The provision of supplementary fresh water improves the breeding success of the globally threatened Northern Bald Ibis Geronticus eremita

The Northern Bald Ibis Geronticus eremita is a globally threatened species with its main remaining world population breeding in an area of sea cliffs and coastal semi‐desert steppe near Agadir in southern Morocco. Between 1998 and 2002, we showed experimentally that the small‐scale provision of fresh water near the breeding colonies led to an increase in the productivity of the birds. The increase was greatest in years with low natural rainfall but was positive in all years tested. The supplementary fresh water appears to help buffer productivity against the impacts of low rainfall and its provision is now part of the ongoing conservation measures for this species.     

Breeding ecology and behaviour of the last wild oriental Northern Bald Ibises (Geronticus eremita) in Syria

A relict colony of Northern Bald Ibis (Geronticus eremita), a critically endangered species, was unexpectedly discovered in Syria in 2002. During six subsequent breeding seasons (2002–2007), the 3, and then 2, breeding pairs of Northern Bald Ibises have shown to be still vital and, when intensively protected, showed a higher average breeding success than that recorded in Morocco, the only other country where these birds still breed in the wild. During the six breeding seasons, a total of 24 chicks fledged and left the breeding area successfully. Between 2004 and 2007, a total of 5 immature ibises have made a return to the colony, separately and later than adults. As a consequence, two recruitment events have taken place (2006 and 2007), partly compensating for the gradual decrease in the number of adults. Breeding adults arrive from migration during the second half of February, separately, and leave together around mid-July. They nest in cavities and ledges of two limestone cliffs of the central Syria desert, located 20 km apart, well protected from the predominant wind. Breeding behaviour and the cycle are described, summarised and compared with data from the wild colonies of Morocco and the colony of Turkey before the extinction. Key threats still in place at the Syrian breeding quarters are human disturbance during settling and incubation, chick depredation by ravens, uncontrolled hunting and habitat degradation. Recommendations on how to enhance the breeding performance and ensure the survival of this colony in the future are given.     

Increasing breeding behaviors in a captive colony of Northern Bald Ibis through conspecific acoustic enrichment

The goal of this study was to increase reproductive behaviors in a captive colony of Northern Bald Ibis (Geronticus eremita) at the Bronx Zoo. The Northern Bald Ibis is classified as critically endangered by the IUCN, with only about 100 known breeding pairs in the wild. Our analysis of zoo breeding and colony size data confirmed earlier observations that small captive colonies of this species do not breed as well as larger colonies, possibly because of insufficient social cues. Using principles from social facilitation theory, we attempted to provide such social cues by presenting acoustic enrichment in the form of conspecific breeding vocalization playbacks. In May 2009, we tracked multiple breeding behaviors during playbacks and control periods. Although breeding behaviors increased in response to playbacks, the colony produced no eggs. We repeated this experiment in April 2010 using playbacks of higher quality recordings acquired from a semi‐wild breeding colony of Northern Bald Ibis in Austria. Breeding behaviors again increased during playbacks. In addition, five pairs in this colony of 15 birds produced 13 eggs, and six chicks successfully fledged—the first reproductive success in this colony since 2007. The acoustic enrichment techniques we employed may encourage increased breeding activity in captive populations of colonial species as well as wild colonies with small populations. Zoo Biol 31:71;–81, 2012. © 2011 Wiley Periodicals, Inc.     

Freilandbeobachtungen am Waldrapp (Geronticus eremita) in Marokko: Verhalten immaturer Individuen

Summary The live stock of the extremely endangered Bald Ibis is still declining. The eastern population is extinct. The remaining three small colonies are concentrated at the Moroccan atlantic coast. In 1989, we recorded 43 breeding pairs with 89 chicks. Within the colonies there were also 15 yearlings and 15 individuals two years old. In January 1990, we found three subadults at the colonies together with the breeding pairs. The rest of the young birds (28) we located at the mouth of the river Tanri.     

