Colonial Waterbirds Research Articles

Dependence of Waterbirds and Shorebirds on Shallow-Water Habitats in the Mid-Atlantic Coastal Region: An Ecological Profile and Management Recommendations

Waterbirds (waterfowl, colonially nesting wading and seabirds, ospreys [Pandion haliaetus], and bald eagles [Haliaeetus leucocephalus]) and shorebirds (sandpipers, plovers, and relatives) may constitute a large fraction of the toplevel carnivore trophic component in many shallow-water areas of the mid-Atlantic region. The large biomass of many species (>1 kg body mass for the two raptors and some waterfowl) and enormous populations (e.g.,>1 million shorebirds in late May in parts of Delaware Bay) reveal the importance of waterbirds as consumers and as linkages in nutrient flux in many shallow-water habitats. Salt and brackish marsh shallow-water habitats, including marsh pannes and tidal pools and creeks as well as constructed impoundments, are used intensively during most months of the year; in fall and winter, mostly by dabbling ducks, in spring and summer by migrant shorebirds and breeding colonial wading birds and seabirds. In adjacent estuaries, the intertidal flats and littoral zones of shallow embayments are heavily used by shorebirds, raptors, and colonial waterbirds in the May to September periods, with use by duck and geese heaviest from October to March. With the regional degradation of estuarine habitats and population declines of many species of waterbirds in the past 20 yr, some management recommedations relevant to shallow waters include: better protection, enhancement, and creation of small bay islands (small and isolated to preclude most mammalian predators) for nesting and brooding birds, especially colonial species; establishment of sanctuaries from human disturbance (e.g., boating, hunting) both in open water (waterfowl) and on land; better allocation of sandy dredged materials to augment islands or stabilize eroding islands; improvement in water management of existing impoundments to ensure good feeding, resting, and nesting opportunities for all the waterbirds; support for policies to preclude point and nonpoint source runoff of chemicals and nutrients to enable submerged aquatic vegetation to recover in many coastal bays; and improvement in environmental education concerning disturbance to wildlife for boaters and recreationists using the coastal zone. *** DIRECT SUPPORT *** A01BY074 00007

Biochemical indicators of contaminant exposure in passerines, colonial waterbirds and snapping turtles of the Great Lakes Basins

Biochemical indicators of contaminant exposure in passerines, colonial waterbirds and snapping turtles of the Great Lakes Basins

Reproductive success, developmental anomalies, and environmental contaminants in double-crested cormorants (Phalacrocorax auritus)

To test an association between environmental contaminants and the prevalence of congenital anomalies in colonial waterbirds, the authors collected representative eggs for chemical analysis from double-crested cormorant nests at colonies in Lake Michigan, Wisconsin, USA, and Lake Winnipegosis, Manitoba, Canada, and periodically revisited the nests to determine the hatching success, survivorship of hatchlings, and number of deformed hatchlings in the remainder of each clutch. Total concentrations of polychlorinated biphenyls (PCBs) in eggs were determined by capillary gas chromatography. The combined activity of planar chlorinated hydrocarbons (PCHs) in the eggs was measured in an in vitro bioassay based on the induction of ethoxyresorufin-O-deethylase (EROD) activity in rat hepatoma cells. The combined EROD induction activity was expressed as 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ). Total concentrations of PCBs and TCDD-EQ were seven to eight times greater in eggs from Lake Michigan (7.8 {micro}g/g and 138 pg/g, respectively) than in those from Lake Winnipegosis (1.0 {micro}g/g and 19 pg/g, respectively). The proportion of eggs hatching at the Lake Michigan colony (59%) was less (p < 0.05) than at Lake Winnipegosis (70%), and the prevalence of hatchlings with deformed bills was greater (p < 0.001) at Lake Michigan (0.79 vs. 0.06%). However, within the Lake Michigan colony,more » concentrations of PCBs and TCDD-EQ were not correlated with either hatching success or the occurrence of deformities in nestlings.« less

The Relevance of the Mediterranean Region to Colonial Waterbird Conservation

The Relevance of the Mediterranean Region to Colonial Waterbird Conservation

The Contribution of Colonial Waterbird Research to Wetland Conservation in the Mediterranean Region

