Waterbird Breeding Research Articles

Global and regional governmental policy and treaties as tools towards the mitigation of the effect of climate change on waterbirds

Climate change will affect the breeding, staging and wintering areas of waterbirds. This may create a problem for the legal protection of important waterbird sites under the present international conventions. We analyse present obligations within a number of international conventions and conservation strategies, and formulate ways to mitigate for the effects of climate change by establishing site conservation within a framework of ecological networks and the overall flyway of species of waterbirds.

HABITAT USE OF SYMPATRICALLY NESTING FISH CROWS AND AMERICAN CROWS

We examined habitat use of sympatric Fish Crows (Corvus ossifragus) and American Crows (C. brachyrhynchos) nesting in the vicinity of waterbird breeding locations at the Rockaway Peninsula, New York City. Fish Crows nested significantly more often at natural habitats, including coastal dunes and salt marsh islands; American Crows nested significantly more often at residential and recreational areas. In regard to potential foraging areas, Fish Crows nested closer to waterbird colonies and to the water's edge while American Crows nested closer to a garbage source and to lawns. Fish Crows nested significantly more often in deciduous trees that were native, while American Crows nested significantly more often in evergreen trees that more frequently were exotic, especially Japanese black pine (Pinus thunbergii). Finally, we consider the potential predatory impact of sympatric crow species on waterbirds in light of their habitat use.

Flow restoration and protection in Australian rivers

AbstractSince 1857 new Australians have constructed many thousands of weirs (3600 in the Murray–Darling Basin alone) and floodplain levee banks, 446 large dams (>10 m crest height) and over 50 intra‐ and inter‐basin water transfer schemes to secure water supplies for human use. Flow regulation has changed the hydrology of major rivers on three temporal sales–the flood pulse (days to weeks), flow history (weeks to years) and the long‐term statistical pattern of flows, or flow regime (decades or longer). The regulation of river flows is widely acknowledged as a major cause of deteriorating conditions in many Australian river and floodplain ecosystems. In response to mounting environmental concerns, all states, territories and the Commonwealth Government have committed the nation to the principles of ecologically sustainable development and a process of national water reform. Rivers and wetlands are now recognized as legitimate ‘users’ of water, and jurisdictions must provide water allocations to sustain and where necessary restore ecological processes and the biodiversity of water‐dependent ecosystems. Progress in the protection and restoration of river and wetland water regimes has been significant, with over half of mainland aquatic systems designated to receive water allocations of some sort. However, exactly how much water they will receive or retain is unclear from the data available. Moreover, the ecological outcomes and benefits of water allocations are not yet apparent in most aquatic ecosystems, with the exception of certain waterbird breeding events, the disruption of algal blooms in weirs and improved fish passage. After reviewing these issues, this paper addresses two vital questions: How much water does a river need? and How can this water be clawed back from other users? Studies conducted to date in Queensland rivers suggest that around 80–92% of natural mean annual flow (and other ecologically relevant hydrological indicators) may be needed to maintain a low risk of environmental degradation. In the Top End of the Northern Territory, some rivers are maintained at 80% of their natural flow, whereas two‐thirds of various flow indicators has been proposed as the restoration target for the River Murray, and 28% of natural mean annual flow has been negotiated for the Snowy River in Victoria. To validate these estimates, ecologists are seeking opportunities to turn river restoration projects into long‐term hypothesis‐driven experiments in ecological restoration, and the funding, time and institutional support to do so. The paper ends with some suggestions to advance the water reforms and achieve higher levels of water allocation for the environment. Copyright © 2003 John Wiley & Sons, Ltd.

Effects of the 1997-1998 El Niño and 1998-1999 La Niña events on breeding waterbirds and sea lions in the Upper Gulf of California, México