Reproductive performance of the Bald Ibis Geronticus calvus in relation to rainfall and grass-burning

Reproductive performance of the Bald Ibis Geronticus calvus was studied during three consecutive nesting seasons (1978–80) at a single large breeding colony in Natal, South Africa. A focal sample of 22 nest sites (out of a total of 60 in the colony) was inspected at frequent intervals to determine clutch sizes, egg survival, hatching success, nestling mortality and fledgling production in each year. Mean clutch size was slightly lower in 1980, compared to the two previous years, although survival and hatching success of eggs were similar in all three years. However, nestling mortality was significantly higher in 1980, largely as a result of parental nest desertion and nestling starvation, so that the proportion of breeding pairs producing at least one fledged offspring, and the average brood size at fledging, were lower compared to 1978 and 1979.
The 1978 and 1979breeding seasons were both preceded by 12 months of above average rainfall, and Bald Ibises fed extensively on small invertebrates obtained in burnt grassland in the study area during the nesting period. By contrast, the onset of nesting in 1980 followed 11 consecutive months of sub-normal rainfall. As a result of the drought, and the consequent lack of controlled burning by landowners in the study area in 1980, very little burnt grassland was available during the Bald Ibis' breeding season, and the birds fed primarily in cultivated pastures during the customary burning period. The lower reproductive performance of Bald Ibises at the study site in 1980 is discussed in relation to the possible effects of drought on the abundance of invertebrate prey and the extent of controlled burning in the species' grassland biotope.     

Optimizing the genetic management of reintroduction projects: genetic population structure of the captive Northern Bald Ibis population

Many threatened species are bred in captivity for conservation purposes and some of these programmes aim at future reintroduction. The Northern Bald Ibis, Geronticus eremita, is a Critically Endangered bird species, with recently only one population remaining in the wild (Morocco, Souss Massa region). During the last two decades, two breeding programs for reintroduction have been started (in Austria and Spain). As the genetic constitution of the founding population can have strong effects on reintroduction success, we studied the genetic diversity of the two source populations for reintroduction (‘Waldrappteam’ and ‘Proyecto eremita’) as well as the European zoo population (all individuals held ex situ) by genotyping 642 individuals at 15 microsatellite loci. To test the hypothesis that the wild population in Morocco and the extinct wild population in the Middle East belong to different evolutionary significant units, we sequenced two mitochondrial DNA fragments. Our results show that the European zoo population is genetically highly structured, reflecting separate breeding lines. Genetic diversity was highest in the historic samples from the wild eastern population. DNA sequencing revealed only a single substitution distinguishing the wild eastern and wild western population. Contrary to that, the microsatellite analysis showed a clear differentiation between them. This suggests that genetic differentiation between the two populations is recent and does not confirm the existence of two evolutionary significant units. The European zoo population appears to be vital and suitable for reintroduction, but the management of the European zoo population and the two source populations for reintroductions can be optimized to reach a higher level of admixture.     

Response of the haematocrit to body condition changes in Northern Bald Ibis Geronticus eremita

We study the usefulness of the haematocrit as a predictor of body condition in birds, using a captive population of the endangered species Northern Bald Ibis (Geronticus eremita). This population is 14% of the worldwide captive population, which is far greater than the known free-living population. The haematocrit, body mass and body condition index responded in the same sense to two different nutritional periods, and there was a statistically significant relationship between changes in condition index and haematocrit of individual birds between the two periods. We discuss the relationship of these parameters with subcutaneous fat and muscle mass, and analyse the individuals' nutritional status in each of the periods studied. The conclusion was that the haematocrit is sensitive to variations in body condition since it responds to mass-loss processes corresponding to phases of mobilization of fat reserves, a situation prior to the mobilization of muscle proteins when there is a manifest deterioration of the individual's aspect.     

Long-term changes in population size,distribution and productivity of skuas (<Emphasis Type="Italic">Stercorarius</Emphasis> spp.) at Signy Island,South Orkney Islands