We summarize the history of waterbird research in the Mediterranean region, how some of these ac- tivities developed into long-term ecological research programs, and how they created awareness of the need to con- serve the species and their wetland habitats. We further analyze the impact of colonial waterbird studies on conservation actions and recommend how current research can be made relevant for conservation. An overview is presented of the development of mid-winter counts and wetland site inventories, and the contri- bution of ecological studies to the conservation of colonial waterbirds and their habitats is summarized. There is still a lack of information on the distribution of the breeding colonies throughout the Mediterranean and of a co- ordinated population monitoring program. Data on feeding habitat and colony site requirements help to recognize those parts of the aquatic ecosystem that ought to be given conservation priority. The study of reproductive biology adds complementary data on the dependence of reproductive performance on environmental conditions. Ulti- mately, the identification of the environmental factors that influence population size is a key requirement for spe- cies conservation programs. This requires long-term studies. However, due to the infrastructure and long-term commitment involved, population studies expanding over decades have remained very few. To make the important investments in the study of colonial waterbird ecology more applicable to the conserva- tion, management and restoration of their wetland habitats in the future, the collection of baseline monitoring data is required throughout the Mediterranean. Successfully tested ecological research methods need to be adopted in different parts of the Mediterranean and used in a coordinated way. Foraging ecology, ecotoxicology and the study of habitat requirements in relation to population dynamics are the research fields that can provide useful informa- tion for site-specific habitat management and restoration programs. Interdisciplinary projects between ecologists, hydraulic engineers, and land-use planners need to be developed. Finally, the results of the scientific studies need to be disseminated more widely, also in a form accessible to the administrator, political decision-maker, and local

Deformities, PCBs, and TCDD-Equivalents in Double-Crested Cormorants ( Phalacrocorax auritus) and Caspian Terns ( Hydroprogne caspia) of the Upper Great Lakes 1986–1991: Testing a Cause-Effect Hypothesis

Deformities have been reported in many species of colonial waterbirds from several localities on the Laurentian Great Lakes. The hypothesis that deformities were caused by either polychlorinated biphenyls (PCBs) or contaminants measured as 2,3,7,8-tetrachlorodibenzo- p-dioxin equivalents (TCDD-EQs) is tested in this review of available data on concentrations of contaminants in eggs and observed deformities in embryos and chicks of double-crested cormorants ( Phalacrocorax auritus) and Caspian terns ( Hydroprogne caspia) between 1986 and 1991. Hatched chicks, live and dead eggs retrieved from 37 colonies in the upper Great Lakes were assessed for gross anatomical deformities. Rates of embryo death from seven regions of the upper Great Lakes were measured annually between 1986–1991. Half the embryos found dead in eggs were deformed. Nineteen types of abnormalities or deformities were observed. Subcutaneous edema in cormorants and gastroschisis in terns were the most common abnormalities in live or dead eggs. One of ten crossed-billed cormorant embryos survived to hatch. No bill-deformed terns hatched, although tern embryos had a greater rate of crossed-bills than cormorants. The suite of deformities and abnormalities found was similar to that produced in chickens by exposure to planar polychlorinated biphenyl (pPCB) and dioxin congeners. Hatching and deformity rates were correlated with concentrations ofpPCBs and TCDD-EQs. Planar PCB congeners that contributed most of the TCDD-EQs were present at concentrations sufficient to cause the observed effects. TCDD-EQs measured by H4IIE rat hepatoma cell 7-ethoxyresorufin O-deethylase (EROD) bioassay were highly correlated with deformity rates observed in cormorant chicks, live and dead eggs, and egg death rates. Similar correlations of TCDD-EQs with deformity rates were found in hatched tern chicks, dead eggs, and egg death rates, but not in live eggs. TCDD-EQs were more highly correlated to deformity and embryo death rates than total PCBs. The weight of evidence and these data are sufficient to reject the null hypothesis that there is no causal relationship between the incidence of deformities in cormorants and terns and exposure to planar halogenated compounds measured as TCDD-EQs or total PCBs in the Great Lakes.