En 1998 y 1999 revisé las colonias de aves acuáticas que anidan en Isla San Jorge, La Purinera e Isla Montague, en el norte del Golfo de California, al igual que la de lobos marinos de la Isla San Jorge. Encontré que El Niño coincidió con que los bobos cafés de San Jorge dejaran de anidar y se ausentaran de la isla, al tiempo que llegaban varios miles de bobos de patas azules. Las condiciones de El Niño coincidieron con un incremento en el número de individuos anidantes de gallitos menor, elegante y máximo y de rayadores, en Montague. Ni los patos buzo orejones en San Jorge, ni los gallitos menores en La Purinera, ni las garzas níveas, perros de agua , gaviotas risueñas, ni gallitos picogrueso, en Montague, parecen haber sido afectados. Los lobos marinos en San Jorge duplicaron aproximadamente su población, sin que esto repercutiera sobre la producción de crías. La Niña coincidió con un regreso de las poblaciones de las especies anteriores a las condiciones previas a El Niño. Además, durante 1999 en San Jorge anidaron gaviotas plomas y patos buzo de Brandt. Esa gaviota había dejado de anidar hacía mucho tiempo en San Jorge, y el pato buzo nunca se había registrado anidando ahí. Es prematuro concluir si estos registros fueron resultado de La Niña o de fenómenos en otra escala.doi: sin doi

Australian waterbirds—products of the continent's ecology

Some aspects of the ecology of 93 waterbird species, found predominantly on freshwater ecosystems, are reviewed. These species, belonging to six major orders—Anseriformes (ducks, geese and Black Swan), Podicipediformes (grebes), Pelecaniformes (Australian Pelican and cormorants), Ciconiiformes (herons, ibis, spoonbills and bitterns), Gruiformes (cranes, rails, crakes and gallinules), and Charadriiformes (waders and terns)—use a wide range of habitats and about half occur throughout the continent. Knowledge of their ecology remains poor for many waterbirds, particularly cryptic and rare species, and is moderate to good for hunted species. Life histories of Australian waterbirds differ from their counterparts elsewhere. Australia's highly variable climate and river-flooding patterns create wetland habitats, the spatial and temporal variability of which strongly influence the ecology of local waterbirds. Many waterbirds respond to newly generated habitats to feed and/or breed and then disperse or die as wetlands dry. Regular movements are not common in most Australian species although some, particularly waders, migrate between Northern Hemisphere breeding grounds and non-breeding habitat in Australia. Breeding of Australian waterbirds coincides with food abundance in the southern spring, the wet season in the tropics and following floods inland. Habitat loss through draining of wetlands, regulation of rivers, diversion of water for irrigation and floodplain development are currently the major threats to waterbirds. Other potentially threatening processes include exotic plants and animals, pollution, climate change and over-harvesting but evidence for the impact of these factors remains poor. Understanding of waterbird, particularly waterfowl, ecology has contributed significantly to the conservation management of wetlands in Australia. Research on single species, studies of movements using satellite technology, further investigation of the effects of hunting, long-term monitoring and large-scale analyses of the availability of wetland habitat should be future research priorities.

Patterns of food abundance for breeding waterbirds in the San Luis Valley of Colorado

We measured the amount and distribution of macroinvertebrates and seeds in four wetland habitats (short emergent, seasonal open water, semipermanent/permanent open water, and saltgrass [Distichlis spicata]) used by breeding ducks and shorebirds at a wetland complex in the San Luis Valley, Colorado, USA. Density of macroinvertebrates did not differ among habitats or sampling periods (P=0.45), but dry mass, crude protein, and gross energy production were greater (P<0.05) in short emergent than in other habitats. These differences were largely due to the greater dry mass of gastropods in short emergent than in other habitats. Total seed density, dry mass, crude protein, and gross energy differed among habitats and periods with interaction effects (P<0.01). Although seed abundance varied among habitats and sampling periods, abundance was greatest in short emergent during all sampling periods. Breeding waterbirds consumed a variety of macroinvertebrates and seeds on the study area. Patterns of abundance among habitats of macroinvertebrates and seeds consumed by six waterbird species were not consistent with patterns of foraging habitat use by most ducks and shorebirds at this wetland complex. Our results indicate that estimates of food or nutrient abundance are useful in assessing the functional role of broad habitat types, but factors other than food abundance also influence avian selection of wetland foraging habitats.