In this study, we investigate the numbers, productivity and territory distribution of the two species of skuas (brown Stercorarius lonnbergi and south polar Stercorarius maccormicki) breeding at Signy Island, South Orkneys, and compare the results with trends elsewhere. Comparison with previous counts indicates a biphasic increase in brown skuas at Signy Island; much faster from 1958/1959 to 1982/1983 (3.3 % per annum), than in subsequent years (0.4 % per annum from 1983/1984 to 2013/2014). Relative distribution of territories has changed little over time. The reduced rate of population growth in recent years was broadly coincident with a decrease in numbers of penguins (and therefore potential prey), which may also explain recent reductions in skua numbers at other Antarctic sites. As prey have become limiting, breeding success of brown skuas at Signy Island is now slightly lower than in the 1950s/early 1960s, but timing of breeding does not appear to have changed. Brown skuas at Signy Island may still have enough resources to start breeding, but as the season progresses and availability of resources declines, chick survival is reduced. South polar skuas have declined from ten pairs in 1982/1983 to one pair in 2013/2014, and mixed pairs have increased from one to three pairs. A review of the literature indicated that although population trend data are available for relatively few sites elsewhere in the subantarctic and Antarctic, numbers of brown skuas appear to be generally decreasing or stable, and of south polar skuas to be stable or increasing.     

Formation and growth of a heronry in a managed wetland in Doñana,southwest Spain

Capsule A newly created wetland has been beneficial for the breeding of five heron species and for the settlement and expansion of Glossy Ibises in the region.

Aim To determine whether created wetland would lead to the establishment of a heron and ibis breeding colony, and if so, to determine its effects on the distribution of these species in the wider region.

Methods Number of pairs breeding at the new wetland and in the region were estimated annually from 1996 to 2008. We investigated whether the growth of the new colony was explained by redistribution of breeding pairs within the region.

Results Purple Herons, Squacco Herons and Glossy Ibises colonised the new wetland in 1996. Black‐crowned Night Herons settled in 1998, while Cattle and Little Egrets were the last species to establish in the mixed colony in 2001. The population increase was particularly marked for Glossy Ibises (which had bred in Doñana only sporadically through the 20th century). Our findings suggest that simple redistribution of pairs does not explain the formation and growth of the new colony. Since the first year of establishment numbers of Glossy Ibises and Purple Herons have shown a significant growth trend at both the new colony and in Doñana.

Conclusion The creation and management of a new wetland has been successful for the conservation of heron and egret species and promoted the expansion of the Glossy Ibis population across the western Mediterranean region.     

Effects of supplementary food on density-reduced breeding in an African eagle: adaptive restraint or ecological constraint?

Increased population density often reduces reproductive output in breeding birds, but the underlying mechanisms (adaptive restraint v reduced food resources) behind decreased productivity are poorly understood. Here I correlatively and experimentally investigated the roles of food, breeding density, latitude, altitude and rainfall in limiting productivity of Wahlberg's Eagles Aquila wahlbergi throughout Africa. Breeding success in equatorial and subtropical Africa (0°–30°S) was highly density-dependent but showed no latitudinal or rainfall-related trends. Pairs in dense populations produced half as many young annually as pairs in low-density populations. Density (but not rainfall or latitude) also explained much of the geographic variation in the mean proportion of pairs attempting to breed each year and the incidence of two-egg clutches.
Breeding within populations was consistent with these density-dependent trends: incidence of two-egg clutches increased in a declining population, and productivity was inversely related to breeding density and rainfall combined. To determine if reduced food resources accounted for reduced output in dense populations, eight pairs were food supplemented: supplementary food failed to induce nonbreeding pairs to breed: nor did it induce earlier laying or increase egg size or clutch-size. Population density itself was unrelated to two correlates of food resources, rainfall and latitude. I conclude that population density influences most aspects of breeding in Wahlberg's Eagles, and reduced food resources do not appear to explain these trends. Hence, adaptive restraint may account for decreased annual reproduction in this species.     

The breeding biology and population dynamics of King Penguins Aptenodytes patagonica on the Crozet Islands

Among King Penguins Aptenodytes patagonica at Possession Island, one of the Crozet Islands, the length of the moult period, pre-laying period, incubating and brooding shifts were highly variable according to the year and to the stage of the breeding season. The moulting period was shorter in late breeders than in early breeders. Only half of the birds which successfully reared a chick bred the following cycle, but late in the season. Almost all these late breeders were unsuccessful. The reasons for the high variability in the breeding pattern observed in this species between years, as well as between colonies and between individuals are discussed. Breeding success was on average 30.6% and survival during the first year at sea could reach 50%. The survival of adult birds has increased during the past 10 years from 90.7% to 95.2% per annum. Despite an almost biennial breeding frequency and a very high rate of chick loss during the winter fast, the King Penguin population of Possession Island has doubled between 1966 and 1985 due to a high survival rate of adult and immature birds. The increase during the last decade in adult survival and in adult and chick condition suggests that the population increase could be the result of an improvement in food availability.     

