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Although a species of conservation concern, little is known about the reproductive success of Least Terns (Sternula antillarum) throughout the southeastern USA where availability of natural beaches for nesting is limited. Daily survival rate (DSR) of nests and chicks was examined at four natural nesting sites in Cape Romain National Wildlife Refuge, South Carolina, 2009–2010. Measures of nest success (n = 257 nests) ranged from 0–93% among colony sites. The DSR of nests was primarily related to colony site, but year and estimates of predation risk also were related to DSR. Predation was the principal cause of identifiable nest loss, accounting for 47% of nest failures when the two years of data were pooled. The probability (± SE) of a chick surviving from hatching to fledging = 0.449 ± 0.01 (n = 92 chicks). DSR of chicks was negatively related to tide height and rainfall. Therefore, productivity of Least Terns is being lost during both the nesting and chick stage through a combination of biotic and abiotic factors that may prove difficult to fully mitigate or manage. Although natural nesting sites within Cape Romain National Wildlife Refuge intermittently produce successful nests, the consistency of productivity over the long term is still unknown. Given that the long term availability of anthropogenic nest sites (e.g., rooftops, dredge-spoil islands) for Least Terns is questionable, further research is required both locally and throughout the region to assess the extent to which natural sites act as population sources or sinks.
Studies must be performed throughout the year to determine how the seasonal energy requirements of Snowy Egrets (Egretta thula) and Great Egrets (Ardea alba) change. Foraging behavior was quantified during the breeding season in Kansas and during the non-breeding season in Florida using energetic algorithms and scan sampling. Fifty-eight percent (n = 287) of breeding Snowy Egrets were observed ambulating while 51% (n = 271) of non-breeding Snowy Egrets were observed loafing. Standing foraging was the most commonly observed behavior among Great Egrets in both the breeding (54%, n = 91) and non-breeding (38%, n = 164) seasons. Behavior was dependent on season for both Snowy Egrets (χ2 = 200.1, P < 0.001) and Great Egrets (χ2 = 187.4, P < 0.001). During the breeding season, Snowy Egrets expended 0.13 ± 0.06 W (Watts) in rivers and 0.08 0.02 W at weirs. During the non-breeding season Snowy Egrets expended 0.06 ± 0.01 W. During the breeding season Great Egrets expended 0.11 0.02 W at both weirs and in rivers, and 0.09 ± 0.02 W during the non-breeding season (F2,46 = 7.86, P < 0.0012). Snowy and Great egrets appear to vary their caloric demand on aquatic systems over the annual cycle. However, the quantity of energy derived from an ecosystem should not be the only factor taken into consideration in determining the value of that ecosystem.
Inter- and intra-specific interactions are potentially important factors influencing the distribution of populations. Aerial survey data, collected during range-wide breeding population surveys for Eastern Prairie Population (EPP) Canada Geese (Branta canadensis interior), 1987–2008, were evaluated to assess factors influencing their nesting distribution. Specifically, associations between nesting Lesser Snow Geese (Chen caerulescens caerulescens) and EPP Canada Geese were quantified; and changes in the spatial distribution of EPP Canada Geese were identified. Mixed-effects Poisson regression models of EPP Canada Goose nest counts were evaluated within a cross-validation framework. The total count of EPP Canada Goose nests varied moderately among years between 1987 and 2008 with no long-term trend; however, the total count of nesting Lesser Snow Geese generally increased. Three models containing factors related to previous EPP Canada Goose nest density (representing recruitment), distance to Hudson Bay (representing brood-habitat), nesting habitat type, and Lesser Snow Goose nest density (inter-specific associations) were the most accurate, improving prediction accuracy by 45% when compared to intercept-only models. EPP Canada Goose nest density varied by habitat type, was negatively associated with distance to coastal brood-rearing areas, and suggested density-dependent intra-specific effects on recruitment. However, a non-linear relationship between Lesser Snow and EPP Canada Goose nest density suggests that as nesting Lesser Snow Geese increase, EPP Canada Geese locally decline and subsequently the spatial distribution of EPP Canada Geese on western Hudson Bay has changed.
While the breeding and wintering ranges of the eastern population of Barrow's Goldeneyes (Bucephala islandica) are generally described, molting locations and links among breeding, molting, and wintering areas are unclear, particularly for adult females. Incubating females from the same breeding location (n = 5) were equipped with satellite transmitters in June 2009. Four molting sites were identified over 2 years, spread broadly across Québec: an inlet in Ungava Bay 1,100 km from the breeding area, a lake 100 km south of Ungava Bay (880 km from breeding area), a lake near Hudson Bay (910 km from breeding area) and the mouth of the Rivière aux Outardes River in the St. Lawrence Estuary (165 km from breeding area). The distance between molting females averaged 755 km and two females molted in regions where males were known to molt. Of four birds with consecutive years of molt locations, three showed inter-annual fidelity to within 5 km of the previous molt sites and the fourth molted in sites that were 968 km apart. Females wintered in different locations within the St. Lawrence Estuary and moved widely throughout the area during winter. The south coast of the St. Lawrence Estuary was used during spring and fall staging, and the north coast during winter. There was not strong migratory connectivity among annual cycle stages in eastern adult female Barrow's Goldeneyes, indicating that they should be considered a single management unit that occurs over a broad range throughout the year.
