We trapped 656 Common Terns (Sterna hirundo) and measured five body dimensions and body mass for each bird; 313 birds were of known age, and 229 were sexed by DNA. Males were larger than females in all five dimensions, but were smaller in body mass. Early-nesting birds were larger than late-nesting birds in all five dimensions: at least for wing length, this difference was related to both laying date and age. Head length (from back of skull to tip of bill) was the most useful measure for sexing Common Terns in the field. Discriminant functions indicated that 75.9% of single birds and 84.5% of pairs could be sexed correctly by head length alone. We present rules and nomograms for field sexing of Common Terns; these provide trade-offs between sensitivity (proportion of birds classified) and specificity (proportion of birds correctly sexed). Three of 80 pairs (4%) included two females: these pairs nested early and were at least as successful as male-female pairs. Within pairs, tarsus lengths were negatively correlated; we found no evidence for positive assortative mating by linear dimensions or body mass. This study confirms some previous reports of sexual dimorphism in this species based on less reliable methods of sexing, but fails to confirm other reports of sexual dimorphism and assortative mating.

We used DNA markers to determine the sexes of 449 breeding adult Black Terns (Chlidonias niger) captured and measured in southeastern Wisconsin from 2000 to 2005. Various morphometric discriminant functions were then generated to classify the sexes of these birds. Other objectives were to examine the effect of sample size on the predictive ability of discriminant function analysis (DFA), to evaluate the temporal stability in the accuracy of DFA for a specific population, and to test the geographic specificity of DFA by comparing separate breeding colonies in southeastern Wisconsin and also by applying a discriminant function, derived from an Oregon population, to terns in Wisconsin. The best discriminant function included head-plus-bill length and body mass, and correctly classified 81% of the birds in the complete sample. Within-pair comparisons increased the classification accuracy to 87%, because males usually were larger than their mates with respect to head-plus-bill length. Sample-size analysis indicated that a satisfactory discriminant function for Black Terns could be generated from a sample of only 10% of the population. Region-wide, classification accuracy was similar among years, indicating temporal stability, but the accuracy of prediction for females tended to erode over time at specific colonies. Discriminant functions generated from birds captured at one site performed equally well on neighboring populations, but the Oregon function performed poorly on the Wisconsin population. Our findings suggest that a discriminant function derived from morphometrics of a single population can be applied to other populations in a limited geographic region but its utility may decrease over time. Our results also validate the previous cautions that geographic variation in the biometry of a species precludes the use of a single discriminant function on widely disjunct populations.

We recorded the daily presence of Double-crested Cormorants (Phalacrocorax auritus) at the nesting island on Oneida Lake, New York, by monitoring the activities of 15 radio-tagged adults from July through September, 2000, using an automated data-logging receiver. A total of 24,464 acceptable detections was obtained for adult cormorants actively attempting to nest on the lake. Tagged cormorants had a bimodal daily activity pattern during the first month, with the fewest birds detected on the island at 09.00 h and 15.00 h Eastern daylight time. The pattern of activity appeared to change slightly in the second month of the study, representative of a post-breeding period for the colony, with a shift from a less synchronous pattern of departures to a greater focus on morning activity also centered around 09.30 h. These results correspond with daily observations of Great Cormorant (P. carbo) foraging activities reported for colonies in Africa and Poland. The data also support the possibility of nocturnal foraging activity, not previously reported for this species on their summer breeding grounds. No correlation was found between total number of daily detections and climatalogical factors or events.

Male Scarlet Ibises (Eudocimus ruber) and White Ibises (Eudocimus albus) have bills that are on average 22% longer than females, yet only half of this difference can be attributed to body-size differences. In this work it is suggested that the sexual dimorphism in bill length and bill shape is based in large part upon the role of bill length in determining the outcome of male bill-sparring contests. Sexual differences in bill morphology and behavior were investigated in a captive flock of 350 Scarlet Ibises. In 29 instances of males sparring with males in contests prior to breeding and in 11 instances of nest take-over during breeding, no significant differences in age, body size, or body condition between winning and losing males were found. However, males winning bill-sparring contests and nest take-overs had significantly longer bills than losing males. Longer billed males also bred significantly earlier than shorter billed males in captivity. Sexual differences in the relationship between bill curvature, bill chord and bill length suggest that male Scarlet and White Ibises are under selection for increased bill length. In addition, among 16 of 23 ibis species for which information was available, sexual dimorphism in bill length was positively associated with colonial nesting but was not associated with group foraging. This result supports the theory that close proximity during nesting is one feature that may facilitate bill sparring between males, resulting in selection for longer bills.

