Joseph K. Shisler

Colony and Nest Site Selection in Laughing Gulls in Response to Tidal Flooding

-We examined colony and nest site selection in Laughing Gulls (Larus atricilla) from 1976 to 1979 in Barnegat Bay, New Jersey. Laughing Gulls nested predominantly in Spartina alterniflora on low salt marsh islands. In 1978, the gulls shifted colony locations to higher islands that contained a higher percentage of S. patens and Phragmites. The gulls nested on spoil areas which were slightly higher in elevation. Differential nesting success occurred as a function of habitat because of high tides in early July which wiped out all nests in S. alterniflora and most of those in S. patens. Chick survival varied as a function of vegetation type. We propose that all larid species exhibit site tenacity because they return to former sites even if they eventually shift locations. Further, we suggest that each species chooses from a wide range of potential colony and nest sites depending upon local conditions and proximate environmental cues. Many species of gulls and terns exhibit remarkable colony site tenacity in that they occupy the same places for decades or longer. This is particularly true of colonies situated in stable habitats such as rocky islands or cliffs: Black-legged Kittiwake (Rissa tridactyla) colonies use the same cliffs every year (Coulson and White 1956, 1958, 1960) and Glaucous Gulls (Larus hyperboreus) often nest on the same rocks in tundra lakes year after year (Snyder 1940). A colony of Black-headed Gulls (L. ridibundus) has remained at Ravenglass in England since the 1600s, nesting amid sand dunes and marram grass (Patterson 1965). Colony site tenacity has also been shown for the Herring Gull (L. argentatus; Tinbergen 1961, Ludwig 1963), Silver Gull (L. novaehollandiae; Murray and Carrick 1964), Glaucous-winged Gull (L. glaucescens; Vermeer 1963), Ring-billed Gull (L. delawarensis; Southern 1967), Black-headed Gull (L. ridibundus; Beer 1961), and Laughing Gull (L. atricilla; Stone 1937, Noble and Wurm 1943). Species that nest in unstable habitats, on the other hand, shift colony locations when habitats become unsuitable. Notable examples of such species are the Blackbilled Gull (L. bulleri, Beer 1966), Franklins Gull (L. pipixcan, Burger 1974a) and Brown-hooded Gull (L. maculipennis, Burger 1974b). The first species nests on sand bars in the middle of rivers, and the latter two nest in marshes that suffer sporadic changes in water levels (Weller and Spatcher 1965). The apparent dichotomy between species nesting in stable habitats versus those in unstable habitats prompted McNicholl (1971, 1975) to postulate that colony tenacity relates to habitat stability. Colony site tenacity may not differ among species, but may relate to the conditions that particular members of each species face. A colony of kittiwakes might shift quickly if their cliff suddenly fell into the sea. Similarly, Laughing Gulls, usually considered to show a high degree of colony site tenacity (Bongiorno 1970, Nisbet 1971), may abandon colony sites when these become temporarily unsuitable. In this paper we report on colony and nest site selection in Laughing Gulls under normal tidal conditions (1976, 1977, 1979) and under unusually high tidal conditions (1978). At the beginning of the study, we did not know when flooding tides would occur, but planned to continue the study until we encountered these conditions. We wished to determine if Laughing Gulls would respond to exceptionally high tides by changing colony sites, changing nest ites, or both. Laughing Gulls nest from the Gulf of Mexico and the Caribbean to the northern Atlantic, although few colonies exist farther north than New Jersey. Along the middle Atlantic coast they nest in tidal salt marshes (Burger and Beer 1975), while south of the Carolinas they nest on sandy islands (Stone 1937, Buckley and Buckley 1972, Dinsmore and Schreiber 1974).

Prevalence of canine lyme disease from an endemic area as determined by serosurvey

From August 1984 through February 1985, 423 dogs from 43 municipalities in 7 New Jersey counties were evaluated for the presence of antibodies to the Lyme disease spirochete (Borrelia burgdorferi). Of these dogs, 34.7% with no apparent clinical symptoms were serologically reactive (IFA greater than or equal to 1:64); titers in this study ranged from non-reactive to 1:2048. Ninety percent of the dogs surveyed had a current vaccination status to Leptospira interrogans serovars canicola and icterohaemorhagiae. Dogs vaccinated to leptospirosis elicited homologous antibody titers of less than or equal to 1:16 and, therefore, did not interfere with interpretation of antibody levels to B. burgdorferi. Effects of age, degree of outdoor activity, travel history, and location of residence were evaluated. The use of serosurveys of dogs as a tool for Lyme disease surveillance is discussed.

Comparison of rates of infection by the Lyme disease spirochete in selected populations of Ixodes dammini and Amblyomma americanum (Acari: Ixodidae)

At a major endemic focus in New Jersey, 50% of 290 adult Ixodes dammini collected in the fall of 1984 were infected with the Lyme disease spirochete (Borrelia burgdorferi), which was statistically higher than the rate found in the 202 adult ticks (39.6%) examined during the spring. Neither sex nor site of collection within the focus significantly affected the infection rate. The observed infection rates were similar to those reported in endemic areas of New York and Connecticut. Borrelia burgdorferi also infected all active stages of Amblyomma americanum ticks. Rates of infection were 5.4% in adults (n = 467) and 3.4% in nymphs (n = 289); 15.6% of clusters of unengorged larvae harbored B. burgdorferi, suggesting transovarial passage of the spirochete. Comparison of the rates of infection in I. dammini and A. americanum and their potential impact on Lyme disease transmission is discussed.