Factors determining the laying date of the Waved Albatross Diomedea irrorata

The Waved Albatross laying period is between mid-April and the end of June. This paper investigates the factors determining when, during this period, a female lays. It is shown that birds breeding for the first time lay relatively late. For older birds, the laying date depends on date and outcome of the previous year's attempt: females that bred successfully in the previous year lay slightly later than in that year, while birds that failed lay earlier. A corresponding difference exists in the dates of arrival at the breeding grounds of successful and failed males. It is argued that one calendar year is not quite sufficient for pairs that have reared a chick successfully to regain breeding condition, while failed breeders can choose the laying date more freely.
Under catastrophic El Niño weather conditions in 1983, all albatrosses arrived late at the breeding grounds, but still the birds that had failed in 1982 were clearly earlier than those that had reared a chick.     

Population dynamics of the bearded vulture Gypaetus barbatus in southern Africa

The essential features of mortality and survivorship of bearded vultures Gypaetus barbatus in southern Africa were deduced from age class plumage characteristics. The population consisted of about 204 adult pairs within a breeding range of about 35,000 sq km. Pairs bred every year and produced, on average, about 0·9 young per pair per year. Young birds made up about 37% of the population, subadults 3·5% and adults 60%. About 182 fledged young were recruited to the population each year. The proportion of young birds in the population in different areas was inversely related to the breeding density of adult birds (range 24–47%). Young bird mortality over the four years to subadult age was 87%, the survival rate of adults was 94% and the mean lifespan of birds surviving to adulthood was 21·4 years. This study demonstrates the need to understand the relationship between adult breeding density and young bird numbers in different parts of their range to accurately deduce population dynamics characteristics.     

Status and abundance of the African Black Oystercatcher Haematopus moquini at the eastern limit of its breeding range

From 1983 to 2004 the breeding population of African Black Oystercatchers along the East London coast has more than trebled. The population increase is probably due to immigration as local breeding success is low. There are three classes of birds: breeding pairs, tenants and visitors, and birds may change status during the breeding season. In the winter, birds aggregate into groups and some birds may disperse from the East London coast. The presence of African Black Oystercatchers in all months of the year shows that they are resident, but may only be resident in the general sense, and at a local level appear to be nomadic, wandering along the coast in search of resources and, in the summer, opportunities to breed. The birds remain at any locality only for as long as conditions are suitable, suggesting that the birds along the East London coast are mostly visitors that have dispersed from their natal areas in the south.     

Climate change may account for the decline in British ring ouzels Turdus torquatus

1. Climate change is already affecting biodiversity, but the number of species for which reliable models relate weather and climate to demographic parameters is low. 2. We modelled the effect of temperature and rainfall on the breeding success and territory occupancy of ring ouzels Turdus torquatus (L.) in northern Britain, using data from a range of study areas, including one where there was a long-term decline in ring ouzel abundance. 3. Timing of breeding was significantly related to meteorological variables affecting birds in the early spring, though there was no evidence that laying dates had advanced. Breeding success was not significantly related to weather variables; instead, over 90% of annual variation in this parameter could be explained by density dependence. 4. Annual change in territory occupancy was linked to rainfall and temperature the preceding summer, after the main breeding season and to rainfall in the wintering grounds 24 months previously, coincident with the period of juniper Juniperus sp. (L.) flowering. High temperature in late summer, intermediate levels of late summer rainfall, and high spring rainfall in Morocco 24 months previously all had negative impacts on territory occupancy the following year. 5. All three weather variables have changed over recent decades, with a significant increase in summer temperature, a significant decrease in summer rainfall, and a nonsignificant decline in Moroccan spring rainfall. A model based on these trends alone predicted an annual decline in occupancy of 3.6% (compared with an observed decline of 1.2%), and suggested that increased summer temperatures may underlie declines in the British ring ouzel population. 6. Changes in summer temperature after the main breeding period could affect the survival rates of adult and/or juvenile birds. An improved understanding of the post-breeding ecology of ring ouzels is required to elucidate the mechanisms and causes of this relationship. Such knowledge might allow management aimed at buffering the impacts of climate change on ring ouzels.     