We used Pacific Loon (Gavia pacifica) and Red-throated Loon (G. stellata) nests with known ages to gauge the efficacy of egg flotation for determining nest age in coastal Alaska. Egg flotation accurately estimated nest age for both species; the mean ± 1SD difference between known age and age determined with egg flotation was -0.05 ± 2.00 d and -0.02 ± 1.63 d for Pacific and Red-throated Loons, respectively. Day of nest initiation did not influence the relationship between known nest age and nest age estimated with egg flotation, indicating incubation period was not shortened in nests initiated later in the season. Additionally, we found no difference in the ability of egg flotation to estimate nest age between two widely dispersed study sites for Pacific Loons, and only a small difference between two of three widely dispersed study sites for Red-throated Loons. Thus, our described relationships between egg flotation categories and nest age should be broadly applicable for these holarctic species. We conclude that for Pacific and Red-throated Loons, egg flotation is a useful technique for determining nest age in the field to better monitor nest fate, and to quantify nest age effects on nest daily survival rate.

During the 2003 and 2005 breeding seasons we conducted ground surveys of historical, potential, and current nesting sites of the VanRossem’s Gull-billed Tern (Gelochelidon nilotica vanrossemi) along the Pacific coast of Mexico. We documented 13 active colonies, including ten previously unrecorded nesting sites. One previously reported colony was inactive. Colony sizes ranged between one and 161 breeding pairs. In 2005, the estimated breeding population size was 526 pairs. Eighty-two percent of the total breeding population was concentrated in three relatively large colonies, Cerro Prieto and Isla Montague, Baja California and Laguna Las Garzas, Nayarit. Gull-billed Terns nested mostly on islets in very shallow waters. Colony associates included other terns, Black Skimmers (Rhynchops niger), gulls, and egrets. The nesting population of this subspecies in Mexico is very small and consists of a few widely separated colonies. This subspecies should be included in Mexico’s official list of species at risk, and a management plan should be developed and implemented to assure its conservation and that of the wetland habitat on which it and other bird species depend.

Little is known about the molt migration of the Surf Scoter (Melanitta perspicillata), a species endemic to North America. Our objective in this study was to document the breeding and molting chronology of Surf Scoters in Québec. Breeding birds were studied at Lake Malbaie, located about 90 km north of Québec City, Canada. Surf Scoters arrived at Lake Malbaie in the fourth week of May and most males stayed only for approximately three weeks. This relatively early departure of males from the breeding areas emphasizes the importance of salt water habitats for these birds. Unsuccessful adult females did not leave with the males but remained on their breeding lake. These females left the lake from mid to late July, nearly a month after the departure of males and much earlier than females with broods which left from mid to late August after abandoning their brood. This departure sequence was observed during the three years of the study. The difference in timing of molt migration between age and sex groups has important management implications as it potentially exposes them to different levels of mortality. For example, late molters, mostly adult females that bred successfully may still be flightless at the beginning of the hunting season in some areas. Better understanding of molt chronology and habitat selection by various sex and age groups will permit a more holistic and efficient management of Surf Scoters.

