The reproductive success of the Snowy Plover (Charadrius alexandrinus) nesting on beaches in central Monterey Bay, California, was monitored before (1984 to 1990) and during (1991 to 1999) predator management. From 1984 to 1990, hatching success of the Snowy Plover declined from 66% to 26% and most nest loss was attributed to Red Fox (Vulpes vulpes) predation. From 1991 to 1999, exclosures were used to protect some nests and after 1993, mammalian nest predators were removed. Predator management increased hatching success and the number of chicks hatched per male, but not fledging success or the number of chicks fledged per male. Predation of chicks by avian predators probably limited fledging success. The number of breeding adults did not increase and incubating adults were subject to greater mortality when nesting in exclosures. Our results indicate that exclosures are useful for increasing hatching success, but we caution that widespread use of exclosures may increase adult mortality rates and contribute to a decline in breeding numbers.

Abstract.—The intertidal area of Fracasso beach at Peninsula Valdés, Argentina is used as a regular stop-over site by the Two-Banded Plover (Charadrius falklandicus), a neotropical Patagonian species. We analyzed the feeding patterns and diet choice of the Two-banded Plover at Fracasso beach based on fecal analyses and measurements of the intertidal invertebrate community. The intertidal area was divided in six zones related to the tide height. Two-banded Plovers are visual foragers that use stop-run-stop as strategy to capture their prey, and invested the bulk of their foraging time in the medium to high shore zones. The most frequent prey found in the droppings was the bivalve mollusk Darina solenoides, the only clam eaten, but when frequency was converted to biomass, the contribution to the diet of the polychaete Glycera americana, one of the three polychaete species eaten, was 15 times higher than the contribution of bivalve mollusk Darina solenoides. Two-banded Plovers selected very small clams compared with the large polychaetes consumed.

The conditions that determine habitat suitability for waterbirds on temporary wetlands in Australia are poorly understood. This study describes the foraging behavior of the Black-fronted Plover (Elseyornis melanops) on two shallow saline lagoons with variable water depths. When water levels were receding, areas were left exposed around the periphery of the lagoons, which formed a succession from substrates still covered by water, to wet mud with a surface layer of water, to moist firm mud and eventually to dry, hard mud. The plovers showed a strong preference for feeding in areas of moist, firm mud and their prey capture rates were highest in this substrate type. When water levels rose following rainfall, previously exposed areas were partially flooded and the birds’ prey capture rates fell significantly. Most abandoned the lagoon. The species was thus highly dependent on receding water levels to provide suitable foraging conditions.

We compared detection rates of passive and playback breeding bird survey techniques on elusive marsh birds--Pied-billed Grebe (Podilymbus podiceps), American Bittern (Botaurus lentiginosus), Least Bittern (Ixobrychus exilis), Virginia Rail (Rallus limicola), and Sora (Porzana carolina)--during a two-year study at Lacreek National Wildlife Refuge, in southwestern South Dakota. We conducted 151 passive point counts followed by playback-response surveys at the same points in marsh-bird habitat on the refuge. Playback surveys detected secretive water birds more frequently than our passive surveys, increasing rates for each species by factors of 2.4 to 7.0. The distance a bird was detected from a point varied with the species and the survey technique.

We surveyed Yellow Rails (Coturnicops noveboracensis) in three marshes located in southeastern James Bay, Canada, in order to document the status and distribution of this species at risk. Night-surveys of calling males were made along 75 km of line transect on 21-25 July 2002, and 186 individual Yellow Rails were recorded: 80 in Cabbage Willows Bay, 77 in Boatswain Bay, and 29 in Hall Cove. Daytime surveys yielded 19 additional calling males, giving a total of 205 male rails. Transects were distributed in plant communities dominated by Slimstem Reedgrass (Calamagrostis stricta), Chaffy Sedge (Carex paleacea), Buckbean (Menyanthes trifoliata), or by Red Fescue (Festuca rubra). There was an overall density of 0.05 calling rails per ha with maximum densities in Boatswain Bay (0.08 male/ha) and Hall Cove (0.06 males/ha). Densities calculated for specific plant communities permitted an estimate of 397 male Yellow Rail inhabiting the marshes: 216 in Boatswain Bay, 132 in Cabbage Willows Bay, and 49 in Hall Cove. The highest densities were in Chaffy Sedge stands, Slimstem Reedgrass stands, and fens dominated by Buckbean. This study indicates that the Yellow Rail is a common bird in coastal high-marshes of the southeastern James Bay, and revealed the highest densities ever reported for the species. The extensive estuarine tidal marshes found in southern James Bay may be home of a thousand or more adult male Yellow Rails and thus represents a key area for this species.