Predators of Dusky Canada Goose goslings and the effect of transmitters on gosling survival

ABSTRACT The population of Dusky Canada Geese (Branta canadensis occidentalis) has been in long‐term decline, likely due to reduced breeding productivity. To identify causes of mortality, we monitored goslings marked with radio transmitters on the western Copper River Delta, Alaska, from 1997 to 1999. Almost all gosling mortality (96%; 81 of 84) was due to predation, with mink (Mustela vison) and Bald Eagles (Haliaeetus leucocephalus) the most important predators. Bald Eagles are also major nest predators and, thus, appear to play a key role in limiting the breeding productivity of Dusky Canada Geese. Daily survival rate for goslings to 28 d of age was lower (0.011; 95% CI 0.002?0.024) for those with transmitters than for those without, but did not differ for older goslings (29?45 d). Although finer resolution in the timing of the transmitter effect within the first 28 d was not possible, we found that, by limiting our sample to goslings that survived until after 2?3 d posthatching, support for a transmitter effect was much reduced. Younger, smaller birds are inherently more vulnerable than older birds to transmitter effects. In addition, the process of radio‐marking may have delayed the departure of goslings from nests and increased their risk of mortality shortly after hatching. Although radio transmitters may often be the only practical means for determining causes of mortality for young waterfowl, we suggest caution in using transmitters because of their potential negative effects, particularly during the first few days after hatching.     

Density-dependent effects on productivity in the Griffon Vulture Gyps fulvus: the role of interference and habitat heterogeneity

Griffon Vultures Gyps fulvus in northern Spain were studied between 1969 and 1994. The number of breeding pairs increased from 221 in 1969–1975 to 1395 in 1994. The annual population growth rate decreased in the last 5 years, and this may reflect population regulation through density-dependent phenomena. Breeding success was monitored in 1994 and examined in relation to colony size, density of breeding pairs within a radius of 25 km (regional density), climate, human disturbance and food availability. We also recorded whether the year of first occupation of each nest site was before 1989 or after 1989 and whether or not the nest had a rocky shelter. The probability of successfully raising young declined as the regional density increased, which suggests that resource limitation would take place at foraging sites because the Griffon Vulture scavenges socially and no permanent feeding hierarchies are established. The other significant variable was the year of occupation of the nest; nests occupied after 1989 had a lower probability of raising a chick. The increase in the regional density of Griffon Vultures produced a decrease in the productivity at both optimal and suboptimal nest sites. This suggests that density-dependent regulation of breeding success operates through interference and that all the individuals in a colony are similarly affected. In birds of prey, prevalence of interference or habitat heterogeneity may be dependent on the social strategy of each species in space exploitation.     

Relationship between breeding activity and rainfall for Swainson's Spurfowl,Pternistis swainsonii,within southern Africa,with specific reference to the Springbok Flats,Limpopo Province,South Africa

We collated the literature available on the breeding activity of the Swainson's Spurfowl Pternistis swainsonii and made use of reliable unpublished reports, nest record cards and field observations within the Springbok Flats, Limpopo Province, South Africa to establish breeding seasons and pairing behaviour. The onset of breeding (egg laying) is closely associated with rainfall, with male gonad development, population density and covey size (pairing behaviour), all correlated with rainfall. Peak breeding activity is from January–April in South Africa, February–May in Zimbabwe and March–June in Botswana. Egg laying has been recorded in all months and sporadic egg laying in the winter months is most likely the result of isolated rainfall. Mean clutch size is 5.2 eggs/hen (n = 140) with an incubation period of 23 days and brood hatching success and chick survival of 69.4% over the southern African sub-region. Current hunting seasons within Limpopo Province are in line with the recommended hunting season for this region and should remain unchanged: 15 June–30 September. The success of this phasianid can be attributed to its extended breeding season, high survival rate of hatchlings and the potential of birds to breed within their first year.     