Barrow’s (Bucephala islandica) and Common (B. clangula) goldeneyes winter in large numbers in the St. Lawrence estuary and little is known of their distribution and diet. The objective of the study was to characterize how these two similar species, co-existed in the St. Lawrence estuary during the non-breeding season. Their local distribution, diet, and dive efficiency were compared. There was little overlap in habitat use by both goldeneyes. Their distribution was not correlated in the autumn (r = 0.04) but was in the spring (0.68). Autumn and spring distributions were more correlated in Common Goldeneyes (r = 0.82) than in Barrow’s Goldeneyes (r = 0.49). Both species moved to the north shore of the estuary during January and February 1999 as south shore intertidal areas froze. Barrow’s Goldeneyes foraged in larger flocks than Common Goldeneyes (x̄ = 20.3 vs 9.8 birds) and flocks were larger in autumn than spring. Both species fed on amphipods but differed in their use of gastropods (Barrow’s Goldeneye) and polychaetes (Common Goldeneye). Dive duration was similar in both species but varied between areas. Pause duration was shorter in Common Goldeneyes than in Barrow’s Goldeneyes but was not affected by area. Dive efficiency was higher in Common Goldeneyes than Barrow’s Goldeneyes and varied between areas. The predominance of polychaetes in the diet of Common Goldeneyes and of amphipods in the diet of Barrow’s Goldeneyes had not been highlighted before. These species provide a good example of niche differentiation between closely related species.

The Double-crested Cormorant (Phalacrocorax auritus) population in the North American Great Lakes region has increased substantially during the past three decades. Cormorants are likely recovering after a period of human-caused suppression; however, their resurgence has raised concerns regarding potential negative interactions with other waterbirds. To examine this issue, we compared measures of nesting success and aggressive behavior in Herring Gulls (Larus argentatus) nesting on two artificial islands in Hamilton Harbour, western Lake Ontario. Only breeding Herring Gulls occupied the first island, whereas a mixed colony of both Herring Gulls and cormorants occupied the second. Over three years, Herring Gulls in the single-species colony had greater nesting success than those in the colony shared with cormorants. Gulls in the mixed colony had more nests that contained cormorant eggs in addition to Herring Gull eggs, or that were usurped by cormorants. Analysis of individual Herring Gull egg fates revealed lower hatching rates and more eggs displaced from nests in the mixed colony. Due to the presence of cormorants, gulls in the mixed colony engaged in more aggressive interactions near their nests than those in the single-species colony. We conclude that at our study site cormorants were competing directly with Herring Gulls for nest sites and nesting material, and contributing to reduced Herring Gull reproductive success in the mixed colony. Our results suggest that interactions between species in mixed colonies may be more subtle than the displacement of breeding adults, and may not be detected by examining nest counts alone. We suggest that further studies examine cormorant interactions with other colonial bird species at additional sites.

Endangered Interior Least Terns (Sterna antillarum athalassos) and threatened Piping Plovers (Charadrius melodus) nest in Nebraska at gravel mines where they are vulnerable to disturbance and nest loss. Conflicts occur when their nesting and protected status delay mining activities. The possibility of shifting nesting from active to inactive mining areas by using a deterrent (mylar flagging), an attractant (gravel and driftwood spread on bare sand), and a control (untreated sand) was evaluated. Experimental plots (mean 0.36 ha) were established at 18 different gravel mines, twelve in 2000 and seven (one repeat) in 2001 along the Platte and Elkhorn rivers prior to nesting season. Of 117 tern nests, 73% were in attractant, 2% in deterrent, and 26% in control plots. Of 23 plover nests, 61% were in attractant, 9% in deterrent, and 30% in control. Colonies used plots containing less vegetation and more driftwood than unused plots. Within control plots, both tern and plover nests were surrounded by more large (>15 mm) gravel and less coarse sand than was available at random points. Within attractant plots, substrate at the nest did not differ from random points. In all plots, Least Tern nests were more likely to have driftwood by the nest than was available at random points. Hatching rates did not differ between attractant and control plots. To attract Least Terns and Piping Plovers, sand covered with 15% small gravel, 5-10% large gravel, <3% vegetation, and about ten pieces driftwood/1,000 m² was found to be effective. As deterrents, mylar streamers 7 m long, 30 mm wide, and 0.025 mm thick, attached to 1 m poles arranged in a 7 m grid were used. The combination of attractant and deterrent treatments provided a mechanism to protect nesting birds and avoid conflicts.

