, levels of DDE and HEOD in eggs decreased and shell-indices increased from south to north within Britain. These gradients fitted with the extent of agricultural land (= pesticide use) and with the extent of Peregrine population decline (both greatest in the south). No south-north trend was apparent in levels of PCBs derived from industrial sources. In some regions eggs from coastal sites were more contaminated than eggs from inland sites, especially with PCBs and mercury. Significant relationships were found between brood sizes and DDE levels, between brood sizes and shell-indices, and between shell-indices and DDE levels. This implied that DDE influenced shell thickness and breeding success. Some evidence was obtained that mercury reduced brood sizes, but no evidence that HEOD and PCB (at the levels found) did so. Overall, DDE and mercury levels together accounted for 17% of the variance in brood sizes during 1963-86. On a regional basis, DDE had no obvious effect on mean productivity when the geometric mean DDE level in collected eggs was less than 3 p.p.m., and when mean shell-index was no more than 8% less than normal. At higher DDE levels, and lower shell-indices, productivity declined markedly. Recovery of regional populations was associated with geometric mean HEOD levels in eggs no greater than 0–7 p.p.m., DDE levels no greater than 15 p.p.m., shell indices no more than about 15–20% below normal, and a mean breeding success exceeding 0–6 young per territorial pair.     

Multi‐season occupancy models identify biotic and abiotic factors influencing a recovering Arctic Peregrine Falcon Falco peregrinus tundrius population

Critical information for evaluating the effectiveness of management strategies for species of concern include distinguishing seldom occupied (or low‐quality) habitat from habitat that is frequently occupied and thus contributes substantially to population trends. Using multi‐season models that account for imperfect detection and a long‐term (1981–2002) dataset on migratory Arctic Peregrine Falcons Falco peregrinus tundrius nesting along the Colville River, Alaska, we quantified the effects of previous year's productivity (i.e. site quality), amount of prey habitat, topography, climate, competition and year on occupancy dynamics across two spatial scales (nest‐sites, cliffs) during recovery of the population. Initial occupancy probability was positively correlated with area of surrounding prey habitat and height of nest‐sites above the Colville River. Colonization probability was positively correlated with nest height and negatively correlated with date of snowmelt. Local extinction probability was negatively correlated with productivity, area of prey habitat and nest height. Colonization and local extinction probabilities were also positively and negatively correlated, respectively, with year. Our results suggest that nest‐sites (or cliffs) along the Colville River do not need equal protection measures. Nest‐sites and cliffs with historically higher productivity were occupied most frequently and had lower probability of local extinction. These sites were on cliffs high above the river drainage, surrounded by adequate prey habitat and with southerly aspects associated with early snowmelt and warmer microclimates in spring. Protecting these sites is likely to encourage continued occupancy by Arctic Peregrine Falcons along the Colville River and other similar areas. Our findings also illustrate the importance of evaluating fitness parameters along with climate and habitat features when analysing occupancy dynamics, particularly with a long‐term dataset spanning a range of annual climate variation.     

Distribution and behaviour of passerines around Peregrine Falco peregrinus eyries in western Greenland

This paper describes the distribution and behaviour of passerine birds within 1 km of Peregrine Falcon Falco peregrinus eyries in western Greenland. Passerine populations were censused in 1983 around six cliffs occupied by nesting Peregrines and at six sites on the open tundra, and in 1984 at two unoccupied sites suitable for Peregrine nesting.
Four passerine species accounted for over 90% of birds seen. Within 400 m of Peregrine occupied cliffs, three species, Lapland Longspur Calcarius lapponicus . Northern Wheatear Oenanthe oenanthe , and Common Redpoll Carduelisflammea , were found in lower than average abundance while the fourth, Snow Bunting Plectrophenax nivalis , was found in increased abundance. Our indirect tests suggest that Peregrine presence, rather than direct predation, was responsible for the distributions of the first three species. The Snow Bunting, however, behaviourally adapts to Peregrine presence in order to exploit nesting habitat available at the cliff base.
These results contrast strongly with those reported by other Arctic workers, where increased abundances of potential prey were observed in close proximity to nesting Peregrines.     