Inventory and conservation of breeding waterbirds at Ojo de Liebre and Guerrero Negro lagoons, Baja California Sur Mexico

Surveys made in 1997/98 at the lagoons of Ojo de Liebre (Scammon´ s Lagoon) and Guerrero Negro, Baja California Sur, Mexico, showed that changes have occurred since 1926 in the species composition of the community of breeding waterbirds, in the arrangement of their nesting substrate and in their population size. Of 17 species breeding in the area in 1926, we found 12 nesting there during our survey. Additional data from other researchers allowed us to conclude that 16 species have nested in the area after 1984. Only one species (Sterna elegans) has not been reported nesting; however, it is still considered to be a local breeder. Three species (Egretta alba, Larus atricilla and Falco peregrinus) became new established breeders. Most of the species that breed on the islands within Scammon´ s Lagoon have a stable population or have increased in number. None of the egret species breeding in 1926 in marshes outside the islands currently nest there. Four species (Sterna antillarum, Charadrius wilsonia, Charadrius alexandrinus and Rallus longirostris) breed on the islands or at other sites in the lagoons and vicinity. Despite development in the region, the natural wetlands and open-water coverage remain almost unchanged. Natural nesting substrates are mostly confined to the islands and are vulnerable to land predators, wave erosion and direct human disturbance. These factors may have caused the shifting of nesting spots from one island to another and to other suitable nesting sites on the lagoons, the urban landscape, the saltworks and man-made structures. Breeding waterbirds have been granted limited protection through reserves and single-species conservation programs. We suggest guidelines to enhance their protection as a community in the context of El Vizcaíno Biosphere Reserve.

Long-term trends in the breeding populations of waterbirds (1951–1985) at a sewage treatment plant

Long-term (1951–1985) data on the breeding waterbird populations and habitat modifications at Cape Flats sewage treatment works (Strandfontein) and Rondevlei Bird Sanctuary (Rondevlei) were assessed to establish the main factors affecting the breeding species richness and nest abundance. Fifty-two 'water-associated' breeding species were recorded in the Zeekoe River catchment waterbodies, 46 (88.5%) at Strandfontein, 38 (73.1%) at Rondevlei Bird Sanctuary (Rondevlei), 33 (63.5%) at Zeekoevlei and ten (19.2%) at Princess Vlei. Thirteen (25.5%) of the species were unique to Strandfontein and five (9.8%) to Rondevlei. Sorenson's similarity indices indicated high similarity (Cs = 0.81) in species richness and low similarity in nest abundance pattern (CN = 0.10) for the paired sites Strandfontein-Rondevlei. The lowest breeding species richness (11 species) was in winter (June) and the peak (42 species) was in spring (October). Twenty-four species joined the breeding population of Strandfontein during 1959–1976 (during which time pond water surface area increased 2372%). The mean breeding species richness increased significantly (χ 2 2 = 14.42, P <0.001) at Strandfontein during three distinctive periods: 1951–1958 (pre-construction), 1959–1976 (construction) and 1977–1985 (stabilization). At Rondevlei there were no significant differences in breeding species richness during the same periods. However, there were significant differences in the nest abundance pattern between these grouped years, both at Strandfontein (χ 2 2 = 1472.2, P <0.001) and at Rondevlei (χ 2 2 = 60.28, P <0.001). It is suggested that the same pool of species use the heterogeneous habitats at all the sites in the catchment according to their availability. The remarkable increase in species richness and nest abundance at Strandfontein after the late 1970s is attributed to higher habitat structural complexity, broad habitat types, stabilization and maturation of pond water and the subsequent increase in food diversity and availability. The decrease in Rondevlei nesting populations after the 1960s is probably related to fluctuations in water levels, cover of mudbanks with vegetation and high density of alien fish. A multipurpose management concept for conservation is proposed for the Zeekoe River catchment area. Strandfontein provides the greatest diversity of aquatic habitats not available elsewhere in the catchment (habitats for rare breeders such as Avocet, Black-winged Stilt, Red-billed Teal and some plovers) Rondevlei has a complementary habitat spectrum (suitable for Great Crested Grebe, Podiceps cristatus, Little Bittern, Ixobrychus minutus, and reedbed species). Zeekoevlei provides a large area of reedbed habitat for colonial breeding species (African Spoonbill and herons) and Princess Vlei is suggested for attracting Laridae.

