The Relationship Between Hemosporidian Parasites and Song Sparrows (Melospiza melodia) Along an Urban Gradient Andrew Bartlow1, Katie White1, and Jeffrey A. Stratford1,2 1Department of Biology, Wilkes University, Wilkes-Barre, PA 2 [email protected] ABSTRACT Humans turn natural landscapes into complex mosaics, which include A. B. agriculture, urban centers, suburbs, and natural remnants. Consequently, interactions between organisms are likely to be altered including parasite- host interactions. Here, we investigate the relationship between song 50 The results show that the probability of sparrows (Melospiza melodia) and several hematozoan parasites in a hemosporidian parasite infection increases with complex landscape within and around Wilkes-Barre, PA. Fifty-four 40 35 increasing forest cover at a local scale (90m around a sparrows were captured in various habitats from urban centers to 28 sample point) and increasing urban cover at a larger relatively rural sites. From each bird, a blood smear was made and 30 scale (210m around a sample point). examined for 15 minutes (30 minutes total) by two observers noting presence/absence of hematozoans. Capture sites served as centers of 20 circular buffers from which we extracted the proportion of urban and 10 10 forest cover. Buffers had diameters of 90, 210 and 990m around each 10 RESULTS point. We created a number of logistic models with presence/absence as C. D. Infections of Percent • Plasmodium is the most frequently detected parasite (Fig. 3) the response variable and arcsine-square-root transformed landscape 0 • The top model includes small scale forest and medium scale variables as the explanatory variables. Using Akaiki Information Criterion Leucocytozoon Plasmodium Haemoproteus Other urban cover (Table 1) (AIC) to rank models, the top model included percent forest cover in 90m • Forest on a small scale within a slightly larger urban landscape buffers and percent urban in 210m buffers. We then used the top model Genus positively affects parasitic infection (Table 2) to build a map where each pixel was represented by the probability of • The probability map shows that the lowest infection rates occur in being infected. This map showed that the highest probabilities occurred the center of the city, while the suburbs surrounding Wilkes-Barre along roads and in urban wood lots and lowest probabilities occurred in Figure 3. The percentage of birds infected with a hemosporidian parasite. The genus that infected song sparrows the most was Plasmodium spp. and Kingston show higher rates of infection. However, the highest shrubby areas and urban centers. Overall, 60% of the birds were infected. Other parasites included infection rates occur when forested areas are surrounded by urban Aegyptianella spp. and one microfilaria larvae. areas (Fig. 2B) INTRODUCTION Human activity changes natural landscapes into a mosaic of land uses including urbanized areas and remnants of native vegetation. Populations Figure 1. Overview of methods A. Banding a bird using banding pliers B. DISCUSSION and biological communities are highly modified in these altered landscapes. Mist net (6 m x 2 m) used to catch individual birds C. Blood smear stained Table 1. Information theoretic methods. Shown are the ΔAIC values The goal of this study was to determine how complex landscape for the null model and for the model that includes forest at 90m plus Avian species richness, for instance, generally declines with increasing with Giemsa stain D. Map of Wilkes-Barre, PA and surrounding areas with patterns affect the spatial pattern of parasitic infection in song the sites of song sparrow capture (flags). urban at 210m. ΔAIC values > 4 from the null model are considered to urbanization yet densities of birds in urban habitats is often higher. be well-supported models. sparrows. We found that increasing local forest area nested within Mosquito abundance is also higher in urban areas. Few studies, however, a larger urban landscape affects parasitism positively. This have looked at avian communities or mosquitoes in areas in between urban Model AIC ΔAIC contradicts the spatial pattern of species richness, which is more and natural areas or in complex landscapes. Birds and their hemosporidian Forest90 + Urban210 71.729 0 influenced by larger landscape-scale forest area (Stratford and parasites offer an excellent model system for exploring how this Robinson 2005, Urban Ecosystems). Our results indicate that small- Forest90 74.242 2.513 relationship is affected by land use. scale forested habitats within an urban area may be important in Forest90+Urban990 74.307 2.578 causing parasitic infection. Therefore, conservation efforts should Forest210 75.788 4.059 be focused on forested landscapes reducing potential situations of Project objectives: determine the scales and combinations of Forest90 + Urban210 + INT 75.890 4.161 small-scale forested areas. Knowing that local factors affect land covers that best explain spatial variation in blood parasite Null 76.192 4.463 parasitism more than the entire landscape, we can continue to look rates in song sparrows Shrub210 76.331 4.602 at the fine details of landscape and urbanization, not only in birds Forest210+Urban210 76.339 4.610 and their hemosporidian parasites, but in other parasite-host METHODS relationships, including parasites that have a harmful impact on Shrub990 77.008 5.279 Birds humans. Because of the small sample size, this study will be Urban90 77.554 5.825 continued. Future plans include increasing the sample size, • Song sparrows (Fig. 1A) were located by haphazardly stopping at sites A Forest90 + Urban90 + INT 77.637 5.908 where the habitat seemed appropriate expanding the sample area, researching vector populations, and Shrub90 78.003 6.274 • A mist net (Fig. 1B) was used to catch individual birds at each site using using molecular techniques (PCR) to determine if the birds are song playback Forest990 78.036 6.307 infected. • Blood samples (~ 10 µl) taken to make blood smears Urban990 78.095 6.366 Parasites Shrub210 + Urban990 78.116 6.387 • Blood smears were fixed in methanol for 10 minutes and stained in Urban210 78.189 6.460 ACKNOWLEDGMENTS Giemsa for 50 minutes Funding for this study was supported by: • Each slide was examined for 15 minutes by two observers using oil Howard Hughes Medical Institute immersion (1000x) The H. Fenner Research Fund, Wilkes University Analysis Table 2. Source table of the top logistic model. The logistic model showing the coefficients and the p-values for forest at 90m and urban • Georeferenced points (Figs. 1D, 2AB) where birds were captured served as at 210m. Both had p-values less than 0.05 and both positively influence Thanks to Chris Nemeth and Amy McNumis for assistance centers of circular buffers in which landscape features (% urban, % forest, parasitic infection. catching sparrows. % scrub) were extracted from a 1996 USGS Land Use/Land Cover map (Fig 2A) B Coefficient se p Assistance with spatial modeling was provided by John • Buffers had diameters of 90m, 210m and 990m Hogland, Montana Department of Natural Resources and Intercept -2.747 1.39 0.048 • Incidence of parasites was fitted to arcsine square root transformed Conservation landscape variables using several logistic models Forest 90m 3.342 1.29 0.01 • The models produced were then ranked using Akaiki Information Figure 2. A. 1996 Land use/land cover map of the Wilkes-Barre/Scranton area. B. Map of the same spatial extent as A but each pixel is now Urban 210m 2.033 1.03 0.048 Criterion (AIC) in order to determine the top model transformed to reflect the probability of a sparrow having blood parasites. • The top model was used to create a spatially explicit probability map of infection (Fig 2B)