Reduced genetic variation in Norwegian Peregrine Falcons Falco peregrinus indicated by minisatellite DNA fingerprinting

The Scandinavian Peregrine Falcon Falco peregrinus population went through a severe population bottleneck during the second half of the twentieth century, and was almost extinct during the 1970s. This event may have reduced the amount of genetic variation in the population. With this background, a comparative study, using multilocus, minisatellite DNA fingerprinting, was carried out on broods of the Peregrine Falcon, the Merlin Falco columbarius and the Eurasian Hobby Falco subbuteo from south-east Norway. Band-sharing analysis of DNA fingerprints was used to test whether broods of Peregrine Falcons showed a greater between-nest similarity in their fingerprint profiles than did broods of the two congeneric species breeding in the same region, which have not undergone any recent population bottlenecks. The results show that broods of Peregrine Falcons were significantly more similar to each other genetically than were broods of either Merlins or Eurasian Hobbies. Furthermore, there was a positive correlation between the similarity in minisatellite DNA and the similarity in a set of 11 microsatellite loci analysed for a subset of the Peregrine Falcon samples. The correlation supports the assumption that minisatellite fingerprints provide a reliable indicator of overall genetic similarity, i.e. relatedness, between breeding pairs in the population. Hence we can conclude that broods of Peregrine Falcons were genetically more related to each other than were broods of the other two species. The high similarity in minisatellite DNA between broods indicates a loss of genetic variation in the Peregrine Falcon population caused by the bottleneck, but this explanation can only be verified through a comparative genetic study of individuals sampled before and after the bottleneck event.     

Changes in egg shell characteristics of the Sparrowhawk (Accipiter nisus) and Peregrine (Falco peregrinus) associated with exposure to environmental pollutants during recent decades

In Britain since the late 1940s, the Sparrowhawk ( Accipiter nisus ) and Peregrine (Falco peregrinus) have laid eggs with unusually thin shells. DDT and its metabolites have been blamed. This paper reports how various properties of modern shells differ from those of older shells of normal thickness.
For the shells of both species, there were roughly proportional reductions in thickness of the two main component layers, the mammillary and palisade layers, suggesting that thin shells resulted from a decreased rate of deposition. In addition, in modern Sparrowhawk shells, the resistant surface layer was especially deficient perhaps due to a further reduction in deposition rate or to slight premature termination. Shell thinning was associated with a proportionately greater decrease in shell strength. For the Peregrine, porosity, measured as the rate of passage of water vapour, was lower for the thin shells than for normal shells. This difference could not be explained by a change in the area of the pore channels, since the modern shells did not have fewer pores and the pore channels were the same size and shape in the two samples of shells. However, in the thin shells of both species, mammillae height increased relative to mammillary layer thickness, and in the Peregrine shells the extent of this increase was related to the change in porosity.     

Appraisal of the consequences of the DDT-induced bottleneck on the level and geographic distribution of neutral genetic variation in Canadian peregrine falcons, Falco peregrinus

Peregrine falcon populations underwent devastating declines in the mid-20th century due to the bioaccumulation of organochlorine contaminants, becoming essentially extirpated east of the Great Plains and significantly reduced elsewhere in North America. Extensive re-introduction programs and restrictions on pesticide use in Canada and the United States have returned many populations to predecline sizes. A proper population genetic appraisal of the consequences of this decline requires an appropriate context defined by (i) meaningful demographic entities; and (ii) suitable reference populations. Here we explore the validity of currently recognized subspecies designations using data from the mitochondrial control region and 11 polymorphic microsatellite loci taken from 184 contemporary individuals from across the breeding range, and compare patterns of population genetic structure with historical patterns inferred from 95 museum specimens. Of the three North American subspecies, the west coast marine subspecies Falco peregrinus pealei is well differentiated genetically in both time periods using nuclear loci. In contrast, the partitioning of continental Falco peregrinus anatum and arctic Falco peregrinus tundrius subspecies is not substantiated, as individuals from these subspecies are historically indistinguishable genetically. Bayesian clustering analyses demonstrate that contemporary genetic differentiation between these two subspecies is mainly due to changes within F. p. anatum (specifically the southern F. p. anatum populations). Despite expectations and a variety of tests, no genetic bottleneck signature is found in the identified populations; in fact, many contemporary indices of diversity are higher than historical values. These results are rationalized by the promptness of the recovery and the possible introduction of new genetic material.     