Effect of river management on colonially-nesting waterbirds in the Barmah-Millewa forest, south-eastern Australia

River management has affected the ability of colonially-nesting waterbirds to reproduce in the Barmah-Millewa forest, south-eastern Australia. Relationships between reproductive performance and flow variability were quantified in order to establish the significance of the impact. The method of investigation involved: developing a conceptual framework describing four breeding–flow relationships (excellent, poor, abandoned and nil); obtaining measures for each relationship using annual breeding records (19 years; 1979–1997), habitat data (two traditional nest sites, one foraging area) and flow data (Murray River at Yarrawonga); and testing their predictive power at a landscape level. The effect of river management on the reproductive performance of colonially-nesting waterbirds was then assessed. Annual pulse dimensions in two runs produced by the monthly simulation model (natural and current flow; 1891–1992) were compared with the breeding–flow measures to obtain computer generated breeding level predictions. A major impact of river management was an 80% reduction in the frequency of successful breeding episodes compared to the natural precedent. The interval between breeding episodes during extended drought periods was identified as the most critical factor likely to affect the long-term stability or persistence of waterbird breeding in the forest. A literature review provided evidence of declining abundance and diversity of colonially-nesting waterbirds, and gave insight to the timing and factors contributing to the decline of many species. The principal conclusion is that three river flow objectives need to be addressed to ensure the long-term stability or persistence of breeding populations in the forest. Copyright © 2001 John Wiley & Sons, Ltd.

Ornithological importance of coastal wetlands in Guinea

Fode, L.C. 2000. Omithological importance of coastal wetlands in Guinea. Ostrich 71 (1 & 2): 343. For a number of years, the Guinean government has given high priority to nature conservation. Currently the conservation and wise use of natural resources are important issues of the country's developmental policy. The country has a rainy season of seven months (May-November), and heavy rainfall in the coastal area, an average of 2 000–4 000 mm/yr. Coastal wetlands cover a large area: 700 km2 mud flats, 600 km2 mangroves, 780 km2 rice fields and several hundred km2 freshwater swamp. Large numbers of waterbirds can be found in the Guinean coastal wetlands, and also in Senegal, Sierra Leone, Liberia, Cöte d'Ivoire, Guinea-Bissau, and Gambia. These countries share the same natural resources with Republic of Guinea, especially during the European winter, when, in addition to the Afrotropical species, there are many palearctic migrants. Over half a million waterbirds winter in the area, of which the palearctic waders, with 430 000, form the major part. Additionally, there are considerable numbers of flamingos, herons, egrets, and terns. The numbers of waterbirds during the European summer amount to 20% of those in winter, of the palearctic waders alone to 10%. In both seasons by far the largest number of waterbirds can be found on the mudflats. Various breeding waterbirds can be found on a few islands (> 3 000 pairs of brown booby, Sula leucogaster on the Isle of Alcatraz), and in the mangroves, rice fields and freshwater swamps. There are considerable breeding numbers of African Darter Anhinga rufa, Green-backed heron Buroroides striatus, White-necked stork Ciconia espiscopus and Caspian Tem Sterna caspia—breeding occurs mainly in the rainy season, except for the island, where most breeding takes place in the dry season. The Guinean coastal wetlands meet also the various criteria developed under the terms of the Ramsar Convention to identify wetlands of international importance. They easily meet the criterion of “regularly supporting 20 000 waterfowl” by the mere occurrence of large numbers during this period. The Guinean coastline, which has a length of 300 km, covers about a quarter of the West African mangrove coast between mid-Senegal and Sierra Leone. Although part of the mangroves have disappeared because of tree cutting and land reclamation for rice cultivation, these tidal forests still form a main part of the Guinean coast. Nearly all the well-developed large scale mangrove areas lie north of Conakry. According to some observations these are the three major threats to the coastal wetlands of Guinea: destruction of the mangrove habitats, hunting, disturbance of breeding sites, the latter being predominantly human disturbance of breeding bird colonies. Especially important is the destruction of parts of the mangrove zones by wood cutting and land reclamation in favour of rice cultivation. The Ninth Pan-African Ornithological Congress should be an opportunity to recommend the execution of appropriate national regional training programmes for concerned African countries. That programme will help to have solid specialists able to present adapted ornithological policies in the interested countries of Africa. The congress should also organise an official regional institution through which periodical contacts of specialists and quthorities can be made at local and international level. The congress must have some international development co-operation in ornithological fields in Africa. The congress may recommend development co-operation policy with Ramsar Convention Office, Wetlands International, WWF, IUCN, and any other concerned institutions.