Populations of Southern Rockhopper (Euduptes chrysocome chrysocome) and Macaroni (E. chrysolophus) Penguins at key breeding sites in the Southern Hemisphere have declined substantially in the past 50 years, but their statuses at important breeding sites in southern Chile are poorly known. In 2002, at two of the largest breeding sites in Chile, the Ildefonso and Diego Ramírez Archipelagos, we determined the number of breeding pairs. Based on nest density checks (quadrat and/or point-distance techniques) in a sample of habitats and calculations of the areas of occupied terrain, we estimated there were 86,400 (CL_95%: 54,000 to 135,000) Rockhopper pairs and 5,660 (2,280 to 11,900) Macaroni pairs at Ildefonso, and 132,721 (88,860 to 185,665) Rockhopper pairs and about 15,600 Macaroni pairs at Diego Ramírez. Combined, the archipelagos hold about 28% of the world population of Southern Rockhopper Penguins.

Thirteen Blue-footed Boobies (Sula nebouxii) born on Isla Isabel, Nayarit, Mexico, nested on Isla El Rancho, Sinaloa. This natal dispersal of about 450 km was unknown for this species. Recruitment of these breeders appeared to happen at between four and seven years of age, slightly higher than the recruitment age reported for Isla Isabel birds that remain there. Age at first detection did not differ between males and females. Immigration to Isla El Rancho could relate to the recent establishment of this colony, and its continuous growth during the last five years. Since there doesn’t seem to be a shortage of nesting sites at Isla Isabel, long distance natal dispersal may be a normal trait in this species of booby.

In June 2000, an oiled Piping Plover (Charadrius melodus melodus), part of the endangered eastern Canadian population, was caught and banded, and a second oiled individual was observed at Flat Bay (48°26’N; 58°32’W) in southwestern Newfoundland. These are the first documented cases of oiled Piping Plover in Canada. The banded plover was subsequently recaptured in July 2001, and appeared healthy. Evidence of another individual surviving exposure to oil was documented in 2005 in Nova Scotia. This suggests that Piping Plovers are vulnerable to oil pollution but may have some capacity to survive minimal oiling.

Piping Plovers (Charadrius melodus) typically nest on unvegetated sand or gravel substrates throughout their breeding range. We report on the atypical habitat characteristics of four Piping Plover nests that we found amongst young cottonwood (Populus deltoides) saplings on a sandbar island in the Missouri River along the South Dakota-Nebraska border. Atypical habitat use could have implications for estimating demographic parameters and management of this protected species. It is important to explore the extent to which Piping Plovers use atypical breeding habitat throughout their range and the quality of this potentially poor habitat.

Tiger Herons (Tigrisoma) are little studied and generally characterized in the literature as being relatively uncommon birds of forested streams and wetlands. Contrary to these expectations, we found Bare-throated Tiger Herons (Tigrisoma lineatum) on the Pearl Islands of the Gulf of Panama to be birds of open, wave-exposed rocky seashores. We also found them to be common birds, inhabiting most shoreline coves. They fed over much of the tidal cycle along beaches and rocky shores, especially on and near surf-washed rocks. They caught crabs and fish by standing and walking slowly and methodically. Feeding efficiency was low, averaging about one prey item per hour. Plumage coloration is highly cryptic against shore rocks; but, in contrast, the bird becomes quite obvious when it expands its bare yellow throat, especially when accentuating a distinctive stretch display used to claim shore-line territory and for within-pair interactions. Tiger herons in the Pearls nested high in trees on ocean-facing cliffs. The habitat choice and behavior of this population of tiger herons that we report extend understanding of the biological scope of the subfamily of tiger herons.

American White Pelicans (Pelecanus erythrorhynchos) that breed on Anaho Island, Pyramid Lake, Nevada, are potentially exposed to a variety of contaminants. Therefore, the reproductive success of this colony was monitored in 1996 and eggs, blood and feathers from nestlings, livers from adults and nestlings, regurgitated fish from nestlings, and fish from representative feeding areas were collected and analyzed for mercury and selenium to determine exposure to the pelicans and sources of contamination. Additional samples were collected and analyzed in 1988, 1992, and 2004. Reproductive success at the Anaho Island colony was normal in 1996 based on hatching rates of eggs (≥75% in undisturbed areas) and survival of nestlings. Mercury and selenium concentrations in eggs were generally below known effect levels and did not appear to have an adverse impact on hatching success. Mercury and selenium concentrations in fish ranged widely, with mercury of greatest concern. Microscopic lesions characteristic of mercury toxicity were absent in pre-fledging nestlings in 1996. Some adult pelicans had elevated mercury concentrations in their livers; however, the potential toxic effects were difficult to evaluate because of probable demethylation of mercury, thereby possibly providing protection from toxicity. Exposure of pelicans to mercury varied among years, most likely in relation to wet-dry cycles and available feeding areas.