Conservation genetics of the black rhinoceros (Diceros bicornis)

We analysed genetic variation in mitochondrial DNA (mtDNA) control region in the Diceros bicornis minor and D. b. michaelianimals at the Western Plains Zoo, which form part of an international ex-situ breeding program. Six of the nine D. b. minor animals were wild-caught from Zimbabwe during the 1990s, and our study revealed five distinct mtDNA haplotypes, and a haplotype diversity of 0.86 in the colony. Phylogenetic relationships between mtDNA haplotypes analyzed using the neighbor joining method reveal that for the small sample available, D. b. minor and D. b. michaeli are reciprocally monophyletic and represent separate ancestral lineages. Nucleotide divergence between the black and and white rhinoceros(Ceratotherium simum) was 14.0%, and nucleotide divergencebetween the D. b. minor and the D. b. michaeli subspecies was 2.6%. This suggests a divergence time for the two blackrhinoceros subspecies of between 0.93 MY and 1.3 MY.     

SOME PHYSICAL REQUIREMENTS FOR OSTRICH EGG INCUBATION

Jarvis, M. J. F., Keffen, R. H. & Jarvis, C. 1985. Some physical requirementsfor Ostrich egg incubation. Ostrich 56: 42–51.

Eggs from wild and domesticated Ostriches Struthio camelus australis were studied to determine temperature and humidity requirements for successful incubation. Wild eggs in Zimbabwe included some collected and incubated artificially, and others that were naturally incubated until just before hatching. Egg-weight losses during incubation were measured. The eggs artificially incubated at 35 °C to 36°C and 40–42% relative humidity, lost nearly the same weight as did eggs in naturally incubated nests. Comparisons were made between the wild eggs and chicks, and those from domesticated hybrid-strain Ostriches in Bophuthatswana. The discussion outlines some of the remaining problems associated with Ostrich egg incubation.     

Radar observations of the stoop of the Peregrine Falcon Falco peregrinus and the Goshawk Accipiter gentilis

Measurements in 10-s intervals by a tracking radar showed average speeds of about 25 ms^-1 for a Peregrine Falcon Falco peregrinus and a Goshawk Accipiter gentilis during four stoops lasting 40–110 s, with angles of dive between 13^o and 64^o, and involving height losses between 450 and 1080 m. Maximum speeds during 10-s intervals were between 31 and 39 ms^-1 in the Peregrine Falcon, and close to 30 ms^-1 in the Goshawk. The observed speeds are well below the maximum possible terminal speeds in steep or vertical dives according to theoretical estimation. By adopting a moderate stooping speed, raptors may gain in hunting precision.     

The role of the hemiparasitic annual Rhinanthus minor in determining grassland community structure

Summary Rhinanthus minor (yellow-rattle) is a widespread hemiparasitic plant of grassland habitats throughout Great Britain. It is usually considered to be indicative of species-rich grassland, but in a survey of 14 habitats throughout Britain it was found that R. minor at the time of flowering normally occupied relatively low-diversity patches within areas of high diversity as determined by the number of species, Simpson's Index and the Shannon-Wiener Index. Following the death of adult plants of R. minor in the summer it was shown that the pattern of species diversity changed such that by the time R. minor germinated in the following spring the differences between the areas containing and not containing R. minor were much less distinct. A perturbation experiment in which R. minor was removed from four sites indicated that the effect of the removal of R. minor on the development of community structure over the next year was to increase species diversity on three of the sites and decrease it on the fourth. Those species which responded to the removal of R. minor by an increase in abundance were shown to be preferred hosts. All three lines of evidence point to the fact R. minor has a significant effect on the species diversity of the communities in which it grows by selectively parasitizing components of the flora and modifying the competitive relationships between plants. However, as the communities generally responded to the removal of R. minor by an increase in diversity and as the general survey indicated that R. minor is generally associated with areas of low diversity it would appear that the plants which are selectively parasitized are generally not the competitive dominants in the community.     

