The drivers of variable disease risk in complex multi-host disease systems have proved very difficult to identify. Here we test a model that explains the entomological risk of Lyme disease (LD) in terms of host community composition. The model was parameterized in a continuous forest tract at the Cary Institute of Ecosystem Studies (formerly the Institute of Ecosystem Studies) in New York State, U.S.A. We report the results of continuing longitudinal observations (10 years) at the Cary Institute, and of a shorter-term study conducted in forest fragments in LD endemic areas of Connecticut, New Jersey, and New York, USA. Model predictions were significantly correlated with the observed nymphal infection prevalence (NIP) in both studies, although the relationship was stronger in the longer-term Cary Institute study. Species richness was negatively, albeit weakly, correlated with NIP (logistic regression), and there was no relationship between the Shannon diversity index (H') and NIP. Although these results suggest that LD risk is in fact dependent on host diversity, the relationship relies explicitly on the identities and frequencies of host species such that conventional uses of the term biodiversity (i.e., richness, evenness, H') are less appropriate than are metrics that include species identity. This underscores the importance of constructing interaction webs for vertebrates and exploring the direct and indirect effects of anthropogenic stressors on host community composition.

We investigated the impacts of urbanization on reproductive success of House Wrens (Troglodytes aedon). We compared reproductive effort and success for 33 nesting attempts in suburban sites (2.5-10 buildings/ha) and 43 nesting attempts in rural sites (Ͻ2.5 buildings/ha) in and around the Washington, D.C.-Baltimore, Maryland, metropolitan area. There were no differences in clutch initiation dates or clutch sizes between suburban and rural nests. However, nestlings at suburban nests weighed less and had smaller body size prior to fledging compared to nestlings at rural nests. Parental feeding rates differed between suburban and rural nests during the ''early nestling stage'' (day 3 to day 6), but not in the ''late nestling stage'' (day 8 to day 12) suggesting average quality of prey for nestlings may be lower at suburban sites. Overall, suburban nests fledged more young than rural nests largely because of higher rates of nest predation on rural nests. Further research on how food availability and predation affects nesting success of House Wrens and other birds along urbanization gradients may provide important insights into impacts of urbanization on birds.

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