Management of water regimes in River Red GumEucalyptus camaldulensiswetlands for waterbird breeding

This study investigated relationships between durations of inundation in River Red Gum wetlands and waterbird breeding, in particular the durations of flooding under nest trees that waterbirds need to breed successfully; and developed guidelines for managing water regimes in River Red Gum wetlands for waterbird breeding. The main study area was the middle section of the Murrumbidgee River in New South Wales. Average lag times between flooding under nest trees and first nests of Darter, cormorants, herons, egrets, Australian White Ibis and spoonbills ranged from two to four months following spring floods, and from four to seven months following autumn floods. The average lag times from flooding under the nest trees to first broods of ducks were one to two months, regardless of season of flooding. Average lag times to peak breeding of Darter, cormorants, herons, egrets, Australian White Ibis and spoonbills were three to five months following a winter/spring flood and six to nine months following an autumn f...

Instream Flow Requirements for The Platypus (Ornithorhynchus anatinus): High Flows. Studies of Water Transfers from The Shoalhaven River System to The Hawkesbury-Nepean River System.

During periods of low flows into the storages of the Hawkesbury-Nepean River system, Sydney Water pumps water from Lake Yarrunga, a storage at the junction of the Shoalhaven and Kangaroo Rivers. to the Wingecarribee Dam in the southern tablelands of New South Wales. From there it can be released into the upper Nepean River storages and/or the Wingecarribee River, which drains into the Wollondilly River and hence into the stored water behind Warragamba Dam. Prior to the formulation of an operational release strategy for this system, controlled releases of water were made into both the systems. During these releases the effects of flows on bank stability, water birds, benthic organisms and platypus populations and habitat were assessed, and a regime of maximum releases formulated. Potential impact on platypus populations was assessed by determining the height and/or area of bank left available for use by platypuses at the various flows. Subjective assessments were also made of the usable sections of the rivers for foraging at various flows. Broken white water was assumed to be unsuitable for foraging. The various investigations indicated that flows of 400 ML/day during September to March (water bird and platypus breeding and nesting season) and 600 ML/day at other times would have minimal impact on the ecology of the two river systems. Monitoring, studies involving netting and observations of platypuses in the upper Nepean River system indicated that operational releases within the suggested regime between July 1994 and May 1995 may have led to slightly reduced body condition in some animals during the higher flows in the winter of 1994. However the smaller discharges during the latter period of releases did not appear to result in platypuses entering the winter of 1995 in poor condition. Assessment of the usefulness of some sections of the river for foraging indicated that minor adjustments to the higher end of the flow regime may be necessary for future releases and that further monitoring needs to be done. Capture and observational monitoring studies indicated that releases of up to 500 ML/day in the Wingecarribee River between February and June 1995 had no noticeable effect on platypus activity or populations. Further monitoring needs to be done prior to, during and after higher flows and/or for longer periods in the Wingecarribee River.

Impact of Water Diversions on Colonially-Nesting Waterbirds in the Macquarie Marshes of Arid Australia

-The building of dams and subsequent diversion of water from the Macquarie River have had a significant impact on the breeding of colonial waterbirds in the Macquarie Marshes, New South Wales, southeastern Australia. Annual flows (1978, 1986-1996), measured at Oxley where the Marshes begin, were significantly related to total colony size (number of nests) and sizes of six nesting Ciconiidae (Intermediate Egret Ardea intermedia, Rufous Night Heron Nycticorax caledonicus, Glossy Ibis Plegadisfalcinellus, Straw-necked Ibis Threskiornis spinicollis, Australian White Ibis Threskiornis mollucca and Royal Spoonbill Platalea regia) colonies. We used these results and available historical flow data extending back to 1944 to demonstrate the probable impact of water diversions on breeding in these colonial nesting species. The impact of Burrendong Dam, opened in 1967, and Windamere Dam, opened in 1984, on the numbers of nests would have been significant. Instead of a colony of more than 100,000 nests in 1969, a colony of less than 10,000 probably established. Similarly, in 1984, a colony of more than 100,000 could have been established with no water diversions, but in all likelihood the colony was less than 5,000. Generally colony sizes were significantly less (100,000 over 11 years) than would be expected without diversions of water upstream. Colony sizes of more than 100,000 nests estimated during the floods of the 1950s are unlikely to occur again. Numbers of annual breeding events also declined with water diversions from ten to seven (1963-1973); eight to seven (1974-1984) and eight to five (1985-1995). Received 18 December 1997, accepted 18 May 1998.