Factors affecting breeding success of Peregrine and Lanner Falcons in South Africa

Jenkins, A.R. 2000. Factors affecting breeding success of Peregrine and Lonner Falcons in South Africa. Ostrich 71 (384): 385-392. Breeding success was recorded for three Peregrine Falcon, Falco peregrinus, populations in South Africa over nine years, and for Peregrine and Lanner Falcon, Ebiarmicus, populations in an area of sympatry over three years. The objectives of the study were to measure geographic and interspecific variation in reproductive performance, and determine environmental correlates of productivity. Territory occupancy, the frequency of breeding per occupied territory and clutch size did not vary significantly between the three Peregrine populations. However, Peregrine breeding success was generally lower on the Cape Peninsula (1. 11 young fledged per territorial poir), higher in the Soutpansberg (1.36) and highest on the Orange River (1.70). Overall, fledging rates of Soutpansberg Peregrines and Lanners were not significantly different, although annual productivity of the Lonner population was consistently higher. Neither species' breeding success was significantly depressed by the presence of close neighbouring pairs of the other, suggesting that they were not active competitors. Breeding performance of Peregrines on the Cape Peninsula correlated strongly with spring weather conditions: egg and hatchling survival was lower in wet years, and fledging rates were higher in warm years. Annual productivity of Orange River Peregrines correlated positively with the height of the river at the onset of breeding, and productivity of Soutpansberg Peregrines was higher in seasons following years of high rainfall. Elements of the physical structure of the nesting habitat (exposure of the nest ledge, height of the nest cliff) correlated positively with Peregrine breeding performance. Breeding success of Soutpansberg Lanners was largely unaffected by any of the environmental variables considered. Overall, it is proposed that Peregrine productivity reflected variation in the physical environment and its affect on prey availability.     

Surprise as a winter hunting strategy in Sparrowhawks Accipiter nisus,Peregrines Falco peregrinus and Merlins F. columbarius

Sparrowhawks Accipiter nisus, Peregrines Falco peregrinus and Merlins Falco columbarius were studied hunting Redshanks Tringa totanus, Dunlins Calidris alpina and Skylarks Alauda arvensis over three winters on a small Scottish estuary. Most Sparrowhawk and Merlin hunts consisted of a single attack (mean = 1.0 and 1.1, respectively), whereas Peregrine hunts often consisted of several attacks (mean = 1.8). Most hunts were short (<1 min), but Peregrine and Merlin hunts occasionally lasted over 5 min. In general, all three raptor species attacked by surprise, although Peregrines were more likely to make nonsurprise attacks. Prey attacked were usually initially very close to the raptor (<100 m); Peregrines attacked prey most often at long distances (>500 m). Chase lengths were mostly <5 second in length, although Peregrines, and particularly Merlins hunting Skylarks, often chased for several minutes. Peregrines attacked most prey in flight from flight, while Merlins and Sparrowhawks attacked birds on the ground with a flight from a perch. All three raptor species preferentially attacked larger Dunlin flocks, but Peregrines also favoured single birds. Capture rates of Redshanks and Dunlins were similar for the three raptor species (C. 10%), but for Skylarks, capture rate by Merlins was much higher (12%) than by Sparrowhawks (3%) or Peregrines (0%). Capture rates were highest when raptors attacked by surprise, particularly for a Peregrine hunting in the first minute of arrival on the study site if no Peregrines had been hunting there for the previous hour (16% success for the first minute compared with 2% in subsequent minutes). Sparrowhawks were more successful when attacking small rather than large Dunlin flocks. The use of short surprise attacks interspersed with long periods of inactivity was common to the three raptor species and was interpreted as a strategy to minimize the amount of energy and risk involved in hunting during the nonbreeding season.     

THE INFLUENCE OF HABITAT ON THE DISTRIBUTION AND ABUNDANCE OF PEREGRINE AND LANNER FALCONS IN SOUTH AFRICA

Jenkins, A.R. 1994. The influence of habitat on the distribution and abundance of Peregrine and Lanner Falcons in South Africa. Ostrich 65: 281–290.

The distribution and abundance of Peregrine and Lanner Falcons in South Africa was compared using recorded sightings from various sources, including the Southern African Bird Atlas Project. Falcon distributions were compared with the distribution of cliffs and vegetation, to quantify differences in the habitat preferences of the two species in the breeding and the non-breeding seasons. Lanner Falcons outnumbered Peregrine Falcons in most areas by at least 10:1. Peregrine Falcons were more habitat specific than Lanner Falcons, in terms of topographic and biotic requirements. Peregrine Falcons were largely restricted to high cliff areas throughout the year and there probably were no large-scale seasonal movements within the population. The bulk of the resident Peregrine Falcon population was found in the fynbos biome, in the southwestern Cape. Outside of this area, Peregrine Falcons were concentrated in woodlands. Lanner Falcons were less dependent on high cliffs, although cliff availability was important in defining the ranges of both species. Lanner Falcons were most common in the sour grasslands in the east of the country in the breeding season, with apparent movements in the non-breeding season into the fynbos, the Nama Karoo and the southern Kalahari. Overall, Peregrine Falcons favoured relatively closed habitats and Lanner Falcons favoured relatively open habitats. The differences in the two species' habitat preferences are proximate factors influencing distribution and abundance.     