Recreational boat traffic is increasing worldwide and there is a need for scientifically based regulations that sustain both seabirds and wildlife viewing. The effects of boat disturbance to seabirds off Vancouver Island, Canada were quantified by testing distances that roosting or nesting birds showed an agitation response to an approaching motorboat or a kayak. The effects of species sensitivity, vessel type, habituation and season on agitation distance were examined. At 40 m from approaching boats, nesting Double-crested (Phalacrocorax auritus) and Pelagic (P. pelagicus) cormorants, Black Oystercatchers (Haematopus bachmani), Glaucous-winged Gulls (Larus glaucescens), and Pigeon Guillemots (Cepphus columba) had less than 6% probability of being agitated with either a kayak or motorboat, while at 50 m there was less than 2% probability of agitation. Roosting birds had larger response distances than nesting birds. Roosting Harlequin Ducks (Histrionicus histrionicus) were particularly sensitive with 24% probability of agitation at distances less than 50 m. Agitation distances were reduced by habituation to boat traffic and a single kayak could approach closer than a motorboat without disturbing seabirds. A general set-back guideline of 50 m would protect most nest and roost sites while allowing viewers to appreciate seabirds. Setbacks could be adjusted to protect locally sensitive sites or species.
Within the context of a limited number of Brown Pelican (Pelecanus occidentalis) breeding sites, promoting new colonies can mitigate localized threats to regional populations. To assess the efficacy of short-distance (∼5 km) translocations and use of decoys to establish new colonies, and thereby increase statewide population viability, research was conducted within the Isles Dernieres archipelago, Louisiana. Translocations of 323 Brown Pelican chicks to an un-colonized island were performed from 2007 to 2009, and from 2008 to 2010, 108 Brown Pelican decoys were deployed on a separate island void of nesting. From 2008 to 2010 band re-sighting surveys detected only one transplanted Brown Pelican chick that returned to the release site. Further, < 1 % of translocated individuals were observed throughout the archipelago, compared to 5% and 9% of banded individuals encountered that fledged from nearby islands. Low detection of translocated Brown Pelicans may be due to translocation stress that can result in disorientation and social disorganization, which may promote increased roaming. At sites with decoys, no loafing or nesting Brown Pelicans were observed. Further, behavioral surveys suggest there was no difference in interest of passing Brown Pelicans to decoys compared to paired control survey areas without decoys. Despite past successes of translocations and decoys for establishing new colonies of Brown Pelicans and other waterbird species, Brown Pelican conservation may be best promoted via restoration and protection of current colony sites.
Semipalmated Sandpipers (Calidris pusilla) use coastal wetlands in the southeastern United States during spring migration, some engaging in short-distance movements and brief refueling stops. Knowledge about the scale and factors that influence these movements could guide conservation planning, but often this information is not available. The influence of inter-wetland distance, prey biomass, amount of foraging habitat at depths of 0–4 cm, and density of migrating Semipalmated Sandpipers on their movement and stopover residency was investigated at the Tom Yawkey Wildlife Center in South Carolina in spring 2007. Tom Yawkey Wildlife Center contains three clusters of coastal wetlands separated by 2.6, 2.8 and 4.1 km. Probability of moving among wetland clusters and stopover residency were estimated using multi-state mark-recapture models and encounter histories from 502 marked Semipalmated Sandpipers. Sixty-four percent of Semipalmated Sandpipers remained within 2 km of site-of-capture for the duration of the study. Movement probabilities were negatively influenced by inter-cluster distance and Semipalmated Sandpiper density. Probability of moving between clusters 2.6–2.8 km apart was higher than clusters separated by 4.1 km. Semipalmated Sandpipers were more likely to depart the study area and resume migration after feeding in wetland clusters with abundant prey and accessible habitat. The interaction between prey and accessible habitat led to instances where Semipalmated Sandpipers were more likely to remain in wetlands with low prey levels, but high accessible habitat, or low accessible habitat, but high prey levels. Local movements among alternative foraging locations were facilitated when wetlands were < 2.8 km apart, highlighting the benefits of integrated management at small scales.
Humphrey and Parkes (1959) developed a molt and plumage nomenclature (the “H-P” system) based on the evolution of prebasic molts in birds from ecdysis events in reptiles, followed by later evolution of inserted molts responding to lineage-specific constraints and adaptations in Aves. Pyle (2005) revised H-P molt and plumage terminology of ducks by tracing the evolution of their molts from geese, whereas Hawkins (2011) defended traditional molt and plumage terminologies that defined molts relative to present-day breeding seasonality, ensuing plumage coloration, and other proximal factors. Apart from misinterpreting H-P's evolutionary approach, Hawkins (2011) confused the first-cycle terms of H-P, Howell et al. (2003), and Pyle (2005), and presented no new data or ideas to support traditional molt terminology in ducks. It is unlikely that inserted molts evolved in ancestral taxa based on yet-to-occur adaptations involving plumage color, and it is inconsistent to define homologous molts based on similar ensuing feather coloration while disregarding the substantially different coloration of homologous plumages within many avian lineages. Here the terminology of Pyle (2005) is defended, an alternative interpretation for the initial evolution of two (rather than one) inserted molts in the definitive cycles of female and male ducks is elaborated upon, and the future application of metabolic signatures to trace homologous molts in ducks and other bird lineages is suggested. Prebasic molts in ducks and other birds likely evolved from whole-scale restorative events common to all vertebrates, whereas distinguishable and less-comprehensive endocrinological and metabolic processes may accompany inserted molts.
