Tidal wetlands are an essential part of coastal systems and provide breeding and foraging habitat for many marsh birds. As human development continues in coastal areas, shoreline properties adjacent to expansive marsh are increasingly used. To gain access to coastal waterways, homeowners must now construct long piers over marsh habitat. To date, no published research has investigated the effect of long piers over tidal marshes on marsh birds. My objectives were to determine the effect of long piers over vegetated tidal marshes on the relative abundance and species richness of marsh birds, and to determine what landscape variables could be used to predict the relative abundance and species richness of marsh birds. I completed 72 surveys (i.e., combined passive and callback) in tidal marsh at 22 sites with long piers and 24 without piers, May–July 2005–2006. The presence of long piers negatively affected obligate marsh bird relative abundance and species richness (P ≤ 0.06), positively affected gulls and terns (P ≤ 0.07) and herons and egrets (P ≤ 0.03) but had no affect on facultative marsh birds (P ≥ 0.213). Long pier density was negatively related to obligate marsh bird relative abundance and species richness (P ≤ 0.06), but was positively related to the relative abundance and species richness of gulls and terns ( P ≤ 0.021). Herons and egrets were not related to long pier density (P ≥ 0.069). Facultative marsh bird relative abundance was not affected by pier density (P>0.696), but species richness was negatively related (P = 0.054). Obligate marsh birds revealed a strong, positive relationship with marsh area (P ≤ 0.001), whereas facultative marsh bird relative abundance was positively related to agriculture (P ≤ 0.003). Herons and egrets showed a negative trend with agriculture and marsh (P ≤ 0.07), whereas gulls and terns were not related to either marsh or agriculture. To reduce negative effects and promote biological integrity of tidal marsh habitat, management should reduce or eliminate long piers over tidal marshes and conserve marsh area.