Surveys were conducted at 35 Great Blue Heron (Ardea herodias) colonies in urban and rural landscapes of south-coastal British Columbia, Canada, to investigate low nesting productivity during 1998 and 1999 compared to a decade ago. Nesting failure was common (59% of 1,247 nests) and widespread (in 90% of 31 colonies) and accounted for 96% of the variation in nesting productivity among colonies in 1999. Nesting failure was more frequent in small colonies (<50 nests) than in large colonies (≥50 nests). Human disturbance has probably increased due to growth in the human population in the region, and direct disturbance from the Bald Eagle (Haliaeetus leucocephalus) was more frequent in 1999 than a decade earlier. Eagles predated eggs, nestlings, and fledglings and were probably responsible for most of the observed nesting failure. Direct disturbance by humans was infrequent, but heron nesting productivity was negatively correlated with the frequency of human pedestrians near colonies. We suggest that Great Blue Heron breeding failure was more frequent in 1998 and 1999 compared to a decade ago because of the combined effects of human disturbance from land development and an increased frequency of eagle predation.

Aggressive behavior of Grey Heron (Ardea cinerea) nestlings was observed in approximately 25% of the nests at two of three heronries (Kiersity and Kąty Rybackie; north Poland) studied in 2000-2002. Pecking (mostly at the youngest chick) was the commonest type of aggressive behavior (over 60% of cases). The chick mortality rate was higher in nests with sibling aggression than in other nests, however significant differences were found only at Kąty Rybackie. Foraging of parent birds nearby, in an area with abundant high quality and easily caught prey, could have caused the lack of sibling aggression in the colony at Mosty. At Kąty Rybackie, many chicks died in nests where aggressive behavior had been noted. It appears that siblicide, not predation, is the most important factor affecting Grey Heron breeding success in these colonies.

The fish community of the Gulf of Puck in the Baltic Sea has changed in recent years following the successful introduction of the Round Goby (Neogobius melanostomus). The first specimen of Round Goby was caught in 1990 and now is estimated in millions of individuals. The Round Goby was a main component of the Grey Heron diet in the colony at Mosty and made up 95% of regurgitated prey items. During chick rearing period, herons mostly flew to the coast to forage in shallow waters and feed on the Round Goby. The numbers of Grey Herons at Mosty have increased recently, especially since 1999 (from 238 in 1999 to 493 nests in 2003; an increase of 107%). The indirect evidence suggests that the rapid expansion of the Round Goby has influenced the Grey Heron and affected both the diet and the numbers of birds feeding and breeding in the vicinity of the Puck Gulf.

The Agami Heron (Agamia agami) is one of the least known species of herons. We report observations on an exceptionally large colony in French Guiana. The estimate of approximately 900 nests exceeds by ten fold the largest colony previously reported. Herons arrived at and departed from the colony and fed young only at night. The characteristic “Gr” call, which was recorded and analyzed, was used a contact-call, which ceased on disturbance. Timing of nesting was highly asynchronous. Nests were over water and in deep shade. Adults shaded young from the sun. Birds appeared to forage individually, possibly at long distances from the colony site.