北戴河朱鹮野化训练种群的繁殖和婚外配北大核心CSCD

为了扩大朱鹮(Nipponia nippon)种群的数量和分布区,于2018年7月从洋县引进20只朱鹮在北戴河建立了朱鹮野化种群。2020年繁殖期,北戴河共有22只朱鹮,其中成年朱鹮17只,雌雄性比为1.1;实际繁殖密度为37.8只/hm2;人工巢的密度为40.0巢/hm2,人工巢筐内径为50 cm。2020年繁殖期,北戴河朱鹮共配对8对,其中6对繁殖成功,营巢成功率为75%;共产卵33枚,平均窝卵数为(4.1±1.8)枚;出壳18只,孵化率54.5%;出飞13只,出飞率72.2%,繁殖成功率为39.4%,繁殖生产力为2.2±1.2。与洋县饲养种群相比,北戴河种群首枚卵的产卵时间晚17 d,与两地温差相吻合。北戴河朱鹮的窝卵数显著高于洋县种群,这可能是由种内巢寄生所致。监控录像表明,北戴河1巢朱鹮的窝卵数高达6枚,超过野生种群平均窝卵数(2或3枚)的2倍,推测发生了种内巢寄生行为。此外,还观察到8号巢朱鹮同时发生了婚外配和种内巢寄生行为,婚外配雌鸟将卵产在该雄鸟的巢中,使得窝卵数高达7枚。此后在该巢中发现3只朱鹮轮流孵卵,以及2只雌性朱鹮并排孵于同一巢中的异常情况。北戴河朱鹮的种内巢寄生行为可能是因网笼内人工巢址密度较高但隐蔽性较低所致,而婚外配行为可能与种群密度和繁殖密度过高有关。本文有关朱鹮异常繁殖行为的研究结果可为野化网笼内人工巢筐的设置和野化种源的选择提供参考,并提示我们进一步关注朱鹮在环境压力下的表型可塑性和生态适应能力。     

Population limitation in migrants

Unlike resident bird species, the population sizes of migratory species can be influenced by conditions in more than one part of the world. Changes in the numbers of migrant birds, either long‐term or year‐to‐year, may be caused by changes in conditions in the breeding or wintering areas or both. The strongest driver of numerical change is provided in whichever area the per capita effects of adverse factors on survival or fecundity are greatest. Examples are given of some species whose numbers have changed in association with conditions in breeding areas, and of others whose numbers have changed in association with conditions in wintering areas. In a few such species, the effects of potential limiting factors have been confirmed locally by experiment. In theory, population sizes might also be limited by severe competition at restricted stopover sites, where bird densities are often high and food supplies heavily depleted, but (with one striking exception) the evidence is as yet no more than suggestive. In some species, habitats occupied in wintering and migration areas, and their associated food supplies, can influence the body condition, migration dates and subsequent breeding success of migrants. Body reserves accumulated in spring by large waterfowl serve for migration and for subsequent breeding, and females with the largest reserves are most likely to produce young. Hence, the conditions experienced by individuals in winter in one region can affect their subsequent breeding success in another region. Such effects are apparent at the level of the individual and at the level of the population. Similarly, the numbers of young produced in one region could, through density‐dependent processes, affect subsequent overall mortality in another region. Events in breeding, migration and wintering areas are thus interlinked in their effects on bird numbers. Although in the last 30–40 years the numbers of some tropical wintering birds have declined in western Europe and others in eastern North America, the causes seem to differ. In Europe, declines have mainly involved species that winter in the arid savannas of tropical Africa, which have suffered from the effects of drought and increasing desertification. In several species, annual fluctuations in numbers and adult survival rates were correlated with annual fluctuations in rainfall, and by implication in winter food supplies. In North America, by contrast, numerical declines have affected many species that breed and winter in forest, especially those eastern species favouring the forest interior. Declines have been attributed ultimately to human‐induced changes in the breeding range, particularly forest fragmentation, which have led to increases in the densities of nest predators and parasitic cowbirds. These in turn are thought to have caused declines in the breeding success of some neotropical migrants, which is now too low to offset the usual adult mortality, but as yet convincing evidence is available for only a minority of species. The breeding rates and population changes of some migratory species have been influenced by natural changes in the availability of defoliating caterpillars. In other species, tropical deforestation is likely to have played the major role in population decline, and if recent rates of tropical deforestation continue, it is likely to affect an increasing range of migratory species in the future. Not all such species are likely to be affected adversely by deforestation, however, and some may benefit from the resulting habitat changes.