Bryan D. Watts

Species-specific accumulation of polybrominated diphenyl ether flame retardants in birds of prey from the Chesapeake Bay region, USA

Compared to organochlorines, little is known about polybrominated diphenyl ether (PBDE) contamination of birds of prey breeding in the Chesapeake Bay, the largest estuary in the U.S. This study examined and compared PBDE contamination in eggs of osprey, double-crested cormorant, brown pelican and peregrine falcon from this area. Several legacy persistent organic pollutants such as PCBs and DDE were also investigated. The level of urbanization of the landscape appeared to influence the level of PBDE exposure. PBDE congener distribution patterns varied between piscivorous and terrestrial-feeding birds. This suggests individual congeners may be subject to differences in bioaccumulation, biomagnification or metabolism in the aquatic and terrestrial food webs. Biomagnification of PBDEs was studied in the Bay aquatic food chains for the first time. A biomagnification factor of 25.1 was estimated for SigmaPBDEs for the fish - osprey egg food chain. Hazard quotients, applied as a preliminary evaluation, indicated that PBDEs may pose a moderate hazard to ospreys and peregrine falcons through impairment of reproductive performance.

Cover Use and Predator-related Mortality in Song and Savannah Sparrows

The predicted relationship between mortality risk and sparrow community structure is simple. It is as- sumed that the risk of predation is nonrandom across a given landscape because of the patchiness of veg- etation used as cover, and that prey species segregate spatially according to their specific abilities to utilize areas of varying risk. Unfortunately, unlike seed use and availability, predation risk is very difficult to quantify. This is so because observations of predatory

Status, Biology, and Conservation Priorities for North America's Eastern Golden Eagle (Aquila chrysaetos) Population

TODD KATZNER,1,2,26 BRIAN W. SMITH,3 TRICIA A. MILLER,4,5 DAVID BRANDES,6 JEFF COOPER,7 MICHAEL LANZONE,5,8 DANIEL BRAUNING,9 CHRISTOPHER FARMER,10 SERGIO HARDING,11 DAVID E. KRAMAR,12 CRAIG KOPPIE,13 CHARLES MAISONNEUVE,14 MARK MARTELL,15 ELIZABETH K. MOJICA,16 CHARLIE TODD,17 JUNIOR A. TREMBLAY,18 MARIA WHEELER,19 DAVID F. BRINKER,20 TONY E. CHUBBS,21 ROLF GUBLER,22 KIERAN O’MALLEY,23 SCOTT MEHUS,24 BRADY PORTER,19 ROBERT P. BROOKS,4 BRYAN D. WATTS,16 AND KEITH L. BILDSTEIN25

Maturation of a constructed tidal marsh relative to two natural reference tidal marshes over 12 years

Abstract Habitat functions of a constructed tidal marsh and two adjacent natural tidal marshes were compared between marshes and with similar data collected in the same marshes 7 years earlier. The marshes were sampled for fish, blue crabs, benthic infauna, vegetation community type, stem density and cover, salinity, temperature, dissolved oxygen, organic carbon, and bird utilization. The constructed marsh has progressed to a general level of function similar to that of nearby natural marshes. Some morphological differences remain, such as the differences in community type ratios. Significant differences in habitat function remain in three areas: sediment organic carbon at depth, mature saltbush density, and bird utilization (related to saltbush density). The addition of organic soil amendments and mature saltbush in the construction of tidal marshes will help in the progression of constructed marshes to functional equivalency with natural marshes. Specific functions can be enhanced for fish utilization (more subtidal habitat) and for birds (more shrub habitat) depending on management priorities.