Estimating productivity for precocial species can be difficult because young birds leave their nest within hours or days of hatching and detectability thereafter can be very low. Recently, a method for using a modified catch-curve to estimate precocial chick daily survival for age based count data was presented using Piping Plover (Charadrius melodus) data from the Missouri River. However, many of the assumptions of the catch-curve approach were not fully evaluated for precocial chicks. We developed a simulation model to mimic Piping Plovers, a fairly representative shorebird, and age-based count-data collection. Using the simulated data, we calculated daily survival estimates and compared them with the known daily survival rates from the simulation model. We conducted these comparisons under different sampling scenarios where the ecological and statistical assumptions had been violated. Overall, the daily survival estimates calculated from the simulated data corresponded well with true survival rates of the simulation. Violating the accurate aging and the independence assumptions did not result in biased daily survival estimates, whereas unequal detection for younger or older birds and violating the birth death equilibrium did result in estimator bias. Assuring that all ages are equally detectable and timing data collection to approximately meet the birth death equilibrium are key to the successful use of this method for precocial shorebirds.
Response of breeding waterbird communities to the effects of hurricanes remains poorly understood. The impact of two 2008 hurricanes on the breeding waterbird community was investigated at the Isles Dernieres Barrier Island Refuge in southern Louisiana using pre- and post-hurricane survey data. After the 2008 hurricanes, the breeding community was reduced from 44,042 breeding pairs in 2008 to 27,977 pairs in 2009 and to 23,544 pairs in 2010. Populations of the five most abundant species, Brown Pelican (Pelecanus occidentalis), Laughing Gull (Leucophaeus atricilla), Royal Tern (Thallasseus maximus), Sandwich Tern (Thallasseus sandvincensis), and Black Skimmer (Rynchops niger), decreased from 2008 to 2010. In contrast, populations of Roseate Spoonbill (Platalea ajaja), Sooty Tern (Onychoprion fuscatus), and Gull-billed Tern (Gelochelidon nilotica) increased from 2008 to 2009 but declined in 2010. The dramatic decline of total breeding pairs in the year following hurricanes demonstrates the vulnerability of this community to tropical storms and habitat degradation. Further investigations of this community are necessary to understand how major disturbances affect resilience and long-term viability of colonial waterbird communities on barrier islands.
Black-faced Cormorants (Phalacrocorax fuscescens) are endemic to marine environments in southern Australia and little is known of their biology. Development of a reliable and practical method for sexing adult birds in the field is necessary to aid research into their behavior and life-history. Eleven measurements from museum specimens (27 male; 31 female) were used to document sexual dimorphism in Black-faced Cormorants using discriminant function analyses (DFA). A simultaneous DFA correctly sexed 81% of birds, while a stepwise DFA correctly sexed 85% of birds based on two measurements (bill length and mid tail length). However, terminal wear of the retrices make this measurement unreliable. A logistic regression using bill length correctly predicted the sex of 78% of individuals. Black-faced Cormorants with a bill ≤ 76 mm long are likely female and ≥ 77 mm long are likely male, therefore providing a reliable method for assigning sex in the field. Black-faced Cormorants exhibit the same pattern of sexual dimorphism found in all other cormorants studied to date: males are larger, more robust and have a longer bill compared to the smaller, relatively gracile and shorter-billed females. The use of this general rule to assign sex to adult Black-faced Cormorants was confirmed through the observation of mating behavior. Therefore, this study provides a dependable and practicable technique for assigning sex in the field without the need to capture birds and disturb their behavior.
Understanding the factors that determine waterfowl nesting site selection is an essential tool for wetland management, but, unfortunately, this information is lacking for most species in the Southern Hemisphere. During the 2007 breeding season, reproductive biology and nesting habitat selection of the Red Shoveler (Anas platalea) were investigated in a wetland of Central Chile. Red Shoveler nests were clumped, primarily in scrubby meadows, containing an average of 8.56 ± 1 eggs (n = 2 3). Nesting microhabitat was characterized by well-covered ground and an intermediate height of the rich herbaceous layer close to the water. Hatching success was 80 ± 20% and was negatively associated with the number of cattle dung piles and the proportion of dry vegetation, but positively explained by herbaceous height and the distance to watercourse. Results suggest that the risk of predation, the access to food, and cattle disturbance would affect the selection of breeding sites and nest success of Red Shoveler. Management should focus on increasing diversity the herbaceous layer, ensuring easy access to water sources, and decreasing livestock pressure during the nesting period.
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