We examined sexual size dimorphism of Arctic Terns (Sterna paradisaea) from a breeding colony in northeastern North America. Each bird was sexed using DNA extracted from feather pulp. Body morphometrics recorded included mass, natural wing chord, head-bill, tail fork, culmen, depth of bill at the gonys, and tarsus. Two discriminant functions identified head-bill and bill depth as the best measurements to identify the sexes. The first function included head-bill only and correctly classified 73% of our sample. The second function included both head-bill and bill depth, correctly classified 74% of our sample and increased the ability to correctly sex individuals within a pair. We provide a method for researchers to calculate the probability of sexing Arctic Terns. This is done by fitting a non-linear equation through a plot of the probability of classifying an individual and the discriminant scores. Male Arctic Terns were generally larger in head-bill and bill depth than female Arctic Terns; however, we did not find evidence for assortative mating. With some species, morphometrics alone can be used to distinguish the sexes but for species such as Arctic Terns, which have a high degree of overlap between the sexes, it is recommended that a combination of morphometrics and genetic analysis is used to obtain the highest accuracy in sexing individuals correctly. Comparison of the morphometrics of northeastern North American and British populations of Arctic Terns suggests that these discriminant functions can be applied to both.

In 1999, we compared demographic and biological parameters in Common Terns (Sterna hirundo) among three colonies located 10-26 km apart in Buzzards Bay, Massachusetts, USA. The three colony sites differed primarily in size, number of pairs, and length of occupancy by terns: Penikese Island (8 ha, 132 pairs, 3 yr), Ram Island (1.1 ha, 1,900 pairs, 8 yr), Bird Island (0.6 ha, 1,800 pairs, >65 yr). This study compared parental ages and origins, nesting phenology, clutch-size, chick growth rates, productivity, chick diets, feeding rates and foraging trip times among the three colonies. Common Terns breeding at the new colony on Penikese Island were significantly younger (mean age 6.8 yr) and laid later (mean laying date 25 May), had higher productivity (2.2 fledged chicks/pair) and higher chick growth rates than those at the old colony on Bird Island (means 11.7 yr, 20 May, 0.8 chicks/pair, respectively). Feeding rates were highest and foraging trip times for all types of prey were shortest at Penikese Island. Birds at Ram Island were intermediate in all these respects. Although productivity of Common Terns at Bird Island was relatively low during the period in which the other two colonies were established (1992-1999), both breeding adults at Bird Island and chicks raised there have been very slow to move to the other colonies, which were colonized mainly by immigrants from outside the region.

We studied relationships among sediment variables (carbon content, C:N, hardness, oxygen penetration, silt-clay fraction), hydrologic variables (dissolved oxygen, salinity, temperature, transparency, water depth), sizes and biomass of common invertebrate classes, and densities of 15 common waterbird species in ponds of impounded freshwater, oligohaline, mesohaline, and unimpounded mesohaline marshes during winters 1997-98 to 1999-2000 on Rockefeller State Wildlife Refuge, Louisiana, USA. Canonical correspondence analysis and forward selection was used to analyze the above variables. Water depth and oxygen penetration were the variables that best segregated habitat characteristics that resulted in maximum densities of common waterbird species. Most common waterbird species were associated with specific marsh types, except Green-winged Teal (Anas crecca) and Northern Shoveler (Anas clypeata). We concluded that hydrologic manipulation of marsh ponds is the best way to manage habitats for these birds, if the hydrology can be controlled adequately.

There is little information on the status and trends of the Black-legged Kittiwake (Rissa tridactyla) colonies in Greenland. This study analyses and evaluates historical counts from 1920-1999 of kittiwake colonies that have had ≥1,000 breeding pairs and have been counted at least twice. Fifty colonies fulfilled these criteria. Thirty-four of these colonies declined by between 50-100%. Data suggest that the decline has occurred throughout most of the country. Only five colonies had increased and eleven had remained stable or fluctuated with no clear trend. The increasing colonies do not compensate for the overall decline. Despite the heterogeneity of the count years and varying degree of count quality, the data suggest a dramatic decline within the last century. Data analysis does not suggest that local hunting, egg collecting or disturbance at the breeding colonies have been major causes for the decline and other causes should be considered. Causes of the decline remain unknown.