WATERFOWL OF THE LARGE FISH POND SYSTEMS IN LITHUANIA

Abstract The aim of this paper was to provide an overview on status, abundance, distribution, habitat use of the dominant waterfowl species in large Lithuanian fish pond systems and to evaluate effects of managed temporary drainages of ponds on waterfowl. In Lithuania large fish ponds are supporting numerous species of rare breeding waterbirds, included into the national Red Data Book. Certain fish ponds are meeting criteria of the Ramsar Convention. In many areas with intensive agriculture and low carrying capacity of natural wetlands large man-made fish ponds are the key feeding, moulting and roosting sites for populations of waterfowl and shorebirds. Seasonal waterfowl assemblages in the largest fish ponds are dominated by 12 abundant species: Great Crested Grebe, Grey Heron, Cormorant, Mute Swan, Whooper Swan, White-fronted Goose, Mallard, Teal, Wigeon, Pochard, Hifted Duck and Coot. Habitat use of the dominant waterfowl species is closely related with the effects of a managed temporary drainage of ponds. New forms of aquaculture in conditions of the market economy may affect most of the key waterbirds habitats in large fish ponds. Therefore the main objective of all management activities related to important bird areas in Lithuanian fish ponds is to maintain the network of these man-made wetlands.

Relationships Between Hydrological Control of River Red Gum Wetlands and Waterbird Breeding

SummaryFourteen wetlands on the floodplain of the Murrumbidgee River (Murray-Darling Basin, Australia) were surveyed for breeding waterbirds during three annual flood periods. Degree of water control in the wetlands ranged from none to slight to medium to heavy. The wetlands comprised open areas with River Red Gums Eucalyptus camaldulensis. Most, but not all, of the red gums were alive. Precocial waterbirds (those that do not feed their young; mostly Anatidae in this study) did not breed at wetlands with highly controlled water regimens. In altricial waterbirds (those that feed their young at the nest; Pelecaniformes and Ciconiiformes in this study) breeding was not directly related to water level control, but depended on areas of River Red Gums that flooded for at least four months. Within the altricial group, Darter Anhinga melanogaster, Great Cormorant Phalacrocorax carbo and Pacific Heron Ardea pacifica preferred sites with large areas of River Red Gum that flooded for at least four months and large areas of dead River Red Gum (which stayed flooded permanently). Little Black Cormorant Phalacrocorax sulcirostris, Little Pied Cormorant P. melanoleucos, White-faced Heron Ardea novaehollandiae and Yellow-billed Spoonbill Platalea flavipes favoured wetlands with large areas of live River Red Gum that flooded for at least four months. River Red Gum wetlands in which water levels are controlled can be managed for nesting Pelecaniformes and Ciconiiformes. Treeless parts of wetlands can be permanently flooded, but nest trees should not be killed by permanent inundation.

Planning for the recovery of Lake Toolibin, Western Australia

Lake Toolibin, an intermittently flooded freshwater wetland in the southwest of Western Australia, is threatened by salinization due to extensive clearing within its catchment. The lake is a Wetland of International Importance under the Ramsar Convention because of the extensive stands of trees on the lake bed and its significance as a waterbird breeding site. Past research and monitoring have identified the causes of wetland vegetation and water quality decline and this information has been used to design a Recovery Plan for the lake. The plan is currently in the early stages of implementation and includes both short-term engineering measures to reduce salinity within the lake and long-term rehabilitation measures within the catchment. Community involvement in the recovery process is an integral part of the plan and ensures that recovery of the lake remains as the focus for ongoing catchment rehabilitation.

Status and Trends of Loon Populations Summering in Alaska, 1971-1993

Loons (Gavia spp.) were counted during the Alaska-Yukon Waterfowl Breeding Population Survey from 1971 to 1993 and the Arctic Coastal Plain Waterbird Breeding Population Survey from 1986 to 1993. Population indices for Alaska (not corrected for visibility bias) are presented by species for boreal forest, tundra, and both habitats combined. Minimum mean population estimates (1977-1993) with 95% confidence intervals were 15,360 (±2,235) Red-throated Loons (G. stellata), 69,498 (±5,596) Pacific Loons (G. pacifica), 8,886 (±843) Common Loons (G. immer) and 2,636 (±614) Yellow-billed Loons (G. adamsii). Populations of Pacific, Common and Yellow-billed Loons did not change significantly between 1977 and 1993, whereas Red-throated Loons declined by 53% to a 1993 level of 9,843 (±2,447) (r 2 = 0.65, P < 0.001). Factors affecting results from aerial surveys are discussed.