The Xisha Archipelago, South China Sea, was surveyed for waterbirds in March-April 2003 and April-August 2004. Forty-five waterbird species were recorded, making a grand total of 53 species for the Archipelago when earlier published records are included. The Archipelago is of great importance for the Red-footed Booby (Sula sula), with an estimated 10% of the world population breeding on Dong Island. Other breeding seabird species were Great Frigatebird (Fregata minor), Great Crested Tern (Sterna bergii) and Sooty Tern (S. fuscata), and it is believed that Black-naped Tern (S. sumatrana) and Roseate Tern (S. dougallii) also breed there. Compared to 1926, the number of seabirds, and the islands on which they breed, has declined greatly. The data for Ardeidae and shorebirds provide information on migration and, possibly, wintering strategies of these species. Despite habitat degradation and human disturbance, the Xisha Archipelago is still important for breeding seabirds and there is an urgent need to improve the conservation status of this bird group.

White-eared Night-heron (Gorsachius magnificus) is the most threatened and geographically restricted of the herons. Its biology is essentially unknown. On 24 May 2004, six adults and four juveniles were found for the first time at Thousand Island Lake, Zhejiang Province, P. R. China. In all, six nests and sixteen eggs were found over three years. Thirteen nestlings survived to fledging from seven breeding pairs. These numbers are the largest ever documented for the species. Our observations of breeding performance serve as an important baseline for future research on this species.

There have been no detailed studies on reproductive biology of the Great Cormorant (Phalacrocorax carbo sinensis) in Qinghai-Tibet Plateau. We conducted such investigations during the breeding seasons of 1999 and 2000 in Qinghai-Lake Bird Isle, China. Great Cormorants began to migrate to Qinghai-Lake for reproduction from the middle of March and left from early October at the end of reproduction. Nesting periods were from early April to mid June and took 50 days. Egg-laying occurred during the three weeks from the end of April to 20 May. Females typically laid an egg every 1-2 days until clutch completion. Mean clutch size in the study area over two years was 3.3 (SE ± 0.13, N = 68, range 1-5) and most (66.18%) fell within the range 3-4 eggs. Length of eggs averaged 61.01 mm and breadth averaged 34.13 mm. Fresh egg weight averaged 57.34 g (SE ± 0.36, range 46.0-73.7 g, N = 179). Hatching success was 48.7% and fledging success was 64.9% over two years. Decline of available fish resources in Qinghai-Lake might be one of main causes of lower reproductive success. The causes of chick loss were possibly high altitude, high winds and prolonged rain.

We recorded the diurnal behaviors of the endangered Black-faced Spoonbill (Platalea minor) for 16 days during the wintering season in Jeju Province, Korea to find an appropriate and effective sampling technique for behavioral study. Two main techniques were used and compared: focal sampling with continuous recording and scan sampling with instantaneous recording at various time intervals. As a result, recording the behavior of a focal bird for more than 20 min per h was the best technique with high accuracy and precision. However, to select less time- and labor-intensive techniques we concluded that scan samplings with less than 10 min intervals or focal samplings with more than 15 min durations are appropriate measurements of the spoonbill’s behaviors. Considering sampling sizes, scan sampling with 5 min recording intervals can be an effective technique but additional methods are also required to obtain significant information for infrequent or occasional behaviors. We suggest that each sampling technique should be validated by preliminary or supplementary surveys to estimate the endangered animal’s behaviors and this can be an important part of the groundwork for conservational efforts on the Black-faced Spoonbill.