Environmental factors affecting patterns of distribution and co‐occurrence of two competing raptor species

Habitat selection is a complex process, that is affected by several factors, including habitat characteristics, environmental conditions, and both intra‐ and interspecific interactions. We analysed habitat preferences of two top avian predators, Peregrine Falcon Falco peregrinus, a medium‐sized diurnal raptor, and Eagle Owl Bubo bubo, a large nocturnal raptor. These two species are known to compete for preferred nest‐sites, and proximity to cliffs with Eagle Owls may reduce Peregrine breeding output through predation of young Falcons. We investigated the environmental factors affecting occurrence and coexistence of the two species and the potential role of habitat suitability in favouring co‐occurrence in 3519 km² of the central pre‐Alps of Italy, where the two species breed on cliffs and sometimes co‐occur on the same cliff. Peregrines settled on long, steep and favourably orientated cliffs in woodland landscapes close to urban areas. Eagle Owls settled on topographically similar cliffs, but in lower rainfall areas compared with cliffs occupied by Peregrines and cliffs unoccupied by either species. Sites where the two species co‐occurred were characterized by more horizontally extended cliffs compared with sites of exclusive occurrence of each species. An analysis of relative habitat suitability revealed that sites where the two species co‐occurred had the highest predicted probability of occupancy for both species, suggesting that those sites should be regarded as high‐quality sites. Breeding productivity of Eagle Owls was negatively affected by the co‐occurrence of Peregrines, whereas the effect of Eagle Owl proximity on Peregrine productivity varied according to cliff suitability for the Peregrines. Habitat selection had fitness consequences for Eagle Owls because breeding productivity increased with cliff length. Environmental conditions, particularly climatic factors, could allow the widespread coexistence of these competing raptors at the landscape scale, whereas at the local scale co‐occurrence could take place only on larger cliffs. These were preferred sites for both species, presumably because breeding at such sites offsets the costs of settling close to the competitor species.     

Plant phenology and seed predation: interactions between gorses and weevils in Brittany (France)

Exapion ulicis (Forster) and Exapion lemovicinum (Hoffmann) (Coleoptera: Curculionoidea: Apionidae) are seed predators of the three gorse species occurring in Brittany (France): Ulex europaeus L., Ulex gallii Planch., and Ulex minor Roth.(Fabaceae). Host‐plant phenology plays a major role in the relationship between apionid weevils and their gorse species, because larvae develop within gorse pods and adults have to wait for pod dehiscence to be released. We monitored flowering and fruiting phenology of gorse species, weevil reproductive behaviour, and egg‐laying patterns in six natural populations in the native area of these gorse species. At each site, U. europaeus, which flowers mainly in spring, was sympatric with one of two autumn flowering gorse species, U. gallii and U. minor. We noticed that E. ulicis laid eggs in spring and was restricted to U. europaeus whereas E. lemovicinum laid eggs in autumn and was restricted to the two autumn‐flowering species U. gallii and U. minor. Therefore, host specificity depended on gorse phenology, and not on geographic proximity. In addition, the infested pod content showed that E. ulicis laid several eggs per pod and suggested that females chose pods with the highest numbers of seeds. In contrast, E. lemovicinum laid a single egg per pod and showed no preference for pods with many seeds. Finally, the impact of seed predation by E. ulicis was higher than that of E. lemovicinum.     

Vocal communication in Peregrine Falcons Falco peregrinus during breeding

The wailing call and the creaking call of the Peregrine Falcon Falco peregrinus were quantified throughout the breeding period. The creaking call was given mainly during the courtship period by both males and females, and its frequency at this time did not differ significantly between sexes. From the start of incubation and thereafter, the creaking call was uttered more frequently by males than by females; during the nestling period, it was mostly related to the male's transfer of food. The wailing call frequency never differed significantly between males and females and increased during the nestling period. This call was less linked with the presence of the mate than was the creaking call.