Margrethe-Kog and the Artificial Saltwater Lagoon: Evaluation of a Habitat Restoration Project in the Danish Wadden Sea

Across the Danish–German border in the Wadden Sea, a new dike was completed in 1981, enclosing formerly productive tidal flats and marsh areas which were most important as feeding grounds to breeding and migrant waterbirds. The bird populations responded immediately by a 50% or more reduction in numbers of resting birds and breeding pairs of most species. This paper reviews the management of the enclosed areas, comparing the differences in approach in the Danish and German areas involved.Most importantly, a saline environment was re-established (a Saltwater Lagoon) in parts of the Danish area by actively pumping in water from the Wadden Sea. Despite sometimes drastic fluctuations in environmental conditions in the Lagoon, an infauna of species important in the birds' diet was maintained, and the Lagoon to some extent counteracted the negative effects of the dike construction.The former marsh areas on the Danish side are drained and partly cultivated. In addition, the land areas are separated from the Lagoon by a dike, preventing a saline environment from being maintained outside the designated Saltwater Lagoon. Overall, the land areas in the Danish part are too dry and intensively used to be optimal to the breeding birds.After construction of the dike, the breeding bird populations shifted more towards the German areas. Here, the land-use is much more beneficial to the breeding birds, because no cultivation has taken place, and a generally high water-level in the marsh areas is preserved. Furthermore, in Germany the new dike was placed closer to the original coastline than in Denmark, but a small area of the original foreland remained outside the dike, providing good breeding sites for colonial waterbirds.It is concluded that, due to the creation of the Saltwater Lagoon, the Danish part of the area again sustains waterbirds in numbers of international importance. But an integrated approach to the Nature management of the enclosed areas — combining the solutions adopted for land management in the German part with the technical solution of re-establishing a saline environment behind the dike as in the Danish part — would have rendered a better compensation for the damage caused by the dike construction and related activities.

Breeding Seasons of Waterbirds in South-western Australia—the Importance of Rainfall

SummaryHalse, S.A. & Jaensch, R.R (1989). Breeding seasons of waterbirds in south-western Australia—the importance of rainfall. Emu 89, 232–249.Breeding seasons are documented for forty-nine species of waterbird in south-western Australia and factors determining time of breeding are examined using data from the RAOU survey of waterbird usage of nature reserves (1981–85) and the RAOU Nest Record Scheme. Most breeding occurs in spring and regression analyses suggest that rainfall is the most important proximate cue stimulating gonadal recrudescence. Few species appear to use photoperiod and those that do nest late in the year. Although comparison of waterbird breeding seasons in various regions of Australia suggests rain-related factors are the most important proximate cues everywhere, the particular rain-related factors used may vary.

Land Cover/Use Analysis of Prespa National Park, Greece

Prespa National Park in Greece is an important breeding-area for rare and endangered waterbird species, but people living within the Park and using its resources create serious conservation problems. An environmental management plan which will regulate mainly the human activities within the Park is therefore necessary. Such a plan should be based on a land cover/use analysis of the area, for which much of the necessary information, in the form of a thematic map, has been collected by interpreting blackand-white aerial photographs. The procedure involved the development of a classification system, transferring the interpreted data onto a base-map, field-checking the results, and tabulating the area measurements with the pertinent errors.Of the total Park area (25,690 ha), 66.5% is classified as terrestrial (forestland, rangeland, agricultural land whether irrigated, non-irrigated, or abandoned, wet meadows/marshland, barren and eroded land, and urban areas), and the remainder as aquatic (water, reedbeds). The most extensive category in the Park is forestland, much of which is seriously degraded. Rangeland provides forage for sheep and goats, being also degraded owing to uncontrolled grazing. Wet meadows/marshland are invaluable as waterbird breeding and feeding habitats, but the present use of this category as grazing fields, and its proximity to agricultural land and to the existing irrigation/drainage system, have all had negative impacts on the resource. Irrigated land is almost half of the cultivated area.The abandoned agricultural land is interspersed within the forestland and is a result of the human population decline in the area, while barren and eroded land has resulted from prolonged land misuse. Twelve old villages are distributed over the Park, being visually unobtrusive. Lake Mikri Prespa is the main water-body and covers almost the entire nucleus of the Park. Extensive reedbeds are found along the lakeshores, which are the main breeding habitats of certain waterbirds. As land cover/use analysis of the Park has shown much serious environmental degradation, conservation measures should be undertaken urgently.