The Effects of the 1989/1990 Drought on the Colonial Waterbirds Nesting at Lake Mikri Prespa, Greece, with Special Emphasis on Pelicans

The Effects of the 1989/1990 Drought on the Colonial Waterbirds Nesting at Lake Mikri Prespa, Greece, with Special Emphasis on Pelicans

Conservation Status of Albanian Coastal Wetlands and Their Colonial Waterbird Populations (Pelecaniformes and Ciconiiformes)

Conservation Status of Albanian Coastal Wetlands and Their Colonial Waterbird Populations (Pelecaniformes and Ciconiiformes)

Fluctuations and Trends in Breeding Populations of Colonial Waterbirds in the Dnestr Delta, Ukraine, Black Sea

Fluctuations and Trends in Breeding Populations of Colonial Waterbirds in the Dnestr Delta, Ukraine, Black Sea

Design and management of bird nesting habitat: tactics for conserving colonial waterbird biodiversity on artificial islands in Hamilton Harbour, Ontario

Design and management of bird nesting habitat: tactics for conserving colonial waterbird biodiversity on artificial islands in Hamilton Harbour, Ontario

Organochlorine Contaminants in Avian Wildlife of Severn Sound

Abstract Organochlorine contaminants were measured in pooled egg samples of colonial waterbirds, red-winged blackbirds and tree swallows breeding in or near Severn Sound, Lake Huron, an area designated by the International Joint Commission as an Area of Concern, during 1991. Breast muscle samples of staging waterfowl were also collected the preceding autumn. PCBs, DDE and mirex were the most prevalent organochlorine contaminants present in eggs (concentration ranges of 0.065 to 5.452, 0.118 to 3.12 and 0.007 to 0.174 mg/kg, respectively), while oxychlordane, cis-chlordane, dieldrin, heptachlor epoxide, trans-nonachlor, cis-nonachlor, OCS, HCB and beta-HCH were also detectable at low levels in some egg samples. Tetra- and pentachlorobenzene, and alpha-and gamma-HCH were not detected in any of the samples. Generally, the following interspecific gradient in contaminant levels in bird eggs was found: herring gulls = Caspian terns &amp;gt; common terns &amp;gt; tree swallows &amp;gt; blackbirds. Concentrations in the eggs of piscivorous birds in Severn Sound were similar or slightly lower than those from other colonies in Georgian Bay and Lake Huron, and considerably lower than those from colonies in Hamilton Harbour, Lake Ontario. Mirex levels in herring gulls and Caspian terns from Severn Sound colonies were an exception in that they were substantially higher than levels from other Lake Huron colonies (0.174 and 0.167 mg.kg-1 for the two species, respectively, versus &amp;lt;0.12 mg.kg-1), although still much lower than those from Lake Ontario (0.50 and 0.719, respectively). It is probable that mirex was accumulated by gulls and terns during winter or migrational stopovers on Lake Ontario. Low contaminant levels in common terns may have been a result of their consumption of a smaller size class of prey fish. Higher contaminant levels in tree swallow eggs in comparison to red-winged blackbird eggs may have been due to the preponderance of aquatic insects in their diets, as opposed to the larger proportion of terrestrial arthropods in blackbird diets. Only PCBs and DDE were detected in the breast muscle of lesser scaup and mallards.

Comparing Aerial Estimates with Ground Counts of Nests in Wood Stork Colonies

Estimates of wood stork (Mycteria americana) nests from fixed-wing aircraft in Florida colonies were calibrated using ground counts to evaluate bias and uncertainty. Inferences were based on linear regressions of log-transformed aerial estimates on log-transformed ground counts. Canopy cover at stork colonies had no effect (P = 0.737) on the relationship between aerial estimates and ground counts. Whereas no difference between ground counts and the expected value of aerial estimates was detected for colonies with a low proportion of other white-plumaged nesting birds (P = 0.241), aerial estimates underestimated (P 109 nests) stork colonies containing a high proportion of other white-plumaged nesting birds. Variability of aerial estimates was large. An approximate 95% confidence interval for the 1993 statewide nesting population, based on the statewide aerial survey, was 3,807-12,653 nests. Recommendations for improving future aerial surveys of colonial waterbirds include incorporating ground counts at selected colonies, training observers in presurvey flights, and replicating counts for each colony.

Polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents in eggs of double-crested cormorants from a colony near Green Bay, Wisconsin, USA.

Great Lakes colonial waterbirds have experienced poor reproduction and a greater incidence of birth defects than those in remote areas. An egg was collected from each of 1,000 marked cormorant nests at Spider Island (Lake Michigan). Nine pools comprised of three eggs were randomly selected for instrumental quantification of polychlorinated biphenyls (PCB) congeners, calculation of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEq) and measurement of equivalents by bioassay (TCDD-EQ). PCB analysis of the nine samples was semi-automated with high performance liquid chromatography (HPLC) columns including a porous graphitic carbon column. TEqs were calculated from concentrations of PCB congeners and bioassay-derived toxic equivalency factors (TEfs), and TCDD-EQ were measured directly with an H4IIE bioassay. Total PCB concentrations ranged from 9.7 to 38 micrograms/g, wet weight (ww). Mean concentrations of PCB 77, 126, and 169 were 2, 7, and 1 ng/g, ww. The mean TEqs and TCDD-EQ were 150 and 350 pg/g, ww, respectively. Thus, PCB congeners contributed less than 50% of the total TCDD-EQs as measured by the bioassay.