We examined several morphological characters of adult Black-legged Kittiwakes (Rissa tridactyla) breeding in Brittany, France, near the southern limit of the species’ range. Males were significantly larger than females in body mass, head length, wing and tarsus, and the French population differed highly significantly in size from previously studied populations in England and Alaska. There was a strong pattern of assortative mating on tarsus length (r₁₆ = 0.87) which was also correlated with arrival date in both sexes. After removing the variance produced by arrival date, assortative mating remained significant, suggesting that it may have been produced via sexual selection.

Bird use of three created salt marsh islands, constructed from dredged material near the Aransas National Wildlife Refuge, Texas, USA, was compared with that of natural marsh to provide feedback prior to additional marsh construction. Habitat associations of four bird groups (shorebirds, perching birds, wading birds, and gulls and terns) were similar in all sites, but relative contributions of each group to total avian abundance differed. Differences in site-use by birds were largely explained by differences in ratios of available habitat types, which were products of their geomorphic designs. Created marsh designs differed substantially from the natural marsh, where the unvegetated exposed-substrate and shallow-water habitats preferred by waterbirds were prominent features. The oldest created site (four years old) differed most from the natural marsh. Intertidal areas in the site were almost completely overgrown by vegetation, resulting in dominance of the avian assemblage by perching birds (especially grackles, Quiscalus spp.) rather than waterbirds. In the newer created sites (two years old), where vegetation had not completely overgrown the intertidal areas, avian assemblages were more typical of the natural marsh. However, vegetation cover was expanding in these sites, causing a reduction in waterbird habitat area. Efforts to ensure availability of unvegetated habitat in created sites will improve their structural similarity to natural marsh in the study area, and will likely increase their functional similarity for avian species.

Within-season nest persistence of large wading bird (Ciconiiformes) rookeries in the Atchafalaya Delta, Louisiana was examined during 1994 and 1995. A sample of rookery trees was permanently marked, and the status of 7,864 nests of ten species was followed through time. Nest construction began in early March, and some rookeries were still active into September during both seasons. Uniform nest persistence rates were calculated for each 28-day time period throughout the nesting season. Nest persistence rates per 28 days ranged from 0.00-0.96. During both years the rates tended to be lowest during the early season and increased into the late season. In 1994, nest persistence rates were significantly different, caused by the interaction of season and late nesting of White Ibis. In 1995, nest persistence rates differed significantly by season. The results call into question the value of nest counts obtained by one visit to a rookery complex, as these may greatly underestimate the numbers of breeding birds.

While Isla Chañaral (29°02’S) in Chile has long been recognized as one of the most important breeding islands for the Humboldt Penguin, the reported numbers of birds there never exceeded 3,500 breeding individuals in the last two decades. However, in 2002, a one-day survey found considerably more penguins present on Isla Chañaral, which exceed the world population estimate for the species (3,300-12,000 birds). Between 9 and 14 February 2003 we conducted a census of the Humboldt Penguin on Isla Chañaral. Two different survey methods were combined to assess the number of penguins. Terrestrial or surface counts were used to survey penguins on open plains or beaches. Small area surveys of randomly established quadrats were conducted to assess the density of penguins in nests and the total number of nest sites. Results from small area surveys were extrapolated using surface size ratios of counting quadrats vs. entire nesting sectors. We determined that approximately 22,000 adult Humboldt Penguins, 3,600 chicks and 117 juveniles were present on the island during the survey. The results were much higher than any previously published estimate. Natural processes alone cannot account for an increase, and penguin numbers on Isla Chañaral previously have been underestimated. The results correspond well with recent publications that suggest that Humboldt Penguin numbers in Chile have been underestimated in the past due to inappropriate or inconsistent census methods. There are concerns about the current protection status of the island in light of its fragility and importance as the premier breeding location of the Humboldt Penguin along its entire distributional range.