Recovery of the Chesapeake Bay Bald Eagle Nesting Population

Abstract We conducted annual aerial surveys throughout the tidal reach of the Chesapeake Bay, USA, between 1977 and 2001 to estimate population size and reproductive performance for bald eagles (Haliaeetus leucocephalus). The population increased exponentially from 73 to 601 pairs with an average doubling time of 8.2 years. Annual population increase was highly variable and exhibited no indication of any systematic decline. A total of 7,590 chicks were produced from 5,685 breeding attempts during this period. The population has exhibited tremendous forward momentum such that >50% of young produced over the 25-year period were produced in the last 6 years. Rapid population growth may reflect the combined benefits of eliminating persistent biocides and active territory management. Reproductive rate along with associated success rate and average brood size increased throughout the study period. Average reproductive rate (chicks/breeding attempt) increased from 0.82 during the first 5 years of the survey to 1.50 during the last 5 years. Average success rate increased from 54.4% to >80.0% during the same time periods. The overall population will likely reach saturation within the next decade. The availability of undeveloped waterfront property has become the dominant limiting factor for bald eagles in the Chesapeake Bay. Maintaining the eagle population in the face of a rapidly expanding human population will continue to be the greatest challenge faced by wildlife biologists.

Osprey Diet Composition and Quality in High- and Low- Salinity Areas of Lower Chesapeake Bay

Abstract Chesapeake Bay, in the northeastern United States, is believed to support the largest concentration of breeding Ospreys (Pandion haliaetus) in the world. Following the banning of DDT, this population exhibited significant spatial variation in growth rates, with the fastest and slowest rates occurring in the lowest and highest salinity areas, respectively. Because salinity can influence fish distributions, we quantitatively analyzed Osprey diet composition along the gradient in the Chesapeake Bay to determine if variation in foraging ecology contributed to this pattern of population recovery. We recorded >1800 hr of food-provisioning behavior for 25 pairs within nine study areas that were classified as either upper estuarine (<5 parts per thousand [ppt] salinity) or lower estuarine (>18 ppt). Atlantic menhaden (Brevoortia tyrannus) and seatrouts (Cynoscion spp.) were dominant dietary components for pairs within lower-estuarine reaches, whereas gizzard shad (Dorosoma cepedianum) and catfish (Ictaluridae) dominated upper-estuarine diets. Lower-estuarine prey fish averaged 6% shorter (Kolmogorov-Smirnov test: D  =  0.203, P  =  0.004), 34% lighter (D  =  0.305, P < 0.001), and 40% lower in energy content (D  =  0.247, P < 0.001) than their upper-estuarine counterparts. We conclude that diet quality may be contributing to spatial variation in the growth rate of the Chesapeake Bay Osprey population.

SALINITY AND POPULATION PARAMETERS OF BALD EAGLES (HALIAEETUS LEUCOCEPHALUS) IN THE LOWER CHESAPEAKE BAY

Abstract We evaluated the relationship between salinity and Bald Eagle (Haliaeetus leucocephalus) population parameters using 26 years of survey data for the lower Chesapeake Bay. Tidal tributaries within the study area were stratified according to the Chesapeake Bay Programs segmentation scheme, and segments with the same salinity classification were considered spatial replicates. Salinity categories included tidal fresh, oligohaline, mesohaline, and polyhaline. Four parameters— colonization rate, nesting density, projected carrying capacity, and productivity— were derived from nesting data within each shoreline segment and compared across the salinity gradient. The study-wide Bald Eagle population is exhibiting exponential growth, with an average doubling time of 7.9 years. All population parameters showed significant directional variation with salinity. Average population doubling time for tidal fresh reaches was <6 years, compared with >16 years for polyhaline areas. Current Bald Eagle nesting density is negatively related to salinity and varies by a factor of 4 across the gradient. Comparison of current densities with projected carrying capacity suggests that these differences will be stable or increasing as the geographic areas approach equilibrium densities. We suggest that fisheries within lower saline reaches, including spring spawning runs of anadromous Clupeidae (shad and herring), are the most likely explanation for salinity effects. Observed distribution patterns suggest that lands along low-salinity waters are the core of the Bald Eagle nesting population within the lower Chesapeake Bay and should be the focus of long-term programs designed to benefit nesting eagles. Salinidad y Parámetros Poblacionales de Haliaeetus leucocephalus en la Bahia de Chesapeake