Effects on fisheries and waterbirds of raising water levels at Kerkini Reservoir, a Ramsar site in northern greece

A new, higher dam was installed at Kerkini Reservoir in 1982, causing habitat and landscape disruption. A decrease in the area of grassland and shallow water areas, the rapid disappearance of reedbeds, the appearance of beds ofNymphaea, and the disappearance of half the forest area were all observed between 1982 and 1991. With the new hydrological regime, a lacustrine system was created, with an extensive, rather deep (4–8 m), pelagic zone favorable for the development of coarse fish species throughout the year. After 1982, an increase in fishing effort and a change in the relative abundance of fish species in the catch, including the disappearance of eels and wels, were observed. The impact of the rise in the water level of breeding aquatic birds led to a general decline in species typical of marshy habitats in favor of species preferring deeper open water habitats. A decrease was recorded in bird species that feed largely on invertebrates and to a lesser extent fish (e.g., glossy ibis) and that require extensive shallow feeding areas. There was a decline in geese, whose nests were regularly flooded, and a major increase in piscivorous birds, particularly diving birds (e.g., cormorants), which prefer deeper open water and benefitted directly from the large increase in coarse fish biomass. The disappearance of birds breeding in flooded meadows (e.g., black-winged stilts) and of those restricted to reedbeds (e.g., marsh harrier) occurred from 1983. Over the same period, the changes in populations of wintering birds at Kerkini were different from those occurring in other wetlands in northern Greece. The changes recorded in the populations of wintering birds at Kerkini did not therefore result from overall regional trends but from the major habitat modifications that occurred to this wetland. As for breeding birds, strictly piscivorous species increased greatly as a result of the increased availability of fish, but also due to the appearance of many suitable night roosting sites (flooded trees) and to the great increase in the area of open water greater than 2 m deep. Today, Kerkini has become the most important breeding site in Greece for a majority of colonial waterbirds. In contrast, wintering shorebirds practically disappeared. The many changes recorded in the status of breeding and wintering birds at Kerkini can mostly be explained by the changes that occurred in the functioning of the ecosystem and in the habitat structure following the inauguration of the new hydrological regime. These changes did not all occur at the same time: some were immediate and others required a delay before they could be detected.

Set‐Back Distances to Protect Nesting Bird Colonies from Human Disturbance in Florida

Breeding colonial waterbirds are particularly susceptible to human disturbance because of their high‐density nesting habits. Identified detriments to reproductive success include egg and nestling mortality, nest evacuation, reduced nestling body mass and slower growth, premature fledging, and modified adult behaviors. Fifteen species of colonial waterbirds nesting at 17 colonies in north and central Florida were exposed to three different human disturbance mechanisms (HDMs) in order to determine recommended set‐back (RS) distances for protecting these mixed‐species nesting assemblages. Both intraspecific and interspecific variation were observed in flushing response distances to the same human disturbance mechanisms. In general, colonial waterbirds exhibited greater average flush distances in reaction to a walking approach than to approaching motor boats. Recommended set‐back distances were estimated using a formula based on the mean plus 1.6495 standard deviations of the observed flushing distances plus 40 meters [X = exp (X + 1.6495X + 40)]. In general, a recommended set‐back distance of about 100 meters for wading bird colonies and 180 meters for mixed tern/skimmer colonies should be adequate to effectively buffer the sites we studies from human disturbance caused by approach of pedestrians and motor boats. We recommend follow‐up studies to test our model at other breeding colonies.