Evolution of a focus of Lyme disease

Epidemiological investigations were initiated in 1984 when significant Lyme disease activity was observed within a 5-km radius of an area previously used as a non-endemic control site for Lyme disease research in New Jersey. Through 1983, collections of Ixodes dammini from vegetation and feral rodents were infrequent and no human cases were identified within a 16-km radius of the control site. In 1984, 4 human cases and 3 serologically reactive canines (greater than or equal to 1:512) were recognized within the area and adult I. dammini populations were over 3-fold greater than those at our primary study location where Lyme disease has been endemic since 1981. Using darkfield microscopy, 53.4% of adult I. dammini were infected with Borrelia burgdorferi as compared to 50.0% of adults collected during the same period at the known endemic study site. These data indicate that a focus of Lyme disease has recently become established at the previously non-endemic control site and that the establishment of new foci may occur more rapidly than once thought.

The immediate effects of ditching a saltmarsh on nesting herring gulls Larus argentatus

Abstract We examined the effects of water management for mosquito control on the behaviour and breeding success of a resident colony of herring gulls. The colony resided on three close islands, one of which was ditched in March before the start of the second breeding season. The number of breeding pairs on the ditched island remained the same before and after ditching although the breeding number increased by 46% and 90% on the other two islands. Breeding chronology was similar on all three areas. However, birds nesting on spoil laid eggs a mean of 8 days later than non-spoil nesting birds. Behavioural observations on aggression and display rates indicated that birds on spoil behaved similarly to those in open grassy areas but differed from those nesting in the bushes. Nest site selection, breeding densities, and breeding success were similar on all three islands. Thus the differences noted were attributed to the appearance of the marsh. We postulated that pairs having nested on the experimental island in the previous year continued to do so after the island was ditched. However, pairs searching for new territory did not move onto the island that was ditched, but instead colonised the nearby islands. Similarly, those pairs breeding on spoil nested later because of the need to defend their nest sites which were situated in areas used for displaying by unmated birds.

The Effects of Ditching a Salt Marsh on Colony and Nest Site Selection by Herring Gulls (Larus argentatus)

Herring gulls recently invaded and now nest on salt marsh islands in New Jersey. In 1971 about 50 pairs nested in an area of Spartina patens that contained a few Iva bushes on Sandy Island. In 1972 one half of the island containing the herring gull colony was ditched with internal ditches connected to the surrounding bay, and the other half of the island was ditched only internally. Although in 1971 the vegetation on both sub-islands was similar (primarily Spartina), the sub-island with ditches connected to tidal areas underwent major changes as bushes moved into over 80% of the area. No significant vegetational changes occurred on the sub-island with only internal ditching, and the gulls moved to this area. Gulls nested in Spartina patens, on spoil piles near bushes. As the highest in the marsh, these areas are thus less susceptible to storm and flood tides. The gulls nesting on spoils built higher nests, laid bigger eggs, and had a higher mean clutch size than birds that did not nest on spoil piles. This suggests that spoil piles are the preferred habitat of the older, more experienced birds. We discuss the nesting behavior of the gulls in terms of the vegetational changes coused by different methods of ditching.

Succession and productivity on perturbed and natural Spartina salt-marsh areas in New Jersey

Vegetation growth on spoil placed on aSpartina patens andS. alterniflora marsh in Barnegat Bay, New Jersey, was examined for two years following spoil deposition. In areas where spoil was leveled to match the elevation of the marsh, the percent cover by the end of the first growing season ranged from 60 to 90%. By the second year, cover was 100% in all study plots. Even during the first year, there was no difference in species diversity or vegetation species in the experimental and control areas. The percentage of shrubs did not increase on the perturbed (spoil) areas compared to the control plots. During the first year, but not the second, live and dead biomass was greater in the perturbed areas compared to the control plots. In an area where the spoil was thicker succession was exceedingly slow and there was only about 5% grass cover by the end of the first growing season. BecauseSpartina colonizes primarily by rhizome growth, the comparatively slow recovery was attributed to the inability of the grass to penetrate the thick spoil layer.

The effect of the marsh elder (IV a frustescens) on the standing crop biomass of Spartina patens and associated wildlife

Abstract A population of Iva frutescens L. associated with Spartina patens (Ait.) Muhl on dredged material piles in a New Jersey saltmarsh previously managed for mosquito control was studied to assess its effect on the standing crop biomass of the grass. Both leaf and wood biomasses of I. frutescens were highly correlated with age. Living biomass of S. patens on the marsh surface, on dredged material piles and on dredged material piles with I. frutescens growth were not statistically different. Standing dead bionass of S. patens on the dredged material piles with I. frutescens was significantly lower than dead S. patens biomass on the marsh surface and dredged material piles without I. frutescens. This was probably a result of increased tidal circulation in the managed marsh. In addition to contributing organic material to the salt marsh-estuarine ecosystem without causing any detrimental effect on the standing crop biomass of S. patens, I. frutescens was shown to provide nesting and foraging sites for various species of birds, and islands of refuge for small mammals and birds.