Breeding Season Status of the American Oystercatcher in Virginia, USA

Abstract Surveys of the American Oystercatcher (Haematopus palliatus) were conducted in all suitable nesting habitat in coastal Virginia, USA during the 2003 breeding season. The total of 588 pairs more than doubles previous estimates for the state, and provides a benchmark for the comparison of future surveys. These results suggest that Virginia supports the largest number of oystercatchers in the breeding season relative to other east coast states. Previous surveys in Virginia focused only on one coastal area, the barrier islands. Over two hundred pairs recorded in the seaside lagoon system of the Delmarva Peninsula in 2003 accounted for the large discrepancy between previous estimates for the state and the results of this survey. Over 89% of the total number of pairs was observed on the islands and in the lagoon system of the Delmarva Peninsula. Approximately 87% of the pairs were on land that is managed or regulated to some degree for the conservation of nesting birds by federal, state, municipal and non-governmental organizations, including 20% that occurred on land closed to public use during the bird-breeding season. Only 13% of the pairs were on land that affords no protection to breeding birds.

Residence Probability and Population Size of Red Knots During Spring Stopover in the Mid-Atlantic Region of the United States

Abstract Weekly counts of western Atlantic red knots (Calidris canutus rufa) at their Delaware Bay migration stopover site have suggested a major decline since the 1980s. We estimated red knot spring passage population size in the New Jersey Coast–Delaware Bay region (DENJ; 2004 and 2006) and Virginia (VA; 2006 and 2007), USA, by correcting weekly aerial counts for mean daily residence probability between counts in a Monte-Carlo simulation. We used daily telemetry relocations in mark–resight models to estimate mean daily residence probability. Average daily residence probability was approximately 1.0 in mid-May, 0.96–0.97 in the week of 22 May, and 0.64–0.77 after May 28 in DENJ in 2004 and 2006 and in VA in 2006. Average daily residency was approximately 0.88 in VA in 2007 from 22 May to 5 June. No birds moved from VA to DENJ in 2006 and only 2 birds (5.5%) moved in 2007. Stopover population sizes (±SE) in DENJ were 17,108 ± 1,322 in 2004 and 19,555 ± 831 in 2006, and in VA were 7,224 ± 389 in 2006 and 8,332 ± 718 in 2007, significantly greater than peak aerial counts. Years with similar peak counts had different residence probabilities; hence, adjustments for turnover should be used in the future to assess annual population changes. Our results suggest that VA can support a significant portion of this red knot subspecies during migration in at least some years. Managing red knots for recovery should entail improving our understanding of the use of other Atlantic Coast sites and protecting key coastal habitat from disturbance and development.

Ospreys of the Chesapeake Bay: Population Recovery, Ecological Requirements, and Current Threats

Abstract The Chesapeake Bay supports the largest Osprey (Pandion haliaetus) breeding population in the world. The population experienced a dramatic reduction due to biocide-induced reproductive suppression in the post World War II era and reached an estimated low of 1,450 pairs by the early 1970s. By the mid 1990s, the population recovered to an estimated 3,500 pairs and breeding was documented on 427 of 878 named tributaries of the tidal Bay. Recovery has been exponential but spatially variable with average doubling times for defined geographic areas varying by more than an order of magnitude. Rates of population growth have been negatively related to salinity with the highest rates occurring within tidal fresh reaches suggesting that recovery has progressed from the main stem of the Bay toward the fall line. Virtually nothing is known about the breeding ecology of Ospreys in the lower saline waters of the Bay. The increase and diversification of man-made structures used for nesting has made a fundamental contribution to recovery and current distribution. A synthesis of information from several field sites throughout the Bay shows a collective increase in reproductive rate (young/active pair) from less than 0.8 in the 1960s to more than 1.2 by the mid-1980s followed by a reduction to below 1.0 in the late 1980s. Threats to the population continue to be the release of new classes of contaminants into the estuary and anthropogenic activities that have the potential to suppress reproductive rates and juvenile/adult survivorship.