Interannual Variation in Greater Flamingo Breeding Success in Relation to Water Levels

In many colonial waterbirds, reproductive success is affected by water levels around the colonies. In a study of the Greater Flamingo (Phoenicopterus ruber roseus) in the Camargue, southern France, we examined annual variation in water levels around the breeding colony site between 1984 and 1991 in relation to (1) the number of breeding pairs, (2) colony productivity (fledglings per breeding pair), and (3) physical condition of fledglings. The number of breeding pairs each year was highly variable and was positively correlated with high water levels during the March—July period. There was no significant relationship between the number of breeding pairs and the number of chicks fledged. Although the productivity of the colony was not affected by water levels during the chick—raising period, fledglings were heavier in years with high water levels. There was no relationship between colony productivity or the absolute number of chicks fledged and the average body condition of chicks in the creche. Differences between the 1984 and 1985 cohorts in the frequency of young birds making breeding attempts (i.e., ages 5 and 6 yr) suggested that body condition at fledging may have important life history consequences. Estimation of reproductive performance in colonial waterbirds, usually limited to the average nest productivity, could be improved by considering average body condition of chicks at fledging as well.

Organochlorine Contaminant Levels in Waterbird Species from Hamilton Harbour, Lake Ontario: an IJC Area of Concern

The levels of organochlorine (OC) contaminants in eggs and tissues of waterbird species nesting in Hamilton Harbour, Ontario, an International Joint Commission Area of Concern, were monitored between 1981 and 1992. PCBs, DDE, and mirex were present at the highest concentrations of the 29 organochlorines and one trace metal measured. Most contaminants in the various species tested showed a declining temporal pattern during that period. Double-crested cormorant eggs generally had higher concentrations of contaminants than those in herring gull eggs which in turn were higher than those in eggs of black-crowned night-herons, Caspian terns and common terns. The levels of contaminants in the eggs reflect the dietary preferences of the species with the fish-eating birds containing consistently higher accumulations of contaminants when compared to the herbivorous Canada goose for which the levels were consistently much lower for all compounds. The concentrations of contaminants detected are among some of the highest in the Great Lakes but when compared to other sites on Lake Ontario, the levels in Hamilton Harbour are generally equal or lower. Elevated levels of contaminants such as PCBs, mirex, and DDE were also detected in liver and muscle tissues of migrant waterfowl species from the harbor. Despite habitat degradation and continued presence of contaminants, the harbor supports a large number and wide variety of waterbird species. Except for black-crowned night-herons, the nesting populations of colonial waterbirds have increased between 21 and 1061 % since the last survey in 1987.

Variation in Parental Care with Offspring Age in the Greater Flamingo

Several studies have predicted how parental investment should change in relation to the age of offspring (Williams 1966, Winkler 1987). The Reproductive Value Hypothesis (RVH) states that parents should be prepared to invest more in older juveniles because they have a higher probability of surviving to breeding age. This may occur because older juveniles are closer to maturation and because the instantaneous rate of juvenile mortality generally decreases with increasing age (Clutton-Brock 1991). Increase in feeding effort with chick age has been documented for some species of colonial waterbirds. In Pigeon Guillemots (Cepphus columba) provisioning rates increased with chick age, only during the first part of the nestling period (Emms and Verbeek 1991). Feeding rates were not observed to vary with chick age in the closely related Black Guillemot (Cepphus grylle), but size of fish delivered to the nest increased with chick age (Cairns 1987). As chicks grow older they also have greater food requirements, and increased parental care might simply correspond to the higher energetics and nutritional demands of the offspring. Further evidence for increased parental care with increasing age of offspring comes from studies of brood defense. Brood defense has been reported to increase with nestling age in several passerine species (Andersson et al. 1980, Redondo and Carranza 1989, but see Knight and Temple 1986, Westmoreland 1989). However, the observed increase in parental care with offspring age can also be influenced by confounding variables such as parental age and or quality. Breeding success is known to increase with parental age in several bird species (Saether 1990) and this can be the result of increased experience with age. In addition, as parents grow older, their potential for future reproduction decreases. Thus the cost of reduced future reproductive success should decline with age and older parents should be selected to invest more in offspring compared to younger parents (Pugesek 1981). Therefore, it is important to control for parental age when considering variation in parental care with offspring age. Here, we analyze data from two years on the duration of feeding bouts by Greater Flamingo (Phoenicopterus ruber roseus) parents of known age and sex to their offspring. We show that only male parental care increases with offspring age. We discuss our results in relation to lifetime reproductive success and costs of reproduction.

Methods of individual identification for captive colonial waterbirds: lessons from the field

The identification of individuals is essential for scientific captive management of colonial birds as well as for field studies. The authors review the methods and techniques available for marking aquatic birds permanently or temporarily and consider the suitability of the systems for captive populations.

Colonial Waterbirds as Bioindicators of Environmental Change

Colonial Waterbirds as Bioindicators of Environmental Change